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Sample records for 2u-globulin hyaline droplet

  1. Hazard evaluation of chemicals that cause accumulation of alpha 2u-globulin, hyaline droplet nephropathy, and tubule neoplasia in the kidneys of male rats.

    PubMed Central

    Hard, G C; Rodgers, I S; Baetcke, K P; Richards, W L; McGaughy, R E; Valcovic, L R

    1993-01-01

    This review paper examines the relationship between chemicals inducing excessive accumulation of alpha 2u-globulin (alpha 2u-g) (CIGA) in hyaline droplets in male rat kidneys and the subsequent development of nephrotoxicity and renal tubule neoplasia in the male rat. This dose-responsive hyaline droplet accumulation distinguishes CIGA carcinogens from classical renal carcinogens. CIGA carcinogens also do not appear to react with DNA and are generally negative in short-term tests for genotoxicity, CIGA or their metabolites bind specifically, but reversibly, to male rat alpha 2u-g. The resulting complex appears to be more resistant to hydrolytic degradation in the proximal tubule than native, unbound alpha 2u-g. Single cell necrosis of the tubule epithelium, with associated granular cast formation and papillary mineralization, is followed by sustained regenerative tubule cell proliferation, foci of tubule hyperplasia in the convoluted proximal tubules, and renal tubule tumors. Although structurally similar proteins have been detected in other species, including humans, renal lesions characteristic of alpha 2u-g nephropathy have not been observed. Epidemiologic investigation has not specifically examined the CIGA hypothesis for humans. Based on cancer bioassays, hormone manipulation studies, investigations in an alpha 2u-g-deficient strain of rat, and other laboratory data, an increased proliferative response caused by chemically induced cytotoxicity appears to play a role in the development of renal tubule tumors in male rats. Thus, it is reasonable to suggest that the renal effects induced in male rats by chemicals causing alpha 2u-g accumulation are unlikely to occur in humans. Images FIGURE 1. FIGURE 2. FIGURE 3. FIGURE 4. FIGURE 5. FIGURE 6. FIGURE 7. FIGURE 8. FIGURE 9. FIGURE 10. FIGURE 11. FIGURE 12. FIGURE 13. PMID:7686485

  2. Hyaline droplets in Kupffer cells: a novel diagnostic clue for autoimmune hepatitis.

    PubMed

    Tucker, Suzanne M; Jonas, Maureen M; Perez-Atayde, Antonio R

    2015-06-01

    Pediatric autoimmune hepatitis (AIH) is relatively common and has a characteristic but relatively nonspecific histopathology with a usually prominent lymphoplasmacytic infiltrate. Herein, we describe for the first time the presence of characteristic hyaline droplets in the cytoplasm of Kupffer cells on routine hematoxylin and eosin (H&E) sections in AIH. The medical records and pathologic material over a 20-year period (1992 to 2012) were reviewed from children with AIH (n=30), hepatitis B virus (n=30), and hepatitis C virus (n=30) from the pathology files at Boston Children's Hospital. All children had percutaneous needle liver biopsies. We reviewed sections stained with H&E, PAS, and PAS with diastase for the presence of hyaline droplets in all 90 biopsies. We also performed immunohistochemical analysis for IgG, IgA, and IgD in 6 biopsies with AIH. Hyaline droplets were identified in Kupffer cells throughout the lobules in 15 of 30 biopsies (easily found in 13 and rare in 2); conversely, no droplets were identified in 15. Droplets were identified in 10 AIH type 1 biopsies, 1 in AIH type 2, 3 in overlap syndrome, and 1 in unclassified. Serum IgG levels, when available, were correlated with biopsy findings. Seventeen patients had serum IgG levels available for review. The average IgG level in patients without droplets in their biopsies was 1364 mg/dL, in contrast to 3424 mg/dL in patients with droplets (P=0.021). Immunohistochemical analysis performed in 6 biopsies revealed that droplets were nearly always positive for IgG, occasionally for IgA, and rarely for IgD. None of the biopsies in patients with hepatitis C contained hyaline droplets. One biopsy of a patient with hepatitis B revealed hyaline droplets; this biopsy had an unusually prominent plasmacytic infiltrate, and the patient was found to have an elevated IgG serum level and antibodies to smooth muscle actin. As far as we are aware, hyaline droplets in Kupffer cells on routine H&E sections have never been

  3. d-Limonene-induced male rat-specific nephrotoxicity: Evaluation of the association between d-limonene and alpha 2u-globulin

    SciTech Connect

    Lehman-McKeeman, L.D.; Rodriguez, P.A.; Takigiku, R.; Caudill, D.; Fey, M.L.

    1989-06-15

    d-Limonene is a naturally occurring monoterpene, which when dosed orally, causes a male rat-specific nephrotoxicity manifested acutely as the exacerbation of protein droplets in proximal tubule cells. Experiments were conducted to examine the retention of (/sup 14/C)d-limonene in male and female rat kidney, to determine whether d-limonene or one or more of its metabolites associates with the male rat-specific protein, alpha 2u-globulin, and if so, to identify the bound material. The results indicated that, 24 hr after oral administration of 3 mmol d-limonene/kg, the renal concentration of d-limonene equivalents was approximately 2.5 times higher in male rats than in female rats. Equilibrium dialysis in the presence or absence of sodium dodecyl sulfate indicated that approximately 40% of the d-limonene equivalents in male rat kidney associated with proteins in a reversible manner, whereas no significant association was observed between d-limonene equivalents and female rat kidney proteins. Association between d-limonene and male rat kidney proteins was characterized by high-performance gel filtration and reverse-phase chromatography. Gel filtration HPLC indicated that d-limonene in male rat kidney is associated with a protein fraction having a molecular weight of approximately 20,000. Separation of alpha 2u-globulin from other kidney proteins by reverse-phase HPLC indicated that d-limonene associated with a protein present only in male rat kidney which was definitively identified as alpha 2u-globulin by amino acid sequencing. The major metabolite associated with alpha 2u-globulin was d-limonene-1,2-oxide. Parent d-limonene was also identified as a minor component in the alpha 2u-globulin fraction.

  4. Differences in alpha 2u-globulins increased in male rat kidneys following treatment with several alpha 2u-globulin accumulating agents: cystein protease(s) play(s) an important role in production of kidney-type-alpha 2u-globulin.

    PubMed

    Saito, K; Kaneko, H; Isobe, N; Nakatsuka, I; Yoshitake, A; Yamada, H

    1992-11-30

    Effects of alpha 2u-globulin accumulating agents on alpha 2u-globulins in rat kidneys were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting analysis. Treatment of male animals with decalin (150 mg/kg), 2,2,4-trimethylpentane (50 mg/kg), isophorone (150 mg/kg), d-limonene (150 mg/kg) or 1,4-dichlorobenzene (150 mg/kg) by gavage for 14 consecutive days in each case resulted in a marked intensification of a protein band corresponding to kidney-type-alpha 2u-globulin, with a molecular mass calculated to be approximately 16 kDa. However, intraperitoneal treatment with leupeptin and E-64 (two times 0.07 mmol/kg, for each), well known cystein protease inhibitors, while only slightly increasing this kidney-type-alpha 2u-globulin band, caused the intensification of a approximately 19-kDa molecular mass protein band which was revealed to be a native-type-alpha 2u-globulin by SDS-PAGE and immunoblotting. These results indicated that at least two types of alpha 2u-globulin can be increased in male rat kidney by chemical treatment. Moreover, cystein protease(s) appear(s) to play an important role in the degradation of alpha 2u-globulin and particularly in the conversion of native-type-alpha 2u-globulin to kidney-type-alpha 2u-globulin in rat kidneys.

  5. Selenium regulates gene expression for estrogen sulfotransferase and alpha 2U-globulin in rat liver.

    PubMed

    Yang, Q; Christensen, M J

    1998-03-01

    Dietary intake of the essential trace element selenium (Se) regulates expression of genes for selenoproteins and certain non-Se-containing proteins. However, these proteins do not account for all of Se's biological effects. The objective of this work was to identify additional genes whose expression is regulated by Se. Identification of these genes may reveal new functions for Se or define mechanisms for its biological effects. Weanling male Sprague-Dawley rats were fed a Torula yeast-based Se-deficient basal diet or the same diet supplemented with 0.5 mg Se/kg diet as sodium selenite for 13 weeks. Total RNA was used as template for RNA fingerprinting. Two differentially expressed cDNA fragments were identified and cloned. The first had 99% nucleotide identity with rat liver estrogen sulfotransferase (EST) isoform-6. The second had 99% nucleotide sequence identity with rat liver alpha 2u-globulin. The mRNA levels for both were markedly reduced in Se deficiency. Laser densitometry showed that EST mRNA in Se deficiency was 7.3% of that in Se-adequate rat liver. The level of alpha 2u-globulin mRNA in Se-deficient rat liver was only 12.6% of that in Se-adequate rat liver. These results indicate that dietary Se may play a role in steroid hormone metabolism in rat liver.

  6. EFFECTS OF FOUR TRIHALOMETHANES ON DNA STRAND BREAKS, RENAL HYALINE DROPLET FORMATION AND SERUM TESTOSTERONE IN MALE F-344 RATS

    EPA Science Inventory

    All four possible trihalomethanes (THMs) containing bromine and chlorine, as well as perchloroethylene (PCE), were evaluated for their ability to produce DNA strand breaks, a2u-globulin rich renal deposits, and testosterone changes in male F-344 rats. Rats received daily equimola...

  7. Effects of a major androgen-dependent urinary protein,. alpha. 2u-globulin on the pituitary-gonadal axis and hypothalamic monoamines in adult male mice

    SciTech Connect

    Ghosh, P.K.; Chandrashekar, V.; Steger, R. Bartke, A. )

    1990-01-01

    The purpose of the present study was to evaluate the effects of alpha-2u-globulin, a sex-dependent male rat urinary protein on pituitary-gonadal functions and hypothalamic monamine contents in male mice. Adult male mice, maintained under standardized laboratory conditions were injected subcutaneously with alpha-2u-globulin or with vehicle daily for 14 days and killed 16 h after the last injection. Plasma levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T) and testicular levels of T were measured by radioimmunoassays. The concentrations of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) in medial basal hypothalamus (MBH) and anterior hypothalamus (AH) were measured by high performance liquid chromatography. Administration of alpha-2u-globulin led to a significant increase in plasma FSH and LH levels. In the MBH of alpha-2u-globulin treated mice, there were significant elevations of NE, DA and 5-HT contents. In the AH, both DA and 5-HT contents were decreased while NE content remained unaltered.

  8. The presence of alpha 2u-globulin is necessary for d-limonene promotion of male rat kidney tumors.

    PubMed

    Dietrich, D R; Swenberg, J A

    1991-07-01

    In a 2-year carcinogenesis bioassay, d-limonene (dL) induced kidney tumors in male F344 rats, but not in female F344 rats or either sex of mice, d-Limonene-1,2-oxide, a metabolite of dL, has been shown to bind reversibly the male rat-specific urinary protein, alpha2u-globulin (alpha 2u-G), lysosomal degradation than alpha 2u-G alone. This reduced degradation of alpha 2u-G-chemical complex leads to an accumulation of this protein in the proximal convoluted tubules of the male rat kidney and to the morphological changes characteristic for alpha 2u-globulin nephropathy. The only male rat strain known to be resistant to this renal disease is the alpha 2u-G deficient NCI-Black-Reiter (NBR) rat. The objectives of this study were to determine whether or not dL causes sustained increases in cell proliferation and has promoting activity for renal adenomas in male rats and if the male rat-specific urinary protein, alpha 2u-G, is required. In a 32-week initiation-promotion assay, male F344 and NBR rats were treated with either 0 or 500 ppm N-ethyl-N-hydroxyethylnitrosamine (EHEN) in the drinking water for 2 weeks. Experimental groups of 31 to 38 rats then received 0 or 150 mg d-limonene/kg/day in corn oil for 30 weeks by p.o. gavage 5 days/week. Cell proliferation in the proximal tubules was assessed via 5-bromo-2'-deoxyuridine-filled osmotic mini-pumps and immunohistochemistry after 7 weeks (2 weeks EHEN + 5 weeks dL) and at the end of the study (2 weeks EHEN + 30 weeks dL). Preneoplastic and neoplastic lesions were quantified in perfusion-fixed kidneys. A 5-fold increase in the labeling index of P2-cells was found after 5 weeks and 30 weeks of promotion in all dL-treated F344 rats, whereas no difference between treatment groups was detected in NBR rats. No increase in tumors or preneoplastic lesions was detected in dL-treated NBR rats, whereas a 10-fold increase in renal adenomas and atypical hyperplasias was found in the EHEN-dL-treated F344 rats compared with F344 rats

  9. Comparative study regarding the association of alpha-2U globulin with the nephrotoxic mechanism of certain petroleum-based Air Force fuels. Final report, 1 September 1986-31 August 1987

    SciTech Connect

    Eurell, T.E.

    1987-10-27

    Alpha-2U globulin is a low-molecular-weight urinary protein which may be associated with a hydrocarbon-induced proximal tubular cell degeneration in the male rat kidney. A new method was developed to obtain monospecific immunologic reagents for alpha-2U globulin using diafiltration, anion exchange and hydroxylapatite chromatography. Isoelectric focusing techniques were developed to isolate the major isoelectric variants of the alpha-2U globulin molecule and to assess changes in alpha-2U globulin after experimental exposure to hydrocarbon compounds. Alpha-2U globulin was isolated from the urine of albino and pigmented male rats to study strain susceptibility to the nephrotoxic process. An alpha-2u globulin isoelectric variant profile distinguishing albino from non-albino male rats was not apparent, however, strain differences were revealed. Fischer 344 male rats appear to have higher levels of the isoelectric variants than the other strains studied. These findings suggest that if a strain susceptibility to the hydrocarbon-induced nephrotoxic lesion exists, it may be associated with the alpha-2U globulin isoelectric variant profile.

  10. Comparative study regarding the association of alpha-2U globulin with the nephrotoxic mechanism of certain petroleum-based Air Force fuels. Final report, 1 September 1984-31 August 1986

    SciTech Connect

    Eurell, T.E.

    1986-10-31

    Fischer 344 male rats have a dose- and time-dependent proximal tubular degeneration induced by certain petroleum-based fuels. This degeneration may be associated with a low molecular weight alpha globulin (termed alpha-2U globulin). A new method was developed to obtain monospecific immunologic reagents for alpha-2U globulin using diafiltration, anion-exchange and hydroxylapatite chromatography. Rocket immunoelectrophoretic and isoelectric focusing techniques were developed to quantitatively and qualitatively assess changes in alpha-2U globulin after experimental exposure to hydrocarbon compounds.

  11. Complex histopathologic response in rat kidney to oral β-myrcene: an unusual dose-related nephrosis and low-dose alpha2u-globulin nephropathy.

    PubMed

    Cesta, Mark F; Hard, Gordon C; Boyce, John T; Ryan, Michael J; Chan, Po C; Sills, Robert C

    2013-01-01

    Oral gavage studies with β-myrcene in male F344 rats showed a complex renal pathology comprising both alpha2u-globulin (α2u-g) nephropathy, an unusual nephrosis involving the outer stripe of outer medulla (OSOM), and an increased incidence of renal tubule tumors by 2 years. In the 90-day and 2-year studies, respectively, α2u-g nephropathy and linear papillary mineralization were observed in males at the two lower doses but were absent from the high dose. Nephrosis was characterized by dilation of the S3 tubules, nuclear enlargement (including karyomegaly), and luminal pyknotic cells, all in the outermost OSOM. Nephrosis was minimal at the higher doses in the 90-day study, but progressed to a severe grade in males dosed with 1,000 mg/kg for 2 years. Renal tubule tumors developed in treated groups with incidences up to 30% in the 250 and 500 mg/kg male dose groups. Tumors at the lower doses in males may have been associated with α2u-g nephropathy, while those at higher doses in both sexes may have been due to the nephrosis. Because β-myrcene induced a complex spectrum of renal pathology, the α2u-g nephropathy mechanism cannot be the sole mechanism of carcinogenesis in these rats.

  12. Methyl isobutyl ketone exposure-related increases in specific measures of α2u-globulin (α2u) nephropathy in male rats along with in vitro evidence of reversible protein binding.

    PubMed

    Borghoff, S J; Poet, T S; Green, S; Davis, J; Hughes, B; Mensing, T; Sarang, S S; Lynch, A M; Hard, G C

    2015-07-03

    Chronic exposure to methyl isobutyl ketone (MIBK) resulted in an increase in the incidence of renal tubule adenomas and occurrence of renal tubule carcinomas in male, but not female Fischer 344 rats. Since a number of chemicals have been shown to cause male rat renal tumors through the α2u nephropathy-mediated mode of action, the objective of this study is to evaluate the ability of MIBK to induce measures of α2u nephropathy including renal cell proliferation in male and female F344 rats following exposure to the same inhalation concentrations used in the National Toxicology Program (NTP) cancer bioassay (0, 450, 900, or 1800ppm). Rats were exposed 6h/day for 1 or 4 weeks and kidneys excised approximately 18h post exposure to evaluate hyaline droplet accumulation (HDA), α2u staining of hyaline droplets, renal cell proliferation, and to quantitate renal α2u concentration. There was an exposure-related increase in all measures of α2u nephropathy in male, but not female rat kidneys. The hyaline droplets present in male rat kidney stained positively for α2u. The changes in HDA and α2u concentration were comparable to d-limonene, an acknowledged inducer of α2u nephropathy. In a separate in vitro study using a two-compartment vial equilibration model to assess the interaction between MIBK and α2u, the dissociation constant (Kd) was estimated to be 1.27×10(-5)M. This Kd is within the range of other chemicals known to bind to α2u and cause nephropathy. Together, the exposure-related increase in measures of α2u nephropathy, sustained increase in renal cell proliferation along with an indication of reversible binding of MIBK to α2u, support the inclusion of MIBK in the category of chemicals exerting renal effects through a protein droplet α2u nephropathy-mediated mode of action (MoA).

  13. Delayed secondary glucocorticoid response elements. Unusual nucleotide motifs specify glucocorticoid receptor binding to transcribed regions of alpha 2u-globulin DNA.

    PubMed

    Chan, G C; Hess, P; Meenakshi, T; Carlstedt-Duke, J; Gustafsson, J A; Payvar, F

    1991-11-25

    Glucocorticoids stimulate the transcription of rat alpha 2u-globulin (RUG) genes. Because this induction occurs after a time lag of several hours and is blocked by inhibitors of protein synthesis, it exemplifies a delayed secondary response to steroid hormones. In this report, we show that a region of RUG-transcribed DNA (approximately +1800 to +2174) contains multiple footprint sites for glucocorticoid receptor that are, apparently, organized into at least three independent binding clusters. The DNA sequences bound by the receptor and the location of binding sites were determined. A family of sequences related to half-sites of the consensus primary glucocorticoid response element (GRE) is discernible at each cluster of sites. Compared to the consensus GRE, which contains two pseudo-palindromic hexanucleotides arranged in a tail-to-tail fashion and separated by three bases, the arrangements of hexanucleotides within this segment of RUG DNA are unusual and heterogeneous. Methylation interference of a binding cluster containing three receptor footprints demonstrates that certain guanines of the GRE-like hexanucleotides are essential for efficient receptor binding. A synthetic 29-base pair (bp) RUG element, containing one receptor footprint from this cluster, selectively binds the receptor. Within this 29-bp element, six nucleotides separate two directly repeated copies of GRE-like hexanucleotides. RUG DNA fragments containing all or part of the three binding clusters, including the 29-bp element, confer a delayed secondary hormone responsiveness upon a linked heterologous promoter and reporter gene in stably transfected cell lines. We speculate that the unusual DNA sequence motifs of the receptor-binding sites are crucial for the generation of certain delayed secondary responses.

  14. Comparative study regarding the association of alpha-2u globulin with the nephrotoxic mechanism of certain petroleum-based air force fuels. Annual report 1 Jul 90-30 Jun 91

    SciTech Connect

    Eurell, T.E.

    1991-08-14

    Adult male rats have a dose and time dependent renal proximal tubular degeneration induced by certain hydrocarbon compounds. This degeneration is associated with a low molecular weight urinary protein called alpha 2U globulin. We are using rat strain variation (Fisher 344 and NCI Black Reiter) and different hydrocarbon compounds (JP-4, JP-8, decalin and trimethylpentane) to investigate the hydrocarbon-induced nephrotoxic response. Preliminary histochemical and morphometric evaluation of NCI-Black Reiter rats exposed to JP-8 suggests that this strain undergoes an intermediate form of the hydrocarbon-induced nephrotoxicity when compared to the albino Fisher 344 strain.

  15. A Study of the Effect of Hydrocarbon Structure on the Induction of Male Rat Nephropathy and Metabolite Structure

    DTIC Science & Technology

    1991-06-17

    Hydrocarbon Structure on the PE - 61102f Induction of Male Rat Nephropathy and Mfetabolite Scructur( PP - 2312...spectronetrv (GC/YS). Histopathologic examination of the kidneys revealed minimal hyaline droplet formation (a2u-globulin nephropathy ) in the proximal tubule...spectrometry (GC/MS). Ilistopathologic examination of the kidneys revealed minimal hyaline droplet formation (a2u-globulin nephropathy ) in the proximal

  16. Physiologically based pharmacokinetic model for ethyl tertiary-butyl ether and tertiary-butyl alcohol in rats: Contribution of binding to α2u-globulin in male rats and high-exposure nonlinear kinetics to toxicity and cancer outcomes.

    PubMed

    Borghoff, Susan J; Ring, Caroline; Banton, Marcy I; Leavens, Teresa L

    2017-05-01

    In cancer bioassays, inhalation, but not drinking water exposure to ethyl tertiary-butyl ether (ETBE), caused liver tumors in male rats, while tertiary-butyl alcohol (TBA), an ETBE metabolite, caused kidney tumors in male rats following exposure via drinking water. To understand the contribution of ETBE and TBA kinetics under varying exposure scenarios to these tumor responses, a physiologically based pharmacokinetic model was developed based on a previously published model for methyl tertiary-butyl ether, a structurally similar chemical, and verified against the literature and study report data. The model included ETBE and TBA binding to the male rat-specific protein α2u-globulin, which plays a role in the ETBE and TBA kidney response observed in male rats. Metabolism of ETBE and TBA was described as a single, saturable pathway in the liver. The model predicted similar kidney AUC0-∞ for TBA for various exposure scenarios from ETBE and TBA cancer bioassays, supporting a male-rat-specific mode of action for TBA-induced kidney tumors. The model also predicted nonlinear kinetics at ETBE inhalation exposure concentrations above ~2000 ppm, based on blood AUC0-∞ for ETBE and TBA. The shift from linear to nonlinear kinetics at exposure concentrations below the concentration associated with liver tumors in rats (5000 ppm) suggests the mode of action for liver tumors operates under nonlinear kinetics following chronic exposure and is not relevant for assessing human risk. Copyright © 2016 The Authors Journal of Applied Toxicology Published by John Wiley & Sons Ltd.

  17. Hyaline fibromatosis syndrome: cutaneous manifestations*

    PubMed Central

    Marques, Silvio Alencar; Stolf, Hamilton Ometto; Polizel, Juliana Ocanha; Munhoz, Tânia; Brandão, Marcela Calixto; Marques, Mariangela Esther Alencar

    2016-01-01

    Hyaline fibromatosis syndrome is the current name for clinical manifestations of diseases previously known as “infantile systemic hyalinosis” and “juvenile hyaline fibromatosis”. The authors report representative clinical cases of each one of the above subtypes with emphasis on cutaneous manifestations and difficulties for early diagnosis in this syndrome, essentially of multidisciplinary approach. PMID:27192526

  18. Fusarium and other opportunistic hyaline fungi

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter focuses on those fungi that grow in tissue in the form of hyaline or lightly colored septate hyphae. These fungi include Fusarium and other hyaline fungi. Disease caused by hyaline fungi is referred to as hyalohyphomycosis. Hyaline fungi described in this chapter include the anamorphic,...

  19. The pathogenesis of hyaline arteriolosclerosis.

    PubMed Central

    Gamble, C. N.

    1986-01-01

    Although hyaline arteriolosclerosis is very common and has been of interest to pathologists for well over 100 years, its pathogenesis has never been determined. This study demonstrates that iC3b bound via an ester linkage to hydroxyl groups on the repeating disaccharide units of hyaluronic acid is a major component of arteriolar hyaline. The deposition of iC3b within the walls of arterioles appears to be due to slow spontaneous activation of the alternative complement pathway and random binding of metastable C3b to proximate hyaluronic acid within the arteriolar wall. Since hyaluronic acid does not activate the alternative complement pathway, bound C3b is rapidly inactivated by factors I and H to iC3b, which, along with factor H, remains bound to hyaluronic acid. The hyaline in some hyalinized arterioles also contains IgM and early and late classical complement pathway components. Indirect evidence suggests that the IgM represents immunoconglutinin, an autoantibody to neoantigens on iC3b and that their interaction results in activation of the classical complement pathway. The gradual accumulation of iC3b, factor H, and, at times, IgM and classical complement pathway components within the walls of arterioles is considered to be a physiologic consequence of aging and probably cannot be prevented, because interruption of the initial binding of metastable C3b to hyaluronic acid would require abrogation of the critically important functions of the alternative complement pathway. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 PMID:2420184

  20. Hyaline protoplasmic astrocytopathy of neocortex.

    PubMed

    Hedley-Whyte, E Tessa; Goldman, James E; Nedergaard, Maiken; Friedman, Alan; Han, Xiaoning; Schmidt, Robert E; Powers, James M

    2009-02-01

    Eosinophilic inclusions in the cytoplasm of protoplasmic astrocytes of the neocortex, usually in the clinical setting of epilepsy and/or psychomotor retardation, were first recognized and illustrated by Alois Alzheimer in 1910. Traditional special stains have failed to elucidate the specific nature of these inclusions. Ultrastructurally, the material was composed predominantly of highly electron-dense, non-membrane-bound, granular material distinct from Rosenthal fibers. Immunohistochemical examination has been informative but also sometimes inconsistent; it has recently been suggested that they may represent a filaminopathy (filamin A). We examined 5 cases with neocortical eosinophilic inclusions (3 autopsies, 2 surgical resections) using a standardized immunohistochemical protocol at a single institution. The specimens were immunostained with 32 antibodies to 30 potentially relevant proteins using several antigen retrieval protocols. We confirmed the presence of filamin A in these inclusions, but several additional proteins, particularly cytoglobin and glutamate transporter 1, were also identified. By electron microscopy in 2 cases, the granular fine structure of the inclusions was confirmed; mitochondria adjacent to, and perhaps within, the inclusions that contained many pleomorphic vesicular and membranous elements were also noted in 1 case. The pathophysiologic relevance of these proteins and the clinical significance of the hyaline inclusions are discussed.

  1. Genetics Home Reference: juvenile hyaline fibromatosis

    MedlinePlus

    ... RJ, Cajaiba MM, Madri J, Lopez MA, Ramirez MC, Martignetti JA, Reyes-Múgica M. Juvenile hyaline fibromatosis ... Citation on PubMed Dowling O, Difeo A, Ramirez MC, Tukel T, Narla G, Bonafe L, Kayserili H, ...

  2. Hyaline Fibromatosis Syndrome: A Rare Inherited Disorder

    PubMed Central

    Mantri, Meeta Dipak; Pradeep, Mahajan M; Kalpesh, Patil O; Pranavsinh, Raj J

    2016-01-01

    Hyaline fibromatosis syndrome (HFS) is rare autosomal recessive disease characterized by the deposition of amorphous hyaline material in skin and visceral organs. It represents a disease spectrum with infantile systemic hyalinosis (ISH) being the severe form and juvenile hyaline fibromatosis (JHF) being the mild form. Dermatologic manifestations include thickened skin, perianal nodules, and facial papules, gingival hyperplasia, large subcutaneous tumors on the scalp, hyperpigmented plaques over the metacarpophalangeal joints and malleoli, and joint contractures. ISH shows a severe visceral involvement, recurrent infections, and early death. We report a case of 2.5-year-old female patient who presented with HFS who had overlapping features of both ISH and JHF. To the best of our knowledge, very few cases of HFS have been reported in Indian literature till date. PMID:27688461

  3. Pulmonary hyalinizing granuloma presenting with dysphagia: a rare presentation.

    PubMed

    Khan, Fazal; Hamid, Arsalan; Fatima, Benish; Hashmi, Shiraz; Fatimi, Saulat

    2017-01-01

    A 25-year-old man presented with a 2-month history of dysphagia and past history of pulmonary and intestinal tuberculosis. A barium swallow showed a point of constriction 42 mm above the gastroesophageal junction. Computed tomography revealed large opacities in bilateral lung fields, encroaching more on the esophagus. The lesion progressively compressed the esophagus as it moved inferiorly. A right posterolateral thoracotomy was performed for sub-anatomical resection of the mass. A biopsy revealed homogenous whirling hyalinized collagen fibers, highly suggestive of pulmonary hyalinizing granuloma, with no evidence of malignancy. Pulmonary hyalinizing granuloma should be considered in the differential diagnosis of longstanding dysphagia.

  4. Pulmonary epithelial permeability in hyaline-membrane disease

    SciTech Connect

    Jefferies, A.L.; Coates, G.; O'Brodovich, H.

    1984-10-25

    Neonatal hyaline-membrane disease is complicated by pulmonary edema, yet left atrial pressures are normal. Alveolar-capillary-membrane permeability may therefore be increased. To assess pulmonary epithelial permeability, we measured the pulmonary clearance and half-life of aerosolized /sup 99m/Tc-diethylenetriamine pentacetate (/sup 99m/Tc-DTPA) on 31 occasions in 15 intubated premature infants with hyaline-membrane disease. Three infants with respiratory failure due to other diseases were studied on four occasions. All studies of infants with hyaline-membrane disease that were performed in the first 72 hours of life demonstrated a biphasic clearance curve with a rapid-phase half-life of 1.6 +/- 0.6 minutes (mean +/- S.D.). As these infants recovered, the curve became monophasic with a half-life of 56.0 +/- 32.1 minutes. Two infants remained dependent on oxygen and ventilator support and had persistent biphasic curves with a rapid-phase half-life of 1.5 +/- 0.7 minutes. All infants without hyaline-membrane disease had monophasic curves with a half-life of 65.4 +/- 33.6 minutes. Using a similar technique, we observed that newborn lambs and piglets have a monophasic pulmonary clearance of /sup 99m/Tc-DTPA (114 +/- 59 minutes in lambs and 52.5 +/- 16.3 minutes in piglets). We conclude that the lungs of neonates with hyaline-membrane disease are abnormally permeable to small solutes and that this abnormality persists in infants with subsequent chronic lung disease.

  5. Myosin storage (hyaline body) myopathy: a case report.

    PubMed

    Shingde, Meena V; Spring, Penelope J; Maxwell, Adam; Wills, Edward J; Harper, Clive G; Dye, Danielle E; Laing, Nigel G; North, Kathryn N

    2006-12-01

    Myosin storage myopathy/hyaline body myopathy is a rare congenital myopathy, with less than 30 cases reported in the literature. It is characterised by the presence of subsarcolemmal hyaline bodies in type 1 muscle fibres and predominantly proximal muscle weakness. Recently, a single mutation (Arg1845Trp) in the slow/beta-cardiac myosin heavy chain gene (MYH7) was identified in four unrelated probands from Sweden and Belgium. The clinical severity and age of onset was variable, despite the same disease-causing mutation and similar histological findings. Here, we report the clinical and morphological findings of two brothers of English/Scottish background with the Arg1845Trp mutation in MYH7. This case report adds to the clinical description of this rare disorder and confirms that Arg1845Trp is a common mutation associated with this phenotype, at least in the White European population.

  6. A Hyalinized Trichilemmoma of the Eyelid in a Teenager.

    PubMed

    Jakobiec, Frederick A; Stagner, Anna M; Sassoon, Jodi; Goldstein, Scott; Mihm, Martin C

    2016-01-01

    A 16-year-old African American male, the youngest patient to date, presented with a well-circumscribed upper eyelid lesion. On excision, the dermal nodule was contiguous with the epidermis, displayed trichohyalin-like bodies in an expanded outer root sheath, and was composed chiefly of small cellular clusters separated by a prominent network of periodic acid Schiff -positive hyaline bands of basement membrane material. The tumor cells were positive for high molecular weight cytokeratins (CK) 5/6, CK14, and CK34βE12 and were negative for CK7, carcinoembryonic antigen and epithelial membrane antigen. Negative S100, glial fibrillary acidic protein, and smooth muscle actin immunoreactions ruled out a myoepithelial lesion. The Ki-67 proliferation index was <10%. The diagnosis was a hyalinized trichilemmoma, contrasting with the more common lobular type. As an isolated lesion, trichilemmoma does not portend Cowden syndrome.

  7. Three new species of Trichoderma with hyaline ascospores from China.

    PubMed

    Zhu, Z X; Zhuang, W Y

    2015-01-01

    Collections of Trichoderma having hyaline ascospores from different areas of China were examined. Using combined analyses of morphological data, culture characters and phylogenetic information based on rDNA sequences of partial nuc translation elongation factor 1-α encoding gene (TEF1-α) and the gene encoding the second largest nuc RNA polymerase subunit (RPB2), three new species, Trichoderma applanatum, T. oligosporum and T. sinoluteum, were discovered and are described. Trichoderma applanatum produces continuous flat to pulvinate, white to cream stromata with dense orange or pale brown ostioles, and simple acremonium-like to verticillium-like conidiophores, belongs to the Hypocreanum clade and is closely related to T. decipiens. Trichoderma oligosporum forms reddish brown stromata with a downy surface, hyaline conidia and gliocladium-like conidiophores, and is closely related to but distinct from T. crystalligenum in the Psychrophila clade. Trichoderma sinoluteum, as a member of the Polysporum clade, is characterized by pale yellow stromata, white pustulate conidiomata, pachybasium-like conidiophores, and hyaline conidia. Differences between the new species and their close relatives are discussed.

  8. Juvenile Hyaline Fibromatosis: A 10-year Follow-up

    PubMed Central

    Baltacioglu, Esra; Guzeldemir, Esra; Sukuroglu, Erkan; Yildiz, Kadriye; Yuva, Pinar; Aydin, Güven; Karacal, Naci

    2017-01-01

    Juvenile hyaline fibromatosis (JHF) is a rare hereditary disease with an autosomal recessive transmission. JHF is characterized by papulonodular skin lesions, osteolytic bone lesions, flexural joint contractures, and gingival hyperplasia and usually diagnosed in infancy or early childhood. JHF is thought to be a disorder of collagen metabolism and characterized by homogenous amorphous eosinophilic material and fibrous tissue. We report the case of a 14-year-old male child with multiple papulonodular skin lesions, progressive flexion contractures of joints, and severe gingival hyperplasia, with a 10-year follow-up. Although the lesions were totally removed thrice during the last 10 years, they recurred rigorously.

  9. Quasi-static elastography comparison of hyaline cartilage structures

    NASA Astrophysics Data System (ADS)

    McCredie, A. J.; Stride, E.; Saffari, N.

    2009-11-01

    Joint cartilage, a load bearing structure in mammals, has only limited ability for regeneration after damage. For tissue engineers to design functional constructs, better understanding of the properties of healthy tissue is required. Joint cartilage is a specialised structure of hyaline cartilage; a poroviscoelastic solid containing fibril matrix reinforcements. Healthy joint cartilage is layered, which is thought to be important for correct tissue function. However, the behaviour of each layer during loading is poorly understood. Ultrasound elastography provides access to depth-dependent information in real-time for a sample during loading. A 15 MHz focussed transducer provided details from scatterers within a small fixed region in each sample. Quasi-static loading was applied to cartilage samples while ultrasonic signals before and during compressions were recorded. Ultrasonic signals were processed to provide time-shift profiles using a sum-squared difference method and cross-correlation. Two structures of hyaline cartilage have been tested ultrasonically and mechanically to determine method suitability for monitoring internal deformation differences under load and the effect of the layers on the global mechanical material behaviour. Results show differences in both the global mechanical properties and the ultrasonically tested strain distributions between the two structures tested. It was concluded that these differences are caused primarily by the fibril orientations.

  10. Dancing Droplets

    NASA Astrophysics Data System (ADS)

    Cira, Nate; Prakash, Manu

    2013-11-01

    Inspired by the observation of intricate and beautifully dynamic patterns generated by food coloring on corona treated glass slides, we have investigated the behavior of propylene glycol and water droplets on clean glass surfaces. These droplets exhibit a range of interesting behaviors including long distance attraction or repulsion, and chasing/fleeing upon contact. We present explanations for each of these behaviors, and propose a detailed model for the long distance interactions based on vapor facilitated coupling. Finally we use our understanding to create several novel devices which: passively sort droplets by surface tension, spontaneously align droplets, drive droplets in circles, and cause droplets to bounce on a vertical surface. The simplicity of this system lends it particularly well to application as a toy model for physical systems with force fields and biological systems such as chemotaxis and motility.

  11. Cytoplasmic filaments of Crooke's hyaline change belong to the cytokeratin class. An immunocytochemical and ultrastructural study.

    PubMed Central

    Neumann, P. E.; Horoupian, D. S.; Goldman, J. E.; Hess, M. A.

    1984-01-01

    Crooke's hyaline change was studied by immunocytochemistry using an anti-adrenocorticotropic hormone (ACTH) antiserum and five different antisera against cytokeratins. Crooke's hyaline appears in basophil cells of the adenohypophysis in patients with hypercortisolism, presumably as a part of the negative feedback on corticotropin secretion. Previous studies have identified the hyaline material as a simple protein, apparently unrelated to ACTH, and electron microscopy has revealed a loss of secretory granules and an accumulation of 6-9-nm filaments in the cytoplasm of affected cells. In this study, the secretory granules in adenohypophysial cells exhibiting Crooke's hyaline change were labeled by anti-ACTH antibodies, while the hyaline material was positive for cytokeratin with each of the five antisera used. The results suggest that high levels of glucocorticoids may stimulate elaboration of cytokeratins in basophils while they suppress the production and release of ACTH. Images Figure 1 Figure 2 Figure 3 PMID:6205591

  12. Brief report: reconstruction of joint hyaline cartilage by autologous progenitor cells derived from ear elastic cartilage.

    PubMed

    Mizuno, Mitsuru; Kobayashi, Shinji; Takebe, Takanori; Kan, Hiroomi; Yabuki, Yuichiro; Matsuzaki, Takahisa; Yoshikawa, Hiroshi Y; Nakabayashi, Seiichiro; Ik, Lee Jeong; Maegawa, Jiro; Taniguchi, Hideki

    2014-03-01

    In healthy joints, hyaline cartilage covering the joint surfaces of bones provides cushioning due to its unique mechanical properties. However, because of its limited regenerative capacity, age- and sports-related injuries to this tissue may lead to degenerative arthropathies, prompting researchers to investigate a variety of cell sources. We recently succeeded in isolating human cartilage progenitor cells from ear elastic cartilage. Human cartilage progenitor cells have high chondrogenic and proliferative potential to form elastic cartilage with long-term tissue maintenance. However, it is unknown whether ear-derived cartilage progenitor cells can be used to reconstruct hyaline cartilage, which has different mechanical and histological properties from elastic cartilage. In our efforts to develop foundational technologies for joint hyaline cartilage repair and reconstruction, we conducted this study to obtain an answer to this question. We created an experimental canine model of knee joint cartilage damage, transplanted ear-derived autologous cartilage progenitor cells. The reconstructed cartilage was rich in proteoglycans and showed unique histological characteristics similar to joint hyaline cartilage. In addition, mechanical properties of the reconstructed tissues were higher than those of ear cartilage and equal to those of joint hyaline cartilage. This study suggested that joint hyaline cartilage was reconstructed from ear-derived cartilage progenitor cells. It also demonstrated that ear-derived cartilage progenitor cells, which can be harvested by a minimally invasive method, would be useful for reconstructing joint hyaline cartilage in patients with degenerative arthropathies.

  13. Droplet Handling

    NASA Astrophysics Data System (ADS)

    Torii, Toru

    When quantitative analysis or quantitative chemical synthesis is performed using a micrototal analysis system (microTAS), the technologies for precise metering, transporting, and mixing of droplets are required. In this chapter, several technologies for the handling of droplets are described. For metering, dispensing and transporting of droplets, pneumatic and electrokinetic forces are used. Separation of cells and particles is also performed by electrical operation. Other handling technique, such as ultrasonic or centrifugal force applications, are also reviewed. Robotic synthesis devices or high throughput screening devices are promising applications for these technologies.

  14. Droplet handling.

    PubMed

    Torii, Toru

    2010-01-01

    When quantitative analysis or quantitative chemical synthesis is performed using a micrototal analysis system (microTAS), the technologies for precise metering, transporting, and mixing of droplets are required. In this chapter, several technologies for the handling of droplets are described. For metering, dispensing and transporting of droplets, pneumatic and electrokinetic forces are used. Separation of cells and particles is also performed by electrical operation. Other handling technique, such as ultrasonic or centrifugal force applications, are also reviewed. Robotic synthesis devices or high throughput screening devices are promising applications for these technologies.

  15. Globular hyaline microthrombi--their nature and morphogenesis.

    PubMed

    Bleyl, U; Rossner, J A

    1976-05-03

    The ultrastructure of globular hyaline microthrombi (GHM) is characterized by a spherical space lattice of frequently interconnected bundles of fibres of different width, with a periodic transverse striation and the fibrin-characteristic axial periodicity of 23 nm. These are surrounded by plump or slender bundles of fibres spreading radially over the surface which are only ocassionally interlinked. These filamentary formations of the so-called corona are also characterized by the fibrin-characteristic periodicity. Part of the GHM, however, lacks this axial periodicity, and periodic striation is then only visible in the radially extending fibrils of the corona. The spherical sace lattices with their plump or slender fibrillary fibrin bundles are also replaced by mosaic-like or nearly amorphous fine-grained precipitates. All intermediate stages between these main types of GHM can be found. The disappearance of the axial periodicity and of the fibrillary structure of the spherical space lattices is considered to be the morphological equivalent of seocndary fibrinolysis, here called endolysis, in the centre of the GHM. The morphogenesis of the GHM in states of shock of different aetiologies is discussed.

  16. Splashing Droplets

    NASA Technical Reports Server (NTRS)

    VanderWal, Randall L.; Kizito, John Patrick; Berger, Gordon M.; Iwan, J.; Alexander, D.; Tryggvason, Gretar

    2002-01-01

    Current data on droplet breakup is scarce for the sizes and velocities typical of practical applications such as in spray combustion processes and coating processes. While much more representative of practical applications, the small spatial scales and rapid time-scales prevent detailed measurement of the internal fluid dynamics and liquid property gradients produced by impinging upon surfaces. Realized through the extended spatial and temporal scales afforded by a microgravity environment, an improved understanding of drop breakup dynamics is sought to understand and ultimately control the impingement dynamics of droplets upon surfaces in practical situations. The primary objective of this research will be to mark the onset of different 'splashing modes' and to determine their temperature, pressure and angle dependence for impinging droplets representative of practical fluids. In addition, we are modeling the evolution of droplets that do not initially splash but rather undergo a 'fingering' evolution observed on the spreading fluid front and the transformation of these fingers into splashed products. An example of our experimental data is presented below. These images are of Isopar V impacting a mirror-polished surface. They were acquired using a high-speed camera at 1000 frames per second. They show the spreading of a single droplet after impact and ensuing finger instabilities. Normal gravity experimental data such as this will guide low gravity measurements in the 2.2 second drop tower and KC-135 aircraft as available. Presently we are in the process of comparing the experimental data of droplet shape evolution to numerical models, which can also capture the internal fluid dynamics and liquid property gradients such as produced by impingement upon a heated surface. To-date isothermal numerical data has been modeled using direct numerical simulations of representative splashing droplets. The data obtained so far indicates that the present model describes well

  17. Droplet microactuator system

    NASA Technical Reports Server (NTRS)

    Pamula, Vamsee K. (Inventor); Srinivasan, Vijay (Inventor); Pollack, Michael G. (Inventor); Eckhardt, Allen E. (Inventor); Paik, Philip Y. (Inventor)

    2010-01-01

    The present invention relates to a droplet microactuator system. According to one embodiment, the droplet microactuator system includes: (a) a droplet microactuator configured to conduct droplet operations; (b) a magnetic field source arranged to immobilize magnetically responsive beads in a droplet during droplet operations; (c) a sensor configured in a sensing relationship with the droplet microactuator, such that the sensor is capable of sensing a signal from and/or a property of one or more droplets on the droplet microactuator; and (d) one or more processors electronically coupled to the droplet microactuator and programmed to control electrowetting-mediated droplet operations on the droplet actuator and process electronic signals from the sensor.

  18. Mesenchymal stem cells display different gene expression profiles compared to hyaline and elastic chondrocytes

    PubMed Central

    Zhai, Li-Jie; Zhao, Ke-Qing; Wang, Zhi-Qiang; Feng, Ya; Xing, Shuang-Chun

    2011-01-01

    Cartilage has a poor intrinsic repair capacity, requiring surgical intervention to effect biological repair. Tissue engineering technologies or regenerative medicine strategies are currently being employed to address cartilage repair. Mesenchymal stem cells (MSCs) are considered to be an excellent cell source for this application. However, the different gene expression profiles between the MSCs and differentiated cartilage remain unclear. In this report, we first examined the gene expression profiles between the MSCs, hyaline and elastic chondrocytes, and then identify candidate genes, which may be important in the process of MSC differentiation into hyaline and elastic cartilage. Several hundred differentially expressed genes were screened initially by microarray, including 417 simultaneously up-regulated genes in both hyaline and elastic chondrocytes, with 313 down-regulated genes. Several genes were identified that were up-regulated in hyaline chondrocytes while down-regulated in elastic chondrocytes. Both RT-PCR and western blot analysis were consistent with those results obtained by microarray analysis. Chondromodulinl (Chm1) was found to be highly expressed in MSCs differentiating to hyaline and elastic cartilage. Both collagen type II, alpha 1 (Col2a1) and cartilage homeo protein 1 (Cart1) were also highly upregulated and may be important early differentiation of MSCs to hyaline cartilage. PMID:21394289

  19. Modular droplet actuator drive

    NASA Technical Reports Server (NTRS)

    Pollack, Michael G. (Inventor); Paik, Philip (Inventor)

    2011-01-01

    A droplet actuator drive including a detection apparatus for sensing a property of a droplet on a droplet actuator; circuitry for controlling the detection apparatus electronically coupled to the detection apparatus; a droplet actuator cartridge connector arranged so that when a droplet actuator cartridge electronically is coupled thereto: the droplet actuator cartridge is aligned with the detection apparatus; and the detection apparatus can sense the property of the droplet on a droplet actuator; circuitry for controlling a droplet actuator coupled to the droplet actuator connector; and the droplet actuator circuitry may be coupled to a processor.

  20. Juvenile Hyaline Fibromatosis: Impact of Periodontal Care on Quality of Life and a Patient Perspective.

    PubMed

    Yonel, Zehra; Parma, Sabrina; Chapple, Iain L C

    2015-09-01

    Juvenile hyaline fibromatosis (JHF) is a rare autosomal recessive inherited condition presenting early in life and characterized by the accumulation of hyaline-like tissue in the skin as well as various organs. Gingival overgrowth is a significant oral manifestation. This paper highlights how early and essential periodontal intervention may be necessary to improve mastication and subsequent weight gain, and to eliminate pain and improve the patient's quality of life. Here we highlight the key features of this condition and demonstrate how appropriate surgical management can have a significant impact on a patient's wellbeing. CPD/CLINICAL RELEVANCE: Juvenile hyaline fibromatosis has a significant impact on patient wellbeing and it is therefore important that clinicians are able to recognize the condition and ensure that patients receive appropriate care and management.

  1. Hyalinizing trabecular tumor of the thyroid gland: characteristic features on ultrasonography.

    PubMed

    Kobayashi, Kaoru; Hirokawa, Mitsuyoshi; Jikuzono, Tomoo; Fukata, Shuji; Amino, Nobuyuki; Miyauchi, Akira; Nakamura, Yasushi

    2007-03-01

    We report a case of hyalinizing trabecular tumor of the thyroid gland and describe the characteristic ultrasonographic features of this tumor. This was a rare tumor of follicular cell origin with a trabecular pattern of growth and marked intratrabecular hyalinization. The tumor had an irregular shape, a delicately jagged border, and hypoechoic and heterogeneous internal echoes on B-mode ultrasonography. Very rich intratumoral blood flow, the so-called "tumor inferno" was evident on power Doppler ultrasonography. In the clinical management of thyroid nodules, clinicians should be aware of this peculiar type of thyroid tumor and its characteristic ultrasonographic findings.

  2. Quantitative assessment of hyaline cartilage elasticity during optical clearing using optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Liu, Chih-Hao; Singh, Manmohan; Li, Jiasong; Han, Zhaolong; Wu, Chen; Wang, Shang; Idugboe, Rita; Raghunathan, Raksha; Zakharov, Valery P.; Sobol, Emil N.; Tuchin, Valery V.; Twa, Michael; Larin, Kirill V.

    2015-03-01

    We report the first study on using optical coherence elastography (OCE) to quantitatively monitor the elasticity change of the hyaline cartilage during the optical clearing administrated by glucose solution. The measurement of the elasticity is verified using uniaxial compression test, demonstrating the feasibility of using OCE to quantify the Young's modulus of the cartilage tissue. As the results, we found that the stiffness of the hyaline cartilage increases during the optical clearing of the tissue. This study might be potentially useful for the early detection of osteoarthritis disease.

  3. Hyaline globules in fine-needle aspiration smears of salivary gland neoplasms

    PubMed Central

    Gupta, Mayank; Bindra, Mandeep Singh

    2015-01-01

    Most salivary gland neoplasms can be accurately diagnosed on fine-needle aspiration cytology. Few cases present with overlapping cytomorphological features, so accurate distinction in these cases may be difficult. We describe a case of pleomorphic adenoma that had a close resemblance to adenoid cystic carcinoma on smears due to presence of numerous hyaline globules and bare nuclei. Careful analysis of cellular details along with corroborative clinical evidence clinched the correct diagnosis. This article discusses cytological features of salivary gland tumours in which hyaline globules can be seen on smears. PMID:25750224

  4. Quantification of collagen distributions in rat hyaline and fibro cartilages based on second harmonic generation imaging

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoqin; Liao, Chenxi; Wang, Zhenyu; Zhuo, Shuangmu; Liu, Wenge; Chen, Jianxin

    2016-10-01

    Hyaline cartilage is a semitransparent tissue composed of proteoglycan and thicker type II collagen fibers, while fibro cartilage large bundles of type I collagen besides other territorial matrix and chondrocytes. It is reported that the meniscus (fibro cartilage) has a greater capacity to regenerate and close a wound compared to articular cartilage (hyaline cartilage). And fibro cartilage often replaces the type II collagen-rich hyaline following trauma, leading to scar tissue that is composed of rigid type I collagen. The visualization and quantification of the collagen fibrillar meshwork is important for understanding the role of fibril reorganization during the healing process and how different types of cartilage contribute to wound closure. In this study, second harmonic generation (SHG) microscope was applied to image the articular and meniscus cartilage, and textural analysis were developed to quantify the collagen distribution. High-resolution images were achieved based on the SHG signal from collagen within fresh specimens, and detailed observations of tissue morphology and microstructural distribution were obtained without shrinkage or distortion. Textural analysis of SHG images was performed to confirm that collagen in fibrocartilage showed significantly coarser compared to collagen in hyaline cartilage (p < 0.01). Our results show that each type of cartilage has different structural features, which may significantly contribute to pathology when damaged. Our findings demonstrate that SHG microscopy holds potential as a clinically relevant diagnostic tool for imaging degenerative tissues or assessing wound repair following cartilage injury.

  5. Characterization of cytoplasmic hyaline bodies in a hepatocellular carcinoma of a dog.

    PubMed

    Masserdotti, Carlo; Rossetti, Enrica; De Lorenzi, Davide; Della Salda, Leonardo; Palmieri, Chiara

    2014-02-01

    This report describes the morphological and immunohistochemical features of intracytoplasmic inclusion bodies found in a 13-year-old Yorkshire dog with a hepatocellular carcinoma and referred for anorexia, lethargy and mild polydipsia. Fine-needle aspirates of the large abdominal mass revealed high number of pleomorphic neoplastic hepatocytes, containing round to polygonal, well-demarcated, hyaline bodies. Same findings were histologically confirmed on multiple biopsies. Immunohistochemically, the inclusion bodies were negative for alpha-1-antitrypsin, carcinoembryonary antigen, fibrinogen, IgG, IgM, cytokeratins 7, 8, 18, 19, 20. By transmission electron microscopy, the cytoplasmic inclusions were composed of granular homogeneous or reticulated electrondense matrix, enclosed within dilated rough endoplasmic reticulum or remnants of its membranes, consistent with proteinaceous material accumulated within neoplastic hepatocytes due to aberrant protein secretion or transport. This is the first detailed characterization of hyaline cytoplasmic inclusion bodies in canine hepatocellular carcinoma.

  6. The Gene for Juvenile Hyaline Fibromatosis Maps to Chromosome 4q21

    PubMed Central

    Rahman, Nazneen; Dunstan, Melanie; Teare, M. Dawn; Hanks, Sandra; Edkins, Sarah J.; Hughes, Jaime; Bignell, Graham R.; Mancini, Grazia; Kleijer, Wim; Campbell, Mary; Keser, Gokhan; Black, Carol; Williams, Nigel; Arbour, Laura; Warman, Matthew; Superti-Furga, Andrea; Futreal, P. Andrew; Pope, F. Michael

    2002-01-01

    Juvenile hyaline fibromatosis (JHF) is an autosomal recessive condition characterized by multiple subcutaneous nodular tumors, gingival fibromatosis, flexion contractures of the joints, and an accumulation of hyaline in the dermis. We performed a genomewide linkage search in two families with JHF from the same region of the Indian state of Gujarat and identified a region of homozygosity on chromosome 4q21. Dense microsatellite analyses within this interval in five families with JHF who were from diverse origins demonstrate that all are compatible with linkage to chromosome 4q21 (multipoint LOD score 5.5). Meiotic recombinants place the gene for JHF within a 7-cM interval bounded by D4S2393 and D4S395. PMID:12214284

  7. [Trabecular hyalinizing adenoma of the thyroid (HAT): A report of two cases].

    PubMed

    Román-González, Alejandro; Simón-Duque, Carlos; Camilo-Pérez, Juan; Vélez-Hoyo, Alejandro

    2016-01-01

    The hyalinizing trabecular adenoma is a rare lesion of the thyroid. There is controversy in the literature about the correct name for this disease. Dr. Carney defended the benign nature of this condition and therefore continues calling it adenoma, the World Health Organization calls for the potential of tumor malignancy, and others qualify it as a variant of papillary carcinoma based on the presence of rearranged in transformation/papillary thyroid carcinoma (RET/PTC) rearrangements. In Latin America there are few reported cases. Two cases of hyalinizing trabecular adenoma are reported. The first is a 40-year-old woman with a thyroid nodule of 3x3 cm. The immunohistochemistry was positive for thyroglobulin and calcitonin and negative for cytokeratin 19 and chromogranin. The second case is a 36-year-old patient with a thyroid nodule of 4x4 cm with an immunohistochemical pattern identical to the first case. Trabecular hyalinizing adenoma is a benign disease, easily confused with papillary or medullary thyroid carcinoma. Awareness of this entity will allow a better classification and management of thyroid conditions.

  8. Arteriolar hyalinization in implantation kidney biopsies as a predictor of graft function.

    PubMed

    Wazna, E; Pazik, J; Perkowska-Ptasińska, A; Lewandowski, Z; Nazarewski, S; Chmura, A; Durlik, M

    2009-10-01

    The shortage of organs suitable for transplantation has caused a constant evolution of donor acceptance criteria, making an implantation biopsy a valuable tool to predict kidney allograft survival. Preimplantation vascular changes may be divided into sclerosis or intimal fibrous thickening or arteriolar hyalinization. Increasing evidence has indicated their impact on graft function. The aim of this study was to evaluate the significance of preimplantation arteriolar hyalinization for the stability of kidney allograft function. Among a prospective cohort study of 53 kidney recipients (implantation: 2006-2007) who showed serum creatinine values between 1 and 2 mg/dL at 3 months after engraftment, the mean observation time was 24 +/- 8.7 months. At the end of the observation, kidney function as defined by the estimated glomerular filtration rate by the Cockcroft-Gault formula (eGFR C-G) was significantly diminished in individuals with preimplantation evidences of arteriolar hyalinization (mean values: 51.2 +/- 14.8 and 62.0 +/- 16.7, respectively; P < .03) or serum creatinine concentrations (1.76 +/- 0.36 vs 1.51 +/- 0.48 mg/dL; P < .09). The negative influence of arteriolar hyalinosis on allograft function was time-dependent; an early satisfactory filtration rate did not preclude progressive kidney dysfunction.

  9. A new droplet generator

    NASA Technical Reports Server (NTRS)

    Slack, W. E.

    1982-01-01

    A new droplet generator is described. A loud speaker driven extractor needle was immersed in a pendant drop. Pulsing the speaker extracted the needle forming a fluid ligament which will decay into a droplet. The droplets were sized by stroboscopic photographs. The droplet's size was changed by varying the amplitude of the speaker pulses and the extractor needle diameter. The mechanism of droplet formation is discussed and photographs of ligament decay are presented. The droplet generator worked well on both oil and water based pesticide formulations. Current applications and results are discussed.

  10. Mechanisms of droplet combustion

    NASA Technical Reports Server (NTRS)

    Law, C. K.

    1982-01-01

    The fundamental physico-chemical mechanisms governing droplet vaporization and combustion are discussed. Specific topics include governing equations and simplifications, the classical d(2)-Law solution and its subsequent modification, finite-rate kinetics and the flame structure, droplet dynamics, near- and super-critical combustion, combustion of multicomponent fuel blends/emulsions/suspensions, and droplet interaction. Potential research topics are suggested.

  11. Arabinogalactan protein-rich cell walls, paramural deposits and ergastic globules define the hyaline bodies of rhinanthoid Orobanchaceae haustoria

    PubMed Central

    Pielach, Anna; Leroux, Olivier; Domozych, David S.; Knox, J. Paul; Popper, Zoë A.

    2014-01-01

    Background and Aims Parasitic plants obtain nutrients from their hosts through organs called haustoria. The hyaline body is a specialized parenchymatous tissue occupying the central parts of haustoria in many Orobanchaceae species. The structure and functions of hyaline bodies are poorly understood despite their apparent necessity for the proper functioning of haustoria. Reported here is a cell wall-focused immunohistochemical study of the hyaline bodies of three species from the ecologically important clade of rhinanthoid Orobanchaceae. Methods Haustoria collected from laboratory-grown and field-collected plants of Rhinanthus minor, Odontites vernus and Melampyrum pratense attached to various hosts were immunolabelled for cell wall matrix glycans and glycoproteins using specific monoclonal antibodies (mAbs). Key Results Hyaline body cell wall architecture differed from that of the surrounding parenchyma in all species investigated. Enrichment in arabinogalactan protein (AGP) epitopes labelled with mAbs LM2, JIM8, JIM13, JIM14 and CCRC-M7 was prominent and coincided with reduced labelling of de-esterified homogalacturonan with mAbs JIM5, LM18 and LM19. Furthermore, paramural bodies, intercellular deposits and globular ergastic bodies composed of pectins, xyloglucans, extensins and AGPs were common. In Rhinanthus they were particularly abundant in pairings with legume hosts. Hyaline body cells were not in direct contact with haustorial xylem, which was surrounded by a single layer of paratracheal parenchyma with thickened cell walls abutting the xylem. Conclusions The distinctive anatomy and cell wall architecture indicate hyaline body specialization. Altered proportions of AGPs and pectins may affect the mechanical properties of hyaline body cell walls. This and the association with a transfer-like type of paratracheal parenchyma suggest a role in nutrient translocation. Organelle-rich protoplasts and the presence of exceptionally profuse intra- and intercellular

  12. Controlled trial of continuous positive airway pressure given by face mask for hyaline membrane disease.

    PubMed Central

    Allen, L P; Reynolds, E R; Rivers, R P; Le Souëf, P M; Wimberley, P D

    1977-01-01

    A controlled trial of elective intervention with continuous positive airway pressure (CPAP) was performed on 24 infants with hyaline membrane disease whose arterial oxygen tension (Pao2) fell below 8kPa (60 mmHg) while they were breathing a fractional inspired oxygen concentration (F1O2) greater than 0.60. A face mask was used to apply the CPAP. The progress of the 12 infants who were treated on entry to the trial was compared with that of 12 infants who were treated later. All 12 infants in the early-intervention group and 8 infants in the late-intervention group survived. When CPAP was started, Pao2 increased and the early-treated infants breathed high concentrations of oxygen for a shorter period than the late-treated infants. The 4 infants in the early-intervention group who required mechanical ventilation needed lower mean airway pressures to achieve satisfactory gas exchange than the 7 ventilated infants in the late-intervention group. We conclude that a Pao2 less than 8 kPa while breathing an F1o2 greater than 0.60 is an adequate indication for giving CPAP in hyaline membrane disease, and that early intervention with CPAP allows infants who go on to require mechanical ventilation to be ventilated at lower pressures. PMID:326199

  13. Talocalcaneal Joint Middle Facet Coalition Resection With Interposition of a Juvenile Hyaline Cartilage Graft.

    PubMed

    Tower, Dyane E; Wood, Ryan W; Vaardahl, Michael D

    2015-01-01

    Talocalcaneal joint middle facet coalition is the most common tarsal coalition, occurring in ≤2% of the population. Fewer than 50% of involved feet obtain lasting relief of symptoms after nonoperative treatment, and surgical intervention is commonly used to relieve symptoms, increase the range of motion, improve function, reconstruct concomitant pes planovalgus, and prevent future arthrosis from occurring at the surrounding joints. Several approaches to surgical intervention are available for patients with middle facet coalitions, ranging from resection to hindfoot arthrodesis. We present a series of 4 cases, in 3 adolescent patients, of talocalcaneal joint middle facet coalition resection with interposition of a particulate juvenile hyaline cartilaginous allograft (DeNovo(®) NT Natural Tissue Graft, Zimmer, Inc., Warsaw, IN). With a mean follow-up period of 42.8 ± 2.9 (range 41 to 47) months, the 3 adolescent patients in the present series were doing well with improved subtalar joint motion and decreased pain, and 1 foot showed no bony regrowth on a follow-up computed tomography scan. The use of a particulate juvenile hyaline cartilaginous allograft as interposition material after talocalcaneal middle facet coalition resection combined with adjunct procedures to address concomitant pes planovalgus resulted in good short-term outcomes in 4 feet in 3 adolescent patients.

  14. Two new hyaline-ascospored species of Trichoderma and their phylogenetic positions.

    PubMed

    Qin, W T; Zhuang, W Y

    2016-01-01

    Collections of hypocrealean fungi found on decaying wood in subtropical regions of China were examined. Two new species, Trichoderma confluens and T. hubeiense, were discovered and are described. Trichoderma confluens is characterized by its widely effuse to rarely pulvinate, yellow stromata with densely disposed yellowish brown ostioles, simple acremonium- to verticillium-like conidiophores, hyaline conidia and multiform chlamydospores. Trichoderma hubeiense has pulvinate, grayish yellow stromata with brownish ostioles, trichoderma- to verticillium-like conidiophores and hyaline conidia. The phylogenetic positions of the two fungi were investigated based on sequence analyses of RNA polymerase II subunit b and translation elongation factor 1-α genes. The results indicate that T. confluens belongs to the Hypocreanum clade and is associated with but clearly separated from T. applanatum and T. decipiens. Trichoderma hubeiense belongs to the Polysporum clade and related to T. bavaricum but obviously differs from other members of the clade in sequence data. Morphological distinctions between the new species and their close relatives are noted and discussed.

  15. Droplet transport system and methods

    NASA Technical Reports Server (NTRS)

    Neitzel, G. Paul (Inventor)

    2010-01-01

    Embodiments of droplet transport systems and methods are disclosed for levitating and transporting single or encapsulated droplets using thermocapillary convection. One method embodiment, among others comprises providing a droplet of a first liquid; and applying thermocapillary convection to the droplet to levitate and move the droplet.

  16. Droplet Combustion Experiment

    NASA Technical Reports Server (NTRS)

    Nayagam, Vedha

    1998-01-01

    Liquid fuel combustion provides a major portion of the world's energy supply. In most practical combustion devices, liquid burns after being separated into a droplet spray. Essential to the design of efficient combustion systems is a knowledge of droplet combustion behavior. The microgravity environment aboard spacecraft provides an opportunity to investigate the complex interactions between the physical and chemical combustion processes involved in droplet combustion without the complications of natural buoyancy. Launched on STS-83 and STS-94 (April 4 and July 1, 1997), the Droplet Combustion Experiment (DCE) investigated the fundamentals of droplet combustion under a range of pressures (0.25 to 1 atm), oxygen mole fractions (<0.5), and droplet sizes (1.5 to 5 mm). Principal DCE flight hardware features were a chamber to supply selected test environments, the use of crew-inserted bottles, and a vent system to remove unwanted gaseous combustion products. The internal apparatus contained the droplet deployment and ignition mechanisms to burn single, freely deployed droplets in microgravity. Diagnostics systems included a 35-mm high-speed motion picture camera (see the following sequence of photos) with a backlight to photograph burning droplets and a camcorder to monitor experiment operations. Additional diagnostics included an ultraviolet-light-sensitive CCD (charge couple discharge) camera to obtain flame radiation from hydroxyl radicals (see the final figure) and a 35-mm SLR (single-lens-reflex) camera to obtain color still photographs of the flames.

  17. Change in the optical properties of hyaline cartilage heated by the near-IR laser radiation

    SciTech Connect

    Bagratashvili, Viktor N; Bagratashvili, N V; Omel'chenko, A I; Sviridov, A P; Sobol', E N; Tsypina, S I; Gapontsev, V P; Minaev, V P; Samartsev, I E; Makhmutova, G Sh

    2001-06-30

    The in vitro dynamics of the change in optical properties of hyaline cartilage heated by fibre lasers at wavelengths 0.97 and 1.56 {mu}m is studied. The laser-induced bleaching (at 1.56 {mu}m) and darkening (at 0.97 {mu}m) of the cartilage, caused by the heating and transport of water as well as by a change in the cartilage matrix, were observed and studied. These effects should be taken into account while estimating the depth of heating of the tissue. The investigated dynamics of light scattering in the cartilage allows one to choose the optimum radiation dose for laser plastic surgery of cartilage tissues. (laser applications and other topics in quantum electronics)

  18. Droplet Combustion Experiment (DCE)

    NASA Technical Reports Server (NTRS)

    Haggard, John B., Jr.; Nayagan, Vedha; Dryer, Frederick L.; Williams, Forman A.

    1998-01-01

    The first space-based experiments were performed on the combustion of free, individual liquid fuel droplets in oxidizing atmospheres. The fuel was heptane, with initial droplet diameters ranging about from 1 mm to 4 mm. The atmospheres were mixtures of helium and oxygen, at pressures of 1.00, 0.50 and 0.25 bar, with oxygen mole fractions between 20% and 40%, as well as normal Spacelab cabin air. The temperatures of the atmospheres and of the initial liquid fuel were nominally 300 K. A total of 44 droplets were burned successfully on the two flights, 8 on the shortened STS-83 mission and 36 on STS-94. The results spanned the full range of heptane droplet combustion behavior, from radiative flame extinction at larger droplet diameters in the more dilute atmospheres to diffusive extinction in the less dilute atmospheres, with the droplet disappearing prior to flame extinction at the highest oxygen concentrations. Quasisteady histories of droplet diameters were observed along with unsteady histories of flame diameters. New and detailed information was obtained on burning rates, flame characteristics and soot behavior. The results have motivated new computational and theoretical investigations of droplet combustion, improving knowledge of the chemical kinetics, fluid mechanics and heat and mass transfer processes involved in burning liquid fuels.

  19. Osseous oral hyaline ring granuloma mimicking a mandible tumor in a child with congenital agenesis of the corpus callosum

    PubMed Central

    Neves-Silva, Rodrigo; Ferreira-Gomes, Camilla-Borges; Palmier, Natalia; Brum-Corrêa, Marcelo; Paes-Almeida, Oslei; Ajudarte-Lopes, Marcio; Agustin-Vargas, Pablo

    2017-01-01

    Background Hyaline ring granuloma (HRG) of the oral cavity is an uncommon disorder considered to be a foreign-body reaction resulting from implantation of food vegetable particles. Microscopically, it is characterized by the presence of structures of hyaline rings in an inflamed fibrous tissue background, which contains multinucleated giant cells. Material and Methods We present the case of a 4-year-old boy diagnosed with a mandible osseous HRG, which showed clinical and tomographic aspects suggestive of an aggressive bone tumor. Results The patient underwent surgical exploration and histopathologic analysis showed fragments composed predominantly of widespread dense connective tissue with an acute and chronic inflammatory infiltrate containing multinucleated giant cells and scattered areas of eosinophilic material associated with hyaline rings, strongly suggestive of vegetable particles. The eosinophilic material was positive for periodic acid-Schiff (PAS) and resistant to diastase digestion. These features led to diagnosis of osseous HRG. Scanning electron microscopy (SEM) analysis was performed for illustrative purposes and the multiple structures resembling vegetable particles were characterized in more detail. Conclusions Although rare, this case highlights the importance of the clinician’s awareness regarding the existence of an osseous counterpart of HRG. Key words:Agenesis of the corpus callosum, child, hyaline ring granuloma, intraosseous, mandible, pulse granuloma. PMID:28210458

  20. Trends in element incorporation in hyaline and porcelaneous foraminifera as a function of pCO2

    NASA Astrophysics Data System (ADS)

    van Dijk, Inge; de Nooijer, Lennart J.; Reichart, Gert-Jan

    2017-02-01

    In this study we analyzed the impact of seawater carbonate chemistry on the incorporation of elements in both hyaline and porcelaneous larger benthic foraminifera. We observed a higher incorporation of Zn and Ba when pCO2 increases from 350 to 1200 ppm. Modeling the activity of free ions as a function of pCO2 shows that speciation of some elements (like Zn and Ba) is mainly influenced by the formation of carbonate complexes in seawater. Hence, differences in foraminiferal uptake of these might be related primarily by the speciation of these elements in seawater. We investigated differences in trends in element incorporation between hyaline (perforate) and porcelaneous (imperforate) foraminifera in order to unravel processes involved in element uptake and subsequent foraminiferal calcification. In hyaline foraminifera we observed a correlation of element incorporation of different elements between species, reflected by a general higher incorporation of elements in species with higher Mg content. Between porcelaneous species, inter-element differences are much smaller. Besides these contrasting trends in element incorporation, however, similar trends are observed in element incorporation as a function of seawater carbonate chemistry in both hyaline and porcelaneous species. This suggests similar mechanisms responsible for the transportation of ions to the site of calcification for these groups of foraminifera, although the contribution of these processes might differ across species.

  1. Universal fluid droplet ejector

    DOEpatents

    Lee, E.R.; Perl, M.L.

    1999-08-24

    A droplet generator comprises a fluid reservoir having a side wall made of glass or quartz, and an end cap made from a silicon plate. The end cap contains a micromachined aperture through which the fluid is ejected. The side wall is thermally fused to the end cap, and no adhesive is necessary. This means that the fluid only comes into contact with the side wall and the end cap, both of which are chemically inert. Amplitudes of drive pulses received by reservoir determine the horizontal displacements of droplets relative to the ejection aperture. The drive pulses are varied such that the dropper generates a two-dimensional array of vertically-falling droplets. Vertical and horizontal inter-droplet spacings may be varied in real time. Applications include droplet analysis experiments such as Millikan fractional charge searches and aerosol characterization, as well as material deposition applications. 8 figs.

  2. Self-propelled droplets

    NASA Astrophysics Data System (ADS)

    Seemann, Ralf; Fleury, Jean-Baptiste; Maass, Corinna C.

    2016-11-01

    Self-propelled droplets are a special kind of self-propelled matter that are easily fabricated by standard microfluidic tools and locomote for a certain time without external sources of energy. The typical driving mechanism is a Marangoni flow due to gradients in the interfacial energy on the droplet interface. In this article we review the hydrodynamic prerequisites for self-sustained locomotion and present two examples to realize those conditions for emulsion droplets, i.e. droplets stabilized by a surfactant layer in a surrounding immiscible liquid. One possibility to achieve self-propelled motion relies on chemical reactions affecting the surface active properties of the surfactant molecules. The other relies on micellar solubilization of the droplet phase into the surrounding liquid phase. Remarkable cruising ranges can be achieved in both cases and the relative insensitivity to their own `exhausts' allows to additionally study collective phenomena.

  3. Hyaline globules in neuroendocrine and solid-pseudopapillary neoplasms of the pancreas: a clue to the diagnosis.

    PubMed

    Meriden, Zina; Shi, Chanjuan; Edil, Barish H; Ellison, Trevor; Wolfgang, Christopher L; Cornish, Toby C; Schulick, Richard D; Hruban, Ralph H

    2011-07-01

    Distinguishing between solid-pseudopapillary neoplasms (SPNs) and pancreatic neuroendocrine tumors (PanNETs) may pose a diagnostic dilemma. Both can demonstrate solid growth patterns, and both can be immunoreactive with neuroendocrine markers such as synaptophysin and CD56. One well-established feature of SPNs is the presence of hyaline globules, which in contrast has only rarely been reported in PanNETs. Clinicopathologic features of 361 cases originally classified as PanNETs were examined. Of these, 24 tumors (6.6%) had hyaline globules, raising the possibility of SPN. Immunohistochemistry for β-catenin was performed on these 24 neoplasms, and showed nuclear labeling in 6 cases. These 6 cases, which also demonstrated cytoplasmic CD10 staining, were reclassified as SPNs. The remaining 18 cases maintained their original diagnosis as PanNETs, and the hyaline globules in these cases were periodic acid-Schiff (PAS) positive, diastase resistant, and immunoreactive with α-1-antitrypsin. All 24 cases were histologically re-evaluated, and the pattern of invasion, presence of clear cells, and nuclear grooves were found to be helpful in distinguishing SPNs from PanNETs. We conclude that the presence of hyaline globules should raise SPNs in the differential diagnosis of a solid cellular neoplasm of the pancreas. However, this should not be used as the sole criterion in the diagnosis of SPNs, as hyaline globules may also be seen in 5% of PanNETs. Immunohistochemical and histologic features supporting the diagnosis of SPNs over PanNETs include CD10 and nuclear β-catenin labeling, an insidious pattern of invasion, clear cells, and nuclear grooves.

  4. Supercritical microgravity droplet vaporization

    NASA Technical Reports Server (NTRS)

    Hartfield, J.; Curtis, E.; Farrell, P.

    1990-01-01

    Supercritical droplet vaporization is an important issue in many combustion systems, such as liquid fueled rockets and compression-ignition (diesel) engines. In order to study the details of droplet behavior at these conditions, an experiment was designed to provide a gas phase environment which is above the critical pressure and critical temperature of a single liquid droplet. In general, the droplet begins as a cold droplet in the hot, high pressure environment. In order to eliminate disruptions to the droplet by convective motion in the gas, forced and natural convection gas motion are required to be small. Implementation of this requirement for forced convection is straightforward, while reduction of natural convection is achieved by reduction in the g-level for the experiment. The resulting experiment consists of a rig which can stably position a droplet without restraint in a high-pressure, high temperature gas field in microgravity. The microgravity field is currently achieved by dropping the device in the NASA Lewis 2.2 second drop tower. The performance of the experimental device and results to date are presented.

  5. Active droplet generation in microfluidics.

    PubMed

    Chong, Zhuang Zhi; Tan, Say Hwa; Gañán-Calvo, Alfonso M; Tor, Shu Beng; Loh, Ngiap Hiang; Nguyen, Nam-Trung

    2016-01-07

    The reliable generation of micron-sized droplets is an important process for various applications in droplet-based microfluidics. The generated droplets work as a self-contained reaction platform in droplet-based lab-on-a-chip systems. With the maturity of this platform technology, sophisticated and delicate control of the droplet generation process is needed to address increasingly complex applications. This review presents the state of the art of active droplet generation concepts, which are categorized according to the nature of the induced energy. At the liquid/liquid interface, an energy imbalance leads to instability and droplet breakup.

  6. Electrostatic charging of jumping droplets

    NASA Astrophysics Data System (ADS)

    Miljkovic, Nenad; Preston, Daniel J.; Enright, Ryan; Wang, Evelyn N.

    2013-09-01

    With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet-surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.

  7. Electrostatic charging of jumping droplets.

    PubMed

    Miljkovic, Nenad; Preston, Daniel J; Enright, Ryan; Wang, Evelyn N

    2013-01-01

    With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet-surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.

  8. Universal fluid droplet ejector

    DOEpatents

    Lee, Eric R.; Perl, Martin L.

    1999-08-24

    A droplet generator comprises a fluid reservoir having a side wall made of glass or quartz, and an end cap made from a silicon plate. The end cap contains a micromachined aperture through which the fluid is ejected. The side wall is thermally fused to the end cap, and no adhesive is necessary. This means that the fluid only comes into contact with the side wall and the end cap, both of which are chemically inert. Amplitudes of drive pulses received by reservoir determine the horizontal displacements of droplets relative to the ejection aperture. The drive pulses are varied such that the dropper generates a two-dimensional array of vertically-falling droplets. Vertical and horizontal interdroplet spacings may be varied in real time. Applications include droplet analysis experiments such as Millikan fractional charge searches and aerosol characterization, as well as material deposition applications.

  9. Microscopic Rayleigh Droplet Beams

    NASA Astrophysics Data System (ADS)

    Doak, R. B.

    2005-11-01

    A periodically triggered Rayleigh Droplet Beam (RDB) delivers a perfectly linear and periodic stream of identical, monoenergetic droplets that are phase-locked to the trigger signal. The droplet diameter and spacing are easily adjusted of choice of nozzle diameter and trigger frequency. Any liquid of low viscosity may be emloyed as the beam fluid. Although the field of nanofluidics is expanding rapidly, little effort has yet been devoted to ``external flows'' such as RDB's. At ASU we have generated RDB's of water and methanol down to 2 microns in droplet diameter. Nozzle clogging is the sole impediment to smaller droplets. Microscopic Rayleigh droplet beams offer tremendous potential for fundamental physical measurements, fluid dynamics research, and nanofabrication. This talk will describe the apparatus and techniques used at ASU to generate RDB's (surprisingly simple and inexpensive), discuss the triboelectric phenomena that play a role (surprisingly significant), present some initial experimental fluid dynamics measurements, and briefly survey RDB applications. Our particular interest in RDB's is as microscopic transport systems to deliver hydrated, undenatured proteins into vacuum for structure determination via serial diffraction of x-rays or electrons. This may offer the first general method for structure determination of non-crystallizable proteins.

  10. Droplet based microfluidics.

    PubMed

    Seemann, Ralf; Brinkmann, Martin; Pfohl, Thomas; Herminghaus, Stephan

    2012-01-01

    Droplet based microfluidics is a rapidly growing interdisciplinary field of research combining soft matter physics, biochemistry and microsystems engineering. Its applications range from fast analytical systems or the synthesis of advanced materials to protein crystallization and biological assays for living cells. Precise control of droplet volumes and reliable manipulation of individual droplets such as coalescence, mixing of their contents, and sorting in combination with fast analysis tools allow us to perform chemical reactions inside the droplets under defined conditions. In this paper, we will review available drop generation and manipulation techniques. The main focus of this review is not to be comprehensive and explain all techniques in great detail but to identify and shed light on similarities and underlying physical principles. Since geometry and wetting properties of the microfluidic channels are crucial factors for droplet generation, we also briefly describe typical device fabrication methods in droplet based microfluidics. Examples of applications and reaction schemes which rely on the discussed manipulation techniques are also presented, such as the fabrication of special materials and biophysical experiments.

  11. Fuel Droplet Burning During Droplet Combustion Experiment

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Fuel ignites and burns in the Droplet Combustion Experiment (DCE) on STS-94 on July 4 1997, MET:2/05:40 (approximate). The DCE was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. DCE used various fuels -- in drops ranging from 1 mm (0.04 inches) to 5 mm (0.2 inches) -- and mixtures of oxidizers and inert gases to learn more about the physics of combustion in the simplest burning configuration, a sphere. The experiment elapsed time is shown at the bottom of the composite image. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.4MB, 13-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available)A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300168.html.

  12. Ectopic production of hair keratin constitutes Rushton's hyaline bodies in association with hematogenous deposits.

    PubMed

    Sakamoto, Kei; Khanom, Rumana; Hamagaki, Miwako; Yamaguchi, Akira

    2012-09-01

    A Rushton's hyaline body (HB) is a concretion occasionally found in odontogenic cysts. Unspecified substances produced by the lining epithelium or derived from blood components have been suggested as possible causes of HB formation, but the origin of HBs is still elusive. This study aimed to clarify the origin of HBs. Ten specimens with HBs were obtained from 400 odontogenic cysts. HBs were stained by orcein and Congo red. Immunohistochemical examination revealed that HBs were positive for hair keratin and keratin 17. Hair keratin was concentrated in HBs, and cells with hair keratin expression were hardly seen, while cells with keratin 17 expression were observed near HBs. HBs were also positive for hemoglobin alpha chain. The presence of hair keratin in HBs was confirmed by Western blot analysis. The present study suggests that HBs are formed as a consequence of two independent events: unusual alteration of epithelial differentiation so as to provide hair keratin, and hemorrhage so as to provide erythrocytic substances. Although the ectopic production of hair keratin appears more essential, our results reconcile the long-standing debate between two theories, the keratin theory versus the hematogenous theory, concluding that both substances are required for the genesis of HBs, and also suggesting that they might be novel non-pathological amyloidogenic proteins.

  13. Prenatal prophylaxis of hyaline membrane disease with prednisolone: advantages and disadvantages.

    PubMed

    Wauer, R R; Hengst, P; Grauel, E L

    1983-01-01

    The purpose of the study was to evaluate the prophylaxis of hyaline membrane disease (HMD) with prenatal steroids from the viewpoint of neonatology. In 397 preterm infants of 27-35 week gestation the prenatal prophylaxis of HMD with prednisolone (200-300 mg over 48-72 h) significantly reduced the HMD morbidity and mortality rate (0-7th day of life), especially in newborns under 33-week gestation. HMD was not detected if a 48-h interval lay between the end of prednisolone application and birth. There was no influence on the severity and the lethality of HMD. The 29-day mortality rate in the prednisolone group (14.6%) corresponded more or less to that of the control group (16%). In the prednisolone group the increase in late mortality rate was due to a significantly higher number of late serious infections. The time interval between the rupture of the membranes and birth did not influence the infection rate and HMD frequency. At this time we cannot recommend a general prenatal glucocorticoid prophylaxis of HMD in cases of threatened preterm labor.

  14. Influence of Structure and Composition on Dynamic Viscoelastic Property of Cartilaginous Tissue: Criteria for Classification between Hyaline Cartilage and Fibrocartilage Based on Mechanical Function

    NASA Astrophysics Data System (ADS)

    Miyata, Shogo; Tateishi, Tetsuya; Furukawa, Katsuko; Ushida, Takashi

    Recently, many types of methodologies have been developed to regenerate articular cartilage. It is important to assess whether the reconstructed cartilaginous tissue has the appropriate mechanical functions to qualify as hyaline (articular) cartilage. In some cases, the reconstructed tissue may become fibrocartilage and not hyaline cartilage. In this study, we determined the dynamic viscoelastic properties of these two types of cartilage by using compression and shear tests, respectively. Hyaline cartilage specimens were harvested from the articular surface of bovine knee joints and fibrocartilage specimens were harvested from the meniscus tissue of the same. The results of this study revealed that the compressive energy dissipation of hyaline cartilage showed a strong dependence on testing frequency at low frequencies, while that of fibrocartilage did not. Therefore, the compressive energy dissipation that is indicated by the loss tangent could become the criterion for the in vitro assessment of the mechanical function of regenerated cartilage.

  15. Nematic droplets on fibers

    NASA Astrophysics Data System (ADS)

    Batista, V. M. O.; Silvestre, N. M.; Telo da Gama, M. M.

    2015-12-01

    The emergence of new techniques for the fabrication of nematic droplets with nontrivial topology provides new routes for the assembly of responsive devices. Here we explore some of the properties of nematic droplets on fibers, which constitute the basic units of a type of device that is able to respond to external stimuli, including the detection of gases. We perform a numerical study of spherical nematic droplets on fibers. We analyze the equilibrium textures for homogeneous and hybrid boundary conditions and find that in some cases the nematic avoids the nucleation of topological defects, which would provide a different optical response. We consider in detail a homeotropic nematic droplet wrapped around a fiber with planar anchoring. We investigate the effect of an electric field on the texture of this droplet. In the presence of a dc field, the system undergoes an orientational transition above a given threshold Ec, for which a ring defect is transformed into a figure-eight defect. We also consider ac fields, at high and low frequencies, and find that the textures are similar to those observed for static fields, in contrast with recently reported experiments.

  16. Microfluidic devices for droplet injection

    NASA Astrophysics Data System (ADS)

    Aubrecht, Donald; Akartuna, Ilke; Weitz, David

    2012-02-01

    As picoliter-scale reaction vessels, microfluidic water-in-oil emulsions have found application for high-throughput, large-sample number analyses. Often, the biological or chemical system under investigation needs to be encapsulated into droplets to prevent cross contamination prior to the introduction of reaction reagents. Previous techniques of picoinjection or droplet synchronization and merging enable the addition of reagents to individual droplets, but present limitations on what can be added to each droplet. We present microfluidic devices that couple the strengths of picoinjection and droplet merging, allowing us to selectively add precise volume to our droplet reactions.

  17. Droplet Combustion Experiment movie

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Droplet Combustion Experiment (DCE) was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1 mission (STS-83, April 4-8 1997; the shortened mission was reflown as MSL-1R on STS-94). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.1 MB, 12-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available)A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300164.html.

  18. A Comparative Study Regarding the Association of Alpha-2U Globulin with the Nephrotoxic Mechanism of Certain Petroleum-Baswd Air Force Fuels

    DTIC Science & Technology

    1990-09-17

    Epidemiologic studies have failed to demonstrate any consistent association between long term, low level human hydrocarbon exposure and renal ... disease . However, the potential human health hazard of environmental or occupational hydrocarbon exposure has warranted continued epidemiological and

  19. Chip-based droplet sorting

    SciTech Connect

    Beer, Neil Reginald; Lee, Abraham; Hatch, Andrew

    2014-07-01

    A non-contact system for sorting monodisperse water-in-oil emulsion droplets in a microfluidic device based on the droplet's contents and their interaction with an applied electromagnetic field or by identification and sorting.

  20. Sessile nanofluid droplet drying.

    PubMed

    Zhong, Xin; Crivoi, Alexandru; Duan, Fei

    2015-03-01

    Nanofluid droplet evaporation has gained much audience nowadays due to its wide applications in painting, coating, surface patterning, particle deposition, etc. This paper reviews the drying progress and deposition formation from the evaporative sessile droplets with the suspended insoluble solutes, especially nanoparticles. The main content covers the evaporation fundamental, the particle self-assembly, and deposition patterns in sessile nanofluid droplet. Both experimental and theoretical studies are presented. The effects of the type, concentration and size of nanoparticles on the spreading and evaporative dynamics are elucidated at first, serving the basis for the understanding of particle motion and deposition process which are introduced afterward. Stressing on particle assembly and production of desirable residue patterns, we express abundant experimental interventions, various types of deposits, and the effects on nanoparticle deposition. The review ends with the introduction of theoretical investigations, including the Navier-Stokes equations in terms of solutions, the Diffusion Limited Aggregation approach, the Kinetic Monte Carlo method, and the Dynamical Density Functional Theory. Nanoparticles have shown great influences in spreading, evaporation rate, evaporation regime, fluid flow and pattern formation of sessile droplets. Under different experimental conditions, various deposition patterns can be formed. The existing theoretical approaches are able to predict fluid dynamics, particle motion and deposition patterns in the particular cases. On the basis of further understanding of the effects of fluid dynamics and particle motion, the desirable patterns can be obtained with appropriate experimental regulations.

  1. Microstructural and compositional features of the fibrous and hyaline cartilage on the medial tibial plateau imply a unique role for the hopping locomotion of kangaroo.

    PubMed

    He, Bo; Wu, Jian Ping; Xu, Jiake; Day, Robert E; Kirk, Thomas Brett

    2013-01-01

    Hopping provides efficient and energy saving locomotion for kangaroos, but it results in great forces in the knee joints. A previous study has suggested that a unique fibrous cartilage in the central region of the tibial cartilage could serve to decrease the peak stresses generated within kangaroo tibiofemoral joints. However, the influences of the microstructure, composition and mechanical properties of the central fibrous and peripheral hyaline cartilage on the function of the knee joints are still to be defined. The present study showed that the fibrous cartilage was thicker and had a lower chondrocyte density than the hyaline cartilage. Despite having a higher PG content in the middle and deep zones, the fibrous cartilage had an inferior compressive strength compared to the peripheral hyaline cartilage. The fibrous cartilage had a complex three dimensional collagen meshwork with collagen bundles parallel to the surface in the superficial zone, and with collagen bundles both parallel and perpendicular to the surface in the middle and deep zones. The collagen in the hyaline cartilage displayed a typical Benninghoff structure, with collagen fibres parallel to the surface in the superficial zone and collagen fibres perpendicular to the surface in the deep zone. Elastin fibres were found throughout the entire tissue depth of the fibrous cartilage and displayed a similar alignment to the adjacent collagen bundles. In comparison, the elastin fibres in the hyaline cartilage were confined within the superficial zone. This study examined for the first time the fibrillary structure, PG content and compressive properties of the central fibrous cartilage pad and peripheral hyaline cartilage within the kangaroo medial tibial plateau. It provided insights into the microstructure and composition of the fibrous and peripheral hyaline cartilage in relation to the unique mechanical properties of the tissues to provide for the normal activities of kangaroos.

  2. Expanding roles for lipid droplets

    PubMed Central

    Welte, Michael A.

    2015-01-01

    Summary Lipid droplets are the intracellular sites for neutral lipid storage. They are critical for lipid metabolism and energy homeostasis, and their dysfunction has been linked to many diseases. Accumulating evidence suggests that the roles lipid droplets play in biology are significantly broader than previously anticipated. Lipid droplets are the source of molecules important in the nucleus: they can sequester transcription factors and chromatin components and generate the lipid ligands for certain nuclear receptors. Lipid droplets have also emerged as important nodes for fatty acid trafficking, both inside the cell and between cells. In immunity, new roles for droplets, not directly linked to lipid metabolism, have been uncovered, as assembly platforms for specific viruses and as reservoirs for proteins that fight intracellular pathogens. Until recently, knowledge about droplets in the nervous system has been minimal, but now there are multiple links between lipid droplets and neurodegeneration: Many candidate genes for Hereditary Spastic Paraplegia also have central roles in lipid-droplet formation and maintenance, and mitochondrial dysfunction in neurons can lead to transient accumulating of lipid droplets in neighboring glial cells, an event that may, in turn, contribute to neuronal damage. As the cell biology and biochemistry of lipid droplets are increasingly well understood, the next few years should yield many new mechanistic insights into these novel functions of lipid droplets. PMID:26035793

  3. Diffraction of walking droplets

    NASA Astrophysics Data System (ADS)

    Harris, Daniel M.; Pucci, Giuseppe; Bush, John W. M.

    2014-11-01

    We present results from our revisitation of the experiment of a walking droplet passing through a single slit, originally investigated by Couder & Fort (PRL, 2006). On each passage, the walker's trajectory is deviated as a result of the spatial confinement of its guiding wave. We explore the role of the droplet size and the bath's vibration amplitude on both the dynamics and statistics. We find the behavior to be remarkably sensitive to these control parameters. A complex physical picture emerges. The authors gratefully acknowledge the financial support of the NSF through Grant CMMI-1333242, DMH through the NSF Graduate Research Fellowship Program, and GP through the Programma Operativo Regionale (POR) Calabria - FSE 2007/2013.

  4. Charged Slurry Droplet Research

    DTIC Science & Technology

    1989-02-20

    verified that -a’/1’ is a constant for a wide variety of fluids including No. 2 Heating Oil and Jet -A, to name but two. Equally startling are the...for a large droplet against 1-g conditions has only been achieved before in the Jet Propulsion Laboratory at California Institute of Technology 10...Drop Levitation Against Gravity," IEEE - CH2272 ( Jet Propulsion Laboratory, California Institute of Technology), 1986, pp. 1338 - 1341. [11] Rhim, Won

  5. Burning Fuel Droplet

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Fuel ignites and burns in the Droplet Combustion Experiment (DCE) on STS-94 on July 4 1997, MET:2/05:40 (approximate). The DCE was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. DCE used various fuels -- in drops ranging from 1 mm (0.04 inches) to 5 mm (0.2 inches) -- and mixtures of oxidizers and inert gases to learn more about the physics of combustion in the simplest burning configuration, a sphere. The experiment elapsed time is shown at the bottom of the composite image. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (121KB JPEG, 654 x 977 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300169.html.

  6. Acoustic droplet vaporization of vascular droplets in gas embolotherapy

    NASA Astrophysics Data System (ADS)

    Bull, Joseph

    2016-11-01

    This work is primarily motivated by a developmental gas embolotherapy technique for cancer treatment. In this methodology, infarction of tumors is induced by selectively formed vascular gas bubbles that arise from the acoustic vaporization of vascular droplets. Additionally, micro- or nano-droplets may be used as vehicles for localized drug delivery, with or without flow occlusion. In this talk, we examine the dynamics of acoustic droplet vaporization through experiments and theoretical/computational fluid mechanics models, and investigate the bioeffects of acoustic droplet vaporization on endothelial cells and in vivo. Functionalized droplets that are targeted to tumor vasculature are examined. The influence of fluid mechanical and acoustic parameters, as well as droplet functionalization, is explored. This work was supported by NIH Grant R01EB006476.

  7. High-Voltage Droplet Dispenser

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.

    2003-01-01

    An apparatus that is extremely effective in dispensing a wide range of droplets has been developed. This droplet dispenser is unique in that it utilizes a droplet bias voltage, as well as an ionization pulse, to release a droplet. Apparatuses that deploy individual droplets have been used in many applications, including, notably, study of combustion of liquid fuels. Experiments on isolated droplets are useful in that they enable the study of droplet phenomena under well-controlled and simplified conditions. In this apparatus, a syringe dispenses a known value of liquid, which emerges from, and hangs onto, the outer end of a flat-tipped, stainless steel needle. Somewhat below the needle tip and droplet is a ring electrode. A bias high voltage, followed by a high-voltage pulse, is applied so as to attract the droplet sufficiently to pull it off the needle. The voltages are such that the droplet and needle are negatively charged and the ring electrode is positively charged.

  8. Evaporation of inclined water droplets.

    PubMed

    Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

    2017-02-16

    When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets.

  9. Evaporation of inclined water droplets

    NASA Astrophysics Data System (ADS)

    Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

    2017-02-01

    When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets.

  10. Evaporation of inclined water droplets

    PubMed Central

    Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

    2017-01-01

    When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets. PMID:28205642

  11. Droplet microfluidics based microseparation systems.

    PubMed

    Xiao, Zhiliang; Niu, Menglei; Zhang, Bo

    2012-06-01

    Lab on a chip (LOC) technology is a promising miniaturization approach. The feature that it significantly reduced sample consumption makes great sense in analytical and bioanalytical chemistry. Since the start of LOC technology, much attention has been focused on continuous flow microfluidic systems. At the turn of the century, droplet microfluidics, which was also termed segmented flow microfluidics, was introduced. Droplet microfluidics employs two immiscible phases to form discrete droplets, which are ideal vessels with confined volume, restricted dispersion, limited cross-contamination, and high surface area. Due to these unique features, droplet microfluidics proves to be a versatile tool in microscale sample handling. This article reviews the utility of droplet microfluidics in microanalytical systems with an emphasize on separation science, including sample encapsulation at ultra-small volume, compartmentalization of separation bands, isolation of droplet contents, and related detection techniques.

  12. Maze Solving by Chemotactic Droplets

    SciTech Connect

    Lagzi, Istvan; Soh, Siowling; Wesson, Paul J.; Browne, Kevin P.; Grzybowski, Bartosz A.

    2010-01-11

    Droplets emitting surface-active chemicals exhibit chemotaxis toward low-pH regions. Such droplets are self-propelled and navigate through a complex maze to seek a source of acid placed at one of the maze’s exits. In doing so, the droplets find the shortest path through the maze. Chemotaxis and maze solving are due to an interplay between acid/base chemistry and surface tension effects.

  13. Gelled MMH hypergolic droplet investigation

    NASA Astrophysics Data System (ADS)

    Solomon, Yair

    Gelled propellants are promising candidates for certain future rocket applications, offering potential improvements in performance and/or safety over conventional liquid and solid systems. In particular, gelled hypergolic propellants can eliminate some handling difficulties by reducing leakage hazard. Before such systems can be developed, however, a fundamental understanding of combustion of the gel droplet is required. This study addresses the combustion behavior of monomethyl hydrazine (MMH) droplet gelled with both hydroxypropyl cellulose (HPC) and fumed silica in an environment of gaseous nitrogen dioxide. All MMH/HPC gel droplets displayed swelling and jetting that are typical to hydrocarbon gels with an organic gelling agent. Burning rates were measured for droplet diameters from 1.8 to 3.2 mm at three ambient pressures of 1.72, 2.06 and 2.89 bar. It was found that the droplet burning rate is dependent on the droplet diameter similarly to liquid MMH. Over the investigated pressure range, no dependence of burning rate on pressure was found. The combustion of MMH/HPC gel was compared to MMH/tetraglyme to examine the influence the type of gelling agent. Droplets of MMH and liquid tetraglyme showed increasing swelling frequencies and volume fluctuations during combustion while the MMH and HPC droplets exhibited a more constant burning history. The MMH/Silica gels showed a different combustion mechanism with the formation of a rigid silica structure, micro-explosions, and up to a 50% reduction in droplet volume during combustion.

  14. Uranium droplet core nuclear rocket

    NASA Technical Reports Server (NTRS)

    Anghaie, Samim

    1991-01-01

    Uranium droplet nuclear rocket is conceptually designed to utilize the broad temperature range ofthe liquid phase of metallic uranium in droplet configuration which maximizes the energy transfer area per unit fuel volume. In a baseline system dissociated hydrogen at 100 bar is heated to 6000 K, providing 2000 second of Isp. Fission fragments and intense radian field enhance the dissociation of molecular hydrogen beyond the equilibrium thermodynamic level. Uranium droplets in the core are confined and separated by an axisymmetric vortex flow generated by high velocity tangential injection of hydrogen in the mid-core regions. Droplet uranium flow to the core is controlled and adjusted by a twin flow nozzle injection system.

  15. Small droplets on superhydrophobic substrates.

    PubMed

    Gross, Markus; Varnik, Fathollah; Raabe, Dierk; Steinbach, Ingo

    2010-05-01

    We investigate the wetting behavior of liquid droplets on rough hydrophobic substrates for the case of droplets that are of comparable size to the surface asperities. Using a simple three-dimensional analytical free-energy model, we have shown in a recent letter [M. Gross, F. Varnik, and D. Raabe, EPL 88, 26002 (2009)] that, in addition to the well-known Cassie-Baxter and Wenzel states, there exists a further metastable wetting state where the droplet is immersed into the texture to a finite depth, yet not touching the bottom of the substrate. Due to this new state, a quasistatically evaporating droplet can be saved from going over to the Wenzel state and instead remains close to the top of the surface. In the present paper, we give an in-depth account of the droplet behavior based on the results of extensive computer simulations and an improved theoretical model. In particular, we show that releasing the assumption that the droplet is pinned at the outer edges of the pillars improves the analytical results for larger droplets. Interestingly, all qualitative aspects, such as the existence of an intermediate minimum and the "reentrant transition," remain unchanged. We also give a detailed description of the evaporation process for droplets of varying sizes. Our results point out the role of droplet size for superhydrophobicity and give hints for achieving the desired wetting properties of technically produced materials.

  16. Nucleation of electrically charged droplets

    NASA Technical Reports Server (NTRS)

    De, B. R.

    1979-01-01

    The nucleating droplets or clusters in many nucleation environments (various colloidal plasmas in laboratory and technological applications, astrophysical condensation environments, etc.) are likely to be at a finite electric potential. This may be due either to the presence of electrons and ions in the gas phase or to the thermal ionization or photoionization of the droplets. The paper demonstrates that this potential may introduce a nontrivial modification in the conventional nucleation theory. Some results for the typical case of nucleation of water droplets are presented. The general conclusion is that the electric potential makes nucleation harder to achieve, thereby demonstrating the importance of a finite droplet potential in the theory of nucleation.

  17. Liquid droplet radiator development status

    NASA Technical Reports Server (NTRS)

    White, K. Alan, III

    1987-01-01

    Development of the Liquid Droplet Radiator (LDR) is described. Significant published results of previous investigators are presented, and work currently in progress is discussed. Several proposed LDR configurations are described, and the rectangular and triangular configurations currently of most interest are examined. Development of the droplet generator, collector, and auxiliary components are discussed. Radiative performance of a droplet sheet is considered, and experimental results are seen to be in very good agreement with analytical predictions. The collision of droplets in the droplet sheet, the charging of droplets by the space plasma, and the effect of atmospheric drag on the droplet sheet are shown to be of little consequence, or can be minimized by proper design. The LDR is seen to be less susceptible than conventional technology to the effects of micrometeoroids or hostile threats. The identification of working fluids which are stable in the orbital environments of interest is also made. Methods for reducing spacecraft contamination from an LDR to an acceptable level are discussed. Preliminary results of microgravity testing of the droplet generator are presented. Possible future NASA and Air Force missions enhanced or enabled by a LDR are also discussed. System studies indicate that the LDR is potentially less massive than heat pipe radiators. Planned microgravity testing aboard the Shuttle or space station is seen to be a logical next step in LDR development.

  18. Coalescence-induced droplet actuation

    NASA Astrophysics Data System (ADS)

    Sellier, Mathieu; Verdier, Claude; Nock, Volker

    2011-11-01

    This work investigates a little explored driving mechanism to actuate droplets: the surface tension gradient which arises during the coalescence of two droplets of liquid having different compositions and therefore surface tensions. The resulting surface tension gradient gives rise to a Marangoni flow which, if sufficiently large, can displace the droplet. In order to understand, the flow dynamics arising during the coalescence of droplets of different fluids, a model has been developed in the lubrication framework. The numerical results confirm the existence of a self-propulsion window which depends on two dimensionless groups representing competing effects during the coalescence: the surface tension contrast between the droplets which promotes actuation and species diffusion which tends to make the mixture uniform thereby anihilating Marangoni flow and droplet motion. In parallel, experiments have been conducted to confirm this self-propulsion behaviour. The experiment consists in depositing a droplet of distilled water on a ``hydrophilic highway.'' This stripe was obtained by plasma-treating a piece of PDMS shielded in some parts by glass coverslips. This surface functionalization was found to be the most convenient way to control the coalescence. When a droplet of ethanol is deposited near the ``water slug,'' coalescence occurs and a rapid motion of the resulting mixture is observed. The support of the Dumont d'Urville NZ-France Science & Technology program is gratefully acknowledged.

  19. Postnatal expression in hyaline cartilage of constitutively active human collagenase-3 (MMP-13) induces osteoarthritis in mice

    PubMed Central

    Neuhold, Lisa A.; Killar, Loran; Zhao, Weiguang; Sung, Mei-Li A.; Warner, Linda; Kulik, John; Turner, James; Wu, William; Billinghurst, C.; Meijers, T.; Poole, A. Robin; Babij, Philip; DeGennaro, Louis J.

    2001-01-01

    It has been suggested that increased collagenase-3 (MMP-13) activity plays a pivotal role in the pathogenesis of osteoarthritis (OA). We have used tetracycline-regulated transcription in conjunction with a cartilage-specific promoter to target a constitutively active human MMP-13 to the hyaline cartilages and joints of transgenic mice. Postnatal expression of this transgene resulted in pathological changes in articular cartilage of the mouse joints similar to those observed in human OA. These included characteristic erosion of the articular cartilage associated with loss of proteoglycan and excessive cleavage of type II collagen by collagenase, as well as synovial hyperplasia. These results demonstrate that excessive MMP-13 activity can result in articular cartilage degradation and joint pathology of the kind observed in OA, suggesting that excessive activity of this proteinase can lead to this disease. PMID:11134178

  20. Hyalinizing cholecystitis with features of immunoglobulin G4-related disease-coincidence or an unrecognized association? A case report.

    PubMed

    Gupta, Rajib K; Patton, Kurt T

    2015-04-01

    Hyalinizing cholecystitis (HC) is a recently described rare subtype of chronic cholecystitis characterized by dense, paucicellular collagenous transmural fibrosis, which usually replaces the mucosa and muscularis propria. Immunoglobulin (Ig)G4-associated cholecystitis is also a newly described cholecystitis variant characterized by transmural or extramural lymphoplasmacytic inflammation, lymphoid follicles, storiform fibrosis, phlebitis, and increased tissue IgG4-positive plasma cells. We describe a case of cholecystitis in an elderly white man who harbored features of both HC and IgG4-associated cholecystitis. In retrospect, the patient also had a significantly elevated serum IgG4 level. To the best of our knowledge, an association between HC and IgG4-related disease has not been previously described in the literature. Although not entirely conclusive, our observations raise the possibility that some cases of HC represent the end stage of IgG4-related disease.

  1. Experiments examining drag in linear droplet packets

    NASA Astrophysics Data System (ADS)

    Nguyen, Q. V.; Dunn-Rankin, D.

    1992-01-01

    This paper presents an experimental study of vertically traveling droplet packets, where the droplets in each packet are aligned linearly, one behind another. The paper describes in detail, an experimental apparatus that produces repeatable, linearly aligned, and isolated droplet packets containing 1 6 droplets per packet. The apparatus is suitable for examining aerodynamic interactions between droplets within each packet. This paper demonstrates the performance of the apparatus by examining the drag reduction and collision of droplets traveling in the wake of a lead droplet. Comparison of a calculated single droplet trajectory with the detailed droplet position versus time data for a droplet packet provides the average drag reduction experienced by the trailing droplets due to the aerodynamic wake of the lead droplet. For the conditions of our experiment (4 droplet packet, 145 μm methanol droplets, 10 m/s initial velocity, initial droplet spacing of 5.2 droplet diameters, Reynolds number approx. 80) the average drag on the first trailing droplet was found to be 75% of the drag on the lead droplet.

  2. Lossless droplet transfer of droplet-based microfluidic analysis

    SciTech Connect

    Kelly, Ryan T; Tang, Keqi; Page, Jason S; Smith, Richard D

    2011-11-22

    A transfer structure for droplet-based microfluidic analysis is characterized by a first conduit containing a first stream having at least one immiscible droplet of aqueous material and a second conduit containing a second stream comprising an aqueous fluid. The interface between the first conduit and the second conduit can define a plurality of apertures, wherein the apertures are sized to prevent exchange of the first and second streams between conduits while allowing lossless transfer of droplets from the first conduit to the second conduit through contact between the first and second streams.

  3. Bacterial encountering with oil droplet

    NASA Astrophysics Data System (ADS)

    Sheng, Jian; Molaei, Mehdi

    2014-11-01

    Encountering of microorganisms with rising oil droplets in aqueous environments is the first and one of the critical steps in the biodegradation of crude oil. Several factors such as droplet sizes, rising velocity, surfactant, and motility of bacteria are expected to affect the encounter rate. We establish well controlled microfluidic devices by applying layer-by-layer technique that allows us to produce horizontal micro droplets with different sizes. The encounter rates of passive particles, motile and non-motile bacteria with these droplets are measured by high speed microscopy. The effects of mobility and motility of these particles on encounter rates are assessed quantitatively. Meanwhile, we visualize reorientation of the particle due to flow filed around the oil droplet. Results show that the motile bacteria have higher probabilities to interact with an oil droplet compare to the passive particles. Ongoing analyses focus on the effect of shear rates, angular dispersion, curvatures of streamlines, and the swimming velocity of bacteria. The ratios of the encounter area to the entire droplet surface at various flow regimes will also been measured. GoMRI.

  4. Droplet resonator based optofluidic microlasers

    NASA Astrophysics Data System (ADS)

    Kiraz, Alper; Jonáš, Alexandr; Aas, Mehdi; Karadag, Yasin; Brzobohatý, Oto; Ježek, Jan; Pilát, Zdeněk.; Zemánek, Pavel; Anand, Suman; McGloin, David

    2014-03-01

    We introduce tunable optofluidic microlasers based on active optical resonant cavities formed by optically stretched, dye-doped emulsion droplets confined in a dual-beam optical trap. To achieve tunable dye lasing, optically pumped droplets of oil dispersed in water are stretched by light in the dual-beam trap. Subsequently, resonant path lengths of whispering gallery modes (WGMs) propagating in the droplet are modified, leading to shifts in the microlaser emission wavelengths. We also report lasing in airborne, Rhodamine B-doped glycerolwater droplets which were localized using optical tweezers. While being trapped near the focal point of an infrared laser, the droplets were pumped with a Q-switched green laser. Furthermore, biological lasing in droplets supported by a superhydrophobic surface is demonstrated using a solution of Venus variant of the yellow fluorescent protein or E. Coli bacterial cells expressing stably the Venus protein. Our results may lead to new ways of probing airborne particles, exploiting the high sensitivity of stimulated emission to small perturbations in the droplet laser cavity and the gain medium.

  5. Droplets, Bubbles and Ultrasound Interactions.

    PubMed

    Shpak, Oleksandr; Verweij, Martin; de Jong, Nico; Versluis, Michel

    2016-01-01

    The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to circulate within blood vessels. Perfluorocarbon liquid droplets can be a potential new generation of microbubble agents as ultrasound can trigger their conversion into gas bubbles. Prior to activation, they are at least five times smaller in diameter than the resulting bubbles. Together with the violent nature of the phase-transition, the droplets can be used for local drug delivery, embolotherapy, HIFU enhancement and tumor imaging. Here we explain the basics of bubble dynamics, described by the Rayleigh-Plesset equation, bubble resonance frequency, damping and quality factor. We show the elegant calculation of the above characteristics for the case of small amplitude oscillations by linearizing the equations. The effect and importance of a bubble coating and effective surface tension are also discussed. We give the main characteristics of the power spectrum of bubble oscillations. Preceding bubble dynamics, ultrasound propagation is introduced. We explain the speed of sound, nonlinearity and attenuation terms. We examine bubble ultrasound scattering and how it depends on the wave-shape of the incident wave. Finally, we introduce droplet interaction with ultrasound. We elucidate the ultrasound-focusing concept within a droplets sphere, droplet shaking due to media compressibility and droplet phase-conversion dynamics.

  6. Asymmetric Wettability Directs Leidenfrost Droplets

    SciTech Connect

    Agapov, Rebecca L; Boreyko, Jonathan B; Briggs, Dayrl P; Srijanto, Bernadeta R; Retterer, Scott T; Collier, Pat; Lavrik, Nickolay V

    2014-01-01

    Leidenfrost phenomena on nano- and microstructured surfaces are of great importance for increasing control over heat transfer in high power density systems utilizing boiling phenomena. They also provide an elegant means to direct droplet motion in a variety of recently emerging fluidic systems. Here, we report the fabrication and characterization of tilted nanopillar arrays (TNPAs) that exhibit directional Leidenfrost water droplets under dynamic conditions, namely on impact with Weber numbers 40 at T 325 C. The batch fabrication of the TNPAs was achieved by glancing-angle anisotropic reactive ion etching of a thermally dewet platinum mask, with mean pillar diameters of 100 nm and heights of 200-500 nm. In contrast to previously implemented macro- and microscopic Leidenfrost ratchets, our TNPAs induce no preferential directional movement of Leidenfrost droplets under conditions approaching steady-state film boiling, suggesting that the observed droplet directionality is not a result of asymmetric vapor flow. Using high-speed imaging, phase diagrams were constructed for the boiling behavior upon impact for droplets falling onto TNPAs, straight nanopillar arrays, and smooth silicon surfaces. The asymmetric impact and directional trajectory of droplets was exclusive to the TNPAs for impacts corresponding to the transition boiling regime, revealing that asymmetric wettability upon impact is the mechanism for the droplet directionality.

  7. Thermocapillary Convection in Liquid Droplets

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The purpose of this video is to understand the effects of surface tension on fluid convection. The fluid system chosen is the liquid sessile droplet to show the importance in single crystal growth, the spray drying and cooling of metal, and the advance droplet radiators of the space stations radiators. A cross sectional representation of a hemispherical liquid droplet under ideal conditions is used to show internal fluid motion. A direct simulation of buoyancy-dominant convection and surface tension-dominant convection is graphically displayed. The clear differences between two mechanisms of fluid transport, thermocapillary convection, and bouncy dominant convection is illustrated.

  8. Shrinking instability of toroidal droplets.

    PubMed

    Fragkopoulos, Alexandros A; Pairam, Ekapop; Berger, Eric; Segre, Phil N; Fernández-Nieves, Alberto

    2017-03-14

    Toroidal droplets are inherently unstable due to surface tension. They can break up, similar to cylindrical jets, but also exhibit a shrinking instability, which is inherent to the toroidal shape. We investigate the evolution of shrinking toroidal droplets using particle image velocimetry. We obtain the flow field inside the droplets and show that as the torus evolves, its cross-section significantly deviates from circular. We then use the experimentally obtained velocities at the torus interface to theoretically reconstruct the internal flow field. Our calculation correctly describes the experimental results and elucidates the role of those modes that, among the many possible ones, are required to capture all of the relevant experimental features.

  9. Droplet spectral broadening in marine stratus

    SciTech Connect

    Hudson, J.G.; Yum, Seong Soo

    1997-11-15

    Broadening of the cloud droplet (diameter < 50 {mu}m) spectrum with increased droplet size was found to depend on the vertical profiles of cloud water. Clouds with liquid water profiles resembling adiabatic conditions displayed constant spectral widths. Other clouds displayed broader droplet spectra and increasing broadness with mean droplet sizes. Less than adiabatic cloud liquid water profiles may be accounted for by conversion to drops (diameter > 50 {mu}m, i.e., drizzle). Broad droplet spectra were most closely associated with drizzle drops. Both the concentration, C and slope, k, of the cloud condensation nuclei (CCN) spectra were theoretically found to affect droplet spectral width. For individual cloud parcels a higher C and lower k each contributed to broader droplet spectra. When mixing among cloud parcels with different updrafts was considered, the predictions deviated especially at larger mean droplet diameters. Variations in updraft velocity result in differences in droplet concentrations and mean droplet sizes. The predictions for this internal mixing process showed greater droplet spectral widths for CCN spectra with higher k, especially at the larger mean droplet diameters. Instead of the individual parcel predictions of narrower droplet spectra at larger mean droplet sizes, internal mixing predicted increasing droplet spectral width with increasing mean droplet size. These predictions are consistent with the observations. First, when only cloud parcels with small mean droplet diameters (< 1 {mu}m) were considered, the polluted clouds that formed on CCN with higher C and lower k displayed broader droplet spectra than clean clouds. Cloud parcels with large mean droplet diameters (>12 {mu}m) and large {sigma} were observed only in clean conditions where k was high. Increasing droplet spectral width with mean droplet diameter (especially > 12 {mu}m) is typical of many observations here and elsewhere.

  10. Decompressing Emulsion Droplets Favors Coalescence

    NASA Astrophysics Data System (ADS)

    Bremond, Nicolas; Thiam, Abdou R.; Bibette, Jérôme

    2008-01-01

    The destabilization process of an emulsion under flow is investigated in a microfluidic device. The experimental approach enables us to generate a periodic train of droplet pairs, and thus to isolate and analyze the basic step of the destabilization, namely, the coalescence of two droplets which collide. We demonstrate a counterintuitive phenomenon: coalescence occurs during the separation phase and not during the impact. Separation induces the formation of two facing nipples in the contact area that hastens the connection of the interfaces prior to fusion. Moreover, droplet pairs initially stabilized by surfactants can be destabilized by forcing the separation. Finally, we note that the fusion mechanism is responsible for a cascade of coalescence events in a compact system of droplets where the separation is driven by surface tension.

  11. Droplet depinning in a wake

    NASA Astrophysics Data System (ADS)

    Hooshanginejad, Alireza; Lee, Sungyon

    2017-03-01

    Pinning and depinning of a windswept droplet on a surface is familiar yet deceptively complex for it depends on the interaction of the contact line with the microscopic features of the solid substrate. This physical picture is further compounded when wind of the Reynolds number greater than 100 blows over pinned drops, leading to the boundary layer separation and wake generation. In this Rapid Communication, we incorporate the well-developed ideas of the classical boundary layer to study partially wetting droplets in a wake created by a leader object. Depending on its distance from the leader, the droplet is observed to exhibit drafting, upstream motion, and splitting, due to the wake-induced hydrodynamic coupling that is analogous to drafting of moving bodies. We successfully rationalize the onset of the upstream motion regime using a reduced model that computes the droplet shape governed by the pressure field inside the wake.

  12. Droplet combustion at reduced gravity

    NASA Technical Reports Server (NTRS)

    Dryer, F. L.; Williams, F. A.

    1988-01-01

    The current work involves theoretical analyses of the effects identified, experiments in the NASA Lewis drop towers performed in the middeck areas of the Space Shuttle. In addition, there is laboratory work associated with the design of the flight apparatus. Calculations have shown that some of the test-matrix data can be obtained in drop towers, and some are achievable only in the space experiments. The apparatus consists of a droplet dispensing device (syringes), a droplet positioning device (opposing, retractable, hollow needles), a droplet ignition device (two matched pairs of retractable spark electrodes), gas and liquid handling systems, a data acquisition system (mainly giving motion-picture records of the combustion in two orthogonal views, one with backlighting for droplet resolution), and associated electronics.

  13. The life of lipid droplets

    PubMed Central

    Walther, Tobias C.; Farese, Robert V.

    2009-01-01

    Lipid droplets are the least characterized of cellular organelles. Long considered simple lipid storage depots, these dynamic and remarkable organelles have recently been implicated in many biological processes, and we are only now beginning to gain insights into their fascinating lives in cells. Here we examine what we know of the life of lipid droplets. We review emerging data concerning their cellular biology and present our thoughts on some of the most salient questions for investigation. PMID:19041421

  14. Magnetic droplets and dynamical skyrmions

    NASA Astrophysics Data System (ADS)

    Akerman, Johan

    2015-03-01

    Nanocontact spin-torque oscillators (NC-STOs) provide an excellent environment for studying nano-magnetic phenomena such as localized and propagating auto-oscillatory spin wave (SW) modes. The recent experimental observation of magnetic droplet solitons in NC-STOs with perpendicular magnetic anisotropy (PMA) free layers, and the numerical and experimental demonstrations of spin transfer torque (STT) nucleated skyrmions in similar magnetic thin films add two interesting and useful nanoscale magnetic objects. Due to the competition between exchange, anisotropy, and, in the case of skyrmions, the Dzyaloshinskii-Moriya interaction (DMI), the droplet and the skyrmion are extremely compact, on the order of 10-100 nm. One of the main differences between a magnetic dissipative droplet soliton and a skyrmion is that the former is a dynamical object with all its spins precessing around an effective field and stabilized by STT, exchange, and PMA, while the latter has static spins and an internal structure stabilized by DMI, exchange, and PMA. The dissipative droplet is furthermore a non-topological soliton, while the skyrmion is topologically protected. In this work I will report on our most recent droplet experiments, including droplet collapse at very high fields, droplets excited in nano-wire based NC-STOs, and studies of the field-current droplet nucleation boundary. I will also demonstrate numerically and analytically that STT driven precession can stabilize so-called dynamical skyrmions even in the absence of DMI, and I will describe their very promising properties in detail. From a more fundamental perspective, precession is hence a third independent possibility to stabilize a skyrmion, without the need for the conventional stabilization from either dipolar energy or DMI.

  15. The liquid droplet heat exchanger

    NASA Astrophysics Data System (ADS)

    Bruckner, A. P.

    Direct contact heat exchange between a gas and a molten metal dispersed into droplets offers an attractive new approach to increasing the efficiency and decreasing the specific weight of thermal power cycles for space applications. The ability of a droplet heat exchanger to transfer heat directly from a liquid metal to a working gas over a wide temperature range circumvents many of the material limitations of conventional tube type heat exchangers and does away with complicated plumbing systems and their tendency toward simple point failure. Droplet heat exchangers offer large surface to volume ratios in a compact geometry, very low pressure drop and high effectiveness. In the simplest configuration the molten material is sprayed axially through a counterflowing, high pressure inert working gas in an insulated cylindrical chamber. The droplets transfer heat directly to the gas by convection as they traverse the heat exchanger and are subsequently collected for recycling through the heat source. A number of suitable liquid metals and eutectic alloys having negligibly low vapor pressures in the temperature range of 350-1300 K were identified. Experimental studies of droplet formation with mercury demonstrated that near perfect control of droplet size can be easily achieved.

  16. Sintering of polydisperse viscous droplets

    NASA Astrophysics Data System (ADS)

    Wadsworth, Fabian B.; Vasseur, Jérémie; Llewellin, Edward W.; Dingwell, Donald B.

    2017-03-01

    Sintering—or coalescence—of compacts of viscous droplets is driven by the interfacial tension between the droplets and the interstitial gas phase. The process, which occurs in a range of industrial and natural settings, such as the manufacture of ceramics and the welding of volcanic ash, causes the compact to densify, to become stronger, and to become less permeable. We investigate the role of droplet polydispersivity in sintering dynamics by conducting experiments in which populations of glass spheres with different size distributions are heated to temperatures above the glass transition interval. We quantify the progress of sintering by tracking changes in porosity with time. The sintering dynamics is modeled by treating the system as a random distribution of interstitial gas bubbles shrinking under the action of interfacial tension only. We identify the scaling between the polydispersivity of the initial droplets and the dynamics of bulk densification. The framework that we develop allows the sintering dynamics of arbitrary polydisperse populations of droplets to be predicted if the initial droplet (or particle) size distribution is known.

  17. Deciphering chondrocyte behaviour in matrix-induced autologous chondrocyte implantation to undergo accurate cartilage repair with hyaline matrix.

    PubMed

    Demoor, M; Maneix, L; Ollitrault, D; Legendre, F; Duval, E; Claus, S; Mallein-Gerin, F; Moslemi, S; Boumediene, K; Galera, P

    2012-06-01

    Since the emergence in the 1990s of the autologous chondrocytes transplantation (ACT) in the treatment of cartilage defects, the technique, corresponding initially to implantation of chondrocytes, previously isolated and amplified in vitro, under a periosteal membrane, has greatly evolved. Indeed, the first generations of ACT showed their limits, with in particular the dedifferentiation of chondrocytes during the monolayer culture, inducing the synthesis of fibroblastic collagens, notably type I collagen to the detriment of type II collagen. Beyond the clinical aspect with its encouraging results, new biological substitutes must be tested to obtain a hyaline neocartilage. Therefore, the use of differentiated chondrocytes phenotypically stabilized is essential for the success of ACT at medium and long-term. That is why researchers try now to develop more reliable culture techniques, using among others, new types of biomaterials and molecules known for their chondrogenic activity, giving rise to the 4th generation of ACT. Other sources of cells, being able to follow chondrogenesis program, are also studied. The success of the cartilage regenerative medicine is based on the phenotypic status of the chondrocyte and on one of its essential component of the cartilage, type II collagen, the expression of which should be supported without induction of type I collagen. The knowledge accumulated by the scientific community and the experience of the clinicians will certainly allow to relief this technological challenge, which influence besides, the validation of such biological substitutes by the sanitary authorities.

  18. Uniform-droplet spray forming

    SciTech Connect

    Blue, C.A.; Sikka, V.K.; Chun, Jung-Hoon; Ando, T.

    1997-04-01

    The uniform-droplet process is a new method of liquid-metal atomization that results in single droplets that can be used to produce mono-size powders or sprayed-on to substrates to produce near-net shapes with tailored microstructure. The mono-sized powder-production capability of the uniform-droplet process also has the potential of permitting engineered powder blends to produce components of controlled porosity. Metal and alloy powders are commercially produced by at least three different methods: gas atomization, water atomization, and rotating disk. All three methods produce powders of a broad range in size with a very small yield of fine powders with single-sized droplets that can be used to produce mono-size powders or sprayed-on substrates to produce near-net shapes with tailored microstructures. The economical analysis has shown the process to have the potential of reducing capital cost by 50% and operating cost by 37.5% when applied to powder making. For the spray-forming process, a 25% savings is expected in both the capital and operating costs. The project is jointly carried out at Massachusetts Institute of Technology (MIT), Tuffs University, and Oak Ridge National Laboratory (ORNL). Preliminary interactions with both finished parts and powder producers have shown a strong interest in the uniform-droplet process. Systematic studies are being conducted to optimize the process parameters, understand the solidification of droplets and spray deposits, and develop a uniform-droplet-system (UDS) apparatus appropriate for processing engineering alloys.

  19. The absence of type II collagen and changes in proteoglycan structure of hyaline cartilage in a case of Langer-Saldino achondrogenesis.

    PubMed

    Feshchenko, S P; Rebrin, I A; Sokolnik, V P; Sher, B M; Sokolov, B P; Kalinin, V N; Lazjuk, G I

    1989-04-01

    Structural analysis of hyaline cartilage extracellular matrix components from the ribs and knee joint of a stillborn female with type II achondrogenesis was carried out. The absence of type II collagen, a decrease in the amount of proteoglycans (PG), and structural changes in PG, namely, increased electrophoretic mobility of PG, lower relative content of chondroitin 4-sulfate (Ch4-S), lower molecular weight and decreased total chondroitin sulfate (ChS) sulfation, were detected. Increased amounts of type I and type III collagens, atypical for hyaline cartilage, were revealed. Among the link proteins (LPs), a large protein with a mol. wt. of 48 kDa was predominant. Molecular and cellular mechanisms of the pathogenesis of achondrogenesis ("chondrogenesis imperfecta") are discussed. The data obtained suggest that the primary defect in type II achondrogenesis involves ChS or type II collagen synthesis.

  20. Hyaline globules and papillary fragments in cytologic smears from two intra-abdominal tumors (ovarian and hepatic) in female patients: A diagnostic pitfall with histologic correlation.

    PubMed

    Machado, Isidro; López-Soto, María Victoria; Pérez-López, Albadio Samir; Domínguez-Álvarez, Carlos; Llombart-Bosch, Antonio

    2016-11-01

    Hyaline globules and papillary fragments in cytologic samples from two intra-abdominal tumors in young females are presented including the cytological features and the correlation with the histopathologic and immunohistochemical findings. In the first case a cytologic study from an ovarian mass showed papillary structures and isolated tumor cells with epithelioid morphology, irregular reniform-like nuclear contour, pale or vacuolated cytoplasm, abundant hyaline globules and occasional glomeruloid structures resembling Schiller-Duval bodies. Yolk sac tumor (YST) was the diagnosis on the histological slides. Tumor cells showed positivity for cytokeratin (AE1/AE3), epithelial membrane antigen (EMA), alpha-fetoprotein (AFP) and Sal-like protein 4 (SALL4). In case number two the cytologic study from a liver metastasis displayed papillary and rosette-like clusters composed of uniform and bland cells showing occasional long cytoplasmic tails, hyaline globules and nuclear grooves. A diagnosis of hepatic metastasis from solid pseudopapillary neoplasm of the pancreas (SPNP) was rendered from the histology. Tumor cells revealed immunoreactivity for cytokeratin (AE1/AE3), Vimentin, Galectin-1 (GAL-1), Neuron specific-enolase, CD10, progesterone and β-catenin (nuclear stain). Regarding differential diagnosis, in the patient with the ovarian mass an ovarian clear cell carcinoma was considered, as well as other germ cell tumors or metastatic carcinoma, while in the patient with a liver metastasis a neuroendocrine carcinoma was taken into account. YST and SPNP share some cytological findings, including hyaline globules, papillary structures, clear cells and intercellular eosinophilic basement membrane deposits. Thus, a detailed study and careful interpretation of the cytological, histological and immunohistochemical findings may be worthwhile to avoid a potential misdiagnosis, particularly in the cytologic specimens of the ovarian and/or intra-abdominal mass, when involving young

  1. Droplets merging through wireless ultrasonic actuation.

    PubMed

    Nayak, Praveen Priyaranjan; Kar, Durga Prasanna; Bhuyan, Satyanarayan

    2016-01-01

    A new technique of droplets merging through wireless ultrasonic actuation has been proposed and experimentally investigated in this work. The proposed method is based on the principle of resonant inductive coupling and piezoelectric resonance. When a mechanical vibration is excited in a piezoelectric plate, the ultrasonic vibration transmitted to the droplets placed on its surface and induces merging. It has been observed that the merging rate of water droplets depends on the operating frequency, mechanical vibration of piezoelectric plate, separation distance between the droplets, and volume of droplets. The investigated technique of droplets merging through piezoelectric actuation is quite useful for microfluidics, chemical and biomedical engineering applications.

  2. Droplet burning at zero G

    NASA Technical Reports Server (NTRS)

    Williams, F. A.

    1978-01-01

    Questions of the importance and feasibility of performing experiments on droplet burning at zero gravity in Spacelab were studied. Information on the physics and chemistry of droplet combustion, with attention directed specifically to the chemical kinetics, heat and mass transfer, and fluid mechanics of the phenomena involved, are presented. The work was divided into three phases, the justification, the feasibility, and the conceptual development of a preliminary design. Results from the experiments performed revealed a few new facts concerning droplet burning, notably burning rates in excess of theoretical prediction and a phenomenon of flash extinction, both likely traceable to accumulation of carbon produced by gas-phase pyrolysis in the fuel-rich zone enclosed by the reaction surface. These experiments also showed that they were primarily due to timing difficulties.

  3. Vibration-Induced Droplet Atomization

    NASA Technical Reports Server (NTRS)

    Smith, M. K.; James, A.; Vukasinovic, B.; Glezer, A.

    1999-01-01

    Thermal management is critical to a number of technologies used in a microgravity environment and in Earth-based systems. Examples include electronic cooling, power generation systems, metal forming and extrusion, and HVAC (heating, venting, and air conditioning) systems. One technique that can deliver the large heat fluxes required for many of these technologies is two-phase heat transfer. This type of heat transfer is seen in the boiling or evaporation of a liquid and in the condensation of a vapor. Such processes provide very large heat fluxes with small temperature differences. Our research program is directed toward the development of a new, two-phase heat transfer cell for use in a microgravity environment. In this paper, we consider the main technology used in this cell, a novel technique for the atomization of a liquid called vibration-induced droplet atomization. In this process, a small liquid droplet is placed on a thin metal diaphragm that is made to vibrate by an attached piezoelectric transducer. The vibration induces capillary waves on the free surface of the droplet that grow in amplitude and then begin to eject small secondary droplets from the wave crests. In some situations, this ejection process develops so rapidly that the entire droplet seems to burst into a small cloud of atomized droplets that move away from the diaphragm at speeds of up to 50 cm/s. By incorporating this process into a heat transfer cell, the active atomization and transport of the small liquid droplets could provide a large heat flux capability for the device. Experimental results are presented that document the behavior of the diaphragm and the droplet during the course of a typical bursting event. In addition, a simple mathematical model is presented that qualitatively reproduces all of the essential features we have seen in a burst event. From these two investigations, we have shown that delayed droplet bursting results when the system passes through a resonance

  4. Snell's law and walking droplets

    NASA Astrophysics Data System (ADS)

    Bush, John; Pucci, Giuseppe; Aubin, Benjamin; Brun, Pierre-Thomas; Faria, Luiz

    2016-11-01

    Droplets walking on the surface of a vibrating bath have been shown to exhibit a number of quantum-like features. We here present the results of a combined experimental and theoretical investigation of such droplets crossing a linear step corresponding to a reduction in bath depth. When the step is sufficiently large, the walker reflects off the step; otherwise, it is refracted as it crosses the step. Particular attention is given to an examination of the regime in which the droplet obeys a form of Snell's Law, a behavior captured in accompanying simulations. Attempts to provide theoretical rationale for the dependence of the effective refractive index on the system parameters are described. Supported by NSF through CMMI-1333242.

  5. Walking droplets in linear channels

    NASA Astrophysics Data System (ADS)

    Filoux, Boris; Hubert, Maxime; Schlagheck, Peter; Vandewalle, Nicolas

    2017-01-01

    When a droplet is placed onto a vertically vibrated bath, it can bounce without coalescing. Upon an increase of the forcing acceleration, the droplet is propelled by the wave it generates and becomes a walker with a well-defined speed. We investigate the confinement of a walker in different rectangular cavities, used as waveguides for the Faraday waves emitted by successive droplet bounces. By studying the walker velocities, we discover that one-dimensional confinement is optimal for narrow channels of width of D ≃1.5 λF . Thereby, the walker follows a quasilinear path. We also propose an analogy with waveguide models based on the observation of the Faraday instability within the channels.

  6. Film boiling of mercury droplets

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Schoessow, G. J.; Chmielewski, C. E.

    1975-01-01

    Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. Diffusion from the upper surface of the drop appears as a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

  7. Microstructures of undercooled germanium droplets

    NASA Technical Reports Server (NTRS)

    Devaud, G.; Turnbull, D.

    1987-01-01

    Undercoolings at crystal nucleation onset of liquid Ge droplets are measured and the microstructures of the droplets are examined. Undercooling values ranging from 150-415 + or 20 C were obtained. It is observed that for the samples undercooled less than 300 C prior to solidification the grain size was greater than 100 microns; for samples undercooled between 300-400 C the grain size was between 50-100 microns; and for samples undercooled greater than 400 C the grain size was 10-20 microns. Consideration is given to dendritic growth and interfacial undercooling. It is noted that there is a correlation between undercooling and as-crystallized grain structure.

  8. Film boiling of mercury droplets

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Schoessow, G. J.; Chmielewski, C. E.

    1975-01-01

    Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. For these data, diffusion from the upper surface of the drop is a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

  9. Materials science: Droplets leap into action

    NASA Astrophysics Data System (ADS)

    Vollmer, Doris; Butt, Hans-Jürgen

    2015-11-01

    What could cause a water droplet to start bouncing on a surface? It seems that a combination of evaporation and a highly water-repellent surface induces droplet bouncing when ambient pressure is reduced. See Letter p.82

  10. Persisting Water Droplets on Water Surfaces†

    PubMed Central

    Klyuzhin, Ivan S.; Ienna, Federico; Roeder, Brandon; Wexler, Adam; Pollack, Gerald H.

    2011-01-01

    Droplets of various liquids may float on the respective surfaces for extended periods of time prior to coalescence. We explored the features of delayed coalescence in highly purified water. Droplets several millimeters in diameter were released from a nozzle onto a water surface. Results showed that droplets had float times up to hundreds of milliseconds. When the droplets did coalesce, they did so in stepwise fashion, with periods of quiescence interspersed between periods of coalescence. Up to six steps were noted before the droplet finally vanished. Droplets were released in a series, which allowed the detection of unexpected abrupt float-time changes throughout the duration of the series. Factors such as electrostatic charge, droplet size, and sideways motion had considerable effect on droplet lifetime, as did reduction of pressure, which also diminished the number of steps needed for coalescence. On the basis of present observations and recent reports, a possible mechanism for noncoalescence is considered. PMID:20961076

  11. Osteochondral lesions in distal tarsal joints of Icelandic horses reveal strong associations between hyaline and calcified cartilage abnormalities.

    PubMed

    Ley, C J; Ekman, S; Hansson, K; Björnsdóttir, S; Boyde, A

    2014-03-25

    Osteochondral lesions in the joints of the distal tarsal region of young Icelandic horses provide a natural model for the early stages of osteoarthritis (OA) in low-motion joints. We describe and characterise mineralised and non-mineralised osteochondral lesions in left distal tarsal region joint specimens from twenty-two 30 ±1 month-old Icelandic horses. Combinations of confocal scanning light microscopy, backscattered electron scanning electron microscopy (including, importantly, iodine staining) and three-dimensional microcomputed tomography were used on specimens obtained with guidance from clinical imaging. Lesion-types were described and classified into groups according to morphological features. Their locations in the hyaline articular cartilage (HAC), articular calcified cartilage (ACC), subchondral bone (SCB) and the joint margin tissues were identified and their frequency in the joints recorded. Associations and correlations between lesion-types were investigated for centrodistal joints only. In centrodistal joints the lesion-types HAC chondrocyte loss, HAC fibrillation, HAC central chondrocyte clusters, ACC arrest and ACC advance had significant associations and strong correlations. These lesion-types had moderate to high frequency in centrodistal joints but low frequencies in tarsometatarsal and talocalcaneal-centroquartal joints. Joint margin lesion-types had no significant associations with other lesion-types in the centrodistal joints but high frequency in both the centrodistal and tarsometatarsal joints. The frequency of SCB lesion-types in all joints was low. Hypermineralised infill phase lesion-types were detected. Our results emphasise close associations between HAC and ACC lesions in equine centrodistal joints and the importance of ACC lesions in the development of OA in low-motion compression-loaded equine joints.

  12. Droplet centrifugation, droplet DNA extraction, and rapid droplet thermocycling for simpler and faster PCR assay using wire-guided manipulations

    PubMed Central

    2012-01-01

    A computer numerical control (CNC) apparatus was used to perform droplet centrifugation, droplet DNA extraction, and rapid droplet thermocycling on a single superhydrophobic surface and a multi-chambered PCB heater. Droplets were manipulated using “wire-guided” method (a pipette tip was used in this study). This methodology can be easily adapted to existing commercial robotic pipetting system, while demonstrated added capabilities such as vibrational mixing, high-speed centrifuging of droplets, simple DNA extraction utilizing the hydrophobicity difference between the tip and the superhydrophobic surface, and rapid thermocycling with a moving droplet, all with wire-guided droplet manipulations on a superhydrophobic surface and a multi-chambered PCB heater (i.e., not on a 96-well plate). Serial dilutions were demonstrated for diluting sample matrix. Centrifuging was demonstrated by rotating a 10 μL droplet at 2300 round per minute, concentrating E. coli by more than 3-fold within 3 min. DNA extraction was demonstrated from E. coli sample utilizing the disposable pipette tip to cleverly attract the extracted DNA from the droplet residing on a superhydrophobic surface, which took less than 10 min. Following extraction, the 1500 bp sequence of Peptidase D from E. coli was amplified using rapid droplet thermocycling, which took 10 min for 30 cycles. The total assay time was 23 min, including droplet centrifugation, droplet DNA extraction and rapid droplet thermocycling. Evaporation from of 10 μL droplets was not significant during these procedures, since the longest time exposure to air and the vibrations was less than 5 min (during DNA extraction). The results of these sequentially executed processes were analyzed using gel electrophoresis. Thus, this work demonstrates the adaptability of the system to replace many common laboratory tasks on a single platform (through re-programmability), in rapid succession (using droplets), and with a high level of

  13. Sophisticated compound droplets on fiber networks

    NASA Astrophysics Data System (ADS)

    Weyer, Floriane; Lismont, Marjorie; Dreesen, Laurent; Vandewalle, Nicolas

    2015-11-01

    Droplets on fibers are part of our everyday lives. Indeed, many phenomena involve drops and fibers such as the formation of dew droplets on a spiderweb, the trapping of water droplets on cactus spines or the dyeing of cotton or wool fibers. Therefore, this topic has been widely studied in the recent years and it appears that droplets on fibers can be the starting point for an open digital microfluidics. We study the behavior of soapy water droplets on a fiber array. When a droplet slides along a vertical fiber and encounters a horizontal fiber, it can either stick there or continue its way. In the latter case, the droplet releases a tiny residue. We study the volume of these residues depending on the geometry of the node. By using this technique, a large number of small droplets can be trapped at the nodes of a fiber array. These residues can be encapsulated and collected by an oil droplet in order to create a multicompound droplet. Moreover, by using optical fibers, we can provoke and detect the fluorescence of the inner droplets. Fibers provide therefore an original way to study compound droplets and multiple reactions. F. Weyer is financially supported by an FNRS grant. This work is also supported by the FRFC 2.4504.12.

  14. Water droplet impact on elastic superhydrophobic surfaces

    PubMed Central

    Weisensee, Patricia B.; Tian, Junjiao; Miljkovic, Nenad; King, William P.

    2016-01-01

    Water droplet impact on surfaces is a ubiquitous phenomenon in nature and industry, where the time of contact between droplet and surface influences the transfer of mass, momentum and energy. To manipulate and reduce the contact time of impacting droplets, previous publications report tailoring of surface microstructures that influence the droplet - surface interface. Here we show that surface elasticity also affects droplet impact, where a droplet impacting an elastic superhydrophobic surface can lead to a two-fold reduction in contact time compared to equivalent rigid surfaces. Using high speed imaging, we investigated the impact dynamics on elastic nanostructured superhydrophobic substrates having membrane and cantilever designs with stiffness 0.5–7630 N/m. Upon impact, the droplet excites the substrate to oscillate, while during liquid retraction, the substrate imparts vertical momentum back to the droplet with a springboard effect, causing early droplet lift-off with reduced contact time. Through detailed experimental and theoretical analysis, we show that this novel springboarding phenomenon is achieved for a specific range of Weber numbers (We >40) and droplet Froude numbers during spreading (Fr >1). The observation of the substrate elasticity-mediated droplet springboard effect provides new insight into droplet impact physics. PMID:27461899

  15. Shock wave-droplet interaction

    NASA Astrophysics Data System (ADS)

    Habibi Khoshmehr, Hamed; Krechetnikov, Rouslan

    2016-11-01

    Disintegration of a liquid droplet under the action of a shock wave is experimentally investigated. The shock wave-pulse is electromagnetically generated by discharging a high voltage capacitor into a flat spiral coil, above which an isolated circular metal membrane is placed in a close proximity. The Lorentz force arising due to the eddy current induced in the membrane abruptly accelerates it away from the spiral coil thus generating a shock wave. The liquid droplet placed at the center of the membrane, where the maximum deflection occurs, is disintegrated in the process of interaction with the shock wave. The effects of droplet viscosity and surface tension on the droplet destruction are studied with high-speed photography. Water-glycerol solution at different concentrations is used for investigating the effect of viscosity and various concentrations of water-sugar and water-ethanol solution are used for studying the effect of surface tension. Here we report on how the metamorphoses, which a liquid drop undergoes in the process of interaction with a shock wave, are affected by varied viscosity and surface tension.

  16. Formation and Levitation of Unconfined Droplet Clusters

    NASA Technical Reports Server (NTRS)

    Liu, S.; Ruff, G. A.

    1999-01-01

    Combustion experiments using arrays of droplets seek to provide a link between single droplet combustion phenomena and the behavior of complex spray combustion systems. Both single droplet and droplet array studies have been conducted in microgravity to better isolate the droplet interaction phenomena and eliminate or reduce the confounding effects of buoyancy-induced convection. In most experiments involving droplet arrays, the droplets are supported on fibers to keep them stationary and close together before the combustion event. The presence of the fiber, however, disturbs the combustion process by introducing a source of heat transfer and asymmetry into the configuration. As the number of drops in a droplet array increases, supporting the drops on fibers becomes less practical because of the cumulative effect of the fibers on the combustion process. The overall objective of this research is to study the combustion of well-characterized drop clusters in a microgravity environment. Direct experimental observations and measurements of the combustion of droplet clusters would fill a large gap in our current understanding of droplet and spray combustion and provide unique experimental data for the verification and improvement of spray combustion models. This paper describes current work on the design and performance of an apparatus to generate and stabilize droplet clusters using acoustic and electrostatic forces.

  17. Passive droplet sorting using viscoelastic flow focusing.

    PubMed

    Hatch, Andrew C; Patel, Apurva; Beer, N Reginald; Lee, Abraham P

    2013-04-07

    We present a study of passive hydrodynamic droplet sorting in microfluidic channels based on intrinsic viscoelastic fluid properties. Sorting is achieved by tuning the droplets' intrinsic viscous and viscoelastic properties relative to the continuous oil phase to achieve a positive or negative lateral migration toward high or low shear gradients in the channel. In the presence of weakly viscoelastic fluid behavior, droplets with a viscosity ratio, κ, between 0.5-10 were found to migrate toward a high shear gradient near the channel walls. For all other κ-values, or Newtonian fluids, droplets would migrate toward a low shear gradient at the channel centerline. It was also found that for strongly viscoelastic fluids with low interfacial tension, droplets would migrate toward the edge even with κ-values lower than 0.5. The resulting bi-directional lateral droplet migration between different droplets allows size-independent sorting. Still, their sorting efficiencies are dependent on droplet size, intrinsic fluid elasticity, viscosity, droplet deformability, and overall fluid shear rates. Based on these findings, we demonstrate >200 Hz passive droplet sorting frequencies and achieve >100 fold enrichment factors without the need to actively sense and/or control active mechanisms. Using a low viscosity oil phase of 6.25 cPs, we demonstrate sorting discrimination of 1 cPs and 5 cPs aqueous droplets with κ-values of 0.2 and 0.8 respectively.

  18. Thermophoresis of water droplets inside carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zambrano, Harvey; Walther, Jh; Oyarzua, Elton; Rojano, Andres

    2016-11-01

    Carbon Nanotubes (CNTs) offer unique possibilities as fluid conduits with applications ranging from lab on a chip devices to encapsulation media for drug delivery. CNTs feature high mechanical strength, chemical and thermal stability and biocompatibility therefore they are promising candidates for nanodevice fabrication. Thermal gradients have been proposed as mechanism to drive particles, fullerenes and droplets inside CNTs. Here, by conducting Molecular Dynamics (MD) simulations, we study thermophoresis of water droplets inside CNTs. We systematically change the size of the droplets, the axial thermal gradient and CNT chirality. We find that the droplet motion in the armchair CNTs exhibits two clearly delimited stages, a regime wherein the droplet is accelerated and subsequently, a regime wherein the droplet moves with constant velocity. Inside the zig zag CNTs, the droplet accelerates during a very short time and then it moves with constant velocity. We compute the net force during the droplet acceleration and find a correlation between the droplet acceleration and the magnitude of the thermal gradient without any dependence on the droplet size. Moreover, we conduct velocity constrained MD simulations to determine the friction and thermophoretic forces acting on the droplet. We acknowledge partial funding from FONDECYT through the Project No. 11130559 and from VRID Universidad de Concepcion.

  19. Dynamics of droplet motion under electrowetting actuation.

    PubMed

    Annapragada, S Ravi; Dash, Susmita; Garimella, Suresh V; Murthy, Jayathi Y

    2011-07-05

    The static shape of droplets under electrowetting actuation is well understood. The steady-state shape of the droplet is obtained on the basis of the balance of surface tension and electrowetting forces, and the change in the apparent contact angle is well characterized by the Young-Lippmann equation. However, the transient droplet shape behavior when a voltage is suddenly applied across a droplet has received less attention. Additional dynamic frictional forces are at play during this transient process. We present a model to predict this transient behavior of the droplet shape under electrowetting actuation. The droplet shape is modeled using the volume of fluid method. The electrowetting and dynamic frictional forces are included as an effective dynamic contact angle through a force balance at the contact line. The model is used to predict the transient behavior of water droplets on smooth hydrophobic surfaces under electrowetting actuation. The predictions of the transient behavior of droplet shape and contact radius are in excellent agreement with our experimental measurements. The internal fluid motion is explained, and the droplet motion is shown to initiate from the contact line. An approximate mathematical model is also developed to understand the physics of the droplet motion and to describe the overall droplet motion and the contact line velocities.

  20. Spectroscopy and optical imaging of coalescing droplets

    NASA Astrophysics Data System (ADS)

    Ivanov, Maksym; Viderström, Michel; Chang, Kelken; Ramírez Contreras, Claudia; Mehlig, Bernhard; Hanstorp, Dag

    2016-09-01

    We report on experimental investigations of the dynamics of colliding liquid droplets by combining optical trapping, spectroscopy and high-speed color imaging. Two droplets with diameters between 5 and 50 microns are suspended in quiescent air by optical traps. The traps allows us to control the initial positions, and hence the impact parameter and the relative velocity of the colliding droplets. Movies of the droplet dynamics are recorded using high-speed digital movie cameras at a frame rate of up to 63000 frames per second. A fluorescent dye is added to one of the colliding droplets. We investigate the temporal evolution of the scattered and fluorescence light from the colliding droplets with concurrent spectroscopy and color imaging. This technique can be used to detect the exchange of molecules between a pair of neutral or charged droplets.

  1. Active droplet sorting in microfluidics: a review.

    PubMed

    Xi, Heng-Dong; Zheng, Hao; Guo, Wei; Gañán-Calvo, Alfonso M; Ai, Ye; Tsao, Chia-Wen; Zhou, Jun; Li, Weihua; Huang, Yanyi; Nguyen, Nam-Trung; Tan, Say Hwa

    2017-02-28

    The ability to manipulate and sort droplets is a fundamental issue in droplet-based microfluidics. Various lab-on-a-chip applications can only be realized if droplets are systematically categorized and sorted. These micron-sized droplets act as ideal reactors which compartmentalize different biological and chemical reagents. Array processing of these droplets hinges on the competence of the sorting and integration into the fluidic system. Recent technological advances only allow droplets to be actively sorted at the rate of kilohertz or less. In this review, we present state-of-the-art technologies which are implemented to efficiently sort droplets. We classify the concepts according to the type of energy implemented into the system. We also discuss various key issues and provide insights into various systems.

  2. Enhanced Droplet Control by Transition Boiling

    NASA Astrophysics Data System (ADS)

    Grounds, Alex; Still, Richard; Takashina, Kei

    2012-10-01

    A droplet of water on a heated surface can levitate over a film of gas produced by its own evaporation in the Leidenfrost effect. When the surface is prepared with ratchet-like saw-teeth topography, these droplets can self-propel and can even climb uphill. However, the extent to which the droplets can be controlled is limited by the physics of the Leidenfrost effect. Here, we show that transition boiling can be induced even at very high surface temperatures and provide additional control over the droplets. Ratchets with acute protrusions enable droplets to climb steeper inclines while ratchets with sub-structures enable their direction of motion to be controlled by varying the temperature of the surface. The droplets' departure from the Leidenfrost regime is assessed by analysing the sound produced by their boiling. We anticipate these techniques will enable the development of more sophisticated methods for controlling small droplets and heat transfer.

  3. Dancing droplets: Contact angle, drag, and confinement

    NASA Astrophysics Data System (ADS)

    Benusiglio, Adrien; Cira, Nate; Prakash, Manu

    2015-11-01

    When deposited on a clean glass slide, a mixture of water and propylene glycol forms a droplet of given contact angle, when both pure liquids spread. (Cira, Benusiglio, Prakash: Nature, 2015). The droplet is stabilized by a gradient of surface tension due to evaporation that induces a Marangoni flow from the border to the apex of the droplets. The apparent contact angle of the droplets depends on both their composition and the external humidity as captured by simple models. These droplets present remarkable properties such as lack of a large pinning force. We discuss the drag on these droplets as a function of various parameters. We show theoretical and experimental results of how various confinement geometries change the vapor gradient and the dynamics of droplet attraction.

  4. Integrated microfluidic system capable of size-specific droplet generation with size-dependent droplet separation.

    PubMed

    Lee, Sangmin; Hong, Seok Jun; Yoo, Hyung Jung; Ahn, Jae Hyun; Cho, Dong-il Dan

    2013-06-01

    Droplet-based microfluidics is receiving much attention in biomedical research area due to its advantage in uniform size droplet generation. Our previous results have reported that droplet size plays an important role in drug delivery actuated by flagellated bacteria. Recently, many research groups have been reported the size-dependent separation of emulsion droplets by a microfluidic system. In this paper, an integrated microfluidic system is proposed to produce and sort specificsized droplets sequentially. Operation of the system relies on two microfluidic transport processes: initial generation of droplets by hydrodynamic focusing and subsequent separation of droplets by a T-junction channel. The microfluidic system is fabricated by the SU-8 rapid prototyping method and poly-di-methyl-siloxane (PDMS) replica molding. A biodegradable polymer, poly-capro-lactone (PCL), is used for the droplet material. Using the proposed integrated microfluidic system, specific-sized droplets which can be delivered by flagellated bacteria are successfully generated and obtained.

  5. Droplet actuator analyzer with cartridge

    NASA Technical Reports Server (NTRS)

    Smith, Gregory F. (Inventor); Sturmer, Ryan A. (Inventor); Paik, Philip Y. (Inventor); Srinivasan, Vijay (Inventor); Pollack, Michael G. (Inventor); Pamula, Vamsee K. (Inventor); Brafford, Keith R. (Inventor); West, Richard M. (Inventor)

    2011-01-01

    A droplet actuator with cartridge is provided. According to one embodiment, a sample analyzer is provided and includes an analyzer unit comprising electronic or optical receiving means, a cartridge comprising self-contained droplet handling capabilities, and a wherein the cartridge is coupled to the analyzer unit by a means which aligns electronic and/or optical outputs from the cartridge with electronic or optical receiving means on the analyzer unit. According to another embodiment, a sample analyzer is provided and includes a sample analyzer comprising a cartridge coupled thereto and a means of electrical interface and/or optical interface between the cartridge and the analyzer, whereby electrical signals and/or optical signals may be transmitted from the cartridge to the analyzer.

  6. Recent developments in droplet epitaxy

    SciTech Connect

    Mano, Takaaki; Jo, Masafumi; Kuroda, Takashi; Abbarchi, Marco; Noda, Takeshi; Sakoda, Kazuaki

    2014-05-15

    The droplet epitaxy allows for self-assembly of lattice-matched GaAs quantum dots (QDs) with high quality and high uniformity. In this article, we show our efforts to realize the GaAs QDs with excellent optical properties. After the optimization of the several growth processes, we achieved current-injection lasing in the GaAs QDs. In addition, formation of further advanced nanostructure is presented.

  7. Vortices catapult droplets in atomization

    SciTech Connect

    Jerome, J. John Soundar Zaleski, Stéphane; Hoepffner, Jérôme; Marty, Sylvain; Matas, Jean-Philippe

    2013-11-15

    A droplet ejection mechanism in planar two-phase mixing layers is examined. Any disturbance on the gas-liquid interface grows into a Kelvin-Helmholtz wave, and the wave crest forms a thin liquid film that flaps as the wave grows downstream. Increasing the gas speed, it is observed that the film breaks up into droplets which are eventually thrown into the gas stream at large angles. In a flow where most of the momentum is in the horizontal direction, it is surprising to observe these large ejection angles. Our experiments and simulations show that a recirculation region grows downstream of the wave and leads to vortex shedding similar to the wake of a backward-facing step. The ejection mechanism results from the interaction between the liquid film and the vortex shedding sequence: a recirculation zone appears in the wake of the wave and a liquid film emerges from the wave crest; the recirculation region detaches into a vortex and the gas flow over the wave momentarily reattaches due to the departure of the vortex; this reattached flow pushes the liquid film down; by now, a new recirculation vortex is being created in the wake of the wave—just where the liquid film is now located; the liquid film is blown up from below by the newly formed recirculation vortex in a manner similar to a bag-breakup event; the resulting droplets are catapulted by the recirculation vortex.

  8. Vortices catapult droplets in atomization

    NASA Astrophysics Data System (ADS)

    Jerome, J. John Soundar; Marty, Sylvain; Matas, Jean-Philippe; Zaleski, Stéphane; Hoepffner, Jérôme

    2013-11-01

    A droplet ejection mechanism in planar two-phase mixing layers is examined. Any disturbance on the gas-liquid interface grows into a Kelvin-Helmholtz wave, and the wave crest forms a thin liquid film that flaps as the wave grows downstream. Increasing the gas speed, it is observed that the film breaks up into droplets which are eventually thrown into the gas stream at large angles. In a flow where most of the momentum is in the horizontal direction, it is surprising to observe these large ejection angles. Our experiments and simulations show that a recirculation region grows downstream of the wave and leads to vortex shedding similar to the wake of a backward-facing step. The ejection mechanism results from the interaction between the liquid film and the vortex shedding sequence: a recirculation zone appears in the wake of the wave and a liquid film emerges from the wave crest; the recirculation region detaches into a vortex and the gas flow over the wave momentarily reattaches due to the departure of the vortex; this reattached flow pushes the liquid film down; by now, a new recirculation vortex is being created in the wake of the wave—just where the liquid film is now located; the liquid film is blown up from below by the newly formed recirculation vortex in a manner similar to a bag-breakup event; the resulting droplets are catapulted by the recirculation vortex.

  9. Grating droplets with a mesh

    NASA Astrophysics Data System (ADS)

    Soto, Dan; Le Helloco, Antoine; Clanet, Cristophe; Quere, David; Varanasi, Kripa

    2016-11-01

    A drop thrown against a mesh can pass through its holes if impacting with enough inertia. As a result, although part of the droplet may remain on one side of the sieve, the rest will end up grated through the other side. This inexpensive method to break up millimetric droplets into micrometric ones may be of particular interest in a wide variety of applications: enhancing evaporation of droplets launched from the top of an evaporative cooling tower or preventing drift of pesticides sprayed above crops by increasing their initial size and atomizing them at the very last moment with a mesh. In order to understand how much liquid will be grated we propose in this presentation to start first by studying a simpler situation: a drop impacting a plate pierced with a single off centered hole. The study of the role of natural parameters such as the radius drop and speed or the hole position, size and thickness allows us to discuss then the more general situation of a plate pierced with multiple holes: the mesh.

  10. Droplet Core Nuclear Rocket (DCNR)

    NASA Technical Reports Server (NTRS)

    Anghaie, Samim

    1991-01-01

    The most basic design feature of the droplet core nuclear reactor is to spray liquid uranium into the core in the form of droplets on the order of five to ten microns in size, to bring the reactor to critical conditions. The liquid uranium fuel ejector is driven by hydrogen, and more hydrogen is injected from the side of the reactor to about one and a half meters from the top. High temperature hydrogen is expanded through a nozzle to produce thrust. The hydrogen pressure in the system can be somewhere between 50 and 500 atmospheres; the higher pressure is more desirable. In the lower core region, hydrogen is tangentially injected to serve two purposes: (1) to provide a swirling flow to protect the wall from impingement of hot uranium droplets: (2) to generate a vortex flow that can be used for fuel separation. The reactor is designed to maximize the energy generation in the upper region of the core. The system can result in and Isp of 2000 per second, and a thrust-to-weight ratio of 1.6 for the shielded reactor. The nuclear engine system can reduce the Mars mission duration to less than 200 days. It can reduce the hydrogen consumption by a factor of 2 to 3, which reduces the hydrogen load by about 130 to 150 metric tons.

  11. Droplet impact on a fiber

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Gil; Kim, Taehong; Kim, Wonjung

    2015-11-01

    We present the results of a combined experimental and theoretical investigation of drop impact on a fiber. We use high-speed videography to characterize the dynamics of drops impacting fibers. Our systematical experiments reveal that the outcome of droplet collision critically depends on the relative magnitude of inertial to capillary forces and the ratio of the thickness of fiber to the diameter of the drop. We identify three outcomes of the collision using a non-dimensional regime map. The selection among the modes of single capturing, single drop falling, and divided drop falling is explained through a scale analysis of forces. We also examine the droplet retention on the fiber after impact. For each mode, we suggest the mathematical models to predict the amount of residual water on the fiber. Our study can be extended to predicting the remaining droplet, the critical problem in air filtration, water collection, and fiber coating. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP) (2009-0083510).

  12. Interfacial Instabilities on a Droplet

    NASA Astrophysics Data System (ADS)

    Jalaal, Maziyar; Mehravaran, Kian

    2013-11-01

    The fragmentation of droplets is an essential stage of several natural and industrial applications such as fuel atomization and rain phenomena. In spite of its relatively long history, the mechanism of fragmentation is not clear yet. This is mainly due to small length and time scales as well as the non-linearity of the process. In the present study, two and three-dimensional numerical simulations have been performed to understand the early stages of the fragmentation of an initially spherical droplet. Simulations are performed for high Reynolds and a range of relatively high Weber numbers (shear breakup). To resolve the small-scale instabilities generated over the droplet, a second-order adaptive finite volume/volume of fluids (FV/VOF) method is employed, where the grid resolution is increased with the curvature of the gas-liquid interface as well as the vorticity magnitude. The study is focused on the onset and growth of interfacial instabilities. The role of Kelvin-Helmholtz instability (in surface wave formation) and Rayleigh-Taylor instability (in azimuthal transverse modulation) are shown and the obtained results are compared with the linear instability theories for zero and non-zero vorticity layers. Moreover, the analogy between the fragmentation of a single drop and a co-axial liquid jet is discussed. The current results can be used for the further development of the current secondary atomization models.

  13. High-Voltage Droplet Dispenser Developed

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; VanderWal, Randy L.

    2001-01-01

    Various techniques have been applied to deploying individual droplets for many applications, such as the study of the combustion of liquid fuels. Isolated droplet studies are useful in that they allow phenomena to be studied under well-controlled and simplified conditions. A high-voltage droplet dispenser has been developed that is extremely effective in dispensing a wide range of droplets. The dispenser is quite unique in that it utilizes a droplet bias voltage, as well as an ionization pulse, to release the droplet. The droplet is deployed from the end of a needle. A flat-tipped, stainless steel needle attached to a syringe dispenses a known value of liquid that hangs on the needle tip. Somewhat below the droplet is an annular ring electrode. A bias voltage, followed by a voltage pulse, is applied to attract the droplet sufficiently to pull it off the needle. The droplet and needle are oppositely charged relative to the annular electrode. The needle is negatively charged, and the annular ring is positively charged.

  14. Droplet interactions during combustion of unsupported droplet clusters in microgravity: Numerical study of droplet interactions at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Ciobanescu Husanu, Irina N.

    2005-09-01

    The present work developed a numerical model to study the combustion of well-characterized drop clusters in microgravity environment using direct numerical simulation by the means of Fire Dynamic Simulator---a CFD model of fire-driven fluid flow. The computational research investigated the combustion of clusters of droplets of different sized and asymmetric three-dimensional configurations in zero gravity environments for zero relative Reynolds numbers. One of the aspects studied is droplet interaction during evaporation and combustion over the lifetime of the droplet. The model developed accounts for variable gas-phase thermophysical properties, unity Lewis number, Stefan velocities and includes the gas-phase radiative transfer (solved by a finite volume method) for finite rate reaction. Mass burning rates are calculated for each droplet in an array and compared to mass burning rate of similar single droplet, the ratio of these two being a correction factor eta. Single droplet combustion has been studied to evaluate and validate the model output. It was found that single droplet combustion does follow the d2-law, mass burning rates being in excellent qualitative agreement with current theories and experimental data. Direct numerical results of multiple droplet combustion were obtained and compared with a point source method as well as with experimental and numerical models developed in the past. Data obtained with proposed method provided results consistent with and in qualitative agreement with multiple droplets combustion theories and experimental investigations. Quantitatively, the numerical model results were in the range of 85% to 95% of the results provided by the investigations found in the literature for droplet array combustion models and in the range of 85% to 90% when compared with single droplet combustion models. The numerical simulation along with the future proposed experiment described in the project is a unique combination of investigative methods

  15. Vibration-induced droplet atomization

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan

    The atomization of liquid drops is investigated experimentally using laser vibrometry, high-speed imaging, and particle tracking techniques. The spray is generated by a novel vibration-induced droplet atomization (VIDA) process in which a sessile drop is atomized by an underlying vibrating thin metal diaphragm, resulting in rapid ejection of small secondary droplets from the free surface of the primary drop. Under some conditions, the primary drop can be atomized extremely rapidly by a bursting-like mechanism (e.g., a 0.1 ml water drop can be atomized in 0.4 seconds). The present research has focused on four major areas: global characteristics of VIDA process, instability modes and free surface dynamics of the forced drop, mechanisms of the interface breakup, and parametric characterization of the ensuing spray. Prior to atomization, the drop free surface undergoes three transitions: from axisymmetric standing waves to azimuthal waves, to a newly-observed lattice mode, and to a disordered pre-ejection state. The droplet ejection results from localized collapse of surface troughs and initiation and ultimate breakup of momentary liquid spikes. Breakup begins with capillary pinch-off from spike tips and can be followed by additional pinching of liquid droplets. For a relatively low-viscosity liquid, e.g., water, a capillary-wave instability of the spike is observed in some cases, while for a very viscous liquid, e.g., a glycerin/water solution, the first breakup occurs near the stem of the spike, with or without subsequent breakup of the detached, elongated thread. Different mechanisms dominating the primary breakup of the spike are operative in the low- and high-viscosity ejection regimes. When ejection of the secondary droplets is triggered, the evolution and rate of atomization depend on the coupled dynamics of the primary drop and the vibrating diaphragm. Due to these dynamics, the process can be either self-intensifying or self-decaying. The resulting VIDA spray

  16. [Micro-droplet characterization and its application for amino acid detection in droplet microfluidic system].

    PubMed

    Yuan, Huiling; Dong, Libing; Tu, Ran; Du, Wenbin; Ji, Shiru; Wang, Qinhong

    2014-01-01

    Recently, the droplet microfluidic system attracts interests due to its high throughput and low cost to detect and screen. The picoliter micro-droplets from droplet microfluidics are uniform with respect to the size and shape, and could be used as monodispensed micro-reactors for encapsulation and detection of single cell or its metabolites. Therefore, it is indispensable to characterize micro-droplet and its application from droplet microfluidic system. We first constructed the custom-designed droplet microfluidic system for generating micro-droplets, and then used the micro-droplets to encapsulate important amino acids such as glutamic acid, phenylalanine, tryptophan or tyrosine to test the droplets' properties, including the stability, diffusivity and bio-compatibility for investigating its application for amino acid detection and sorting. The custom-designed droplet microfluidic system could generate the uniformed micro-droplets with a controllable size between 20 to 50 microm. The micro-droplets could be stable for more than 20 h without cross-contamination or fusion each other. The throughput of detection and sorting of the system is about 600 micro-droplets per minute. This study provides a high-throughput platform for the analysis and screening of amino acid-producing microorganisms.

  17. Assessment of apoptosis and MMP-1, MMP-3 and TIMP-2 expression in tibial hyaline cartilage after viable medial meniscus transplantation in the rabbit

    PubMed Central

    Stasikowska-Kanicka, Olga; Danilewicz, Marian; Fabiś, Jarosław

    2012-01-01

    Introduction The porpuse of this animal study was to assess chondrocyte apoptosis and MMP-1, MMP-3 and TIMP-2 expression in rabbit tibial cartilage 6 months after viable medial meniscal autografts and allografts. Material and methods Twenty white male New Zealand rabbits were chosen for the study. The medial meniscus was excised from 14 animals and stored under tissue culture conditions for 2 weeks, following which t of them were implantated as autografts and 7 as allografts. The control group consisted of 6 animals which underwent arthtrotomy. When the animals were eutanized, the tibial cartilage was used for immunohisochemical examination. Apoptosis (TUNEL method) and MMP-1, MMP-3 and TIMP-2 expression were estimated semiquantatively. Results An increased level of chodrocyte apoptosis in the tibail cartilage was observed after both kinds of transplants (p < 0.05), allografts (1.43 ±0.98) and autografts (0.86 ±0.69); no statistical diferences existed between them. An increased level of metalloproteinases and TIMP-2 expression was obreved only after allografts with statistical differences among the allograft group, the autograft group nad the control group (p < 0.05). Conclusions Our findings suggest that the meniscal graft does not protect the hyaline cartilage against excessive apoptosis. The results of experimantal studies on humans indicate the need to device a method of apoptosis inhibition in the hyaline cartilage to improve long-term results of meniscal transplantation. PMID:23319989

  18. A Case of Hyalinizing Clear Cell Carcinoma, So-Called Clear Cell Carcinoma, Not Otherwise Specified, of the Minor Salivary Glands of the Buccal Mucosa

    PubMed Central

    Yamanishi, Takahiro; Kutsuma, Kiwako; Masuyama, Keisuke

    2015-01-01

    Hyalinizing clear cell carcinoma (HCCC), so-called clear cell carcinoma, not otherwise specified (CCC (NOS)), of the salivary glands is a rare and low-grade malignant tumor. We report a case of HCCC so-called CCC (NOS) (referred to as HCCC) of the minor salivary gland of the buccal mucosa. A 52-year-old woman had presented with a gradually growing and indolent mass in the right buccal mucosa for about two years. The first biopsy histopathologically suggested the possibility of malignancy derived from the minor salivary glands. A month later, she visited our hospital. The tumor measured approximately 1.5 cm in diameter and was elastic hard, smooth, and well movable. Image examinations demonstrated internal homogeneity of the lesion, which had a smooth margin, in the right buccal mucosa. Complete tumor resection followed by covering with a polyglycolic acid sheet and fibrin glue spray was performed without surgical flap reconstruction. Histopathological findings revealed proliferating tumor cells with clear cytoplasm surrounded by hyalinizing stroma in the submucosal minor salivary glands. Immunohistochemical stains revealed these tumor cells to be positive for epithelial cell markers but negative for myoepithelial ones. These findings confirmed the diagnosis of HCCC. Good wound healing and no evidence of local recurrence and metastasis have been shown since surgery. PMID:26600962

  19. Programmed Application of Transforming Growth Factor β3 and Rac1 Inhibitor NSC23766 Committed Hyaline Cartilage Differentiation of Adipose-Derived Stem Cells for Osteochondral Defect Repair

    PubMed Central

    Zhu, Shouan; Chen, Pengfei; Wu, Yan; Xiong, Si; Sun, Heng; Xia, Qingqing; Shi, Libing

    2014-01-01

    Hyaline cartilage differentiation is always the challenge with application of stem cells for joint repair. Transforming growth factors (TGFs) and bone morphogenetic proteins can initiate cartilage differentiation but often lead to hypertrophy and calcification, related to abnormal Rac1 activity. In this study, we developed a strategy of programmed application of TGFβ3 and Rac1 inhibitor NSC23766 to commit the hyaline cartilage differentiation of adipose-derived stem cells (ADSCs) for joint cartilage repair. ADSCs were isolated and cultured in a micromass and pellet culture model to evaluate chondrogenic and hypertrophic differentiation. The function of Rac1 was investigated with constitutively active Rac1 mutant and dominant negative Rac1 mutant. The efficacy of ADSCs with programmed application of TGFβ3 and Rac1 inhibitor for cartilage repair was studied in a rat model of osteochondral defects. The results showed that TGFβ3 promoted ADSCs chondro-lineage differentiation and that NSC23766 prevented ADSC-derived chondrocytes from hypertrophy in vitro. The combination of ADSCs, TGFβ3, and NSC23766 promoted quality osteochondral defect repair in rats with much less chondrocytes hypertrophy and significantly higher International Cartilage Repair Society macroscopic and microscopic scores. The findings have illustrated that programmed application of TGFβ3 and Rac1 inhibitor NSC23766 can commit ADSCs to chondro-lineage differentiation and improve the efficacy of ADSCs for cartilage defect repair. These findings suggest a promising stem cell-based strategy for articular cartilage repair. PMID:25154784

  20. Bouncing droplets on a billiard table.

    PubMed

    Shirokoff, David

    2013-03-01

    In a set of experiments, Couder et al. demonstrate that an oscillating fluid bed may propagate a bouncing droplet through the guidance of the surface waves. I present a dynamical systems model, in the form of an iterative map, for a droplet on an oscillating bath. I examine the droplet bifurcation from bouncing to walking, and prescribe general requirements for the surface wave to support stable walking states. I show that in addition to walking, there is a region of large forcing that may support the chaotic motion of the droplet. Using the map, I then investigate the droplet trajectories in a square (billiard ball) domain. I show that in large domains, the long time trajectories are either non-periodic dense curves or approach a quasiperiodic orbit. In contrast, in small domains, at low forcing, trajectories tend to approach an array of circular attracting sets. As the forcing increases, the attracting sets break down and the droplet travels throughout space.

  1. Supercritical droplet combustion and related transport phenomena

    NASA Technical Reports Server (NTRS)

    Yang, Vigor; Hsieh, K. C.; Shuen, J. S.

    1993-01-01

    An overview of recent advances in theoretical analyses of supercritical droplet vaporization and combustion is conducted. Both hydrocarbon and cryogenic liquid droplets over a wide range of thermodynamic states are considered. Various important high-pressure effects on droplet behavior, such as thermodynamic non-ideality, transport anomaly, and property variation, are reviewed. Results indicate that the ambient gas pressure exerts significant control of droplet gasification and burning processes through its influence on fluid transport, gas-liquid interfacial thermodynamics, and chemical reactions. The droplet gasification rate increases progressively with pressure. However, the data for the overall burnout time exhibit a considerable change in the combustion mechanism at the criticl pressure, mainly as a result of reduced mass diffusivity and latent heat of vaporization with increased pressure. The influence of droplet size on the burning characteristics is also noted.

  2. Electropermanent magnet actuation for droplet ferromicrofluidics

    PubMed Central

    Padovani, José I.; Jeffrey, Stefanie S.; Howe, Roger T.

    2016-01-01

    Droplet actuation is an essential mechanism for droplet-based microfluidic systems. On-demand electromagnetic actuation is used in a ferrofluid-based microfluidic system for water droplet displacement. Electropermanent magnets (EPMs) are used to induce 50 mT magnetic fields in a ferrofluid filled microchannel with gradients up to 6.4 × 104 kA/m2. Short 50 µs current pulses activate the electropermanent magnets and generate negative magnetophoretic forces that range from 10 to 70 nN on 40 to 80 µm water-in-ferrofluid droplets. Maximum droplet displacement velocities of up to 300 µm/s are obtained under flow and no-flow conditions. Electropermanent magnet-activated droplet sorting under continuous flow is demonstrated using a split-junction microfluidic design. PMID:27583301

  3. Impact of Viscous Droplets on Superamphiphobic Surfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Binyu; Chen, Longquan; Deng, Xu

    2016-11-01

    Superamphiphobic coating is promising for various applications in industry, e.g. self-cleaning windows, where the impingement of droplets on surfaces is commonly encountered. In this work, we experimentally investigated the impact of droplets with similar surface tension (63-72 mN/m) but much different viscosity (1-150 mPa s) on superamphiphobic surfaces. We found that droplets can rebound from the superamphiphobic surfaces when the impact velocity is larger than a critical value, which linearly increases with the liquid viscosity. Droplet with higher viscosity spreads, retracts slower, and eventually rebounds lower and fewer times than that of low viscous droplet. These findings have important implications for surface engineers to use superamphiphobic coatings. Furthermore, we measured the maximum spreading factors for droplet impact on superamphiphobic surfaces and proposed a simple model based on energy conversation to describe its relationship to the Weber number and Reynolds number.

  4. A parameterization of cloud droplet nucleation

    SciTech Connect

    Ghan, S.J.; Chuang, C.C.; Penner, J.E.

    1994-01-01

    Droplet nucleation is a fundamental cloud process. The number of aerosols activated to form cloud droplets influences not only the number of aerosols scavenged by clouds but also the size of the cloud droplets. Cloud droplet size influences the cloud albedo and the conversion of cloud water to precipitation. Global aerosol models are presently being developed with the intention of coupling with global atmospheric circulation models to evaluate the influence of aerosols and aerosol-cloud interactions on climate. If these and other coupled models are to address issues of aerosol-interactions, the droplet nucleation process must be adequately represented. Ghan et al. have introduced a droplet nucleation parameterization for a single aerosol type that offers certain advantages over the popular Twomey parameterization. Here we describe the generalization of that parameterization to the case of multiple aerosol types, with estimation of aerosol mass as well as number activated.

  5. Electroporation of cells in microfluidic droplets.

    PubMed

    Zhan, Yihong; Wang, Jun; Bao, Ning; Lu, Chang

    2009-03-01

    Droplet-based microfluidics has raised a lot of interest recently due to its wide applications to screening biological/chemical assays with high throughput. Despite the advances on droplet-based assays involving cells, gene delivery methods that are compatible with the droplet platform have been lacking. In this report, we demonstrate a simple microfluidic device that encapsulates cells into aqueous droplets and then electroporates the encapsulated cells. The electroporation occurs when the cell-containing droplets (in oil) flow through a pair of microelectrodes with a constant voltage established in between. We investigate the parameters and characteristics of the electroporation. We demonstrate delivering enhanced green fluorescent protein (EGFP) plasmid into Chinese hamster ovary (CHO) cells. We envision the application of this technique to high-throughput functional genomics studies based on droplet microfluidics.

  6. Oscillatory combustion of liquid monopropellant droplets

    NASA Technical Reports Server (NTRS)

    Chanin, S. P.; Faeth, G. M.

    1976-01-01

    A theoretical investigation was conducted on the open-loop combustion response of monopropellant droplets and sprays to imposed pressure oscillations. The theoretical model was solved as a perturbation analysis through first order, yielding linear response results. Unsteady gas phase effects were considered in some cases, but the bulk of the calculations assumed a quasi-steady gas phase. Calculations were conducted using properties corresponding to hydrazine decomposition. Zero-order results agreed with earlier measurements of hydrazine droplet burning in combustion gases. The droplet response was greatest (exceeding unity in some cases) for large droplets with liquid phase temperature gradients; at frequencies near the characteristic frequency of the liquid phase thermal wave. The response of a spray is less than that of its largest droplet, however, a relatively small percentage of large droplets provides a substantial response (exceeding unity in some cases).

  7. Droplet Deformation Prediction With the Droplet Deformation and Breakup Model (DDB)

    NASA Technical Reports Server (NTRS)

    Vargas, Mario

    2012-01-01

    The Droplet Deformation and Breakup Model was used to predict deformation of droplets approaching the leading edge stagnation line of an airfoil. The quasi-steady model was solved for each position along the droplet path. A program was developed to solve the non-linear, second order, ordinary differential equation that governs the model. A fourth order Runge-Kutta method was used to solve the equation. Experimental slip velocities from droplet breakup studies were used as input to the model which required slip velocity along the particle path. The center of mass displacement predictions were compared to the experimental measurements from the droplet breakup studies for droplets with radii in the range of 200 to 700 mm approaching the airfoil at 50 and 90 m/sec. The model predictions were good for the displacement of the center of mass for small and medium sized droplets. For larger droplets the model predictions did not agree with the experimental results.

  8. Droplet Deformation Prediction with the Droplet Deormation and Break Up Model (DDB)

    NASA Technical Reports Server (NTRS)

    Vargas, Mario

    2012-01-01

    The Droplet Deformation and Breakup Model was used to predict deformation of droplets approaching the leading edge stagnation line of an airfoil. The quasi-steady model was solved for each position along the droplet path. A program was developed to solve the non-linear, second order, ordinary differential equation that governs the model. A fourth order Runge-Kutta method was used to solve the equation. Experimental slip velocities from droplet breakup studies were used as input to the model which required slip velocity along the particle path. The center of mass displacement predictions were compared to the experimental measurements from the droplet breakup studies for droplets with radii in the range of 200 to 700 mm approaching the airfoil at 50 and 90 m/sec. The model predictions were good for the displacement of the center of mass for small and medium sized droplets. For larger droplets the model predictions did not agree with the experimental results.

  9. Dispersion of Droplet Clouds in Turbulence.

    PubMed

    Bocanegra Evans, Humberto; Dam, Nico; Bertens, Guus; van der Voort, Dennis; van de Water, Willem

    2016-10-14

    We measure the absolute dispersion of clouds of monodisperse, phosphorescent droplets in turbulent air by means of high-speed image-intensified video recordings. Laser excitation allows the initial preparation of well-defined, pencil-shaped luminous droplet clouds in a completely nonintrusive way. We find that the dispersion of the clouds is faster than the dispersion of fluid elements. We speculate that preferential concentration of inertial droplet clouds is responsible for the enhanced dispersion.

  10. Droplet Vaporization in a Supercritical Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Curtis, E. W.; Farrell, P. V.

    1987-01-01

    A model is presented which describes single liquid droplet vaporization at nearly critical liquid pressures and temperatures. A modified Redlich-Kwong equation of state is used to evaluate the fugacities and liquid and vapor mole fractions at the interface under the assumption of interface equilibrium. Results obtained for different droplet sizes and conditions indicate significant differences in behavior in comparison with low-pressure quasi-steady droplet vaporization.

  11. Combustion of Unconfined Droplet Clusters in Microgravity

    NASA Technical Reports Server (NTRS)

    Ruff, G. A.; Liu, S.

    2001-01-01

    Combustion experiments using arrays of droplets seek to provide a link between single droplet combustion phenomena and the behavior of complex spray combustion systems. Both single droplet and droplet array studies have been conducted in microgravity to better isolate the droplet interaction phenomena and eliminate or reduce the confounding effects of buoyancy-induced convection. In most experiments involving droplet arrays, the droplets are supported on fibers to keep them stationary and close together before the combustion event. The presence of the fiber, however, disturbs the combustion process by introducing a source of heat transfer and asymmetry into the configuration. As the number of drops in a droplet array increases, supporting the drops on fibers becomes less practical because of the cumulative effect of the fibers on the combustion process. To eliminate the effect of the fiber, several researchers have conducted microgravity experiments using unsupported droplets. Jackson and Avedisian investigated single, unsupported drops while Nomura et al. studied droplet clouds formed by a condensation technique. The overall objective of this research is to extend the study of unsupported drops by investigating the combustion of well-characterized drop clusters in a microgravity environment. Direct experimental observations and measurements of the combustion of droplet clusters would fill a large gap in our current understanding of droplet and spray combustion and provide unique experimental data for the verification and improvement of spray combustion models. In this work, the formation of drop clusters is precisely controlled using an acoustic levitation system so that dilute, as well as dense clusters can be created and stabilized before combustion in microgravity is begun. This paper describes the design and performance of the 1-g experimental apparatus, some preliminary 1-g results, and plans for testing in microgravity.

  12. Droplet vaporization in a supercritical microgravity environment

    NASA Astrophysics Data System (ADS)

    Curtis, E. W.; Farrell, P. V.

    1987-10-01

    A model is presented which describes single liquid droplet vaporization at nearly critical liquid pressures and temperatures. A modified Redlich-Kwong equation of state is used to evaluate the fugacities and liquid and vapor mole fractions at the interface under the assumption of interface equilibrium. Results obtained for different droplet sizes and conditions indicate significant differences in behavior in comparison with low-pressure quasi-steady droplet vaporization.

  13. Pyrolysis of Large Black Liquor Droplets

    NASA Technical Reports Server (NTRS)

    Bartkus, Tadas P.; T'ien, James S.; Dietrich, Daniel L.; Wessel, Richard A.

    2007-01-01

    This paper presents the results of experiments involving the pyrolysis of large black liquor droplets in the NASA KC-135 reduced gravity aircraft. The reduced gravity environment facilitated the study of droplets up to 9 mm in diameter extending the results of previous studies to droplet sizes that are similar to those encountered in recovery boilers. Single black liquor droplets were rapidly inserted into a 923 K oven. The primary independent variables were the initial droplet diameter (0.5 mm to 9 mm), the black liquor solids content (66.12% - 72.9% by mass), and the ambient oxygen mole fraction (0.0 - 0.21). Video records of the experiments provided size and shape of the droplets as a function of time. The results show that the particle diameter at the end of the drying stage (D(sub DRY) ) increases linearly with the initial particle diameter (D(sub O)). The results further show that the ratio of the maximum swollen diameter (D(sub MAX)) to D(sub O) decreases with increasing D(sub O) for droplets with D(sub O) less than 4 mm. This ratio was independent of D(sub O) for droplets with D(sub O) greater than 4 mm. The particle is most spherical at the end of drying, and least spherical at maximum swollen size, regardless of initial sphericity and droplet size.

  14. Pyrolysis of Large Black Liquor Droplets

    NASA Technical Reports Server (NTRS)

    Bartkus, Tadas P.; Dietrich, Daniel L.; T'ien, James S.; Wessel, Richard A.

    2007-01-01

    This paper presents the results of experiments involving the pyrolysis of large black liquor droplets in the NASA KC-135 reduced gravity aircraft. The reduced gravity environment facilitated the study of droplets up to 9 mm in diameter extending the results of previous studies to droplet sizes that are similar to those encountered in recovery boilers. Single black liquor droplets were rapidly inserted into a 923 K oven. The primary independent variables were the initial droplet diameter (0.5 mm to 9 mm), the black liquor solids content (66.12% - 72.9% by mass), and the ambient oxygen mole fraction (0.0 - 0.21). Video records of the experiments provided size and shape of the droplets as a function of time. The results show that the particle diameter at the end of the drying stage (D(sub DRY)) increases linearly with the initial particle diameter (D(sub O)). The results further show that the ratio of the maximum swollen diameter (D(sub MAX)) to D(sub O) decreases with increasing D(sub O) for droplets with D(sub O) less than 4 mm. This ratio was independent of D(sub O) for droplets with D(sub O) greater than 4 mm. The particle is most spherical at the end of drying, and least spherical at maximum swollen size, regardless of initial sphericity and droplet size.

  15. A Theory of Shape-Shifting Droplets

    NASA Astrophysics Data System (ADS)

    Haas, Pierre; Goldstein, Raymond; Smoukov, Stoyan; Denkov, Nikolai

    2016-11-01

    Recent observations of cooled oil emulsion droplets uncovered a remarkable array of shape transformations: the initially spherical droplets flatten into polygonal shapes, first hexagons, then triangles or quadrilaterals that ultimately grow thin protrusions from their corners. These transformations are driven by a partial phase transition of the bulk liquid phase. In this talk, we explore theoretically the simplest geometric competition between this phase transition and surface tension in planar polygons. We recover the experimental sequence of shapes and predict shape statistics in qualitative agreement with experiments. Extending the model to capture some of the three-dimensional structure of the droplets, we analyse the topological transition of droplet puncture observed in experiments.

  16. Janus droplet as a catalytic micromotor

    NASA Astrophysics Data System (ADS)

    Shklyaev, Sergey

    2015-06-01

    Self-propulsion of a Janus droplet in a solution of surfactant, which reacts on a half of a drop surface, is studied theoretically. The droplet acts as a catalytic motor creating a concentration gradient, which generates its surface-tension-driven motion; the self-propulsion speed is rather high, 60 μ \\text{m/s} and more. This catalytic motor has several advantages over other micromotors: simple manufacturing, easily attained neutral buoyancy. In contrast to a single-fluid droplet, which demonstrates a self-propulsion as a result of symmetry breaking instability, for the Janus one no stability threshold exists; hence, the droplet radius can be scaled down to micrometers.

  17. Liquid Droplets on a Highly Deformable Membrane

    NASA Astrophysics Data System (ADS)

    Schulman, Rafael; Dalnoki-Veress, Kari

    2015-11-01

    We present measurements of the deformation produced by micro-droplets atop thin elastomeric and glassy free-standing films. Due to the Laplace pressure, the droplets deform the elastic membrane thereby forming a bulge. Thus, there are two angles that define the droplet/membrane geometry: the angle the liquid surface makes with the film and the angle the deformed bulge makes with the film. The contact line geometry is well captured by a Neumann construction which includes contributions from interfacial and mechanical tensions. Finally, we show that a droplet atop a film with biaxial tension assumes an equilibrium shape which is elongated along the axis of high tension.

  18. Droplet evaporation with complexity of evaporation modes

    NASA Astrophysics Data System (ADS)

    Hwang, In Gyu; Kim, Jin Young; Weon, Byung Mook

    2017-01-01

    Evaporation of a sessile droplet often exhibits a mixed evaporation mode, where the contact radius and the contact angle simultaneously vary with time. For sessile water droplets containing polymers with different initial polymer concentrations, we experimentally study their evaporation dynamics by measuring mass and volume changes. We show how diffusion-limited evaporation governs droplet evaporation, regardless of the complexity of evaporation behavior, and how the evaporation rate depends on the polymer concentration. Finally, we suggest a unified expression for a diffusion-limited evaporation rate for a sessile droplet with complexity in evaporation dynamics.

  19. Tin droplets for LPP EUV sources

    NASA Astrophysics Data System (ADS)

    Rollinger, Bob; Bozinova, Luna; Gambino, Nadia; Abhari, Reza S.

    2012-03-01

    The tin droplet generator is a key component of EUV LPP sources. Small tin droplets, when combined with a high power laser, form a regenerative target with high CE. A major challenge associated with today's EUV sources is energy stability, which directly correlates with the stability of the fuel delivery system. The LEC droplet dispenser is now in its 5th generation design, with several years of development, including studies of different nozzle types, excitation mechanisms, thermal management approaches and contamination control systems. The dispenser produces droplets in the frequency range required for both metrology and HVM EUV sources. The two relevant instability modes are drop-to-drop jitter and lateral instabilities. The low frequency content of the lateral droplet displacement is compensated by a newly implemented dispenser positioning system. The drop-to-drop jitter, which is studied over 2000 s, equals 11.2% (3σ) of the mean droplet spacing, which makes individual droplet laser triggering necessary. The lateral instabilities, which are mainly relevant in the plane perpendicular to the laser axis, are determined to be in the range of 7.1% (3σ) of the droplet diameter. The lateral displacements are recorded over 2.2 hrs. The related EUV temporal energy stability (open-loop) is estimated to be 0.35% (3σ) for the worst case scenario, a laser spot size which matches the droplet diameter.

  20. Droplet Charging Effects in the Space Environment

    SciTech Connect

    Joslyn, Thomas B.; Ketsdever, Andrew D.

    2011-05-20

    Several applications exist for transiting liquid droplets through the near-Earth space environment. Numerical results are presented for the charging of liquid droplets of trimethyl pentaphenyl siloxane (DC705) in three different plasma environments: ionosphere, auroral, and geosynchronous Earth orbit (GEO). Nominal and high geomagnetic activity cases are investigated. In general, high levels of droplet charging (>100 V) exist only in GEO during periods of high geomagnetic or solar activity. An experiment was conducted to assess the charging of silicon-oil droplets due to photoemission. The photoemission yield in the 120-200 nm wavelength range was found to be approximately 0.06.

  1. Coffee Stain Effect with Liquid Droplets

    NASA Astrophysics Data System (ADS)

    Mitra, Sushanta; Das, Siddhartha

    2012-11-01

    We discuss the dynamics of immiscible bidispersed oil droplets that are suspended in an evaporating water sessile drop. Therefore, in contrast to classical coffee stain problem, the depositing ``particles'' are replaced by microscopic oil droplets - hence, we discuss a liquid-droplet coffee stain phenomenon. We show experimentally that unlike colloidal particles in a classical coffee stain problem, liquid oil droplets cannot reach the three phase contact line (TPCL) due to the aversion of the oil droplets to form finite oil-air interface in water medium. Therefore, the oil droplets get positioned at a finite distance from the TPCL. We call this distance the ``enclosure'' distance, which being a function of the droplet size, triggers a spontaneous size-based oil droplet separation. In addition, the ``enclosure'' effect is a function of the surface energies of the oil droplet and the rate of evaporation. We develop a theory to describe this effect, and the results show excellent agreement with the experimental findings. NSERC Banting Postdoctoral Fellowship for S. Das.

  2. Fiber Supported Droplet Combustion-2 (FSDC-2)

    NASA Technical Reports Server (NTRS)

    Colantonio, Renato; Dietrich, Daniel; Haggard, John B., Jr.; Nayagan, Vedha; Dryer, Frederick L.; Shaw, Benjamin D.; Williams, Forman A.

    1998-01-01

    Experimental results for the burning characteristics of fiber supported, liquid droplets in ambient Shuttle cabin air (21% oxygen, 1 bar pressure) were obtained from the Glove Box Facility aboard the STS-94/MSL-1 mission using the Fiber Supported Droplet Combustion - 2 (FSDC-2) apparatus. The combustion of individual droplets of methanol/water mixtures, ethanol, ethanol/water azeotrope, n-heptane, n-decane, and n-heptane/n-hexadecane mixtures were studied in quiescent air. The effects of low velocity, laminar gas phase forced convection on the combustion of individual droplets of n-heptane and n-decane were investigated and interactions of two droplet-arrays of n-heptane and n-decane droplets were also studied with and without gas phase convective flow. Initial diameters ranging from about 2mm to over 6mm were burned on 80-100 micron silicon fibers. In addition to phenomenological observations, quantitative data were obtained in the form of backlit images of the burning droplets, overall flame images, and radiometric combustion emission measurements as a function of the burning time in each experiment. In all, 124 of the 129 attempted experiments (or about twice the number of experiments originally planned for the STS-94/MSL-1 mission) were conducted successfully. The experimental results contribute new observations on the combustion properties of pure alkanes, binary alkane mixtures, and simple alcohols for droplet sizes not studied previously, including measurements on individual droplets and two-droplet arrays, inclusive of the effects of forced gas phase convection. New phenomena characterized experimentally for the first time include radiative extinction of droplet burning for alkanes and the "twin effect" which occurs as a result of interactions during the combustion of two-droplet arrays. Numerical modeling of isolated droplet combustion phenomenon has been conducted for methanol/water mixtures, n-heptane, and n-heptane/n-hexadecane mixtures, and results

  3. Quantitative DNA Analysis Using Droplet Digital PCR.

    PubMed

    Vossen, Rolf H A M; White, Stefan J

    2017-01-01

    Droplet digital PCR (ddPCR) is based on the isolated amplification of thousands of individual DNA molecules simultaneously, with each molecule compartmentalized in a droplet. The presence of amplified product in each droplet is indicated by a fluorescent signal, and the proportion of positive droplets allows the precise quantification of a given sequence. In this chapter we briefly outline the basis of ddPCR, and describe two different applications using the Bio-Rad QX200 system: genotyping copy number variation and quantification of Illumina sequencing libraries.

  4. Lipid-induced structural turnover of water droplets to liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Sidiq, Sumyra; Pal, Santanu Kumar

    2014-04-01

    For the first time direct observation of structural turnover of water droplets to liquid crystal (LC) droplets with radial LC ordering was observed in presence of surfactants and lipids. Study of interactions between enzymes with the topological defects in the LC mediate the response of these droplets suggesting new principles for the design of chemical and biological sensors.

  5. Walking droplets in confined domains

    NASA Astrophysics Data System (ADS)

    Sáenz, Pedro; Bush, John

    2016-11-01

    A millimetric liquid drop can walk spontaneously along the surface of a vibrating fluid bath, propelled by a resonant interaction with its own wave field. These walking droplets exhibit features previously thought to be exclusive to the microscopic quantum realm. We here explore experimentally the dynamics and statistics of this macroscopic wave-particle system in confined domains, or 'corrals'. Particular attention is given to characterizing the influence of the corral geometry on the emergent probability distributions. The relation to analogous quantum systems (specifically, quantum corrals, the quantum mirage and scarring in Bose-Einstein condensates) is discussed. NSF support via CMMI-1333242.

  6. Droplet Vaporization In A Levitating Acoustic Field

    NASA Technical Reports Server (NTRS)

    Ruff, G. A.; Liu, S.; Ciobanescu, I.

    2003-01-01

    Combustion experiments using arrays of droplets seek to provide a link between single droplet combustion phenomena and the behavior of complex spray combustion systems. Both single droplet and droplet array studies have been conducted in microgravity to better isolate the droplet interaction phenomena and eliminate or reduce the effects of buoyancy-induced convection. In most experiments involving droplet arrays, the droplets are supported on fibers to keep them stationary and close together before the combustion event. The presence of the fiber, however, disturbs the combustion process by introducing a source of heat transfer and asymmetry into the configuration. As the number of drops in a droplet array increases, supporting the drops on fibers becomes less practical because of the cumulative effect of the fibers on the combustion process. To eliminate the effect of the fiber, several researchers have conducted microgravity experiments using unsupported droplets. Jackson and Avedisian investigated single, unsupported drops while Nomura et al. studied droplet clouds formed by a condensation technique. The overall objective of this research is to extend the study of unsupported drops by investigating the combustion of well-characterized drop clusters in a microgravity environment. Direct experimental observations and measurements of the combustion of droplet clusters would provide unique experimental data for the verification and improvement of spray combustion models. In this work, the formation of drop clusters is precisely controlled using an acoustic levitation system so that dilute, as well as dense clusters can be created and stabilized before combustion in microgravity is begun. While the low-gravity test facility is being completed, tests have been conducted in 1-g to characterize the effect of the acoustic field on the vaporization of single and multiple droplets. This is important because in the combustion experiment, the droplets will be formed and

  7. Effect of droplet shape on ring stains from dried liquid

    NASA Astrophysics Data System (ADS)

    Santiago, Melvin; Brown, Katherine; Mathur, Harsh

    A landmark experimental paper on coffee stains by Deegan et al included a simple theoretical analysis of circular droplets. The analysis was based on a model informally called the Maxwell House equations. It describes the evolving height profile of the droplet, the evaporation of the solvent and the outflow of solute to the rim of the droplet. Since typical droplets are not circles, here we extend the analysis to more general shapes. We find that for thin droplets the height profile may be determined by solving Poisson's equation in a domain corresponding to the footprint of the droplet. Evaporation is treated in a simple approximation via an electrostatic analogy and is dominated by the sharp edges of the droplet. Assuming zero vorticity allows us to analyze the solvent flow in droplets of arbitrary shape. We compare circular droplets to other shapes including long linear droplets, ring shaped droplets and droplets with an elliptical footprint

  8. Vortices catapult droplets in atomization

    NASA Astrophysics Data System (ADS)

    John Soundar Jerome, J.; Marty, Sylvain; Matas, Jean-Philippe; Zaleski, Stephane; Hoepffner, Jerome

    2013-11-01

    A droplet ejection mechanism in planar two-phase mixing layers is examined. Any disturbance on the gas-liquid interface grows into a Kelvin-Helmholtz wave and the wave crest forms a thin liquid film that flaps as the wave grows downstream. Increasing the gas speed, it is observed that the film breaks-up into droplets which are eventually thrown into the gas stream at large angles. In a flow where most of the momentum is in the horizontal direction, it is surprising to observe these large ejection angles. Our experiments and simulations show that a recirculation region grows downstream of the wave and leads to vortex shedding similar to the wake of a backward-facing step. The ejection mechanism results from the interaction between the liquid film and the vortex shedding sequence: a recirculation zone appears in the wake of the wave and a liquid film emerges from the wave crest; the recirculation region detaches into a vortex and the gas flow over the wave momentarily reattaches due to the departure of the vortex; this reattached flow pushes the liquid film down; by now, a new recirculation vortex is being created in the wake of the wave-just where the liquid film is now located; the liquid film is blown-up from below by the newly formed recirculation vortex in a manner similar to a bag-breakup event.

  9. Droplet turbulence interactions under subcritical and supercritical conditions

    NASA Technical Reports Server (NTRS)

    Coy, E. B.; Greenfield, S. C.; Ondas, M. S.; Song, Y.-H.; Spegar, T. D.; Santavicca, D. A.

    1993-01-01

    The goal of this research is to experimentally characterize the behavior of droplets in vaporizing liquid sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag, droplet heating, droplet vaporization, droplet distortion, and secondary droplet breakup, under both subcritical and supercritical conditions. The paper presents a brief description of the specific accomplishments which have been made over the past year.

  10. Synchronous universal droplet logic and control

    NASA Astrophysics Data System (ADS)

    Katsikis, Georgios; Cybulski, James S.; Prakash, Manu

    2015-07-01

    Droplets are versatile digital materials; they can be produced at high throughput, perform chemical reactions as miniature beakers and carry biological entities. Droplets have been manipulated with electric, optical, acoustic and magnetic forces, but all these methods use serial controls to address individual droplets. An alternative is algorithmic manipulation based on logic operations that automatically compute where droplets are stored or directed, thereby enabling parallel control. However, logic previously implemented in low-Reynolds-number droplet hydrodynamics is asynchronous and thus prone to errors that prevent scaling up the complexity of logic operations. Here we present a platform for error-free physical computation via synchronous universal logic. Our platform uses a rotating magnetic field that enables parallel manipulation of arbitrary numbers of ferrofluid droplets on permalloy tracks. Through the coupling of magnetic and hydrodynamic interaction forces between droplets, we developed AND, OR, XOR, NOT and NAND logic gates, fanouts, a full adder, a flip-flop and a finite-state machine. Our platform enables large-scale integration of droplet logic, analogous to the scaling seen in digital electronics, and opens new avenues in mesoscale material processing.

  11. Orientation Dependence of Jumping Droplet Condensation

    NASA Astrophysics Data System (ADS)

    Berrier, Austin; Boreyko, Jonathan; Nature-Inspired Fluids; Interfaces Team

    2015-11-01

    On nanostructured superhydrophobic surfaces, microscopic condensate exhibits out-of-plane jumping that minimizes the average droplet size for maximal phase-change heat transfer. This jumping-droplet phenomenon occurs independently of gravity and is due to surface energy being partially converted to kinetic energy upon coalescence events. Although the initial departure of the jumping droplets is independent of gravity, the subsequent trajectories exhibit a dependence upon the orientation of the substrate. The drop size distribution of jumping-droplet condensation growing on a superhydrophobic substrate was characterized for both horizontal and vertical surface orientations. With the horizontal orientation, jumping condensate returns to the substrate by gravity. While this can result in chain reactions with other droplets to trigger further jumping events, eventually the rebounding droplets become too large to jump and are stuck on the surface. In contrast, droplets jumping off a vertically oriented surface do not return to the substrate. For this reason, the maximum droplet diameters during condensation growth were found to be significantly larger on the horizontally oriented superhydrophobic surface than on the vertical orientation.

  12. Analysis of coalescence behavior for compressed droplets

    NASA Astrophysics Data System (ADS)

    Choi, Sung Woong; Lee, Dong Eon; Lee, Woo Il; Kim, Han Sang

    2017-03-01

    Coalescence of droplets is a significant phenomenon, and it has been adapted to many applications such as raindrop formation, emulsion polymerization, ink-jet printing, coating, and multiphase flows. In this study, the morphological characteristics of two compressed adjacent droplets between two parallel plates were investigated to study the phenomenon of coalescence of droplets. By controlling the distance of the dispensed droplets, various results for coalescence of droplets were evaluated, especially, from the view of the minor axis, major axis, and meniscus liquid bridge of the coalesced droplet. Experimental results show that the length of the meniscus liquid bridge rapidly increases and then the rate of increase slows with time. The increase rate of the major and minor axes is largely influenced by the meniscus liquid bridge, which is mainly due to the curvature between the droplets. The numerical modeling of the coalescence of the two compressed droplets between two parallel plates was presented and simulation was conducted to realize the coalescence behavior. Comparison with numerical simulation showed that there was a good agreement with the experimental results.

  13. Binary droplet collision at high Weber number

    NASA Astrophysics Data System (ADS)

    Pan, Kuo-Long; Chou, Ping-Chung; Tseng, Yu-Jen

    2009-09-01

    By using the techniques developed for generating high-speed droplets, we have systematically investigated binary droplet collision when the Weber number (We) was increased from the range usually tested in previous studies on the order of 10 to a much larger value of about 5100 for water (a droplet at 23 m/s with a diameter of 0.7 mm). Various liquids were also used to explore the effects of viscosity and surface tension. Specifically, beyond the well-known regimes at moderate We’s, which exhibited coalescence, separation, and separation followed by satellite droplets, we found different behaviors showing a fingering lamella, separation after fingering, breakup of outer fingers, and prompt splattering into multiple secondary droplets as We was increased. The critical Weber numbers that mark the boundaries between these impact regimes are identified. The specific impact behaviors, such as fingering and prompt splattering or splashing, share essential similarity with those also observed in droplet-surface impacts, whereas substantial variations in the transition boundaries may result from the disparity of the boundary conditions at impacts. To compare the outcomes of both types of collisions, a simple model based on energy conservation was carried out to predict the maximum diameter of an expanding liquid disk for a binary droplet collision. The results oppose the dominance of viscous drag, as proposed by previous studies, as the main deceleration force to effect a Rayleigh-Taylor instability and ensuing periphery fingers, which may further lead to the formations of satellite droplets.

  14. Dynamic Morphologies of Microscale Droplet Interface Bilayers

    SciTech Connect

    Mruetusatorn, Prachya; Boreyko, Jonathan B; Sarles, Stephen A; Venkatesan, Guru; Hayes, Douglas G; Collier, Pat

    2014-01-01

    Droplet interface bilayers (DIBs) are a powerful platform for studying the dynamics of synthetic cellular membranes; however, very little has been done to exploit the unique dynamical features of DIBs. Here, we generate microscale droplet interface bilayers ( DIBs) by bringing together femtoliter-volume water droplets in a microfluidic oil channel, and characterize morphological changes of the DIBs as the droplets shrink due to evaporation. By varying the initial conditions of the system, we identify three distinct classes of dynamic morphology. (1) Buckling and Fission: When forming DIBs using the lipid-out method (lipids in oil phase), lipids in the shrinking monolayers continually pair together and slide into the bilayer to conserve their mass. As the bilayer continues to grow, it becomes confined, buckles, and eventually fissions one or more vesicles. (2) Uniform Shrinking: When using the lipid-in method (lipids in water phase) to form DIBs, lipids uniformly transfer from the monolayers and bilayer into vesicles contained inside the water droplets. (3) Stretching and Unzipping: Finally, when the droplets are pinned to the wall(s) of the microfluidic channel, the droplets become stretched during evaporation, culminating in the unzipping of the bilayer and droplet separation. These findings offer a better understanding of the dynamics of coupled lipid interfaces.

  15. Droplet freezing, docking, and the exchange of immiscible phase and surfactant around frozen droplets.

    PubMed

    Sgro, Allyson E; Chiu, Daniel T

    2010-07-21

    This paper describes a platform for cooling microfluidic chips so as to freeze aqueous droplets flowing in oil. Using a whole-chip cooling chamber, we can control the ambient temperature surrounding a microfluidic chip and induce cooling and freezing inside the channels. When combined with a droplet generation and droplet docking chip, this platform allows for the facile freezing of droplets immobilized in resistance-based docks. Depending on the design and shape of the docks, the frozen droplets can either be trapped stably in the docks or be released because deformed non-frozen aqueous droplets turn spherical when frozen, and thus can become dislodged from the docks. Additionally, using this chamber and chip combination we are able to exchange immiscible phases and surfactants surrounding the frozen droplets. The materials and methods are inexpensive and easily accessible to microfluidics researchers, making this a simple addition to an existing microfluidic platform.

  16. Fiber-Supported Droplet Combustion Experiment-2

    NASA Technical Reports Server (NTRS)

    Colantonio, Renato O.

    1998-01-01

    A major portion of the energy produced in the world today comes from the burning of liquid hydrocarbon fuels in the form of droplets. Understanding the fundamental physical processes involved in droplet combustion is not only important in energy production but also in propulsion, in the mitigation of combustion-generated pollution, and in the control of the fire hazards associated with handling liquid combustibles. Microgravity makes spherically symmetric combustion possible, allowing investigators to easily validate their droplet models without the complicating effects of gravity. The Fiber-Supported Droplet Combustion (FSDC-2) investigation was conducted in the Microgravity Glovebox facility of the shuttles' Spacelab during the reflight of the Microgravity Science Laboratory (MSL- 1R) on STS-94 in July 1997. FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and duo droplets with and without forced air convection. FSDC-2 is sponsored by the NASA Lewis Research Center, whose researchers are working in cooperation with several investigators from industry and academia. The rate at which a droplet burns is important in many commercial applications. The classical theory of droplet burning assumes that, for an isolated, spherically symmetric, single-fuel droplet, the gas-phase combustion processes are much faster than the droplet surface regression rate and that the liquid phase is at a uniform temperature equal to the boiling point. Recent, more advanced models predict that both the liquid and gas phases are unsteady during a substantial portion of the droplet's burning history, thus affecting the instantaneous and average burning rates, and that flame radiation is a dominant mechanism that can extinguish flames in a microgravity environment. FSDC-2 has provided well-defined, symmetric droplet burning data including radiative emissions to validate these theoretical

  17. Settling of fixed erythrocyte suspension droplets

    NASA Technical Reports Server (NTRS)

    Omenyi, S. N.; Snyder, R. S.

    1983-01-01

    It is pointed out that when particles behave collectively rather than individually, the fractionation of micron-size particles on the basis of size, density, and surface characteristics by centrifugation and electrophoresis is hindered. The formation and sedimentation of droplets containing particles represent an extreme example of collective behavior and pose a major problem for these separation methods when large quantities of particles need to be fractionated. Experiments are described that measure droplet sizes and settling rates for a variety of particles and droplets. Expressions relating the particle concentration in a drop to measurable quantities of the fluids and particles are developed. The number of particles in each droplet is then estimated, together with the effective droplet density. Red blood cells from different animals fixed in glutaraldehyde provide model particle groups.

  18. Droplet microfluidics in (bio)chemical analysis.

    PubMed

    Basova, Evgenia Yu; Foret, Frantisek

    2015-01-07

    Droplet microfluidics may soon change the paradigm of performing chemical analyses and related instrumentation. It can improve not only the analysis scale, possibility for sensitivity improvement, and reduced consumption of chemical and biological reagents, but also the speed of performing a variety of unit operations. At present, microfluidic platforms can reproducibly generate monodisperse droplet populations at kHz or higher rates with droplet sizes suitable for high-throughput experiments, single-cell detection or even single molecule analysis. In addition to being used as microreactors with volume in the micro- to femtoliter range, droplet based systems have also been used to directly synthesize particles and encapsulate biological entities for biomedicine and biotechnology applications. This minireview summarizes various droplet microfluidics operations and applications for (bio)chemical assays described in the literature during the past few years.

  19. Removal of biofilms by impinging water droplets

    NASA Astrophysics Data System (ADS)

    Cense, A. W.; van Dongen, M. E. H.; Gottenbos, B.; Nuijs, A. M.; Shulepov, S. Y.

    2006-12-01

    The process of impinging water droplets on Streptococcus mutans biofilms was studied experimentally and numerically. Droplets were experimentally produced by natural breakup of a cylindrical liquid jet. Droplet diameter and velocity were varied between 20 and 200 μm and between 20 and 100 m/s, respectively. The resulting erosion process of the biofilm was determined experimentally with high-speed recording techniques and a quantitative relationship between the removal rate, droplet size, and velocity was determined. The shear stress and the pressure on the surface during droplet impact were determined by numerical simulations, and a qualitative agreement between the experiment and the simulation was obtained. Furthermore, it was shown that the stresses on the surface are strongly reduced when a water film is present.

  20. Kinetics of complex plasma with liquid droplets

    NASA Astrophysics Data System (ADS)

    Misra, Shikha; Mishra, S. K.; Sodha, M. S.

    2013-12-01

    This paper provides a theoretical basis for the reduction of electron density by spray of water (or other liquids) in hot plasma. This phenomenon has been observed in a hypersonic flight experiment for relief of radio black out, caused by high ionization in the plasma sheath of a hypersonic vehicle, re-entering the atmosphere. The analysis incorporates a rather little known phenomenon for de-charging of the droplets, viz., evaporation of ions from the surface and includes the charge balance on the droplets and number cum energy balance of electrons, ions, and neutral molecules; the energy balance of the evaporating droplets has also been taken into account. The analysis has been applied to a realistic situation and the transient variations of the charge and radius of water droplets, and other plasma parameters have been obtained and discussed. The analysis through made in the context of water droplets is applicable to all liquids.

  1. Capillary droplet propulsion on a fibre.

    PubMed

    Haefner, Sabrina; Bäumchen, Oliver; Jacobs, Karin

    2015-09-21

    A viscous liquid film coating a fibre becomes unstable and decays into droplets due to the Rayleigh-Plateau instability (RPI). Here, we report on the generation of uniform droplets on a hydrophobized fibre by taking advantage of this effect. In the late stages of liquid column breakup, a three-phase contact line can be formed at one side of the droplet by spontaneous rupture of the thinning film. The resulting capillary imbalance leads to droplet propulsion along the fibre. We study the dynamics and the dewetting speed of the droplet as a function of molecular weight as well as temperature and compare to a force balance model based on purely viscous dissipation.

  2. Soot agglomeration in isolated, free droplet combustion

    NASA Technical Reports Server (NTRS)

    Choi, M. Y.; Dryer, F. L.; Green, G. J.; Sangiovanni, J. J.

    1993-01-01

    Under the conditions of an isolated, free droplet experiment, hollow, carbonaceous structures, called soot spheres, were observed to form during the atmospheric pressure, low Reynolds number combustion of 1-methylnaphthalene. These structures which are agglomerates composed of smaller spheroidal units result from both thermophoretic effects induced by the envelope flame surrounding each drop and aerodynamic effects caused by changes in the relative gas/drop velocities. A chemically reacting flow model was used to analyze the process of sootshell formation during microgravity droplet combustion. The time-dependent temperature and gas property field surrounding the droplet was determined, and the soot cloud location for microgravity combustion of n-heptane droplets was predicted. Experiments showed that the sooting propensity of n-alkane fuel droplets can be varied through diluent substitution, oxygen-index variations, and ambient pressure reductions.

  3. Droplet mixers: Microfluidics, mixing measures and optimization

    NASA Astrophysics Data System (ADS)

    Stone, Zachary; Stone, Howard

    2003-11-01

    Rapid mixing is essential in a variety of microfluidic applications but is often difficult to achieve at low Reynolds numbers. Inspired by a recently developed microdevice that mixes reagents in droplets, which simply flow along a periodic serpentine channel (Song, Tice and Ismagilov, 2003), we investigate a model ``droplet mixer". The model consists of a spherical droplet immersed in a periodic sequence of distinct external flows, which are superpositions of uniform and shear flows. We label the fluid inside the droplet with two colors and visualize mixing with a method we call ``backtrace imaging", which allows us to render cross-sections of the droplet at arbitrary times during the mixing cycle. To analyze our results, we present a simple measure of mixing, which allows us to locate sets of parameters that optimize mixing over a small number of flow cycles. We also consider shear flows in multiple directions and the effect of random variations in the durations of external flows.

  4. Autophagy and Lipid Droplets in the Liver.

    PubMed

    Martinez-Lopez, Nuria; Singh, Rajat

    2015-01-01

    Autophagy is a conserved quality-control pathway that degrades cytoplasmic contents in lysosomes. Autophagy degrades lipid droplets through a process termed lipophagy. Starvation and an acute lipid stimulus increase autophagic sequestration of lipid droplets and their degradation in lysosomes. Accordingly, liver-specific deletion of the autophagy gene Atg7 increases hepatic fat content, mimicking the human condition termed nonalcoholic fatty liver disease. In this review, we provide insights into the molecular regulation of lipophagy, discuss fundamental questions related to the mechanisms by which autophagosomes recognize lipid droplets and how ATG proteins regulate membrane curvature for lipid droplet sequestration, and comment on the possibility of cross talk between lipophagy and cytosolic lipases in lipid mobilization. Finally, we discuss the contribution of lipophagy to the pathophysiology of human fatty liver disease. Understanding how lipophagy clears hepatocellular lipid droplets could provide new ways to prevent fatty liver disease, a major epidemic in developed nations.

  5. The Lipid-Droplet Proteome Reveals that Droplets Are a Protein-Storage Depot

    SciTech Connect

    Cermelli, Silvia; Guo, Yi; Gross, Steven P.; Welte, Michael

    2006-09-19

    Lipid droplets are ubiquitous organelles that are among the basic building blocks of eukaryotic cells. Despite central roles for cholesterol homeostasis and lipid metabolism, their function and protein composition are poorly understood. Results: We purified lipid droplets from Drosophila embryos and analyzed the associated proteins by capillary LC-MS-MS. Important functional groups include enzymes involved in lipid metabolism, signaling molecules, and proteins related to membrane trafficking. Unexpectedly, histones H2A, H2Av, and H2B were present. Using biochemistry, genetics, real-time imaging, and cell biology, we confirm that roughly 50% of certain embryonic histones are physically attached to lipid droplets, a localization conserved in other fly species. Histone association with droplets starts during oogenesis and is prominent in early embryos, but it is undetectable in later stages or in cultured cells. Histones on droplets are not irreversibly trapped; quantitation of droplet histone levels and transplantation experiments suggest that histones are transferred from droplets to nuclei as development proceeds. When this maternal store of histones is unavailable because lipid droplets are mislocalized, zygotic histone production starts prematurely. Conclusions: Because we uncover a striking proteomic similarity of Drosophila droplets to mammalian lipid droplets, Drosophila likely provides a good model for understanding droplet function in general. Our analysis also reveals a new function for these organelles; the massive nature of histone association with droplets and its developmental time-course suggest that droplets sequester maternally provided proteins until they are needed. We propose that lipid droplets can serve as transient storage depots for proteins that lack appropriate binding partners in the cell. Such sequestration may provide a general cellular strategy for handling excess proteins.

  6. Two Droplets on Wire Approaching Ignition

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber-Supported Droplet Combustion (FSDC) uses two droplets positioned on the fiber wire, instead of the usual one. Two droplets more closely simulates the environment in engines, which ignite many fuel droplets at once. The behavior of the burning was also unexpected -- the droplets moved together after ignition, generating quite a bit of data for understanding the interaction of fuel droplets while they burn. This MPEG movie (1.3 MB) shows a time-lapse of this burn (3x speed). Because FSDC is backlit (the bright glow behind the drops), you carnot see the glow of the droplets while they burn -- instead, you see them shrink! The small blobs left on the wire after the burn are the beads used to center the fuel droplet on the wire. This image was taken on STS-94, July 12, 1997, MET:10/19:13 (approximate). FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations planned for the International Space Station. (1.3MB, 12-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300178.html.

  7. Droplet migration characteristics in confined oscillatory microflows

    NASA Astrophysics Data System (ADS)

    Chaudhury, Kaustav; Mandal, Shubhadeep; Chakraborty, Suman

    2016-02-01

    We analyze the migration characteristics of a droplet in an oscillatory flow field in a parallel plate microconfinement. Using phase field formalism, we capture the dynamical evolution of the droplet over a wide range of the frequency of the imposed oscillation in the flow field, drop size relative to the channel gap, and the capillary number. The latter two factors imply the contribution of droplet deformability, commonly considered in the study of droplet migration under steady shear flow conditions. We show that the imposed oscillation brings an additional time complexity in the droplet movement, realized through temporally varying drop shape, flow direction, and the inertial response of the droplet. As a consequence, we observe a spatially complicated pathway of the droplet along the transverse direction, in sharp contrast to the smooth migration under a similar yet steady shear flow condition. Intuitively, the longitudinal component of the droplet movement is in tandem with the flow continuity and evolves with time at the same frequency as that of the imposed oscillation, although with an amplitude decreasing with the frequency. The time complexity of the transverse component of the movement pattern, however, cannot be rationalized through such intuitive arguments. Towards bringing out the underlying physics, we further endeavor in a reciprocal identity based analysis. Following this approach, we unveil the time complexities of the droplet movement, which appear to be sufficient to rationalize the complex movement patterns observed through the comprehensive simulation studies. These results can be of profound importance in designing droplet based microfluidic systems in an oscillatory flow environment.

  8. Extensively Myxoid and Hyalinized Sinonasal Capillary Hemangiomas: A Clinicopathologic Study of 16 Cases of a Distinctive and Potentially Confusing Hemangioma Variant.

    PubMed

    Guo, Ruifeng; Folpe, Andrew L

    2015-11-01

    Capillary hemangiomas, the most common vascular tumors of the sinonasal region, are benign endothelial neoplasms, typically growing in an easily recognized lobular pattern. Some sinonasal capillary hemangiomas may show atypical features, such as high cellularity or mitotic activity, and represent more challenging diagnoses. Over the past several years we have seen in consultation a number of examples of sinonasal capillary hemangiomas displaying very striking stromal myxoid change and hyalinization, features that have received scant attention in the past. Available slides from 16 sinonasal capillary hemangiomas previously coded as showing such changes were retrieved from our archives. Submitting diagnoses included "query angiofibroma, rule out malignancy" (N=4), "vascular polyp, rule out malignancy" (N=3), "query malignant vascular tumor" (N=4), "sinonasal hemangiopericytoma" (N=1), and "benign vascular tumor" (N=1). Available radiographic studies often showed worrisome features. Grossly, the tumors ranged from 1.1 to 6.0 cm and appeared as ulcerated, vascular-appearing polyps. Microscopically, the tumors showed striking stromal myxoid change and/or hyalinization, which largely obscured the underlying lobular capillary arrangement. Within this myxohyaline matrix, a florid capillary proliferation was present, frequently with nonatypical mitotic activity. In some instances a branching, "hemangiopericytoma-like" vascular pattern was present in areas. The overall cellularity was low to moderate, and endothelial atypia or hyperchromatism was absent. Ulceration and thrombosis were frequently present. Immunostains to CD31, CD34, and SMA highlighted areas of lobular growth pattern inapparent on the routinely stained slides. Four tested cases were negative for androgen receptors and β-catenin. Follow-up from 12 patients revealed no local recurrences or metastases. Awareness of that sinonasal capillary hemangioma may show these unusual stromal changes, and the use of

  9. Directional Movement of Droplets in Grooves: Suspended or Immersed?

    PubMed Central

    Xu, Wei; Lan, Zhong; Peng, Benli; Wen, Rongfu; Chen, Yansong; Ma, Xuehu

    2016-01-01

    The behavior of droplets trapped in geometric structures is essential to droplet manipulation applications such as for droplet transport. Here we show that directional droplet movement can be realized by a V-shaped groove with the movement direction controlled by adjusting the surface wettability of the groove inner wall and the cross sectional angle of the groove. Experiments and analyses show that a droplet in a superhydrophobic groove translates from the immersed state to the suspended state as the cross sectional angle of the groove decreases and the suspended droplet departs from the groove bottom as the droplet volume increases. We also demonstrate that this simple grooved structure can be used to separate a water-oil mixture and generate droplets with the desired sizes. The structural effect actuated droplet movements provide a controllable droplet transport method which can be used in a wide range of droplet manipulation applications. PMID:26743167

  10. Directional Movement of Droplets in Grooves: Suspended or Immersed?

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Lan, Zhong; Peng, Benli; Wen, Rongfu; Chen, Yansong; Ma, Xuehu

    2016-01-01

    The behavior of droplets trapped in geometric structures is essential to droplet manipulation applications such as for droplet transport. Here we show that directional droplet movement can be realized by a V-shaped groove with the movement direction controlled by adjusting the surface wettability of the groove inner wall and the cross sectional angle of the groove. Experiments and analyses show that a droplet in a superhydrophobic groove translates from the immersed state to the suspended state as the cross sectional angle of the groove decreases and the suspended droplet departs from the groove bottom as the droplet volume increases. We also demonstrate that this simple grooved structure can be used to separate a water-oil mixture and generate droplets with the desired sizes. The structural effect actuated droplet movements provide a controllable droplet transport method which can be used in a wide range of droplet manipulation applications.

  11. Combustion of interacting droplet arrays in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Dietrich, Daniel L.

    1995-01-01

    This research program involves the study of one and two dimensional arrays of droplets in a buoyant-free environment. The purpose of the work is to extend the database and theories that exist for single droplets into the regime where droplet interactions are important. The eventual goal being to use the results of this work as inputs to models on spray combustion where droplets seldom burn individually; instead the combustion history of a droplet is strongly influenced by the presence of the neighboring droplets. Throughout the course of the work, a number of related aspects of isolated droplet combustion have also been investigated. This paper will review our progress in microgravity droplet array combustion, advanced diagnostics (specifically L2) applied to isolated droplet combustion, and radiative extinction large droplet flames. A small-scale droplet combustion experiment being developed for the Space Shuttle will also be described.

  12. Fluoropolymer surface coatings to control droplets in microfluidic devices.

    PubMed

    Riche, Carson T; Zhang, Chuchu; Gupta, Malancha; Malmstadt, Noah

    2014-06-07

    We have demonstrated the application of low surface energy fluoropolymer coatings onto poly(dimethylsiloxane) (PDMS) microfluidic devices for droplet formation and extraction-induced merger of droplets. Initiated chemical vapor deposition (iCVD) was used to pattern fluoropolymer coatings within microchannels based on geometrical constraints. In a two-phase flow system, the range of accessible flow rates for droplet formation was greatly enhanced in the coated devices. The ability to controllably apply the coating only at the inlet facilitated a method for merging droplets. An organic spacer droplet was extracted from between a pair of aqueous droplets. The size of the organic droplet and the flow rate controlled the time to merge the aqueous droplets; the process of merging was independent of the droplet sizes. Extraction-induced droplet merging is a robust method for manipulating droplets that could be applied in translating multi-step reactions to microfluidic platforms.

  13. Spreading of a granular droplet

    NASA Astrophysics Data System (ADS)

    Clement, Eric; Sanchez, Ivan; Raynaud, Franck; Lanuza, Jose; Andreotti, Bruno; Aranson, Igor

    2008-03-01

    The influence of controlled vibrations on the granular rheology is investigated in a specifically designed experiment in which a granular film spreads under the action of horizontal vibrations. A nonlinear diffusion equation is derived theoretically that describes the evolution of the deposit shape. A self-similar parabolic shape (the``granular droplet'') and a spreading dynamics are predicted that both agree quantitatively with the experimental results. The theoretical analysis is used to extract effective friction coefficients between the base and the granular layer under sustained and controlled vibrations. A shear thickening regime characteristic of dense granular flows is evidenced at low vibration energy, both for glass beads and natural sand. Conversely, shear thinning is observed at high agitation.

  14. Freezing of stratospheric aerosol droplets

    NASA Astrophysics Data System (ADS)

    Luo, Beiping; Peter, Thomas; Crutzen, Paul

    Theoretical calculations are presented for homogeneous and heterogeneous freezing of sulfuric acid droplets under stratospheric conditions, based on classical nucleation theory. In contrast to previous results it is shown that a prominent candidate for freezing, sulfuric acid tetrahydrate (SAT ≡ H2SO4·4H2O), does not freeze homogeneously. The theoretical results limit the homogeneous freezing rate at 200 K to much less than 1 cm-3s-1, a value that may be estimated from bulk phase laboratory experiments. This suggests that the experimental value is likely to be a measure of heterogeneous, not homogeneous nucleation. Thus, under statospheric conditions, freezing of SAT can only occur in the presence of suitable nuclei; however, even for heterogeneous nucleation experimental results impose strong constraints. Since a nitric acid trihydrate (NAT) embryo probably needs a solid body for nucleation, these results put an important constraint on the theory of NAT formation in polar stratospheric clouds.

  15. Numerical simulations of pendant droplets

    NASA Astrophysics Data System (ADS)

    Pena, Carlos; Kahouadji, Lyes; Matar, Omar; Chergui, Jalel; Juric, Damir; Shin, Seungwon

    2015-11-01

    We simulate the evolution of a three-dimensional pendant droplet through pinch-off using a new parallel two-phase flow solver called BLUE. The parallelization of the code is based on the technique of algebraic domain decomposition where the velocity field is solved by a parallel GMRes method for the viscous terms and the pressure by a parallel multigrid/GMRes method. Communication is handled by MPI message passing procedures. The method for the treatment of the fluid interfaces uses a hybrid Front Tracking/Level Set technique which defines the interface both by a discontinuous density field as well as by a local triangular Lagrangian mesh. This structure allows the interface to undergo large deformations including the rupture and coalescence of fluid interfaces. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

  16. Self-propelled droplet behavior during condensation on superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Chu, Fuqiang; Wu, Xiaomin; Zhu, Bei; Zhang, Xuan

    2016-05-01

    Self-propelled droplet motion has applications in various engineering fields such as self-cleaning surfaces, heat transfer enhancement, and anti-icing methods. A superhydrophobic surface was fabricated using two simultaneous chemical reactions with droplet condensation experiments performed on the horizontal superhydrophobic surface to characterize the droplet behavior. The droplet behavior is classified into three types based on their motion features and leftover marks as immobile droplet coalescence, self-propelled droplet jumping, and self-propelled droplet sweeping. This study focuses on the droplet sweeping that occurs due to the ultra-small rolling angle of the superhydrophobic surface, where the resulting droplet sweeps along the surface, merging with all the droplets it meets and leaving a long, narrow, clear track with a large droplet at the end of the track. An easy method is developed to predict the droplet sweeping direction based on the relative positions of the droplets just before coalescence. The droplet sweeping always absorbs dozens of droplets and is not limited by the surface structures; thus, this sweeping has many useful applications. In addition, the relationships between the droplet behavior and the number of participating droplets are also analyzed statistically.

  17. Small GTPase Rab40c Associates with Lipid Droplets and Modulates the Biogenesis of Lipid Droplets

    PubMed Central

    Tan, Ran; Wang, Weijie; Wang, Shicong; Wang, Zhen; Sun, Lixiang; He, Wei; Fan, Rong; Zhou, Yunhe; Xu, Xiaohui; Hong, Wanjin; Wang, Tuanlao

    2013-01-01

    The subcellular location and cell biological function of small GTPase Rab40c in mammalian cells have not been investigated in detail. In this study, we demonstrated that the exogenously expressed GFP-Rab40c associates with lipid droplets marked by neutral lipid specific dye Oil red or Nile red, but not with the Golgi or endosomal markers. Further examination demonstrated that Rab40c is also associated with ERGIC-53 containing structures, especially under the serum starvation condition. Rab40c is increasingly recruited to the surface of lipid droplets during lipid droplets formation and maturation in HepG2 cells. Rab40c knockdown moderately decreases the size of lipid droplets, suggesting that Rab40c is involved in the biogenesis of lipid droplets. Stimulation for adipocyte differentiation increases the expression of Rab40c in 3T3-L1 cells. Rab40c interacts with TIP47, and is appositionally associated with TIP47-labeled lipid droplets. In addition, over-expression of Rab40c causes the clustering of lipid droplets independent of its GTPase activity, but completely dependent of the intact SOCS box domain of Rab40c. In addition, Rab40c displayed self-interaction as well as interaction with TIP47 and the SOCS box is essential for its ability to induce clustering of lipid droplets. Our results suggest that Rab40c is a novel Rab protein associated with lipid droplets, and is likely involved in modulating the biogenesis of lipid droplets. PMID:23638186

  18. Droplet vaporization in supercritical pressure environments

    NASA Astrophysics Data System (ADS)

    Farrell, Patrick V.; Peters, Bruce D.

    For most liquid-fueled combustion systems the behavior of the fuel as it is introduced to the combustion zone, often by spray injection, will have a significant impact on combustion. The subsequent combustion may be affected to a considerable degree by the initial spread of the liquid, break-up of larger fuel sheets and droplets into droplets of various sizes, droplet vaporization, and diffusion of gaseous fuel. Among the many factors which affect spray break-up and droplet vaporization are the environmental conditions into which the spray is introduced. For both diesel engines and rockets the environment pressure and temperature may be above the critical pressure and temperature of the injected fuel. In a compression-ignition internal combustion engine, the environment consists primarily of air, at pressures from 20 to 100 atmospheres and temperatures ranging from 900 to 1500 K. Even higher pressures are encountered in turbocharged diesels. A typical diesel reference fuel, dodecane, has a thermodynamic critical pressure of about 17 atmospheres, and a critical temperature of 600 K. Fuel is injected into a diesel engine environment in which ambient pressures exceed the critical pressure. While droplet temperatures are subcritical at first, they may rise to the critical temperature or higher. This paper will survey current understanding of supercritical pressure droplet vaporization. Specifically, the topics covered will include: liquid phase behavior; vapor phase behavior; thermodynamic and transport properties; droplet distribution and break-up; micro-explosions; and effects of microgravity.

  19. Three dimensional force balance of asymmetric droplets

    NASA Astrophysics Data System (ADS)

    Kim, Yeseul; Lim, Su Jin; Cho, Kun; Weon, Byung Mook

    2016-11-01

    An equilibrium contact angle of a droplet is determined by a horizontal force balance among vapor, liquid, and solid, which is known as Young's law. Conventional wetting law is valid only for axis-symmetric droplets, whereas real droplets are often asymmetric. Here we show that three-dimensional geometry must be considered for a force balance for asymmetric droplets. By visualizing asymmetric droplets placed on a free-standing membrane in air with X-ray microscopy, we are able to identify that force balances in one side and in other side control pinning behaviors during evaporation of droplets. We find that X-ray microscopy is powerful for realizing the three-dimensional force balance, which would be essential in interpretation and manipulation of wetting, spreading, and drying dynamics for asymmetric droplets. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1D1A1B01007133).

  20. Mechanical vibration of viscoelastic liquid droplets

    NASA Astrophysics Data System (ADS)

    Sharp, James; Harrold, Victoria

    2014-03-01

    The resonant vibrations of viscoelastic sessile droplets supported on different substrates were monitored using a simple laser light scattering technique. In these experiments, laser light was reflected from the surfaces of droplets of high Mw poly acrylamide-co-acrylic acid (PAA) dissolved in water. The scattered light was allowed to fall on the surface of a photodiode detector and a mechanical impulse was applied to the drops using a vibration motor mounted beneath the substrates. The mechanical impulse caused the droplets to vibrate and the scattered light moved across the surface of the photodiode. The resulting time dependent photodiode signal was then Fourier transformed to obtain the mechanical vibrational spectra of the droplets. The frequencies and widths of the resonant peaks were extracted for droplets containing different concentrations of PAA and with a range of sizes. This was repeated for PAA loaded water drops on surfaces which displayed different values of the three phase contact angle. The results were compared to a simple model of droplet vibration which considers the formation of standing wave states on the surface of a viscoelastic droplet. We gratefully acknowledge the support of the Leverhulme trust under grant number RPG-2012-702.

  1. Lipid droplet dynamics in skeletal muscle.

    PubMed

    Bosma, Madeleen

    2016-01-15

    The skeletal muscle is subjected to high mechanical and energetic demands. Lipid droplets are an important source of energy substrates for the working muscle. Muscle cells contain a variety of lipid droplets, which are fundamentally smaller than those found in adipocytes. This translates into a greater lipid droplet surface area serving as the interface for intracellular lipid metabolism. The skeletal muscle has a high plasticity, it is subjected to major remodeling following training and detraining. This coincides with adaptations in lipid droplet characteristics and dynamics. The majority of lipid droplets in skeletal muscle are located in the subsarcolemmal region or in-between the myofibrils, in close vicinity to mitochondria. The vastly organized nature of skeletal muscle fibers limits organelle mobility. The high metabolic rate and substrate turnover in skeletal muscle demands a strict coordination of intramyocellular lipid metabolism and LD dynamics, in which lipid droplet coat proteins play an important role. This review provides insights into the characteristics, diversity and dynamics of skeletal muscle lipid droplets.

  2. Bi-Component Droplet Combustion Experiment Designed

    NASA Technical Reports Server (NTRS)

    Dietrich, Daniel L.

    2002-01-01

    The combustion of liquid fuels is a major source of energy in the world today, and the majority of these fuels are burned in the form of a spray. The research at the NASA Glenn Research Center in droplet combustion has the overall goal of providing a better understanding of spray combustion by studying the smallest element in a spray, the single droplet. The Bi-Component Droplet Combustion Experiment (BCDCE) extends the work at Glenn from pure, or single-component, fuels to an idealized liquid fuel composed of two completely miscible components. The project is a collaborative effort between Glenn and Prof. B.D. Shaw of the University of California, Davis. The BCDCE project is planned to fly onboard the International Space Station in the Multi-User Droplet Combustion Apparatus. The unique feature of this experiment is that it will be the first droplet combustion experiment to perform a detailed characterization of the flow inside a liquid fuel droplet. The experiment will use a relatively new technique called Digital Particle Imaging Velocimetry (DPIV) to characterize the liquid flow. In this technique, very small (approx. 5-mm diameter) particles are dispersed throughout a liquid droplet. These particles are illuminated by a thin laser sheet. Images of the particle motion are recorded on a computer, which then tracks the motion of the particles to determine the flow characteristics.

  3. Statistical steady state in turbulent droplet condensation

    NASA Astrophysics Data System (ADS)

    Siewert, Christoph; Bec, Jérémie; Krstulovic, Giorgio

    2017-01-01

    Motivated by systems in which droplets grow and shrink in a turbulence-driven supersaturation field, we investigate the problem of turbulent condensation in a general manner. Using direct numerical simulations we show that the turbulent fluctuations of the supersaturation field offer different conditions for the growth of droplets which evolve in time due to turbulent transport and mixing. Based on that, we propose a Lagrangian stochastic model for condensation and evaporation of small droplets in turbulent flows. It consists of a set of stochastic integro-differential equations for the joint evolution of the squared radius and the supersaturation along the droplet trajectories. The model has two parameters fixed by the total amount of water and the thermodynamic properties, as well as the Lagrangian integral timescale of the turbulent supersaturation. The model reproduces very well the droplet size distributions obtained from direct numerical simulations and their time evolution. A noticeable result is that, after a stage where the squared radius simply diffuses, the system converges exponentially fast to a statistical steady state independent of the initial conditions. The main mechanism involved in this convergence is a loss of memory induced by a significant number of droplets undergoing a complete evaporation before growing again. The statistical steady state is characterised by an exponential tail in the droplet mass distribution. These results reconcile those of earlier numerical studies, once these various regimes are considered.

  4. Photoacoustic spectral characterization of perfluorocarbon droplets

    NASA Astrophysics Data System (ADS)

    Strohm, Eric; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael

    2012-02-01

    Perfluorocarbon droplets containing optical absorbing nanoparticles have been developed for use as theranostic agents (for both imaging and therapy) and as dual-mode contrast agents. Droplets can be used as photoacoustic contrast agents, vaporized via optical irradiation, then the resulting bubbles can be used as ultrasound imaging and therapeutic agents. The photoacoustic signals from micron-sized droplets containing silica coated gold nanospheres were measured using ultra-high frequencies (100-1000 MHz). The spectra of droplets embedded in a gelatin phantom were compared to a theoretical model which calculates the pressure wave from a spherical homogenous liquid undergoing thermoelastic expansion resulting from laser absorption. The location of the spectral features of the theoretical model and experimental spectra were in agreement after accounting for increases in the droplet sound speed with frequency. The agreement between experiment and model indicate that droplets (which have negligible optical absorption in the visible and infrared spectra by themselves) emitted pressure waves related to the droplet composition and size, and was independent of the physical characteristics of the optical absorbing nanoparticles. The diameter of individual droplets was calculated using three independent methods: the time domain photoacoustic signal, the time domain pulse echo ultrasound signal, and a fit to the photoacoustic model, then compared to the diameter as measured by optical microscopy. It was found the photoacoustic and ultrasound methods calculated diameters an average of 2.6% of each other, and 8.8% lower than that measured using optical microscopy. The discrepancy between the calculated diameters and the optical measurements may be due to the difficulty in resolving the droplet edges after being embedded in the translucent gelatin medium.

  5. Mass Spectrometry of Acoustically Levitated Droplets

    PubMed Central

    Westphall, Michael S.; Jorabchi, Kaveh; Smith, Lloyd M.

    2008-01-01

    Containerless sample handling techniques such as acoustic levitation offer potential advantages for mass spectrometry, by eliminating surfaces where undesired adsorption/desorption processes can occur. In addition, they provide a unique opportunity to study fundamental aspects of the ionization process as well as phenomena occurring at the air–droplet interface. Realizing these advantages is contingent, however, upon being able to effectively interface levitated droplets with a mass spectrometer, a challenging task that is addressed in this report. We have employed a newly developed charge and matrix-assisted laser desorption/ionization (CALDI) technique to obtain mass spectra from a 5-μL acoustically levitated droplet containing peptides and an ionic matrix. A four-ring electrostatic lens is used in conjunction with a corona needle to produce bursts of corona ions and to direct those ions toward the droplet, resulting in droplet charging. Analyte ions are produced from the droplet by a 337-nm laser pulse and detected by an atmospheric sampling mass spectrometer. The ion generation and extraction cycle is repeated at 20 Hz, the maximum operating frequency of the laser employed. It is shown in delayed ion extraction experiments that both positive and negative ions are produced, behavior similar to that observed for atmospheric pressure matrix-assisted laser absorption/ionization. No ion signal is observed in the absence of droplet charging. It is likely, although not yet proven, that the role of the droplet charging is to increase the strength of the electric field at the surface of the droplet, reducing chargere combination after ion desorption. PMID:18582090

  6. Fog droplet distribution functions for lidar.

    PubMed

    Mallow, J V

    1982-04-15

    The interpretation of lidar data on fog has been limited by two obstacles: approximations in the form of the Mie scattering cross sections for water droplets, and droplet size distribution functions whose relationship to the experiment has not been clear. This paper develops a method for generating distribution functions from experimental data. These functions are then used with newly available Mie cross sections to obtain backscattering and extinction coefficients for singly scattered ruby laser pulses in fog. The results show what experimental lidar accuracies are needed to uniquely determine fog droplet size distribution.

  7. Fog droplet distribution functions for lidar

    SciTech Connect

    Mallow, J.V.

    1982-04-15

    The interpretation of lidar data on fog has been limited by two obstacles: approximations in the form of the Mie scattering cross sections for water droplets, and droplet size distribution functions whose relationship to the experiment has not been clear. This paper develops a method for generating distribution functions from experimental data. These functions are then used with newly available Mie cross sections to obtain backscattering and extinction coefficients for singly scattered ruby laser pulses in fog. The results show what experimental lidar accuracies are needed to uniquely determine fog droplet size distribution.

  8. Foam droplet separation for nanoparticle synthesis

    NASA Astrophysics Data System (ADS)

    Tyree, Corey A.; Allen, Jonathan O.

    2008-03-01

    A novel approach to nanoparticle synthesis was developed whereby foam bubble bursting produced aerosol droplets, an approach patterned after the marine foam aerosol cycle. The droplets were dried to remove solvent, leaving nanometer-sized particles composed of precursor material. Nanoparticles composed of sodium chloride (mean diameter, bar{D}_p≈ 100 nm), phosphotungstic acid (bar{D}_p≈ 55 nm), and bovine insulin ({D}_p≈ 5-30 nm) were synthesized. Foam droplet separation can be carried out at ambient temperature and pressure. The `soft' nature of the process makes it compatible with a wide range of materials.

  9. Orbiting droplets on a vibrated bath

    NASA Astrophysics Data System (ADS)

    Sampara, Naresh; Burger, Loic; Gilet, Tristan; Microfluidics, university of liege Team

    2015-11-01

    A millimeter-sized oil droplet can bounce on a vertically vibrated liquid bath for unlimited time. It may couple to the surface wave it emits; leading to horizontal self-propulsion called walking. When several walkers coexist close to one another, they either repel or attract each other, in response to the superposition of the waves they generate. Attraction leads to various bound states, including droplets that orbit around each other. We have experimentally investigated the variety of quantized orbital motions exhibited by two, three and more identical walkers, as a function of forcing acceleration. Each motion is quantified in terms of droplet and wave energy.

  10. The effects of turbulence on droplet drag and secondary droplet breakup

    NASA Technical Reports Server (NTRS)

    Song, Y.-H.; Coy, E.; Greenfield, S.; Ondas, M.; Prevish, T.; Spegar, T.; Santavicca, D.

    1994-01-01

    The objective of this research is to obtain an improved understanding of the behavior of droplets in vaporizing sprays, particularly under conditions typical of those in high pressure rocket sprays. Experiments are conducted in a variety of high pressure, high temperature, optically-accessible flow systems, including one which is capable of operation at pressures up to 70 atm, temperatures up to 600 K, gas velocities up to 30 m/sec and turbulence intensities up to 40 percent. Single droplets, 50 to 500 micron in diameter, are produced by an aerodynamic droplet generator and transversely injected into the flow. Measurements are made of the droplet position, size, velocity and temperature and of the droplet's vapor wake from which droplet drag, dispersion, heating, vaporization and breakup are characterized.

  11. Numerical methods and calculations for droplet flow, heating and ignition

    NASA Technical Reports Server (NTRS)

    Dwyer, H. A.; Sanders, B. R.; Dandy, D.

    1982-01-01

    A numerical method was devised and employed to solve a variety of problems related to liquid droplet combustion. The basic transport equations of mass, momentum and energy were formulated in terms of generalized nonorthogonal coordinates, which allows for adaptive griding and arbitrary particle shape. Example problems are solved for internal droplet heating, droplet ignition and high Reynolds number flow over a droplet.

  12. Selectively splitting a droplet using superhydrophobic stripes on hydrophilic surfaces.

    PubMed

    Song, Dong; Song, Baowei; Hu, Haibao; Du, Xiaosong; Zhou, Feng

    2015-06-07

    Superhydrophobic patterns were fabricated on hydrophilic surfaces by selective painting. The impinging process of water droplets on these hybrid surfaces was investigated. The droplet can be split by impinging on the hydrophilic surface with a single stripe at a high velocity. The time to split the droplet is independent of the impact velocity and it is smaller than the contact time of a droplet impinging on the fully superhydrophobic surface. The volume ratios of the split mini-droplets could be precisely controlled by adjusting the landing position of the original droplet. The droplet could be split uniformly into more mini-marbles by increasing the stripe numbers.

  13. A review of droplet resonators: Operation method and application

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Li, Hanyang; Zhao, Liyuan; Wu, Bing; Liu, Shuangqiang; Liu, Yongjun; Yang, Jun

    2016-12-01

    Droplet resonators hold promise as a special class of optical cavities for numerous applications in micro-optical. Owing to liquid surface tension, droplet resonators possess nearly perfect spherical geometry and exceptionally smooth surfaces that prompt more and more meritorious applications to be exploit. Herein, we survey two typical operation methods of the droplet resonators, passive and active droplet resonator. Besides, droplet applications as high-performance lasers and sensors have been discussed. Although these applications have brought us tremendous value, the research for droplet resonators are still in its infancy, added potential application and intrinsic investigation of the droplet resonators should be developed in the future work.

  14. Interaction Effects on Combustion of Alcohol Droplet Pairs

    NASA Astrophysics Data System (ADS)

    Okai, Keiichi; Ono, Yutaka; Moriue, Osamu; Shiba, Seiji; Araki, Mikiya; Nomura, Hiroshi; Shiga, Seiichi; Tsue, Mitsuhiro; Kono, Michikata

    Experimental investigation was conducted on two droplet-array combustion of methanol and methanol/dodecanol mixture fuels in microgravity. For methanol, effects of ambient pressure and droplet spacing were examined. Results show that the droplet lifetime decreases with increasing spacing at relatively low pressure and the droplet lifetime becomes independent of spacing at higher-subcritical and supercritical pressures. For methanol/dodecanol mixture, effects of pressure, fuel composition were investigated in terms of occurrence of disruption. Disruption of droplet during combustion was demonstrated both for single droplet and droplet pairs.

  15. Quasistatic packings of droplets in flat microfluidic channels

    NASA Astrophysics Data System (ADS)

    Kadivar, Erfan

    2016-02-01

    As observed in recent experiments, monodisperse droplets self-assemble spontaneously in different ordered packings. In this work, we present a numerical study of the droplet packings in the flat rectangular microfluidic channels. Employing the boundary element method, we numerically solve the Stokes equation in two-dimension and investigate the appearance of droplet packing and transition between one and two-row packings of monodisperse emulsion droplets. By calculating packing force applied on the droplet interface, we investigate the effect of flow rate, droplet size, and surface tension on the packing configurations of droplets and transition between different topological packings.

  16. Electrostatic charging and control of droplets in microfluidic devices.

    PubMed

    Zhou, Hongbo; Yao, Shuhuai

    2013-03-07

    Precharged droplets can facilitate manipulation and control of low-volume liquids in droplet-based microfluidics. In this paper, we demonstrate non-contact electrostatic charging of droplets by polarizing a neutral droplet and splitting it into two oppositely charged daughter droplets in a T-junction microchannel. We performed numerical simulation to analyze the non-contact charging process and proposed a new design with a notch at the T-junction in aid of droplet splitting for more efficient charging. We experimentally characterized the induced charge in droplets in microfabricated devices. The experimental results agreed well with the simulation. Finally, we demonstrated highly effective droplet manipulation in a path selection unit appending to the droplet charging. We expect our work could enable precision manipulation of droplets for more complex liquid handling in microfluidics and promote electric-force based manipulation in 'lab-on-a-chip' systems.

  17. Effects of droplet interactions on droplet transport at intermediate Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.

    1986-01-01

    Effects of droplet interactions on drag, evaporation, and combustion of a planar droplet array, oriented perpendicular to the approaching flow, are studied numerically. The three-dimensional Navier-Stokes equations, with variable thermophysical properties, are solved using finite-difference techniques. Parameters investigated include the droplet spacing, droplet Reynolds number, approaching stream oxygen concentration, and fuel type. Results are obtained for the Reynolds number range of 5 to 100, droplet spacing from 2 to 24 diameters, oxygen concentrations of 0.1 and 0.2, and methanol and n-butanol fuels. The calculations show that the gasification rates of interacting droplets decrease as the droplet spacings decrease. The reduction in gasification rates is significant only at small spacings and low Reynolds numbers. For the present array orientation, the effects of interactions on the gasification rates diminish rapidly for Reynolds numbers greater than 10 and spacings greater than 6 droplet diameters. The effects of adjacent droplets on drag are shown to be small.

  18. Tetrachromacy, oil droplets and bird plumage colours.

    PubMed

    Vorobyev, M; Osorio, D; Bennett, A T; Marshall, N J; Cuthill, I C

    1998-11-01

    There is a growing body of data on avian eyes, including measurements of visual pigment and oil droplet spectral absorption, and of receptor densities and their distributions across the retina. These data are sufficient to predict psychophysical colour discrimination thresholds for light-adapted eyes, and hence provide a basis for relating eye design to visual needs. We examine the advantages of coloured oil droplets, UV vision and tetrachromacy for discriminating a diverse set of avian plumage spectra under natural illumination. Discriminability is enhanced both by tetrachromacy and coloured oil droplets. Oil droplets may also improve colour constancy. Comparison of the performance of a pigeon's eye, where the shortest wavelength receptor peak is at 410 nm, with that of the passerine Leiothrix, where the ultraviolet-sensitive peak is at 365 nm, generally shows a small advantage to the latter, but this advantage depends critically on the noise level in the sensitivity mechanism and on the set of spectra being viewed.

  19. Investigation of critical burning of fuel droplets

    NASA Technical Reports Server (NTRS)

    Faeth, G. M.

    1979-01-01

    The general problem of spray combustion was investigated. The combustion of bipropellent droplets; combustion of hydrozine fuels; and combustion of sprays were studied. A model was developed to predict mean velocities and temperatures in a combusting gas jet.

  20. Immersed Boundary Simulations of Active Fluid Droplets

    PubMed Central

    Hawkins, Rhoda J.

    2016-01-01

    We present numerical simulations of active fluid droplets immersed in an external fluid in 2-dimensions using an Immersed Boundary method to simulate the fluid droplet interface as a Lagrangian mesh. We present results from two example systems, firstly an active isotropic fluid boundary consisting of particles that can bind and unbind from the interface and generate surface tension gradients through active contractility. Secondly, a droplet filled with an active polar fluid with homeotropic anchoring at the droplet interface. These two systems demonstrate spontaneous symmetry breaking and steady state dynamics resembling cell motility and division and show complex feedback mechanisms with minimal degrees of freedom. The simulations outlined here will be useful for quantifying the wide range of dynamics observable in these active systems and modelling the effects of confinement in a consistent and adaptable way. PMID:27606609

  1. Nucleation pressure threshold in acoustic droplet vaporization

    NASA Astrophysics Data System (ADS)

    Miles, Christopher; Doering, Charles; Kripfgans, Oliver

    2016-11-01

    We combine classical nucleation theory with superharmonic focusing to predict necessary pressures to induce nucleation in acoustic droplet vaporization. We show that linear acoustics is a valid approximation to leading order when particle displacements in the sound field are small relative the radius of the droplet. This is done by perturbation analysis of an axisymmetric compressible inviscid flow about a droplet with small surface perturbations relative to the mean radius subjected to an incoming ultrasonic wave. The necessary nucleation pressure threshold inside the droplet is calculated to be - 9 . 33 +/- 0 . 30 MPa for typical experimental parameters by employing results from classical homogeneous nucleation theory. As a result we are able to predict if a given incident pressure waveform will induce nucleation. This research was supported by the Rackham Merit Fellowship, the University of Michigan Physics department, the University of Michigan's MCubed program, and NSF awards PHY-1205219 and DMS-1515161.

  2. Swimming active droplet: A theoretical analysis

    NASA Astrophysics Data System (ADS)

    Schmitt, M.; Stark, H.

    2013-02-01

    Recently, an active microswimmer was constructed where a micron-sized droplet of bromine water was placed into a surfactant-laden oil phase. Due to a bromination reaction of the surfactant at the interface, the surface tension locally increases and becomes non-uniform. This drives a Marangoni flow which propels the squirming droplet forward. We develop a diffusion-advection-reaction equation for the order parameter of the surfactant mixture at the droplet interface using a mixing free energy. Numerical solutions reveal a stable swimming regime above a critical Marangoni number M but also stopping and oscillating states when M is increased further. The swimming droplet is identified as a pusher whereas in the oscillating state it oscillates between being a puller and a pusher.

  3. Impact of droplet on superheated surfaces

    NASA Astrophysics Data System (ADS)

    Lohse, Detlef; Staat, Hendrik J. J.; Tran, Tuan; Prosperetti, Andrea; Sun, Chao

    2012-11-01

    At impact of a liquid droplet on a smooth surface heated way above the liquid's boiling point, the droplet spreads without any surface contact, floating on its own (Leidenfrost-type) vapor layer, and then bounces back. We show that the dimensionless maximum spreading factor Γ, defined by the ratio of the maximal spreading diameter and the droplet diameter, shows a universal scaling Γ ~ Weγ with the Weber number We - regardless of surface temperature and of liquid properties - which is much steeper than that for the impact on non-heated (hydrophilic or hydrophobic) surfaces, for which γ = 1 / 4 . Based on the idea that the vapor shooting out of the gap between the droplet and the superheated surface drags the liquid outwards, we derive scaling laws for the spreading factor Γ, the vapor layer thickness, and the vapor flow velocity.

  4. Droplet Breakup in Expansion-contraction Microchannels

    PubMed Central

    Zhu, Pingan; Kong, Tiantian; Lei, Leyan; Tian, Xiaowei; Kang, Zhanxiao; Wang, Liqiu

    2016-01-01

    We investigate the influences of expansion-contraction microchannels on droplet breakup in capillary microfluidic devices. With variations in channel dimension, local shear stresses at the injection nozzle and focusing orifice vary, significantly impacting flow behavior including droplet breakup locations and breakup modes. We observe transition of droplet breakup location from focusing orifice to injection nozzle, and three distinct types of recently-reported tip-multi-breaking modes. By balancing local shear stresses and interfacial tension effects, we determine the critical condition for breakup location transition, and characterize the tip-multi-breaking mode quantitatively. In addition, we identify the mechanism responsible for the periodic oscillation of inner fluid tip in tip-multi-breaking mode. Our results offer fundamental understanding of two-phase flow behaviors in expansion-contraction microstructures, and would benefit droplet generation, manipulation and design of microfluidic devices. PMID:26899018

  5. Droplet Microfluidics for Chip-Based Diagnostics

    PubMed Central

    Kaler, Karan V. I. S.; Prakash, Ravi

    2014-01-01

    Droplet microfluidics (DMF) is a fluidic handling technology that enables precision control over dispensing and subsequent manipulation of droplets in the volume range of microliters to picoliters, on a micro-fabricated device. There are several different droplet actuation methods, all of which can generate external stimuli, to either actively or passively control the shape and positioning of fluidic droplets over patterned substrates. In this review article, we focus on the operation and utility of electro-actuation-based DMF devices, which utilize one or more micro-/nano-patterned substrates to facilitate electric field-based handling of chemical and/or biological samples. The underlying theory of DMF actuations, device fabrication methods and integration of optical and opto-electronic detectors is discussed in this review. Example applications of such electro-actuation-based DMF devices have also been included, illustrating the various actuation methods and their utility in conducting chip-based laboratory and clinical diagnostic assays. PMID:25490590

  6. Numerical Simulations of Acoustically Driven, Burning Droplets

    NASA Technical Reports Server (NTRS)

    Kim, H.-C.; Karagozian, A. R.; Smith, O. I.; Urban, Dave (Technical Monitor)

    1999-01-01

    This computational study focuses on understanding and quantifying the effects of external acoustical perturbations on droplet combustion. A one-dimensional, axisymmetric representation of the essential diffusion and reaction processes occurring in the vicinity of the droplet stagnation point is used here in order to isolate the effects of the imposed acoustic disturbance. The simulation is performed using a third order accurate, essentially non-oscillatory (ENO) numerical scheme with a full methanol-air reaction mechanism. Consistent with recent microgravity and normal gravity combustion experiments, focus is placed on conditions where the droplet is situated at a velocity antinode in order for the droplet to experience the greatest effects of fluid mechanical straining of flame structures. The effects of imposed sound pressure level and frequency are explored here, and conditions leading to maximum burning rates are identified.

  7. Dispensing nano-pico droplets of ferrofluids

    NASA Astrophysics Data System (ADS)

    Irajizad, Peyman; Farokhnia, Nazanin; Ghasemi, Hadi

    2015-11-01

    Dispensing miniature volumes of a ferrofluid is of fundamental and practical importance for diverse applications ranging from biomedical devices, optics, and self-assembly of materials. Current dispensing systems are based on microfluidics flow-focusing approaches or acoustic actuation requiring complicated structures. A simple method is presented to continuously dispense the miniature droplets from a ferrofluid reservoir. Once a jet of the ferrofluid is subjected to a constrained flux through a membrane and an inhomogeneous magnetic field, the jet experiences a curvature-driven instability and transforms to a droplet. Ferrofluid droplets in the range of 0.1-1000 nl are dispensed with tunable dispensing frequencies. A model is developed that predicts the dispensed volume of the ferrofluid droplets with an excellent agreement with the measurements.

  8. Biofilm Formation in Microscopic Double Emulsion Droplets

    NASA Astrophysics Data System (ADS)

    Chang, Connie; Weitz, David

    2012-02-01

    In natural, medical, and industrial settings, there exist surface-associated communities of bacteria known as biofilms. These highly structured films are composed of bacterial cells embedded within self-produced extracellular matrix, usually composed of exopolysaccharides, proteins, and nucleic acids; this matrix serves to protect the bacterial community from antibiotics and environmental stressors. Here, we form biofilms encapsulated within monodisperse, microscopically-sized double emulsion droplets using microfluidics. The bacteria self-organize at the inner liquid-liquid droplet interfaces, multiply, and differentiate into extracellular matrix-producing cells, forming manifold three-dimensional shell-within-a-shell structures of biofilms, templated upon the inner core of spherical liquid droplets. By using microfluidics to encapsulate bacterial cells, we have the ability to view individual cells multiplying in microscopically-sized droplets, which allows for high-throughput analysis in studying the genetic program leading to biofilm development, or cell signaling that induces differentiation.

  9. Vibrational modes of elongated sessile liquid droplets.

    PubMed

    Temperton, Robert H; Sharp, James S

    2013-04-16

    Vibrations of small (microliter) sessile liquid droplets were studied using a simple optical deflection technique. The droplets were made to elongate in one direction by taking advantage of the anisotropic wetting of the liquids on structured diffraction grating surfaces. They were vibrated by applying a puff of nitrogen gas. Motion of the droplets was monitored by scattering laser light from their surfaces. The scattered light was collected using a photodiode, and the resulting time-dependent intensity signals were Fourier-transformed to obtain the vibrational response of the drops. The vibrational spectra of elongated sessile drops were observed to contain two closely spaced peaks. A simple model that considers the frequency of capillary wave fluctuations on the surfaces of the drops was used to show that the vibrational frequencies of these peaks correspond to standing wave states that exist along the major and minor profile lengths of the droplets.

  10. Micro-droplets lubrication film thickness dynamics

    NASA Astrophysics Data System (ADS)

    Huerre, Axel; Theodoly, Olivier; Cantat, Isabelle; Leshansky, Alexander; Valignat, Marie-Pierre; Jullien, Marie-Caroline; MMN Team; LAI Team; IPR Team; Department of Chemical Engineering Team

    2014-11-01

    The motion of droplets or bubbles in confined geometries has been extensively studied; showing an intrinsic relationship between the lubrication film thickness and the droplet velocity. When capillary forces dominate, the lubrication film thickness evolves non linearly with the capillary number due to viscous dissipation between meniscus and wall. However, this film may become thin enough that intermolecular forces come into play and affect classical scalings. We report here the first experimental evidence of the disjoining pressure effect on confined droplets by measuring droplet lubrication film thicknesses in a microfluidic Hele-Shaw cell. We find and characterize two distinct dynamical regimes, dominated respectively by capillary and intermolecular forces. In the former case rolling boundary conditions at the interface are evidenced through film thickness dynamics, interface velocity measurement and film thickness profile.

  11. How faceted liquid droplets grow tails

    PubMed Central

    Guttman, Shani; Sapir, Zvi; Schultz, Moty; Butenko, Alexander V.; Ocko, Benjamin M.; Deutsch, Moshe; Sloutskin, Eli

    2016-01-01

    Liquid droplets, widely encountered in everyday life, have no flat facets. Here we show that water-dispersed oil droplets can be reversibly temperature-tuned to icosahedral and other faceted shapes, hitherto unreported for liquid droplets. These shape changes are shown to originate in the interplay between interfacial tension and the elasticity of the droplet’s 2-nm-thick interfacial monolayer, which crystallizes at some T = Ts above the oil’s melting point, with the droplet’s bulk remaining liquid. Strikingly, at still-lower temperatures, this interfacial freezing (IF) effect also causes droplets to deform, split, and grow tails. Our findings provide deep insights into molecular-scale elasticity and allow formation of emulsions of tunable stability for directed self-assembly of complex-shaped particles and other future technologies. PMID:26733673

  12. Droplet Breakup in Expansion-contraction Microchannels

    NASA Astrophysics Data System (ADS)

    Zhu, Pingan; Kong, Tiantian; Lei, Leyan; Tian, Xiaowei; Kang, Zhanxiao; Wang, Liqiu

    2016-02-01

    We investigate the influences of expansion-contraction microchannels on droplet breakup in capillary microfluidic devices. With variations in channel dimension, local shear stresses at the injection nozzle and focusing orifice vary, significantly impacting flow behavior including droplet breakup locations and breakup modes. We observe transition of droplet breakup location from focusing orifice to injection nozzle, and three distinct types of recently-reported tip-multi-breaking modes. By balancing local shear stresses and interfacial tension effects, we determine the critical condition for breakup location transition, and characterize the tip-multi-breaking mode quantitatively. In addition, we identify the mechanism responsible for the periodic oscillation of inner fluid tip in tip-multi-breaking mode. Our results offer fundamental understanding of two-phase flow behaviors in expansion-contraction microstructures, and would benefit droplet generation, manipulation and design of microfluidic devices.

  13. Manipulation of microfluidic droplets by electrorheological fluid.

    PubMed

    Zhang, Menying; Gong, Xiuqing; Wen, Weijia

    2009-09-01

    Microfluidics, especially droplet microfluidics, attracts more and more researchers from diverse fields, because it requires fewer materials and less time, produces less waste and has the potential of highly integrated and computer-controlled reaction processes for chemistry and biology. Electrorheological fluid, especially giant electrorheological fluid (GERF), which is considered as a kind of smart material, has been applied to the microfluidic systems to achieve active and precise control of fluid by electrical signal. In this review article, we will introduce recent results of microfluidic droplet manipulation, GERF and some pertinent achievements by introducing GERF into microfluidic system: digital generation, manipulation of "smart droplets" and droplet manipulation by GERF. Once it is combined with real-time detection, integrated chip with multiple functions can be realized.

  14. Effect of oil droplet size on activation energy for coalescence of oil droplets in an O/W emulsion.

    PubMed

    Miyagawa, Yayoi; Katsuki, Kazutaka; Matsuno, Ryuichi; Adachi, Shuji

    2015-01-01

    The activation energy of a reasonable order of magnitude was estimated for the coalescence of oil droplets in an O/W emulsion by formulating the balance of forces acting on a droplet that crosses over the potential barrier to coalesce with another droplet by the DLVO theory and Stokes' law. An emulsion with smaller oil droplets was shown to be more stable.

  15. Fluid Flow in An Evaporating Droplet

    NASA Technical Reports Server (NTRS)

    Hu, H.; Larson, R.

    1999-01-01

    Droplet evaporation is a common phenomenon in everyday life. For example, when a droplet of coffee or salt solution is dropped onto a surface and the droplet dries out, a ring of coffee or salt particles is left on the surface. This phenomenon exists not only in everyday life, but also in many practical industrial processes and scientific research and could also be used to assist in DNA sequence analysis, if the flow field in the droplet produced by the evaporation could be understood and predicted in detail. In order to measure the fluid flow in a droplet, small particles can be suspended into the fluid as tracers. From the ratio of gravitational force to Brownian force a(exp 4)(delta rho)(g)/k(sub B)T, we find that particle's tendency to settle is proportional to a(exp 4) (a is particle radius). So, to keep the particles from settling, the droplet size should be chosen to be in a range 0.1 -1.0 microns in experiments. For such small particles, the Brownian force will affect the motion of the particle preventing accurate measurement of the flow field. This problem could be overcome by using larger particles as tracers to measure fluid flow under microgravity since the gravitational acceleration g is then very small. For larger particles, Brownian force would hardly affect the motion of the particles. Therefore, accurate flow field could be determined from experiments in microgravity. In this paper, we will investigate the fluid flow in an evaporating droplet under normal gravity, and compare experiments to theories. Then, we will present our ideas about the experimental measurement of fluid flow in an evaporating droplet under microgravity.

  16. Laser diagnostics for microgravity droplet studies

    NASA Technical Reports Server (NTRS)

    Winter, Michael

    1993-01-01

    Rapid advances have recently been made in numerical simulation of droplet combustion under microgravity conditions, while experimental capabilities remain relatively primitive. Calculations can now provide detailed information on mass and energy transport, complex gas-phase chemistry, multi-component molecular diffusion, surface evaporation and heterogeneous reaction, which provides a clearer picture of both quasi-steady as well as dynamic behavior of droplet combustion. Experiments concerning these phenomena typically result in pictures of the burning droplets, and the data therefrom describe droplet surface regression along with flame and soot shell position. With much more precise, detailed, experimental diagnostics, significant gains could be made on the dynamics and flame structural changes which occur during droplet combustion. Since microgravity experiments become increasingly more expensive as they progress from drop towers and flights to spaceborne experiments, there is a great need to maximize the information content from these experiments. Sophisticated measurements using laser diagnostics on individual droplets and combustion phenomena are now possible. These include measuring flow patterns and temperature fields within droplets, vaporization rates and vaporization enhancement, radical species profiling in flames and gas-phase flow-tagging velocimetry. Although these measurements are sophisticated, they have undergone maturation to the degree where with some development, they are applicable to studies of microgravity droplet combustion. This program beginning in September of 1992, will include a series of measurements in the NASA Learjet, KC-135 and Drop Tower facilities for investigating the range of applicability of these diagnostics while generating and providing fundamental data to ongoing NASA research programs in this area. This program is being conducted in collaboration with other microgravity investigators and is aimed toward supplementing

  17. Floating Droplet Array: An Ultrahigh-Throughput Device for Droplet Trapping, Real-time Analysis and Recovery

    PubMed Central

    Labanieh, Louai; Nguyen, Thi N.; Zhao, Weian; Kang, Dong-Ku

    2016-01-01

    We describe the design, fabrication and use of a dual-layered microfluidic device for ultrahigh-throughput droplet trapping, analysis, and recovery using droplet buoyancy. To demonstrate the utility of this device for digital quantification of analytes, we quantify the number of droplets, which contain a β-galactosidase-conjugated bead among more than 100,000 immobilized droplets. In addition, we demonstrate that this device can be used for droplet clustering and real-time analysis by clustering several droplets together into microwells and monitoring diffusion of fluorescein, a product of the enzymatic reaction of β-galactosidase and its fluorogenic substrate FDG, between droplets. PMID:27134760

  18. Dictyostelium Lipid Droplets Host Novel Proteins

    PubMed Central

    Du, Xiaoli; Barisch, Caroline; Paschke, Peggy; Herrfurth, Cornelia; Bertinetti, Oliver; Pawolleck, Nadine; Otto, Heike; Rühling, Harald; Feussner, Ivo; Herberg, Friedrich W.

    2013-01-01

    Across all kingdoms of life, cells store energy in a specialized organelle, the lipid droplet. In general, it consists of a hydrophobic core of triglycerides and steryl esters surrounded by only one leaflet derived from the endoplasmic reticulum membrane to which a specific set of proteins is bound. We have chosen the unicellular organism Dictyostelium discoideum to establish kinetics of lipid droplet formation and degradation and to further identify the lipid constituents and proteins of lipid droplets. Here, we show that the lipid composition is similar to what is found in mammalian lipid droplets. In addition, phospholipids preferentially consist of mainly saturated fatty acids, whereas neutral lipids are enriched in unsaturated fatty acids. Among the novel protein components are LdpA, a protein specific to Dictyostelium, and Net4, which has strong homologies to mammalian DUF829/Tmem53/NET4 that was previously only known as a constituent of the mammalian nuclear envelope. The proteins analyzed so far appear to move from the endoplasmic reticulum to the lipid droplets, supporting the concept that lipid droplets are formed on this membrane. PMID:24036346

  19. Droplet Suspended on a Wire Begins Ignition

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber Supported Droplet Combustion Experiment completing a number of successful burns on STS-94, July 11, 1997, MET:9/17:40 (approximate). The photo shows a droplet of 95% heptane and 5% hexadecane, suspended and positioned by the fiber wire, just as it is being ignited by the glowing coil beneath. Study of the physical properties of burning fuel from this experiment is expected to contribute to more efficient use of fossil fuels and reduction of combustion by-products on Earth. The sequence is from a time-lapse movie (34 seconds condensed to 12 seconds), and clearly shows particles emanating from the droplet during the burn. The droplet shrank to nothing as it was consumed. FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.2 MB, 11-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300180.html.

  20. Ignition of Droplet Suspended on a Wire

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber Supported Droplet Combustion Experiment completing a number of successful burns on STS-94, July 11, 1997, MET:9/17:40 (approximate). The photo shows a droplet of 95% heptane and 5% hexadecane, suspended and positioned by the fiber wire, just as it is being ignited by the glowing coil beneath. Study of the physical properties of burning fuel from this experiment is expected to contribute to more efficient use of fossil fuels and reduction of combustion by-products on Earth. The sequence is from a time-lapse movie (34 seconds condensed to 12 seconds), and clearly shows particles emanating from the droplet during the burn. The droplet shrank to nothing as it was consumed. FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (133KB JPEG, 656 x 741 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300181.html.

  1. Predicting Droplet Formation on Centrifugal Microfluidic Platforms

    NASA Astrophysics Data System (ADS)

    Moebius, Jacob Alfred

    Centrifugal microfluidics is a widely known research tool for biological sample and water quality analysis. Currently, the standard equipment used for such diagnostic applications include slow, bulky machines controlled by multiple operators. These machines can be condensed into a smaller, faster benchtop sample-to-answer system. Sample processing is an important step taken to extract, isolate, and convert biological factors, such as nucleic acids or proteins, from a raw sample to an analyzable solution. Volume definition is one such step. The focus of this thesis is the development of a model predicting monodispersed droplet formation and the application of droplets as a technique for volume definition. First, a background of droplet microfluidic platforms is presented, along with current biological analysis technologies and the advantages of integrating such technologies onto microfluidic platforms. Second, background and theories of centrifugal microfluidics is given, followed by theories relevant to droplet emulsions. Third, fabrication techniques for centrifugal microfluidic designs are discussed. Finally, the development of a model for predicting droplet formation on the centrifugal microfluidic platform are presented for the rest of the thesis. Predicting droplet formation analytically based on the volumetric flow rates of the continuous and dispersed phases, the ratios of these two flow rates, and the interfacial tension between the continuous and dispersed phases presented many challenges, which will be discussed in this work. Experimental validation was completed using continuous phase solutions of different interfacial tensions. To conclude, prospective applications are discussed with expected challenges.

  2. Burning Heptane Droplets on STS-94

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Fuel ignites and burns in the Droplet Combustion Experiment (DCE) on STS-94 on July 11, 1997. This round of experiments burned heptane droplets in 1/2 atmosphere pressure consisting of oxygen and helium. During this mission, scientists have seen for the first time droplets which stop burning due to heat loss by radiation. From these data, the investigators hope to understand the physical and chemical processes that take place in droplet combustion in different environments, including conditions under which the flames extinguish, the chemistry of the combustion reaction, and the production of pollutants such as nitrogen oxides and soot particles. The DCE was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station.(983KB, 9-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300172.html.

  3. Structure of DNA cholesteric spherulitic droplet dispersions

    NASA Astrophysics Data System (ADS)

    Goldar, Arach; Thomson, Hellen; Seddon, John M.

    2008-01-01

    The aggregation of short (294-base-pair) linear double-stranded DNA molecules into cholesteric spherulitic droplets in a brine solution of polyethylene glycol has been studied using polarized light microscopy. The DNA concentration within the droplet is found to be constant and therefore the cholesteric pitch is independent of the total DNA concentration. The size of the droplets grows as a power law of the total concentration of DNA. The exponent of the power law relation is calculated using a progressive nucleation and growth model. The exponent is found to be equal to two-thirds and is in good agreement with the experimental data. By analysing fields of spherulitic droplets at low magnification using either hydrophobic or hydrophilic slides and cover-slips, we demonstrate that the positions of the droplets are correlated in solution. The long range correlation between the droplets indicates some kinetic arrest of the phase separating solution that may have been induced by the finite size of the system.

  4. Caustics and the growth of droplets

    NASA Astrophysics Data System (ADS)

    Govindarajan, Rama; Ravichandran, S.; Ray, Samriddhi; Deepu, P.

    Caustics are formed when inertial particles of very different velocities collide in a flow, and are a consequence of the dissipative nature of particle motion in a suspension. Using a model vortex-dominated flow with heavy droplets in a saturated environment, we suggest that sling caustics form only within a neighbourhood around a vortex, the square of whose radius is proportional to the product of circulation and particle inertia. Droplets starting close to this critical radius congregate very close together, resulting in large spikes in (Lagrangian) number density. Allowing for merger when droplets collide, we show that droplets starting out close to the critical radius display a much more rapid growth in size than those starting elsewhere, and a large fraction of the large droplets are those that originate within the caustics-forming region. We test these predictions in a two-dimensional simulation of turbulent flow. We hope that our study will be of interest in long-standing problems of physical interest such as the mechanism of broadening of droplet spectra in a turbulent flow. Support from the Ministry of Earth Sciences, Government of India for the project Coupled physical processes in the Bay of Bengal and monsoon air-sea interaction under OMM is gratefully acknowledged.

  5. Whole Teflon valves for handling droplets.

    PubMed

    Cybulski, Olgierd; Jakiela, Slawomir; Garstecki, Piotr

    2016-06-21

    We propose and test a new whole-Teflon gate valve for handling droplets. The valve allows droplet plugs to pass through without disturbing them. This is possible due to the geometric design, the choice of material and lack of any pulses of flow generated by closing or opening the valve. The duct through the valve resembles a simple segment of tubing, without constrictions, change in lumen or side pockets. There are no extra sealing materials with different wettability or chemical resistance. The only material exposed to liquids is FEP Teflon, which is resistant to aggressive chemicals and fully biocompatible. The valve can be integrated into microfluidic systems: we demonstrate a complex system for culturing bacteria in hundreds of microliter droplet chemostats. The valve effectively isolates modules of the system to increase precision of operations on droplets. We verified that the valve allowed millions of droplet plugs to safely pass through, without any cross-contamination with bacteria between the droplets. The valve can be used in automating complex microfluidic systems for experiments in biochemistry, biology and organic chemistry.

  6. Rayleigh wave scattering from sessile droplets

    NASA Astrophysics Data System (ADS)

    Quintero, R.; Simonetti, F.

    2013-10-01

    Radiation of energy by large-amplitude leaky Rayleigh waves is regarded as one of the key physical mechanisms regulating the actuation and manipulation of droplets in surface acoustic wave (SAW) microfluidic devices. The interaction between a SAW and a droplet is highly complex and is presently the subject of extensive research. This paper investigates the existence of an additional interaction mechanism based on the propagation of quasi-Stoneley waves inside sessile droplets deposited on a solid substrate. In contrast with the leaky Rayleigh wave, the energy of the Stoneley wave is confined within a thin fluid layer in contact with the substrate. The hypothesis is confirmed by three-dimensional finite element simulations and ultrasonic scattering experiments measuring the reflection of Rayleigh waves from droplets of different diameters. Moreover, real-time monitoring of the droplet evaporation process reveals a clear correlation between the droplet contact angle and the spectral information of the reflected Rayleigh signal, thus paving the way for ultrasonic measurements of surface tension.

  7. Mechanical vibrations of pendant liquid droplets.

    PubMed

    Temperton, Robert H; Smith, Michael I; Sharp, James S

    2015-07-01

    A simple optical deflection technique was used to monitor the vibrations of microlitre pendant droplets of deuterium oxide, formamide, and 1,1,2,2-tetrabromoethane. Droplets of different volumes of each liquid were suspended from the end of a microlitre pipette and vibrated using a small puff of nitrogen gas. A laser was passed through the droplets and the scattered light was collected using a photodiode. Vibration of the droplets resulted in the motion of the scattered beam and time-dependent intensity variations were recorded using the photodiode. These time-dependent variations were Fourier transformed and the frequencies and widths of the mechanical droplet resonances were extracted. A simple model of vibrations in pendant/sessile drops was used to relate these parameters to the surface tension, density and viscosity of the liquid droplets. The surface tension values obtained from this method were found to be in good agreement with results obtained using the standard pendant drop technique. Damping of capillary waves on pendant drops was shown to be similar to that observed for deep liquid baths and the kinematic viscosities obtained were in agreement with literature values for all three liquids studied.

  8. Studies of droplet burning and extinction

    NASA Technical Reports Server (NTRS)

    Williams, Forman A.

    1993-01-01

    A project on droplet combustion, pursued jointly with F.L. Dryer of Princeton University, has now been in progress for many years. The project involves experiments on the burning of single droplets in various atmospheres, mainly at normal atmosperic pressure and below, performed in drop towers and designed to be performed aboard space-based platforms such as the Space Shuttle or the Space Station. It also involves numerical computations on droplet burning, performed mainly at Princeton, and asymptotic analyses of droplet burning, performed mainly at UCSD. The focus of the studies rests primarily on time-dependent droplet-burning characteristics and on extinction phenomena. The presentation to be given here concerns the recent research on application of asymptotic methods to investigation of the flame structure and extinction of hydrocarbon droplets. These theoretical studies are investigating the extent to which combustion of higher hydrocarbons - heptane, in particular - can be described by four-step reduced chemistry of the kind that has achieved a good degree of success for methane flames. The studies have progressed to a point at which a number of definite conclusions can now be stated. These conclusions and the reasoning that led to them are outlined here.

  9. Gel-like double-emulsion droplets

    NASA Astrophysics Data System (ADS)

    Guzowski, Jan; Korczyk, Piotr; Garstecki, Piotr; Stone, Howard

    2015-11-01

    We experimentally study the problem of packing of micro-droplets inside a droplet of another immiscible liquid phase. We use microfluidics to encapsulate multiple monodisperse aqueous segments inside a drop of oil. For small numbers N (N<10) of the aqueous droplets and at their volume fraction in oil exceeding the close-packing threshold we observe multiple metastable structures with well-defined point-group symmetries. We attribute the observed metastability to the deformability of the droplets which leads to effective many-body interactions and energy barriers for rearrangement. By changing the composition of the oil phase we find that when the surface tensions of the droplets and of the encapsulating phase are comparable, the energy barriers are high enough to trap elongated structures or even linear chains, independently of N. However, when the surface tension of the encapsulating phase is much larger than that of the droplets, non-spherical morphologies are stable only at sufficiently high N. In such a case multiple internal interfaces can hold stresses and prevent relaxation of the global deformations which leads to a plastic, gel-like behavior. Our findings can serve as guidelines for synthesis of functional particles as well as for designing biomimetic materials, e.g. for tissue engineering. J.G. acknowledges financial support from Polish Ministry of Science provided within the framework Mobility Plus.

  10. Studies of droplet burning and extinction

    NASA Technical Reports Server (NTRS)

    Williams, F. A.

    1995-01-01

    A project on droplet combustion, pursued jointly with F. L. Dryer of Princeton University, has now been in progress for many years. The project involves experiments on the burning of single droplets in various atmospheres, mainly at normal atmospheric pressure and below, performed in drop towers and designed to be performed aboard space-based platforms such as the Space Shuttle or the Space Station and currently manifest for Spacelab in the MSL-1 flight of the Space Shuttle in April of 1997. It also involves numerical computations on droplet burning, performed mainly at Princeton, and asymptotic analyses of droplet burning, performed mainly at UCSD. The focus of the studies rests primarily on time-dependent droplet-burning characteristics and on extinction phenomena. The presentation to be given here concerns the recent research on application of asymptotic methods to investigation of the flame structure and extinction of alcohol droplets. These theoretical studies are relevant to the second of the proposed space-flight tests and are currently investigating the extent to which combustion of alcohols can be described by four-step reduced chemistry similar to that which has achieved a good degree of success for alkane flames. These studies have progressed to a point at which a number of definite conclusions can now be stated. These conclusions and the reasoning that led to them are outlined.

  11. Modeling spreading of nematic droplets

    NASA Astrophysics Data System (ADS)

    Lin, Te-Sheng; Cummings, Linda; Kondic, Lou

    2011-03-01

    Experiments by Poulard & Cazabat on spreading droplets of nematic liquid crystal reveal a surprisingly rich variety of behavior, including at least two different emerging lengthscales resulting from a contact line instability. In earlier work we modified a lubrication model for nematic liquid crystals due to Ben Amar and Cummings, and showed that, in a qualitative sense, it can account for much of the observed behavior. In the present work we propose a new approach, that allows us to explore the effect of anchoring variations on the substrate. This in turn gives a simple way to model the presence of defects, which are always present during such liquid crystal flows. The new model leads to additional terms in the governing equation. We first explore the influence of these additional terms for some simple flow scenarios, to gain a basic understanding of their influence, before extending our simulations to the experimental geometry and comparing our results to the experiments. This work was partially supported by NSF Grant No. DMS-0908158.

  12. Lipid droplets, lipophagy, and beyond.

    PubMed

    Wang, Chao-Wen

    2016-08-01

    Lipids are essential components for life. Their various structural and physical properties influence diverse cellular processes and, thereby, human health. Lipids are not genetically encoded but are synthesized and modified by complex metabolic pathways, supplying energy, membranes, signaling molecules, and hormones to affect growth, physiology, and response to environmental insults. Lipid homeostasis is crucial, such that excess fatty acids (FAs) can be harmful to cells. To prevent such lipotoxicity, cells convert excess FAs into neutral lipids for storage in organelles called lipid droplets (LDs). These organelles do not simply manage lipid storage and metabolism but also are involved in protein quality management, pathogenesis, immune responses, and, potentially, neurodegeneration. In recent years, a major trend in LD biology has centered around the physiology of lipid mobilization via lipophagy of fat stored within LDs. This review summarizes key findings in LD biology and lipophagy, offering novel insights into this rapidly growing field. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.

  13. Acoustic Droplet Vaporization in Microchannels

    NASA Astrophysics Data System (ADS)

    Li, David; Fabiilli, Mario; Kripfgans, Oliver; Fowlkes, J. Brian; Bull, Joseph

    2014-11-01

    Gas embolotherapy is a proposed cancer therapy where gas bubbles acting as embolic agents are selectively generated near the tumor site to block blood supply, resulting to tumor necrosis. The gas bubbles are generated by using focused ultrasound to selective vaporize intravenously injected microdroplets. In this study, albumin encapsulated dodecafluorocarbon microdroplets were isolated in 25 to 100 micron diameter polydimethylsiloxane microchannels. The droplets were vaporized at 37 °C using a single pulse from a 7.5 MHz single element focused transducer with 8-32 cycles at 2.2 to 5.6 MPa peak negative pressure. The vaporization process was recorded using an ultra-high speed camera attached to an inverted microscope. A theoretical Rayleigh-Plesset like model was derived to describe the both the expansion of small spherical bubbles as well as cylindrical bubbles in a long microchannel. The gas phase was described as an ideal gas and the liquid DDFP and bulk fluid were viscous Newtonian fluids. Additionally, surface tension, viscous losses from the channel, and the phase change process were included in the model. The theoretical model matched very well to experiments with channel diameters or 50 micron or less. This work was supported by NIH Grant R01EB006476.

  14. An Experimental Investigation of Vibration-Induced Single Droplet Ejection.

    NASA Astrophysics Data System (ADS)

    Range, Kai; Smith, Marc K.; Glezer, Ari

    1998-11-01

    Vibration-induced droplet atomization occurs when small secondary droplets are ejected from the free surface of a larger droplet placed on a vibrating membrane. To model a single ejection event, a liquid droplet is placed on a small piston and vibrated using an electromagnetic driver. The droplet oscillates in a characteristic mode shape that depends on the driving frequency and amplitude, the properties of the liquid, and the size of the droplet. When the excitation amplitude is large enough, a small secondary droplet is ejected from the primary droplet. Observations of this process using high-speed digital video imaging show that droplet ejection occurs when a small liquid column or jet appears on the primary droplet and a secondary droplet forms on the column by a capillary-pinching mechanism. The liquid column or jet emanates from a crater in the primary droplet. As the driving frequency increases, this crater becomes smaller and the diameter of the ejected droplet decreases. We shall present results showing how the ejected droplet diameter and speed depends on the driving frequency and amplitude, the liquid properties, and the primary droplet volume.

  15. Hyalinizing cholecystitis and associated carcinomas: clinicopathologic analysis of a distinctive variant of cholecystitis with porcelain-like features and accompanying diagnostically challenging carcinomas.

    PubMed

    Patel, Samip; Roa, Juan Carlos; Tapia, Oscar; Dursun, Nevra; Bagci, Pelin; Basturk, Olca; Cakir, Asli; Losada, Hector; Sarmiento, Juan; Adsay, Volkan

    2011-08-01

    We describe a clinicopathologically distinct subtype of cholecystitis, the extensively calcific version of which has been presented in the clinical literature as "porcelain gallbladder (PG)." This cholecystitis, which we propose to refer to as hyalinizing cholecystitis (HC), is characterized by dense, paucicellular hyaline fibrosis transforming the gallbladder (GB) wall into a relatively thin and uniform band. The process diffusely effaces most of the normal structures of GB, and some cases show calcifications. To determine the clinicopathologic associations of HC, we systematically analyzed 4231 cholecystectomies (606 of which had carcinoma) histopathologically, in addition to a targeted search in our databases. Ninety-six cases of HC were identified (1.6% of cholecystectomies). Patients with HC were a decade older than ordinary cholecystitis patients (56 vs. 47; P<0.001), suggesting that HC may be a long-term complication of chronic injury in some patients. Calcifications of variable amounts and degrees were identified in two thirds of the cases. In addition, 10 cases showed diffuse marked calcifications and were considered separately as "complete porcelain" GB. Thirty-eight HC cases had carcinoma with a calculated frequency of 15% and an odds ratio of cancer risk of 4.6. Only 42% of the invasive cases were associated with calcifications; none of the 10 diffusely calcific cases had carcinoma. HC-related carcinomas were challenging diagnostically. They did not form distinct masses or any significant thickening (mean thickness, 2.6 vs. 4.0 mm in ordinary adenocarcinomas; P<0.002). Microscopically, they had widely scattered and bland-appearing glands embedded in the thin band of hyaline stroma of HC, commonly showing a disappearing lining, leaving behind the granular, necrotic intraluminal debris (regression) with or without calcifications, which could be the only sign of cancer in some sections. The morphologic features that allowed the recognition of these glands

  16. Theory of droplet. Part 1: Renormalized laws of droplet vaporization in non-dilute sprays

    NASA Technical Reports Server (NTRS)

    Chiu, H. H.

    1989-01-01

    The vaporization of a droplet, interacting with its neighbors in a non-dilute spray environment is examined as well as a vaporization scaling law established on the basis of a recently developed theory of renormalized droplet. The interacting droplet consists of a centrally located droplet and its vapor bubble which is surrounded by a cloud of droplets. The distribution of the droplets and the size of the cloud are characterized by a pair-distribution function. The vaporization of a droplet is retarded by the collective thermal quenching, the vapor concentration accumulated in the outer sphere, and by the limited percolative passages for mass, momentum and energy fluxes. The retardation is scaled by the local collective interaction parameters (group combustion number of renormalized droplet, droplet spacing, renormalization number and local ambient conditions). The numerical results of a selected case study reveal that the vaporization correction factor falls from unity monotonically as the group combustion number increases, and saturation is likely to occur when the group combustion number reaches 35 to 40 with interdroplet spacing of 7.5 diameters and an environment temperature of 500 K. The scaling law suggests that dense sprays can be classified into: (1) a diffusively dense cloud characterized by uniform thermal quenching in the cloud; (2) a stratified dense cloud characterized by a radial stratification in temperature by the differential thermal quenching of the cloud; or (3) a sharply dense cloud marked by fine structure in the quasi-droplet cloud and the corresponding variation in the correction factor due to the variation in the topological structure of the cloud characterized by a pair-distribution function of quasi-droplets.

  17. Scavenging dissolved oxygen via acoustic droplet vaporization.

    PubMed

    Radhakrishnan, Kirthi; Holland, Christy K; Haworth, Kevin J

    2016-07-01

    Acoustic droplet vaporization (ADV) of perfluorocarbon emulsions has been explored for diagnostic and therapeutic applications. Previous studies have demonstrated that vaporization of a liquid droplet results in a gas microbubble with a diameter 5-6 times larger than the initial droplet diameter. The expansion factor can increase to a factor of 10 in gassy fluids as a result of air diffusing from the surrounding fluid into the microbubble. This study investigates the potential of this process to serve as an ultrasound-mediated gas scavenging technology. Perfluoropentane droplets diluted in phosphate-buffered saline (PBS) were insonified by a 2 MHz transducer at peak rarefactional pressures lower than and greater than the ADV pressure amplitude threshold in an in vitro flow phantom. The change in dissolved oxygen (DO) of the PBS before and after ADV was measured. A numerical model of gas scavenging, based on conservation of mass and equal partial pressures of gases at equilibrium, was developed. At insonation pressures exceeding the ADV threshold, the DO of air-saturated PBS decreased with increasing insonation pressures, dropping as low as 25% of air saturation within 20s. The decrease in DO of the PBS during ADV was dependent on the volumetric size distribution of the droplets and the fraction of droplets transitioned during ultrasound exposure. Numerically predicted changes in DO from the model agreed with the experimentally measured DO, indicating that concentration gradients can explain this phenomenon. Using computationally modified droplet size distributions that would be suitable for in vivo applications, the DO of the PBS was found to decrease with increasing concentrations. This study demonstrates that ADV can significantly decrease the DO in an aqueous fluid, which may have direct therapeutic applications and should be considered for ADV-based diagnostic or therapeutic applications.

  18. Production velocity of sea spray droplets

    NASA Astrophysics Data System (ADS)

    Andreas, Edgar L.; Jones, Kathleen F.; Fairall, Christopher W.

    2010-12-01

    The sea spray generation function dF/dr0 predicts the rate at which droplets of initial radius r0 are produced at the sea surface. Because this function is not readily measurable in the marine environment, however, it is often inferred from measurements of the near-surface droplet concentration, C(r0), through an assumed velocity scale, the effective spray production velocity. This paper proceeds in reverse, though: It uses a reliable estimate of dF/dr0 and 13 sets of measurements of C(r0) over the ocean to calculate the implied effective production velocity, Veff, for droplets with initial radii r0 from 5 to 300 μm. It then compares these Veff values with four candidate expressions for this production velocity: the dry-deposition velocity, VDh; the mean wind speed at the significant wave amplitude (A1/3), ? the standard deviation in vertical droplet velocity, σwd; and laboratory measurements of the ejection velocity of jet droplets, Vej. The velocity scales ? and Vej agree best with the implied Veff values for 20 ≤ r0 ≤ 300 μm. The deposition velocity, VDh, which is the velocity most commonly used in this application, agrees worst with the Veff values. For droplets with r0 less than about 20 μm, the analysis also rejects the main hypothesis: that dF/dr0 and C(r0) can be related through a velocity scale. These smaller droplets simply have residence times that are too long for spray concentrations to be in local equilibrium with the spray production rate.

  19. Modeling of Droplet Evaporation on Superhydrophobic Surfaces.

    PubMed

    Fernandes, Heitor C M; Vainstein, Mendeli H; Brito, Carolina

    2015-07-14

    When a drop of water is placed on a rough surface, there are two possible extreme regimes of wetting: the one called Cassie-Baxter (CB) with air pockets trapped underneath the droplet and the one called the Wenzel (W) state characterized by the homogeneous wetting of the surface. A way to investigate the transition between these two states is by means of evaporation experiments, in which the droplet starts in a CB state and, as its volume decreases, penetrates the surface's grooves, reaching a W state. Here we present a theoretical model based on the global interfacial energies for CB and W states that allows us to predict the thermodynamic wetting state of the droplet for a given volume and surface texture. We first analyze the influence of the surface geometric parameters on the droplet's final wetting state with constant volume and show that it depends strongly on the surface texture. We then vary the volume of the droplet, keeping the geometric surface parameters fixed to mimic evaporation and show that the drop experiences a transition from the CB to the W state when its volume reduces, as observed in experiments. To investigate the dependency of the wetting state on the initial state of the droplet, we implement a cellular Potts model in three dimensions. Simulations show very good agreement with theory when the initial state is W, but it disagrees when the droplet is initialized in a CB state, in accordance with previous observations which show that the CB state is metastable in many cases. Both simulations and the theoretical model can be modified to study other types of surfaces.

  20. Transient burning of a convective fuel droplet

    SciTech Connect

    Wu, Guang; Sirignano, William A.

    2010-05-15

    The transient burning of an n-octane fuel droplet in a hot gas stream at 20 atmosphere pressure is numerically studied, with considerations of droplet regression, deceleration due to the drag of the droplet, internal circulation inside the droplet, variable properties, non-uniform surface temperature, and the effect of surface tension. An initial envelope flame is found to remain envelope in time, and an initial wake flame is always transitioned into an envelope flame at a later time, with the normalized transition delay controlled by the initial Reynolds number and the initial Damkohler number. The initial flame shape is primarily determined by the initial Damkohler number, which has a critical value of Da{sub 0}=1.02. The burning rates are modified by the transition, and are influenced by the intensity of forced convection which is determined by initial Reynolds number. The influence of surface tension is also studied as the surface temperature is non-uniform. Surface tension affects the liquid motion at the droplet surface significantly and affects the change of surface temperature and burning rate modestly. The influence of surface tension generally increases with increasing initial Reynolds number within the range without droplet breakup. We also studied cases with constant relative velocity between the air stream and the droplet. The results show that in these cases the initial envelope flame still remains envelope, but the evolution from an initial wake flame to an envelope flame is inhibited. Validation of our analysis is made by comparing with a published porous-sphere experiment Raghavan et al. (2005) which used methanol fuel. (author)

  1. Droplet confinement and leakage: Causes, underlying effects, and amelioration strategies

    PubMed Central

    Debon, Aaron P.; Wootton, Robert C. R.

    2015-01-01

    The applicability of droplet-based microfluidic systems to many research fields stems from the fact that droplets are generally considered individual and self-contained reaction vessels. This study demonstrates that, more often than not, the integrity of droplets is not complete, and depends on a range of factors including surfactant type and concentration, the micro-channel surface, droplet storage conditions, and the flow rates used to form and process droplets. Herein, a model microfluidic device is used for droplet generation and storage to allow the comparative study of forty-four different oil/surfactant conditions. Assessment of droplet stability under these conditions suggests a diversity of different droplet failure modes. These failure modes have been classified into families depending on the underlying effect, with both numerical and qualitative models being used to describe the causative effect and to provide practical solutions for droplet failure amelioration in microfluidic systems. PMID:26015831

  2. Vibration-Induced Droplet Atomization --- A Theoretical Investigation.

    NASA Astrophysics Data System (ADS)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1997-11-01

    The atomization of a liquid droplet placed on a vibrating membrane starts with the development of Faraday free surface waves. As the excitation amplitude increases, the waves grow in amplitude and ultimately begin to eject smaller secondary droplets from the wave crests. The rate of droplet ejection can be large enough to completely drain the primary droplet, an event we call bursting. The evolution of the droplet ejection process depends on a coupled system dynamic between the droplet and the membrane. When droplets are ejected the resonant frequency of the system increases. This changes the acceleration felt by the droplet and, in turn, the rate of droplet ejection. Depending on the excitation frequency and amplitude, various types of bursting or droplet ejection processes may occur. A simple, single degree-of-freedom model of this coupled system is presented. The model is used to illustrate the effect of the excitation frequency and amplitude and the initial droplet size on the acceleration of the membrane and the droplet ejection rate. The results of the model will be compared to our experimental data on droplet ejection. Additional work is directed towards an understanding of the mechanism behind the droplet ejection process.

  3. Thermocapillary migration of an isolated droplet and interaction of two droplets in zero gravity

    NASA Astrophysics Data System (ADS)

    Alhendal, Yousuf; Turan, Ali; Kalendar, Abdulrahim

    2016-09-01

    Fluid transfer within a stagnant liquid presents a significant challenge in zero-gravity conditions due to the lack of buoyancy effects. This challenge can be overcome by the utilisation of the Marangoni effect, or more specifically thermocapillary migration. The thermocapillary migration of droplets is driven by temperature gradients within the multiphase system which bring about a surface tension gradient driving the flow from the cold to the hot region. The migration speed of the droplet is significantly impacted by the heat transfer both inside the droplet and in its surroundings. This paper presents the analysis of drop movement in a stagnant liquid using computational fluid dynamics (CFD). The commercial software package Ansys-Fluent v.13 [1] is used to solve the governing continuum conservation equations for two-phase flow using the Volume of Fluid (VOF) method to track the liquid/liquid interface in 2D domain. This approach has been shown to be a valuable tool for studying the phenomena of liquid-liquid interaction. A strong agreement has been found with experimental observations conducted in microgravity. The inherent velocity of drops has been found to decrease with increasing Marangoni number. This finding is in line with the previous space experiments of Xie et al. (2005) [2] and in contrast to the numerical results of Ma (1999) [3] using the same liquid for the droplet and the host liquid. Data obtained in the present numerical study has been used to derive an expression predicting the scaled droplet velocity as a function of Marangoni number. A numerical study of the interaction of two spherical droplets undergoing thermocapillary migration in microgravity is also presented. The temperature thrust from the leading droplet towards the trailing droplet was found to disturb its migration velocity, but the trailing droplet was found to have no influence on the migration of the leading droplet.

  4. Homogeneous Freezing of Water Droplets and its Dependence on Droplet Size

    NASA Astrophysics Data System (ADS)

    Schmitt, Thea; Möhler, Ottmar; Höhler, Kristina; Leisner, Thomas

    2014-05-01

    The formulation and parameterisation of microphysical processes in tropospheric clouds, such as phase transitions, is still a challenge for weather and climate models. This includes the homogeneous freezing of supercooled water droplets, since this is an important process in deep convective systems, where almost pure water droplets may stay liquid until homogeneous freezing occurs at temperatures around 238 K. Though the homogeneous ice nucleation in supercooled water is considered to be well understood, recent laboratory experiments with typical cloud droplet sizes showed one to two orders of magnitude smaller nucleation rate coefficients than previous literature results, including earlier results from experiments with single levitated water droplets and from cloud simulation experiments at the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) facility. This motivated us to re-analyse homogeneous droplet freezing experiments conducted during the previous years at the AIDA cloud chamber. This cloud chamber has a volume of 84m3 and operates under atmospherically relevant conditions within wide ranges of temperature, pressure and humidity, whereby investigations of both tropospheric mixed-phase clouds and cirrus clouds can be realised. By controlled adiabatic expansions, the ascent of an air parcel in the troposphere can be simulated. According to our new results and their comparison to the results from single levitated droplet experiments, the homogeneous freezing of water droplets seems to be a volume-dependent process, at least for droplets as small as a few micrometers in diameter. A contribution of surface induced freezing can be ruled out, in agreement to previous conclusions from the single droplet experiments. The obtained volume nucleation rate coefficients are in good agreement, within error bars, with some previous literature data, including our own results from earlier AIDA experiments, but they do not agree with recently published lower volume

  5. Purification and characterization of an oviposition-stimulating protein of the long hyaline tubules in the male migratory grasshopper, Melanoplus sanguinipes.

    PubMed

    Yi, S -X.; Gillott, C

    1999-02-01

    An oviposition-stimulating protein (OSP) was isolated and purified from the long hyaline tubules of the male accessory gland complex in the migratory grasshopper, Melanoplus sanguinipes. Gel filtration of the native OSP, using Sephadex G-100, indicates its molecular weight to be about 60000Da with the oviposition-stimulating activity while sodium dodecyl sulphate-polyacrylamide gel electrophoresis shows that the OSP comprises two subunits, each with a molecular weight of 30000Da. The purified OSP appears as a single symmetric peak on fast performance liquid chromatography using Mono Q. Isoelectric focusing of the OSP indicates an apparent pI of 5.5. Injection of the OSP induces oviposition in about 70% of ovulated virgin females within 48h. Stimulation of oviposition can be blocked by a polyclonal antibody raised against the OSP 30000Da subunits. Amino acid analysis of the dimer and its subunits shows a comparatively high content of aspartic acid/asparagine (14.8%) as well as leucine (12.2%) and glutamic acid/glutamine (12.0%). The N-terminal 21 amino acid sequence of the OSP shows little similarity to known peptides. Immunoreactivity with the anti-OSP antibody was observed in the viscous secretion, spermatheca, and the egg-pod froth of mated females, confirming transfer of the OSP from male to female during copulation.

  6. BMP-2, Hypoxia, and COL1A1/HtrA1 siRNAs Favor Neo-Cartilage Hyaline Matrix Formation in Chondrocytes

    PubMed Central

    Ollitrault, David; Legendre, Florence; Drougard, Carole; Briand, Mélanie; Benateau, Hervé; Goux, Didier; Chajra, Hanane; Poulain, Laurent; Hartmann, Daniel; Vivien, Denis; Shridhar, Vijayalakshmi; Baldi, Alfonso; Mallein-Gerin, Frédéric; Boumediene, Karim; Demoor, Magali

    2015-01-01

    Osteoarthritis (OA) is an irreversible pathology that causes a decrease in articular cartilage thickness, leading finally to the complete degradation of the affected joint. The low spontaneous repair capacity of cartilage prevents any restoration of the joint surface, making OA a major public health issue. Here, we developed an innovative combination of treatment conditions to improve the human chondrocyte phenotype before autologous chondrocyte implantation. First, we seeded human dedifferentiated chondrocytes into a collagen sponge as a scaffold, cultured them in hypoxia in the presence of a bone morphogenetic protein (BMP), BMP-2, and transfected them with small interfering RNAs targeting two markers overexpressed in OA dedifferentiated chondrocytes, that is, type I collagen and/or HtrA1 serine protease. This strategy significantly decreased mRNA and protein expression of type I collagen and HtrA1, and led to an improvement in the chondrocyte phenotype index of differentiation. The effectiveness of our in vitro culture process was also demonstrated in the nude mouse model in vivo after subcutaneous implantation. We, thus, provide here a new protocol able to favor human hyaline chondrocyte phenotype in primarily dedifferentiated cells, both in vitro and in vivo. Our study also offers an innovative strategy for chondrocyte redifferentiation and opens new opportunities for developing therapeutic targets. PMID:24957638

  7. Integrated droplet analysis system with electrospray ionization-mass spectrometry using a hydrophilic tongue-based droplet extraction interface.

    PubMed

    Zhu, Ying; Fang, Qun

    2010-10-01

    This paper describes a simple, robust, and integrated microchip-based system for droplet analysis with electrospray ionization-mass spectrometry (ESI-MS) detection. The microchip integrated multiple modules including a droplet generator, a droplet extraction interface, and a monolithic ESI emitter. The novel droplet extraction interface based on hydrophilic tongue structure was developed. The interface could transfer droplets from segmented phase to aqueous phase with high reliability and high controllability by coupling with a back pressure regulator. The flow injection mode was adopted to introduce the transferred droplets to the ESI emitter for minimizing the cross-contamination between droplets and achieving droplet matrix modification. The system performance was evaluated using angiotensin as a model sample, and high sensitivity (<1 μM) and a good reproducibility of 5.2% RSD (n = 7) were obtained. The present device was further applied in the online monitoring of droplet-based microreaction for alkylation of peptide.

  8. Bioeffects due to acoustic droplet vaporization

    NASA Astrophysics Data System (ADS)

    Bull, Joseph

    2015-11-01

    Encapsulated micro- and nano-droplets can be vaporized via ultrasound, a process termed acoustic droplet vaporization. Our interest is primarily motivated by a developmental gas embolotherapy technique for cancer treatment. In this methodology, infarction of tumors is induced by selectively formed vascular gas bubbles that arise from the acoustic vaporization of vascular microdroplets. Additionally, the microdroplets may be used as vehicles for localized drug delivery, with or without flow occlusion. In this talk, we examine the dynamics of acoustic droplet vaporization through experiments and theoretical/computational fluid mechanics models, and investigate the bioeffects of acoustic droplet vaporization on endothelial cells and in vivo. Early timescale vaporization events, including phase change, are directly visualized using ultra-high speed imaging, and the influence of acoustic parameters on droplet/bubble dynamics is discussed. Acoustic and fluid mechanics parameters affecting the severity of endothelial cell bioeffects are explored. These findings suggest parameter spaces for which bioeffects may be reduced or enhanced, depending on the objective of the therapy. This work was supported by NIH grant R01EB006476.

  9. Simulation of sliding of liquid droplets

    NASA Astrophysics Data System (ADS)

    Alen, Saif Khan; Farhat, Nazia; Rahman, Md. Ashiqur

    2016-07-01

    Numerical simulations of sliding behavior of liquid droplets on flat and periodic microgrooved surfaces with a range of groove geometry are conducted. A numerical model is developed which is capable of predicting the critical sliding angle of the drop by comparing the advancing and the receding angles obtained from numerical and experimental findings. The effect of microgroove topography, droplet size and inclination angle on the droplet sliding characteristics is analysed. Using an open-source platform (Surface Evolver), a 3D drop-shape model is developed to numerically determine the drop stability and contact angle hysteresis on tilted surfaces. In this numerical model, the three phase contact line of the drop is obtained by numerically calculating the vertex force and local contact angle at each vertex of the base contour. Several numerical models are developed based on various assumptions of base contour shape (circular or elliptical) and implementation of gravitational force to the droplet. Droplet shapes and critical sliding angles, obtained from these numerical models, are compared with those of experimental results and are found to be in very good agreement.

  10. Mathematical Modeling of an Oscillating Droplet

    NASA Technical Reports Server (NTRS)

    Berry, S.; Hyers, R. W.; Racz, L. M.; Abedian, B.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Oscillating droplets are of interest in a number of disciplines. A practical application is the oscillating drop method, which is a technique for measuring surface tension and viscosity of liquid metals. It is especially suited to undercooled and highly reactive metals, because it is performed by electromagnetic levitation. The natural oscillation frequency of the droplets is related to the surface tension of the material, and the decay of oscillations is related to its viscosity. The fluid flow inside the droplet must be laminar in order for this technique to yield good results. Because no experimental method has yet been developed to visualize flow in electromagnetically-levitated oscillating metal droplets, mathematical modeling is required to determine whether or not turbulence occurs. Three mathematical models of the flow: (1) assuming laminar conditions, (2) using the k-epsilon turbulence model, and (3) using the RNG turbulence model, respectively, are compared and contrasted to determine the physical characteristics of the flow. It is concluded that the RNG model is the best suited for describing this problem. The goal of the presented work was to characterize internal flow in an oscillating droplet of liquid metal, and to verify the accuracy of the characterization by comparing calculated surface tension and viscosity.

  11. Dielectrophoretic manipulation of nematic and isotropic droplets

    NASA Astrophysics Data System (ADS)

    Lee, Bomi; Song, Jang-Kun

    2016-03-01

    Dielectrophoresis can provide a delicate tool to control electrically neutral particles in colloid. The dielectrophoresis is usually applied to solid particles or heterogeneous liquid droplet in continuous liquid, but we devised and investigated the dielectrophoresis of isotropic droplets within nematic phase or vice versa. Using multi-components liquid crystal mixtures that exhibit relatively wide temperature range of nematic-isotropic coexistence, we achieved a field-induced phase separation between isotropic and nematic. We also fabricated the isotropic-nematic filaments that was achieved using a biased surface preference for either isotropic or nematic phase of the alignment layer [1]. The dielectrophoresis manipulations of isotropic and nematic droplets required much lower voltage compared to that for the electro wetting type devices. In addition, we observed the bi-directional actuation of isotropic droplets using anisotropic dielectric property of liquid crystal, which is not possible in usual dielectrophoresis. The bidirectional actuation was achieved by controlling the LC director within the cell so as to change the sign of the difference between the effective dielectric constant of nematic and isotropic liquid crystals. We simulated the bi-directional dielectrophoresis by performing the LC director calculation and the corresponding dielectrophoresis. The simulation results matched well with the experimental data. Thus, the bi-directional dielectrophoresis using isotropic and nematic droplets may open new possibility of electro- optical applications using liquid crystals.

  12. Bead mediated separation of microparticles in droplets

    PubMed Central

    Sung, Ki-Joo; Lin, Xiaoxia Nina; Burns, Mark A.

    2017-01-01

    Exchange of components such as particles and cells in droplets is important and highly desired in droplet microfluidic assays, and many current technologies use electrical or magnetic fields to accomplish this process. Bead-based microfluidic techniques offer an alternative approach that uses the bead’s solid surface to immobilize targets like particles or biological material. In this paper, we demonstrate a bead-based technique for exchanging droplet content by separating fluorescent microparticles in a microfluidic device. The device uses posts to filter surface-functionalized beads from a droplet and re-capture the filtered beads in a new droplet. With post spacing of 7 μm, beads above 10 μm had 100% capture efficiency. We demonstrate the efficacy of this system using targeted particles that bind onto the functionalized beads and are, therefore, transferred from one solution to another in the device. Binding capacity tests performed in the bulk phase showed an average binding capacity of 5 particles to each bead. The microfluidic device successfully separated the targeted particles from the non-targeted particles with up to 98% purity and 100% yield. PMID:28282412

  13. Droplet impact on soft viscoelastic surfaces.

    PubMed

    Chen, Longquan; Bonaccurso, Elmar; Deng, Peigang; Zhang, Haibo

    2016-12-01

    In this work, we experimentally investigate the impact of water droplets onto soft viscoelastic surfaces with a wide range of impact velocities. Several impact phenomena, which depend on the dynamic interaction between the droplets and viscoelastic surfaces, have been identified and analyzed. At low We, complete rebound is observed when the impact velocity is between a lower and an upper threshold, beyond which droplets are deposited on the surface after impact. At intermediate We, entrapment of an air bubble inside the impinging droplets is found on soft surfaces, while a bubble entrapment on the surface is observed on rigid surfaces. At high We, partial rebound is only identified on the most rigid surface at We≳92. Rebounding droplets behave similarly to elastic drops rebounding on superhydrophobic surfaces and the impact process is independent of surface viscoelasticity. Further, surface viscoelasticity does not influence drop spreading after impact-as the surfaces behave like rigid surfaces-but it does affect drop recoiling. Also, the postimpact drop oscillation on soft viscoelastic surfaces is influenced by dynamic wettability of these surfaces. Comparing sessile drop oscillation with a damped harmonic oscillator allows us to conclude that surface viscoelasticity affects the damping coefficient and liquid surface tension sets the spring constant of the system.

  14. Simulating droplet motion on virtual leaf surfaces

    PubMed Central

    Mayo, Lisa C.; McCue, Scott W.; Moroney, Timothy J.; Forster, W. Alison; Kempthorne, Daryl M.; Belward, John A.; Turner, Ian W.

    2015-01-01

    A curvilinear thin film model is used to simulate the motion of droplets on a virtual leaf surface, with a view to better understand the retention of agricultural sprays on plants. The governing model, adapted from Roy et al. (2002 J. Fluid Mech. 454, 235–261 (doi:10.1017/S0022112001007133)) with the addition of a disjoining pressure term, describes the gravity- and curvature-driven flow of a small droplet on a complex substrate: a cotton leaf reconstructed from digitized scan data. Coalescence is the key mechanism behind spray coating of foliage, and our simulations demonstrate that various experimentally observed coalescence behaviours can be reproduced qualitatively. By varying the contact angle over the domain, we also demonstrate that the presence of a chemical defect can act as an obstacle to the droplet's path, causing break-up. In simulations on the virtual leaf, it is found that the movement of a typical spray size droplet is driven almost exclusively by substrate curvature gradients. It is not until droplet mass is sufficiently increased via coalescence that gravity becomes the dominating force. PMID:26064657

  15. Droplet Number Concentration Value Added Product

    SciTech Connect

    Chitra Sivaraman, PNNL

    2015-08-06

    Cloud droplet number concentration is an important factor in understanding aerosol-cloud interactions. As aerosol concentration increases, it is expected that droplet number concentration (Nd) will increase and droplet size will decrease, for a given liquid water path. This will greatly affect cloud albedo as smaller droplets reflect more shortwave radiation; however, the magnitude and variability of these processes under different environmental conditions is still uncertain.McComiskey et al. (2009) have implemented a method, based onBoers and Mitchell (1994), for calculating Nd from ground-based remote sensing measurements of optical depth and liquid water path. They show that the magnitude of the aerosol-cloud interactions (ACI) varies with a range of factors, including the relative value of the cloud liquid water path (LWP), the aerosol size distribution, and the cloud updraft velocity. Estimates of Nd under a range of cloud types and conditions and at a variety of sites are needed to further quantify the impacts of aerosol cloud interactions. In order to provide data sets for studying aerosol-cloud interactions, the McComiskey et al. (2009) method was implemented as the Droplet Number Concentration (NDROP) value-added product (VAP).

  16. Droplet impact on soft viscoelastic surfaces

    NASA Astrophysics Data System (ADS)

    Chen, Longquan; Bonaccurso, Elmar; Deng, Peigang; Zhang, Haibo

    2016-12-01

    In this work, we experimentally investigate the impact of water droplets onto soft viscoelastic surfaces with a wide range of impact velocities. Several impact phenomena, which depend on the dynamic interaction between the droplets and viscoelastic surfaces, have been identified and analyzed. At low We , complete rebound is observed when the impact velocity is between a lower and an upper threshold, beyond which droplets are deposited on the surface after impact. At intermediate We , entrapment of an air bubble inside the impinging droplets is found on soft surfaces, while a bubble entrapment on the surface is observed on rigid surfaces. At high We , partial rebound is only identified on the most rigid surface at We ≳92 . Rebounding droplets behave similarly to elastic drops rebounding on superhydrophobic surfaces and the impact process is independent of surface viscoelasticity. Further, surface viscoelasticity does not influence drop spreading after impact—as the surfaces behave like rigid surfaces—but it does affect drop recoiling. Also, the postimpact drop oscillation on soft viscoelastic surfaces is influenced by dynamic wettability of these surfaces. Comparing sessile drop oscillation with a damped harmonic oscillator allows us to conclude that surface viscoelasticity affects the damping coefficient and liquid surface tension sets the spring constant of the system.

  17. 3D Spray Droplet Distributions in Sneezes

    NASA Astrophysics Data System (ADS)

    Techet, Alexandra; Scharfman, Barry; Bourouiba, Lydia

    2015-11-01

    3D spray droplet clouds generated during human sneezing are investigated using the Synthetic Aperture Feature Extraction (SAFE) method, which relies on light field imaging (LFI) and synthetic aperture (SA) refocusing computational photographic techniques. An array of nine high-speed cameras are used to image sneeze droplets and tracked the droplets in 3D space and time (3D + T). An additional high-speed camera is utilized to track the motion of the head during sneezing. In the SAFE method, the raw images recorded by each camera in the array are preprocessed and binarized, simplifying post processing after image refocusing and enabling the extraction of feature sizes and positions in 3D + T. These binary images are refocused using either additive or multiplicative methods, combined with thresholding. Sneeze droplet centroids, radii, distributions and trajectories are determined and compared with existing data. The reconstructed 3D droplet centroids and radii enable a more complete understanding of the physical extent and fluid dynamics of sneeze ejecta. These measurements are important for understanding the infectious disease transmission potential of sneezes in various indoor environments.

  18. Spontaneous Droplet Jump with Electro-Bouncing

    NASA Astrophysics Data System (ADS)

    Schmidt, Erin; Weislogel, Mark

    2016-11-01

    We investigate the dynamics of water droplet jumps from superhydrophobic surfaces in the presence of an electric field during a step reduction in gravity level. In the brief free-fall environment of a drop tower, when a strong non-homogeneous electric field (with a measured strength between 0 . 39 and 2 . 36 kV/cm) is imposed, body forces acting on the jumped droplets are primarily supplied by polarization stress and Coulombic attraction instead of gravity. The droplet charge, measured to be on the order of 2 . 3 . (10-11) C, originates by electro-osmosis of charged species at the (PTFE coated) hydrophobic surface interface. This electric body force leads to a droplet bouncing behavior similar to well-known phenomena in 1-g, though occurring for larger drops 0.1 mL for a given range of impact Weber numbers, We < 20 . In 1-g, for We > 0 . 4 , impact recoil behavior on a super-hydrophobic surface is normally dominated by damping from contact line hysteresis and by air-layer interactions. However, in the strong electric field, the droplet bounce dynamics additionally include electrohydrodynamic effects on wettability and Cassie-Wenzel transition. This is qualitatively discussed in terms of coefficients of restitution and trends in contact time. This work was supported primarily by NASA Cooperative Agreement NNX12A047A.

  19. Droplet breakup dynamics of weakly viscoelastic fluids

    NASA Astrophysics Data System (ADS)

    Marshall, Kristin; Walker, Travis

    2016-11-01

    The addition of macromolecules to solvent, even in dilute quantities, can alter a fluid's response in an extensional flow. For low-viscosity fluids, the presence of elasticity may not be apparent when measured using a standard rotational rheometer, yet it may still alter the response of a fluid when undergoing an extensional deformation, especially at small length scales where elastic effects are enhanced. Applications such as microfluidics necessitate investigating the dynamics of fluids with elastic properties that are not pronounced at large length scales. In the present work, a microfluidic cross-slot configuration is used to study the effects of elasticity on droplet breakup. Droplet breakup and the subsequent iterated-stretching - where beads form along a filament connecting two primary droplets - were observed for a variety of material and flow conditions. We present a relationship on the modes of bead formation and how and when these modes will form based on key parameters such as the properties of the outer continuous-phase fluid. The results are vital not only for simulating the droplet breakup of weakly viscoelastic fluids but also for understanding how the droplet breakup event can be used for characterizing the extensional properties of weakly-viscoelastic fluids.

  20. Edge effects on water droplet condensation

    NASA Astrophysics Data System (ADS)

    Royon, Laurent; Montgruel, Anne; Medici, Marie Gabrielle; Beysens, Daniel

    2014-11-01

    The effect of geometrical or thermal discontinuities on the growth of water droplets condensing on a cooled substrate is investigated. Edges, corners, cooled/non cooled boundaries can have a strong effect on the vapor concentration profile and mass diffusion around the drops. In comparison to growth in a pattern where droplets have to compete to catch vapor, which results in a linear water concentration profile directed perpendicular to the substrate, droplets near discontinuities can get more vapor (outer edges, corners), resulting in faster growth or less vapor (inner edges), giving lower growth. When the cooling heat flux limits growth instead of mass diffusion (substrate with low thermal conductivity, strong heat exchange with air), edges effects can be canceled. In certain cases, the growth enhancement can reach nearly 500% on edges or corners which, on an inclined substrate, make droplets near the edges detach sooner than in the middle of the substrate. This effect is frequently observed with dew condensing on windows or car windshields. Such droplets, acting as wipers, can thus appreciably increase dew collection on a substrate.

  1. Droplet Combustion in a Slow Convective Flow

    NASA Technical Reports Server (NTRS)

    Nayagam, V.; Hicks, M. C.; Ackerman, M.; Haggard, J. B., Jr.; Williams, F. A.

    2003-01-01

    The influences of slow convective flow on droplet combustion, particularly in the low Reynolds number regime, have received very little attention in the past. Most studies in the literature are semi-empirical in nature and they were motivated by spray combustion applications in the moderate to high Reynolds number regime. None of the limited number of fundamental theoretical studies applicable to low Reynolds numbers have been verified by rigorous experimental data. Moreover, many unsteady phenomena associated with fluid-dynamic unsteadiness, such as impulsive starting or stopping of a burning droplet, or flow acceleration/deceleration effects, have not been investigated despite their importance in practical applications. In this study we investigate the effects of slow convection on droplet burning dynamics both experimentally and theoretically. The experimental portion of the study involves both ground-based experiments in the drop towers and future flight experiments on board the International Space Station. Heptane and methanol are used as test fuels, and this choice complements the quiescent-environment studies of the Droplet Combustion Experiment (DCE). An analytical model that employs the method of matched asymptotic expansions and uses the ratio of the convective velocity far from the droplet to the Stefan velocity at its surface as the small parameter for expansion has also been developed as a part of this investigation. Results from the ground-based experiments and comparison with the analytical model are presented in this report.

  2. The dynamics of laser droplet generation

    NASA Astrophysics Data System (ADS)

    Krese, Blaž; Perc, Matjaž; Govekar, Edvard

    2010-03-01

    We propose an experimental setup allowing for the characterization of laser droplet generation in terms of the underlying dynamics, primarily showing that the latter is deterministically chaotic by means of nonlinear time series analysis methods. In particular, we use a laser pulse to melt the end of a properly fed vertically placed metal wire. Due to the interplay of surface tension, gravity force, and light-metal interaction, undulating pendant droplets are formed at the molten end, which eventually completely detach from the wire as a consequence of their increasing mass. We capture the dynamics of this process by employing a high-speed infrared camera, thereby indirectly measuring the temperature of the wire end and the pendant droplets. The time series is subsequently generated as the mean value over the pixel intensity of every infrared snapshot. Finally, we employ methods of nonlinear time series analysis to reconstruct the phase space from the observed variable and test it against determinism and stationarity. After establishing that the observed laser droplet generation is a deterministic and dynamically stationary process, we calculate the spectra of Lyapunov exponents. We obtain a positive largest Lyapunov exponent and a negative divergence, i.e., sum of all the exponents, thus indicating that the observed dynamics is deterministically chaotic with an attractor as solution in the phase space. In addition to characterizing the dynamics of laser droplet generation, we outline industrial applications of the process and point out the significance of our findings for future attempts at mathematical modeling.

  3. Mechanical stability of particle-stabilized droplets under micropipette aspiration

    NASA Astrophysics Data System (ADS)

    Samudrala, Niveditha; Nam, Jin; Sarfati, Raphaël; Style, Robert W.; Dufresne, Eric R.

    2017-01-01

    We investigate the mechanical behavior of particle-stabilized droplets using micropipette aspiration. We observe that droplets stabilized with amphiphilic dumbbell-shaped particles exhibit a two-stage response to increasing suction pressure. Droplets first drip, then wrinkle and buckle like an elastic shell. While particles have a dramatic impact on the mechanism of failure, the mechanical strength of the droplets is only modestly increased. On the other hand, droplets coated with the molecular surfactant sodium dodecyl sulfate are even weaker than bare droplets. In all cases, the magnitude of the critical pressure for the onset of instabilities is set by the fluid surface tension.

  4. Effect of confinement on droplet coalescence in shear flow.

    PubMed

    Chen, Dongju; Cardinaels, Ruth; Moldenaers, Paula

    2009-11-17

    The effect of confinement on the coalescence of Newtonian (polydimethylsiloxane) droplets in a Newtonian (polyisobutylene) matrix is investigated experimentally. A counter rotating parallel plate device, equipped with a microscopy setup, is used to visualize two interacting droplets during shear flow. The ratio of droplet-to-matrix viscosity is kept constant at 1.1. Droplet collisions are studied for a range of droplet sizes, both in bulk conditions and for gap spacings that are comparable to the droplet size. As a result, we present the first quantitative experimental data set for the coalescence of two equal-sized droplets in a pure shear flow with varying degrees of confinement. Compared to bulk conditions, for droplets smaller than roughly 0.2 times the gap spacing, a slight degree of confinement only decreases the orientation angle at which the droplets coalesce whereas the critical conditions for coalescence remain unaltered. For more confined conditions, the critical capillary number up to which coalescence can occur, increases. Therefore, confinement clearly promotes coalescence. In addition, the droplet trajectories, the time-dependent orientation angle of the droplet pair, and the droplet deformation prior to the coalescence event are systematically studied, and a comparison between the confined and the unconfined situation is provided. It is shown that the presence of two parallel walls can induce changes in the flow field around the droplet pair, which cause an increase of the interaction time between the droplets. Moreover, for sufficiently confined droplets, the additional force originating from the presence of the walls becomes comparable to the hydrodynamic force on the droplet pair, thus influencing the drainage of the matrix film between the droplet surfaces.

  5. Physics of puffing and microexplosion of emulsion fuel droplets

    NASA Astrophysics Data System (ADS)

    Shinjo, J.; Xia, J.; Ganippa, L. C.; Megaritis, A.

    2014-10-01

    The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.

  6. Droplet sizes, dynamics and deposition in vertical annular flow

    SciTech Connect

    Lopes, J C.B.; Dukler, A E

    1985-10-01

    The role of droplets in vertical upwards annular flow is investigated, focusing on the droplet size distributions, dynamics, and deposition phenomena. An experimental program was performed based on a new laser optical technique developed in these laboratories and implemented here for annular flow. This permitted the simultaneous measurement of droplet size, axial and radial velocity. The dependence of droplet size distributions on flow conditions is analyzed. The Upper-Log Normal function proves to be a good model for the size distribution. The mechanism controlling the maximum stable drop size was found to result from the interaction of the pressure fluctuations of the turbulent flow of the gas core with the droplet. The average axial droplet velocity showed a weak dependence on gas rates. This can be explained once the droplet size distribution and droplet size-velocity relationship are analyzed simultaneously. The surprising result from the droplet conditional analysis is that larger droplet travel faster than smaller ones. This dependence cannot be explained if the drag curves used do not take into account the high levels of turbulence present in the gas core in annular flow. If these are considered, then interesting new situations of multiplicity and stability of droplet terminal velocities are encountered. Also, the observed size-velocity relationship can be explained. A droplet deposition is formulated based on the particle inertia control. This permitted the calculation of rates of drop deposition directly from the droplet size and velocities data.

  7. [Evaporating Droplet and Imaging Slip Flows

    NASA Technical Reports Server (NTRS)

    Larson, R. G.

    2002-01-01

    In this report, we summarize work on Evaporating Droplet and Imaging Slip Flows. The work was primarily performed by post-doc Hue Hu, and partially by grad students Lei Li and Danish Chopra. The work includes studies on droplet evaporation and its effects on temperature and velocity fields in an evaporating droplet, new 3-D microscopic particle image velocimetry and direct visualization on wall slip in a surfactant solution. With the exception of the slip measurements, these projects were those proposed in the grant application. Instead of slip flow, the original grant proposed imaging electro-osmotic flows. However, shortly after the grant was issued, the PI became aware of work on electro-osmotic flows by the group of Saville in Princeton that was similar to that proposed, and we therefore elected to carry out work on imaging slip flows rather than electro-osmotic flows.

  8. String-merging of meso- viscoelastic droplets

    NASA Astrophysics Data System (ADS)

    Xu, Yuanze; Xu, Jianmao

    2007-03-01

    Great challenge exists in the multi-scale rheological modeling of immiscible polyblends with non-linear morphology changes, including viscoelastic drop break-up and collapse. A new type mechanism of merging and coalescence, called string-merging of meso- viscoelastic droplets was described and analyzed. By iterative stretching and relaxation in a four-roll mill rheometer, one droplet containing high molar mass PIB (polyisobutene), was separated into two droplets connected by a string in a dumbbell shape suspending in polydimethylsiloxane (PDMS) medium. In quiescent state, the string pulled the two spheres merging closer and collapsed into one spherical drop finally. The process exhibits interesting features, different from capillary breakup mechanism. By adding the viscoelasticity of the systems to the force balance of Laplace force and viscous drag, the phenomenon may be well analyzed. The necessity to involve the microscopic consideration of the highly oriented entangled state are discussed.

  9. Combustion of emulsified fuel droplets under microgravity

    NASA Astrophysics Data System (ADS)

    Okajima, S.; Kanno, H.; Kumagai, S.

    Single-droplet experiments have been conducted under a zero-gravity condition in a freely falling chamber as a fundamental step of study on the spray combustion of hydrocarbon-water emulsified fuels. Such a behavior as the secondary micro-atomization was observed by taking schlieren photographs with a 35-mm movie camera installed on the falling assembly. Under zero gravity the emulsion droplet initiates steam discharge and puffing—that is, a mild atomization—at a time from ignition, but it does not lead to such a micro-explosion or disruption as is experienced under normal gravity. The apparent burning rate constant under zero gravity is about 30% smaller than that under normal gravity. These facts suggest that the internal convection in emulsion droplets plays an important role in causing the micro-explosion.

  10. Versatile microfluidic droplets array for bioanalysis.

    PubMed

    Hu, Shan-Wen; Xu, Bi-Yi; Ye, Wei-Ke; Xia, Xing-Hua; Chen, Hong-Yuan; Xu, Jing-Juan

    2015-01-14

    We propose a novel method to obtain versatile droplets arrays on a regional hydrophilic chip that is fabricated by PDMS soft lithography and regional plasma treatment. It enables rapid liquid dispensation and droplets array formation just making the chip surface in contact with solution. By combining this chip with a special Christmas Tree structure, the droplets array with concentrations in gradient is generated. It possesses the greatly improved performance of convenience and versatility in bioscreening and biosensing. For example, high throughput condition screening of toxic tests of CdSe quantum dots on HL-60 cells are conducted and cell death rates are successfully counted quickly and efficiently. Furthermore, a rapid biosensing approach for cancer biomarkers carcinoma embryonic antigen (CEA) is developed via magnetic beads (MBs)-based sandwich immunoassay methods.

  11. Edge effects on water droplet condensation

    NASA Astrophysics Data System (ADS)

    Medici, Marie-Gabrielle; Mongruel, Anne; Royon, Laurent; Beysens, Daniel

    2014-12-01

    In this study we investigate the effect of geometrical or thermal discontinuities on the growth of water droplets condensing on a cooled substrate. Edges, corners, and cooled and noncooled boundaries can have a strong effect on the vapor concentration profile and mass diffusion around the drops. In comparison to growth in a pattern where droplets have to compete to catch vapor, which results in a linear water concentration profile directed perpendicularly to the substrate, droplets near discontinuities can get more vapor (outer edges, corners), resulting in faster growth or less vapor (inner edges), giving lower growth. When the cooling heat flux limits growth instead of mass diffusion (substrate with low thermal conductivity, strong heat exchange with air), edge effects can be canceled. In certain cases, growth enhancement can reach nearly 500% on edges or corners.

  12. Droplet Spreading with Sol-Gel Transition

    NASA Astrophysics Data System (ADS)

    Jalaal, Maziyar; Stoeber, Boris; Balmforth, Neil J.

    2014-11-01

    The impact and spreading of liquid droplets on a smooth solid substrate is a classical subject with several industrial applications such as ink-jet printing, spray cooling, coating, and many others. For many of these deposition processes, controlling the final shape of the drop is critical. In the current research, a new technique for controlling the spreading of droplets impacting a substrate is presented. This technique exploits the rheology of a thermo-responsive polymer solution that undergoes a reversible sol/gel transition above a critical temperature. Experiments are conducted using a combination of shadowgraphy and micro-PIV to observe spreading drops. It is shown that the final diameter of a droplet can be controlled through the temperature of the substrate and the tunable sol/gel transition temperature of the fluid.A mathematical model is provided to further elucidate the flow dynamics.

  13. Optical droplet vaporization of micron-sized perfluorocarbon droplets and their photoacoustic detection

    NASA Astrophysics Data System (ADS)

    Strohm, Eric; Rui, Min; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael

    2011-03-01

    An acoustic and photoacoustic characterization of micron-sized perfluorocarbon (PFC) droplets is presented. PFC droplets are currently being investigated as acoustic and photoacoustic contrast agents and as cancer therapy agents. Pulse echo measurements at 375 MHz were used to determine the diameter, ranging from 3.2 to 6.5 μm, and the sound velocity, ranging from 311 to 406 m/s of nine droplets. An average sound velocity of 379 +/- 18 m/s was calculated for droplets larger than the ultrasound beam width of 4.0 μm. Optical droplet vaporization, where vaporization of a single droplet occurred upon laser irradiation of sufficient intensity, was verified using pulse echo acoustic methods. The ultrasonic backscatter amplitude, acoustic impedance and attenuation increased after vaporization, consistent with a phase change from a liquid to gas core. Photoacoustic measurements were used to compare the spectra of three droplets ranging in diameter from 3.0 to 6.2 μm to a theoretical model. Good agreement in the spectral features was observed over the bandwidth of the 375 MHz transducer.

  14. Droplet Combustion in a Slow Convective Flow

    NASA Technical Reports Server (NTRS)

    Nayagam, V.; Hicks, M. C.; Kaib, N.; Ackerman, M.; Haggard, J. B., Jr.; Williams, F. A.

    2001-01-01

    The objective of the present flight experiment definition study is to investigate the effects of slow forced convective flows on the dynamics of isolated single droplet combustion and is designed to complement the quiescent, microgravity droplet combustion experiments (DCE-1 and DCE-2) of Williams and Dryer. The fuels selected for this study are the same as those of DCE, namely, a sooting alkane fuel (heptane) and a non-sooting alcohol (methanol), and imposed flow rates are chosen between 0 and 20 cm/s with varying ambient oxygen concentrations and pressures. Within this velocity range, both accelerating and decelerating flow effects will also be investigated. Two different approaches to generate the forced flow are currently under development in ground-based facilities; the first is a flow tunnel concept where the forced flow is imposed against a stationary droplet, and in the second a tethered droplet is translated at a specified velocity in a quiescent ambient medium. Depending upon the engineering feasibility a selection will be made between these two approaches so that the experiment can be accommodated in the Multiple Droplet Combustion Apparatus (MDCA) currently being designed for the International Space Station. Recently, we have finished designing and fabricating the experimental rigs using both the above mentioned concepts. The flow tunnel concept is implemented in a 2.2 second drop tower rig. Preliminary experiments have been carried out using heptane and methanol in air at atmospheric pressure. The translating droplet apparatus is scheduled to be tested in the 5 second drop facility in the near future. This report presents some of the experimental results obtained for heptane.

  15. TRAJECTORY AND INCINERATION OF ROGUE DROPLETS IN A TURBULENT DIFFUSION FLAME

    EPA Science Inventory

    The trajectory and incineration efficiency of individual droplet streams of a fuel mixture injected into a swirling gas turbulent diffusion flame were measured as a function of droplet size, droplet velocity, interdroplet spacing, and droplet injection angle. Additional experimen...

  16. Free running droplets on packed powder beds

    NASA Astrophysics Data System (ADS)

    Whitby, Catherine P.; Bian, Xun; Sedev, Rossen

    2013-06-01

    We observed that water drops placed on horizontal beds of fine molybdenite particles move freely over the bed surface for about 1 second. The drops collect an irregular coating of unevenly distributed particles as they bounce and roll. We manipulated the distance that the drops travel, and hence the area of the droplet surface coated with particles, by varying the water surface tension and the kinetic energy of the initial droplet impact on the bed surface. Our results highlight the role of contact angle hysteresis in particle encapsulation of liquid drops.

  17. Nonspherical liquid droplet falling in air

    NASA Astrophysics Data System (ADS)

    Agrawal, Meenu; Premlata, A. R.; Tripathi, Manoj Kumar; Karri, Badarinath; Sahu, Kirti Chandra

    2017-03-01

    The dynamics of an initially nonspherical liquid droplet falling in air under the action of gravity is investigated via three-dimensional numerical simulations of the Navier-Stokes and continuity equations in the inertial regime. The surface tension is considered to be high enough so that a droplet does not undergo breakup. Vertically symmetric oscillations which decay with time are observed for low inertia. The amplitude of these oscillations increases for high Gallilei numbers and the shape asymmetry in the vertical direction becomes prominent. The reason for this asymmetry has been attributed to the higher aerodynamic inertia. Moreover, even for large inertia, no path deviations or oscillations are observed.

  18. Optical vortices from liquid crystal droplets.

    PubMed

    Brasselet, Etienne; Murazawa, Naoki; Misawa, Hiroaki; Juodkazis, Saulius

    2009-09-04

    We report on the generation of mono- and polychromatic optical phase singularities from micron-sized birefringent droplets. This is done experimentally by using liquid crystal droplets whose three dimensional architecture of the optical axis is controlled within the bulk by surfactant agents. Because of its microscopic size these optical vortex generators are optically trapped and manipulated at will, thus realizing a robust self-aligned micro-optical device for orbital angular momentum conversion. Experimental observations are supported by a simple model of optical spin-orbit coupling in uniaxial dielectrics that emphasizes the prominent role of the transverse optical anisotropy with respect to the beam propagation direction.

  19. Hydrodynamic dispensing and electrical manipulation of attolitre droplets

    NASA Astrophysics Data System (ADS)

    Zhang, Yanzhen; Zhu, Benliang; Liu, Yonghong; Wittstock, Gunther

    2016-08-01

    Dispensing and manipulation of small droplets is important in bioassays, chemical analysis and patterning of functional inks. So far, dispensing of small droplets has been achieved by squeezing the liquid out of a small orifice similar in size to the droplets. Here we report that instead of squeezing the liquid out, small droplets can also be dispensed advantageously from large orifices by draining the liquid out of a drop suspended from a nozzle. The droplet volume is adjustable from attolitre to microlitre. More importantly, the method can handle suspensions and liquids with viscosities as high as thousands mPa s markedly increasing the range of applicable liquids for controlled dispensing. Furthermore, the movement of the dispensed droplets is controllable by the direction and the strength of an electric field potentially allowing the use of the droplet for extracting analytes from small sample volume or placing a droplet onto a pre-patterned surface.

  20. Droplet motion driven by electro-elasto-capillary effects

    NASA Astrophysics Data System (ADS)

    Shah, Jaymeen; Yang, Xin; Sun, Ying

    2013-11-01

    The motion of droplets on natural and synthetic fibers underlines many technological applications including flexible displays, insulation, and smart filters. However, there is a lack of fundamental understanding of the coupled electrical, elastic, and capillary forces on droplets in fiber networks. In the present study, the motion of a water droplet suspended between two electrically insulated fibers of different Young's modulus, lengths and diameters are examined under electric fields. The results on rigid fibers reveal a critical voltage, under which the droplet remain stationary. Above this critical voltage, droplet self-propulsion is observed as a result of the interplay of electro, elasto and capillary forces on the droplet. The effects of the inter-fiber distance and Young's modulus on droplet motion are also discussed. The controllable motion of droplets can be used to manipulate or transport liquid at small scales.

  1. The measurement of droplet temperature using thermochromic liquid crystals

    SciTech Connect

    Peterson, D.; Hu, S.H.; Richards, C.D.; Richards, R.F.

    1995-12-31

    A noninvasive technique to determine the temperature of droplets in flight is under development. The technique involves atomizing droplets of neat thermochromic liquid crystals and then inferring the droplet temperatures form the liquid crystals` color-play. Previous work has shown the feasibility of atomizing the neat liquid crystal. The present work reports results of a calibration of the temperature response of 200 to 300 micron droplets of neat liquid crystal. The calibration is accomplished by suspending droplets of the neat liquid crystal on a microthermocouple within a controlled temperature environment. The droplet is imaged using a long-distance microscope, an RGB video camera, and a frame grabber. Images of the droplet are acquired and digitized to quantify changes in RGB values (color) with temperature. The RGB information is transformed into hue, saturation, intensity (HSI) space to relate hue, H, to temperature. The temperature of the droplet is measured directly with the micro-thermocouple.

  2. Heat transfer and phase change in an impinging droplet

    NASA Astrophysics Data System (ADS)

    Rangchian, Aysan; Shirazi, Nikki L.; Kavehpour, H. Pirouz

    2016-11-01

    Non isothermal droplet impact on solid surfaces has several industrial applications such as spray cooling and 3D printing. Impinging of a droplet on a surface involves an initial phase of spreading followed by a subsequent return to the equilibrium shape. Thermal energy exchanged within the droplet fluid as well as between liquid/solid during the impact has been studied using an ultra high speed infrared camera. Variable parameters in the experiment include droplet temperature and kinetic energy of the droplet during the impact. The evolution of droplet shape viewed by IR camera is similar to what previously observed by high speed photography. The thermal map of droplet over time in these experiments agrees with previously reported numerical simulation. In addition, spacial and temporal temperature variations of liquid droplets on a surface as they solidify are presented. IR camera provides an accurate temperature diagram as the phase change occurs, which is essential for understanding the physics of 3D printing.

  3. Hydrodynamic dispensing and electrical manipulation of attolitre droplets

    PubMed Central

    Zhang, Yanzhen; Zhu, Benliang; Liu, Yonghong; Wittstock, Gunther

    2016-01-01

    Dispensing and manipulation of small droplets is important in bioassays, chemical analysis and patterning of functional inks. So far, dispensing of small droplets has been achieved by squeezing the liquid out of a small orifice similar in size to the droplets. Here we report that instead of squeezing the liquid out, small droplets can also be dispensed advantageously from large orifices by draining the liquid out of a drop suspended from a nozzle. The droplet volume is adjustable from attolitre to microlitre. More importantly, the method can handle suspensions and liquids with viscosities as high as thousands mPa s markedly increasing the range of applicable liquids for controlled dispensing. Furthermore, the movement of the dispensed droplets is controllable by the direction and the strength of an electric field potentially allowing the use of the droplet for extracting analytes from small sample volume or placing a droplet onto a pre-patterned surface. PMID:27514279

  4. Combinatorial microfluidic droplet engineering for biomimetic material synthesis

    PubMed Central

    Bawazer, Lukmaan A.; McNally, Ciara S.; Empson, Christopher J.; Marchant, William J.; Comyn, Tim P.; Niu, Xize; Cho, Soongwon; McPherson, Michael J.; Binks, Bernard P.; deMello, Andrew; Meldrum, Fiona C.

    2016-01-01

    Although droplet-based systems are used in a wide range of technologies, opportunities for systematically customizing their interface chemistries remain relatively unexplored. This article describes a new microfluidic strategy for rapidly tailoring emulsion droplet compositions and properties. The approach uses a simple platform for screening arrays of droplet-based microfluidic devices and couples this with combinatorial selection of the droplet compositions. Through the application of genetic algorithms over multiple screening rounds, droplets with target properties can be rapidly generated. The potential of this method is demonstrated by creating droplets with enhanced stability, where this is achieved by selecting carrier fluid chemistries that promote titanium dioxide formation at the droplet interfaces. The interface is a mixture of amorphous and crystalline phases, and the resulting composite droplets are biocompatible, supporting in vitro protein expression in their interiors. This general strategy will find widespread application in advancing emulsion properties for use in chemistry, biology, materials, and medicine. PMID:27730209

  5. Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets

    NASA Technical Reports Server (NTRS)

    Dorsch, R. G.; Hacker, P. T.

    1950-01-01

    A photomicrographic technique for investigating eupercooled. water droplets has been devised and. used. to determine the spontaneous freezing temperatures of eupercooled. water droplets of the size ordinarily found. in the atmosphere. The freezing temperatures of 4527 droplets ranging from 8.75 to 1000 microns in diameter supported on a platinum surface and 571 droplets supported on copper were obtained. The average spontaneous freezing temperature decreased with decrease in the size of the droplets. The effect of size on the spontaneous freezing temperature was particularly marked below 60 microns. Frequency-distribution curves of the spontaneous freezing temperatures observed for droplets of a given size were obtained. Although no droplet froze at a temperature above 20 0 F, all droplets melted at 32 F. Results obtained with a copper support did not differ essentially from those obtained with a platinum surface.

  6. Deforming water droplets with a superhydrophobic silica coating.

    PubMed

    Li, Xiaoguang; Shen, Jun

    2013-11-04

    The surface liquidity of a water droplet is eliminated by rubbing hydrophobic particles onto the droplet surface using a sol-gel silica coating with extremely weak binding force, which results in solid-like deformability of a liquid drop.

  7. Light Driven Formation and Rupture of Droplet Bilayers

    PubMed Central

    Dixit, Sanhita S.; Kim, Hanyoup; Vasilyev, Arseny; Eid, Aya; Faris, Gregory W.

    2010-01-01

    We demonstrate optical manipulation of nanoliter aqueous droplets containing surfactant or lipid molecules and immersed in an organic liquid using near infrared light. The resulting emulsion droplets are manipulated using both the thermocapillary effect and convective fluid motion. Droplet pair-interactions induced in the emulsion upon optical initiation and control provide direct observations of the coalescence steps in intricate detail. Droplet-droplet adhesion (bilayer formation) is observed under several conditions. Selective bilayer rupture is also realized using the same infrared laser. The technique provides a novel approach to study thin film drainage and interface stability in emulsion dynamics. The formation of stable lipid bilayers at the adhesion interface between interacting water droplets can provide an optical platform to build droplet-based lipid bilayer assays. The technique also has relevance for understanding and improving microfluidics applications by devising Petri dish based droplet assays requiring no substrate fabrication. PMID:20361732

  8. A novel coarsening mechanism of droplets in immiscible fluid mixtures

    NASA Astrophysics Data System (ADS)

    Shimizu, Ryotaro; Tanaka, Hajime

    2015-06-01

    In our daily lives, after shaking a salad dressing, we see the coarsening of oil droplets suspended in vinegar. Such a demixing process is observed everywhere in nature and also of technological importance. For a case of high droplet density, domain coarsening proceeds with inter-droplet collisions and the resulting coalescence. This phenomenon has been explained primarily by the so-called Brownian-coagulation mechanism: stochastic thermal forces exerted by molecules induce random motion of individual droplets, causing accidental collisions and subsequent interface-tension-driven coalescence. Contrary to this, here we demonstrate that the droplet motion is not random, but hydrodynamically driven by the composition Marangoni force due to an interfacial tension gradient produced in each droplet as a consequence of composition correlation among droplets. This alters our physical understanding of droplet coarsening in immiscible liquid mixtures on a fundamental level.

  9. Sensitive and predictable separation of microfluidic droplets by size using in-line passive filter.

    PubMed

    Ding, Ruihua; Ung, W Lloyd; Heyman, John A; Weitz, David A

    2017-01-01

    Active manipulation of droplets is crucial in droplet microfluidics. However, droplet polydispersity decreases the accuracy of active manipulation. We develop a microfluidic "droplet filter" that accurately separates droplets by size. The droplet filter has a sharp size cutoff and is capable of distinguishing droplets differing in volume by 20%. A simple model explains the behavior of the droplets as they pass through the filter. We show application of the filter in improving dielectric sorting efficiency.

  10. Computational Study of Colloidal Droplet Interactions with Three Dimensional Structures

    DTIC Science & Technology

    2015-05-18

    SECURITY CLASSIFICATION OF: The colloidal droplet spreading on and sorption into a porous medium is important to 3D printing technology. In this study... colloidal fluid distribution in the porous structure after sorption of single/multiple droplets in powder beds. The spreading of the droplet on the surface...Feb-2015 Approved for Public Release; Distribution Unlimited Final Report: Computational Study of Colloidal Droplet Interactions with Three Dimensional

  11. Pressure-volume curves, static compliances and gas exchange in hyaline membrane disease during conventional mechanical and high-frequency ventilation.

    PubMed

    Pfenninger, J; Minder, C

    1988-01-01

    Eight premature infants with hyaline membrane disease needing artificial ventilation were studied at a mean age of 26.5 h. After a preparative phase they were randomly assigned either first to conventional mechanical ventilation (CMV; delivered by a Siemens Servo 900 C), followed by high-frequency ventilation (HFV; delivered by Percussionaire VDR 1 at 10 Hz) or vice versa, each period lasting 4 h. At the end of each period, arterial blood gases, lung volumes and alveolar pressures (Palv) during CMV or HFV and pressure-volume (P-V) curves of the total respiratory system were determined. Expiratory volumes were measured spirometrically, Palv by the clamping method, and the P-V curve was constructed by the syringe method. Single point static compliance at end-inspiration was higher during HFV (0.40 +/- 0.10 vs. 0.32 +/- 0.08 ml/cmH2O.kg-1; p = 0.02), whereas at end-expiration no difference was noted. Two points static compliances were also better during HFV than during CMV (0.32 +/- 0.08 vs. 0.24 +/- 0.06 ml/cmH2O.kg-1; p = 0.01). Static compliances derived from the steepest part of the inflation limb of the P-V curve were 0.55 +/- 0.12 after CMV and 0.50 +/- 0.12 ml/cmH2O.kg-1 after HFV (n.s.). Compared to CMV, HFV resulted in similar oxygenation and CO2-elimination at equal mean lung volumes, but at significantly lower mean Palv. It is concluded that recruitment of lung volume is achieved with less static recoil pressure by HFV. These findings are explained by differences in inspiration allowing more time for volume recruitment during HFV.

  12. In-situ birth of MSCs multicellular spheroids in poly(L-glutamic acid)/chitosan scaffold for hyaline-like cartilage regeneration.

    PubMed

    Zhang, Kunxi; Yan, Shifeng; Li, Guifei; Cui, Lei; Yin, Jingbo

    2015-12-01

    The success of mesenchymal stem cells (MSCs) based articular cartilage tissue engineering is limited by the presence of fibrous tissue in generated cartilage, which is associated with the current scaffold strategy that promotes cellular adhesion and spreading. Here we design a non-fouling scaffold based on amide bonded poly(l-glutamic acid) (PLGA) and chitosan (CS) to drive adipose stem cells (ASCs) to aggregate to form multicellular spheroids with diameter of 80-110 μm in-situ. To illustrate the advantage of the present scaffolds, a cellular adhesive scaffold based on the same amide bonded PLGA and CS was created through a combination of air-drying and freeze-drying to limit the hydration effect while also achieving porous structure. Compared to ASCs spreading along the surface of pores within scaffold, the dense mass of aggregated ASCs in PLGA/CS scaffold exhibited enhanced chondrogenic differentiation capacity, as determined by up-regulated GAGs and COL II expression, and greatly decreased COL I deposition during in vitro chondrogenesis. Furthermore, after 12 weeks of implantation, neo-cartilages generated by ASCs adhered on scaffold significantly presented fibrous matrix which was characterized by high levels of COL I deposition. However, neo-cartilage at 12 weeks post-implantation generated by PLGA/CS scaffold carrying ASC spheroids possessed similar high level of GAGs and COL II and low level of COL I as that in normal cartilage. The in vitro and in vivo results indicated the present strategy could not only promote chondrogenesis of ASCs, but also facilitate hyaline-like cartilage regeneration with reduced fibrous tissue formation which may attenuate cartilage degradation in future long-term follow-up.

  13. Droplet-based microsystem for multi-step bioreactions.

    PubMed

    Wang, Fang; Burns, Mark A

    2010-06-01

    A droplet-based microfluidic platform was used to perform on-chip droplet generation, merging and mixing for applications in multi-step reactions and assays. Submicroliter-sized droplets can be produced separately from three identical droplet-generation channels and merged together in a single chamber. Three different mixing strategies were used for mixing the merged droplet. For pure diffusion, the reagents were mixed in approximately 10 min. Using flow around the stationary droplet to induce circulatory flow within the droplet, the mixing time was decreased to approximately one minute. The shortest mixing time (10 s) was obtained with bidirectional droplet motion between the chamber and channel, and optimization could result in a total time of less than 1 s. We also tested this on-chip droplet generation and manipulation platform using a two-step thermal cycled bioreaction: nested TaqMan PCR. With the same concentration of template DNA, the two-step reaction in a well-mixed merged droplet shows a cycle threshold of approximately 6 cycles earlier than that in the diffusively mixed droplet, and approximately 40 cycles earlier than the droplet-based regular (single-step) TaqMan PCR.

  14. Versatile on-demand droplet generation for controlled encapsulation

    PubMed Central

    Rhee, Minsoung; Liu, Peng; Meagher, Robert J.; Light, Yooli K.; Singh, Anup K.

    2014-01-01

    We present a droplet-based microfluidic system for performing bioassays requiring controlled analyte encapsulation by employing highly flexible on-demand droplet generation. On-demand droplet generation and encapsulation are achieved pneumatically using a microdispensing pump connected to a constant pressure source. The system generates single droplets to the collection route only when the pump is actuated with a designated pressure level and produces two-phase parallel flow to the waste route during the stand-by state. We analyzed the effect of actuation pressure on the stability and size of droplets and optimized conditions for generation of stable droplets over a wide pressure range. By increasing the duration of pump actuation, we could either trigger a short train of identical size droplets or generate a single larger droplet. We also investigated the methodology to control droplet contents by fine-tuning flow rates or implementing a resistance bridge between the pump and main channels. We demonstrated the integrated chip for on-demand mixing between two aqueous phases in droplets and on-demand encapsulation of Escherichia coli cells. Our unique on-demand feature for selective encapsulation is particularly appropriate for bioassays with extremely dilute samples, such as pathogens in a clinical sample, since it can significantly reduce the number of empty droplets that impede droplet collection and subsequent data analysis. PMID:25379072

  15. Response of two-phase droplets to intense electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.

    1993-01-01

    The behavior of two-phase droplets subjected to high intensity radiation pulses is studied. Droplets are highly absorbing solids in weakly absorbing liquid medium. The objective of the study was to define heating thresholds required for causing explosive boiling and secondary atomization of the fuel droplet. The results point to mechanisms for energy storage and transport in two-phase systems.

  16. Dynamic Melting of Freezing Droplets on Ultraslippery Superhydrophobic Surfaces.

    PubMed

    Chu, Fuqiang; Wu, Xiaomin; Wang, Lingli

    2017-03-08

    Condensed droplet freezing and freezing droplet melting phenomena on the prepared ultraslippery superhydrophobic surface were observed and discussed in this study. Although the freezing delay performance of the surface is common, the melting of the freezing droplets on the surface is quite interesting. Three self-propelled movements of the melting droplets (ice- water mixture) were found including the droplet rotating, the droplet jumping, and the droplet sliding. The melting droplet rotating, which means that the melting droplet rotates spontaneously on the superhydrophobic surface like a spinning top, is first reported in this study and may have some potential applications in various engineering fields. The melting droplet jumping and sliding are similar to those occurring during condensation but have larger size scale and motion scale, as the melting droplets have extra-large specific surface area with much more surface energy available. These self-propelled movements make all the melting droplets on the superhydrophobic surface dynamic, easily removed, which may be promising for the anti-icing/frosting applications.

  17. Encapsulation of single cells into monodisperse droplets by fluorescence-activated droplet formation on a microfluidic chip.

    PubMed

    Hu, Rui; Liu, Pian; Chen, Pu; Wu, Liang; Wang, Yao; Feng, Xiaojun; Liu, Bi-Feng

    2016-06-01

    Random compartmentalization of cells by common droplet formation methods, i.e., T-junction and flow-focusing, results in low occupancy of droplets by single cells. To resolve this issue, a fluorescence-activated droplet formation method was developed for the on-command generation of droplets and encapsulation of single cells. In this method, droplets containing one cell were generated by switching on/off a two-phase hydrodynamic gating valve upon optical detection of single cells. To evaluate the developed method, flow visualization experiments were conducted with fluorescein. Results indicated that picoliter droplets of uniform sizes (RSD<4.9%) could be generated. Encapsulation of single fluorescent polystyrene beads demonstrated an average of 94.3% droplets contained one bead. Further application of the developed methods to the compartmentalization of individual HeLa cells indicated 82.5% occupancy of droplets by single cells, representing a 3 fold increase in comparison to random compartmentalization.

  18. Fabrication of Janus droplets by evaporation driven liquid-liquid phase separation.

    PubMed

    Zhang, Qingquan; Xu, Meng; Liu, Xiaojun; Zhao, Wenfeng; Zong, Chenghua; Yu, Yang; Wang, Qi; Gai, Hongwei

    2016-04-11

    We present a universal and scalable method to fabricate Janus droplets based on evaporation driven liquid-liquid phase separation. In this work, the morphologies and chemical properties of separate parts of the Janus droplets can be flexibly regulated, and more complex Janus droplets (such as core-shell Janus droplets, ternary Janus droplets, and multiple Janus droplets) can be constructed easily.

  19. Analysis of the equilibrium droplet shape based on an ellipsoidal droplet model.

    PubMed

    Lubarda, Vlado A; Talke, Kurt A

    2011-09-06

    The extent of a droplet's spreading over a flat, smooth solid substrate and its equilibrium height in the presence of gravity are determined approximately, without a numerical solution of the governing nonlinear differential equation, by assuming that the droplet takes on the shape of an oblate spheroidal cap and by minimizing the corresponding free energy. The comparison with the full numerical evaluations confirms that the introduced approximation and the obtained results are accurate for contact angles below about 120° and for droplet sizes on the order of the capillary length of the liquid. The flattening effect of gravity is to increase the contact radius and decrease the height of the droplet, with these being more pronounced for higher values of the Bond number.

  20. Electrocoalescence based serial dilution of microfluidic droplets.

    PubMed

    Bhattacharjee, Biddut; Vanapalli, Siva A

    2014-07-01

    Dilution of microfluidic droplets where the concentration of a reagent is incrementally varied is a key operation in drop-based biological analysis. Here, we present an electrocoalescence based dilution scheme for droplets based on merging between moving and parked drops. We study the effects of fluidic and electrical parameters on the dilution process. Highly consistent coalescence and fine resolution in dilution factor are achieved with an AC signal as low as 10 V even though the electrodes are separated from the fluidic channel by insulator. We find that the amount of material exchange between the droplets per coalescence event is high for low capillary number. We also observe different types of coalescence depending on the flow and electrical parameters and discuss their influence on the rate of dilution. Overall, we find the key parameter governing the rate of dilution is the duration of coalescence between the moving and parked drop. The proposed design is simple incorporating the channel electrodes in the same layer as that of the fluidic channels. Our approach allows on-demand and controlled dilution of droplets and is simple enough to be useful for assays that require serial dilutions. The approach can also be useful for applications where there is a need to replace or wash fluid from stored drops.

  1. Microfluidic droplet enrichment for targeted sequencing

    PubMed Central

    Eastburn, Dennis J.; Huang, Yong; Pellegrino, Maurizio; Sciambi, Adam; Ptáček, Louis J.; Abate, Adam R.

    2015-01-01

    Targeted sequence enrichment enables better identification of genetic variation by providing increased sequencing coverage for genomic regions of interest. Here, we report the development of a new target enrichment technology that is highly differentiated from other approaches currently in use. Our method, MESA (Microfluidic droplet Enrichment for Sequence Analysis), isolates genomic DNA fragments in microfluidic droplets and performs TaqMan PCR reactions to identify droplets containing a desired target sequence. The TaqMan positive droplets are subsequently recovered via dielectrophoretic sorting, and the TaqMan amplicons are removed enzymatically prior to sequencing. We demonstrated the utility of this approach by generating an average 31.6-fold sequence enrichment across 250 kb of targeted genomic DNA from five unique genomic loci. Significantly, this enrichment enabled a more comprehensive identification of genetic polymorphisms within the targeted loci. MESA requires low amounts of input DNA, minimal prior locus sequence information and enriches the target region without PCR bias or artifacts. These features make it well suited for the study of genetic variation in a number of research and diagnostic applications. PMID:25873629

  2. Two Droplets Burning Side by Side

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber-Supported Droplet Combustion (FSDC) experiment team got more than twice as many burns have been completed as were originally scheduled for STS-95. This image was taken July 12, 1997, MET:10/08:13 (approximate). As shown here, scientists were able to burn two droplets side by side, more closely mimicking behavior of burning fuel in an engine. This shows ignition of a single drop that subsequently burned while a fan blew through the chamber, giving the scientists data on burning with convection, but no buoyancy -- an important distinction when you're trying to solve a problem by breaking it into parts. FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.1 MB, 11-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300176.html.

  3. The effects of sooting in droplet combustion

    NASA Technical Reports Server (NTRS)

    Lee, Kyeong-Ook; Jensen, Kirk; Choi, Mun Young

    1995-01-01

    The study of the burning of a single droplet is an ideal problem from which to gain fundamental understanding of diffusion flame characteristics. Droplet combustion is a complex physico-chemical process that involves a chemically-reacting two-phase flow with phase changes and yet simple experiments and analysis can be used to attain important insights into the burning rate, flame dynamics, kinetic extinction and disruption processes. It is a subject that has been actively studied for the past 40 years with most of the fundamental experiments being performed under reduced-gravity conditions for direct comparisons with theoretical/computational analyses that invoke spherical symmetry assumptions. In the earlier studies, the effects of sooting on the overall burning characteristics were not considered. However, recent microgravity investigations performed at the NASA-LeRC droptowers (Droplet Combustion Experiment) and others indicate that effects of soot and sootcloud formation may be significant during the lifetime of the droplet and therefore must be included in the analysis.

  4. Droplet vaporization in a supercritical microgravity environment

    NASA Astrophysics Data System (ADS)

    Curtis, E. W.; Farrell, P. V.

    A model has been developed for non-convective vaporization of liquid fuel droplets in an environment above the liquid critical pressure and near or above the liquid critical temperature. The model employs conservation of mass, energy and chemical species, along with transport properties which vary with temperature and species concentration. The liquid interface is assumed to be in thermodynamic equilibrium. The interface problem is solved using the Gibbs-Duhem relationship, and evaluating mixture fugacities using a modified Redlich-Kwong equation of state for the mixture. Due to the limited range of this equation, a curve-fit equation of state suitable for conditions far from the liquid critical point was applied. Results are presented for an n-octane liquid drop in nitrogen gas. For two gas conditions, several droplet sizes are modeled. Results include droplet size histories, surface temperature histories, and liquid and gas phase temperature profiles. The liquid vaporization rate is increased significantly for supercritical conditions compared to subcritical conditions. Using the specified equation of state for the ambient conditions tested, the droplet is completely vaporized before the liquid surface is heated to the liquid critical temperature.

  5. The Physics of Foams, Droplets and Bubbles

    ERIC Educational Resources Information Center

    Sarker, Dipak K.

    2013-01-01

    Foams or bubble dispersions are common to milkshakes, bread, champagne froth, shaving mousse, shampoo, crude oil extraction systems, upholstery packing and bubble wrap, whereas the term droplet is often synonymous with either a small drop of water or a drop of oil--a type of coarse dispersion. The latter are seen in butter and milk, household…

  6. Confined ferrofluid droplet in crossed magnetic fields.

    PubMed

    Jackson, D P; Miranda, J A

    2007-08-01

    When a ferrofluid drop is trapped in a horizontal Hele-Shaw cell and subjected to a vertical magnetic field, a fingering instability results in the droplet evolving into a complex branched structure. This fingering instability depends on the magnetic field ramp rate but also depends critically on the initial state of the droplet. Small perturbations in the initial droplet can have a large influence on the resulting final pattern. By simultaneously applying a stabilizing (horizontal) azimuthal magnetic field, we gain more control over the mode selection mechanism. We perform a linear stability analysis that shows that any single mode can be selected by appropriately adjusting the strengths of the applied fields. This offers a unique and accurate mode selection mechanism for this confined magnetic fluid system. We present the results of numerical simulations that demonstrate that this mode selection mechanism is quite robust and "overpowers" any initial perturbations on the droplet. This provides a predictable way to obtain patterns with any desired number of fingers.

  7. Lung deposition of droplet aerosols in monkeys.

    PubMed

    Cheng, Y S; Irshad, H; Kuehl, P; Holmes, T D; Sherwood, R; Hobbs, C H

    2008-09-01

    Nonhuman primates are often the animal models of choice to study the infectivity and therapy of inhaled infectious agents. Most animal models for inhaled infectious diseases use aerosol/droplets generated by an atomization technique such as a Collison nebulizer that produces particles in the size range of 1 to 3 microm in diameter. There are few data in the literature on deposition patterns in monkeys. Our study was designed to measure the deposition pattern in monkeys using droplets having diameters of 2 and 5 microm using an exposure system designed to expose monkeys to aerosols of infectious agents. Six cynomolgus monkeys were exposed to droplets. The aerosol solution was generated from a Vero cell supernate containing DMEM + 10% fetal bovine serum tagged with Tc-99m radiolabel. Collison and Retec nebulizers were used to generate small and large droplets, respectively. The particle size (as determined from a cascade impactor) showed an activity median aerodynamic diameter (AMAD) of 2.3 and 5.1 microm for the Collison and Retec nebulizer, respectively. The animals were anesthetized, placed in a plethysmography box, and exposed to the aerosol. The deposition pattern was determined using a gamma camera. Deposition in the head airways was 39% and 58% for 2.3- and 5.1-microm particle aerosols, respectively, whereas the deposition in the deep lung was 12% and 8%, respectively. This information will be useful in developing animal models for inhaled infectious agents.

  8. CFD Simulations of Vibration Induced Droplet Ejection.

    NASA Astrophysics Data System (ADS)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1998-11-01

    Vibration-induced droplet ejection is a process that occurs when a liquid droplet is placed on a vibrating membrane. Above a critical value of the excitation amplitude, Faraday waves form on the surface of the drop. As the amplitude is increased secondary drops are ejected from the wave crests. A Navier-Stokes solver designed to simulate the transient fluid mechanics of the process is presented. The solver is based on a MAC method on a staggered grid. A volume of fluid method is implemented to track the free surface. The volume fraction is advected via a second-order, unsplit method that minimizes numerical diffusion of the interface. Surface tension is incorporated as a continuum surface force. This work is intended to provide a comprehensive description of the fluid dynamics involved in vibration-induced droplet ejection, with the aim of understanding the mechanism behind the ejection process. The evolution of the interface through droplet ejection will be simulated. The dependence of the ejection process on the driving parameters will be evaluated and the resonance characteristics of the drop will be determined. The results of the computations will be compared with experimental results.

  9. Electrocoalescence based serial dilution of microfluidic droplets

    PubMed Central

    Bhattacharjee, Biddut; Vanapalli, Siva A.

    2014-01-01

    Dilution of microfluidic droplets where the concentration of a reagent is incrementally varied is a key operation in drop-based biological analysis. Here, we present an electrocoalescence based dilution scheme for droplets based on merging between moving and parked drops. We study the effects of fluidic and electrical parameters on the dilution process. Highly consistent coalescence and fine resolution in dilution factor are achieved with an AC signal as low as 10 V even though the electrodes are separated from the fluidic channel by insulator. We find that the amount of material exchange between the droplets per coalescence event is high for low capillary number. We also observe different types of coalescence depending on the flow and electrical parameters and discuss their influence on the rate of dilution. Overall, we find the key parameter governing the rate of dilution is the duration of coalescence between the moving and parked drop. The proposed design is simple incorporating the channel electrodes in the same layer as that of the fluidic channels. Our approach allows on-demand and controlled dilution of droplets and is simple enough to be useful for assays that require serial dilutions. The approach can also be useful for applications where there is a need to replace or wash fluid from stored drops. PMID:25379096

  10. Precise quantitative addition of multiple reagents into droplets in sequence using glass fiber-induced droplet coalescence.

    PubMed

    Li, Chunyu; Xu, Jian; Ma, Bo

    2015-02-07

    Precise quantitative addition of multiple reagents into droplets in sequence is still a bottleneck in droplet-based analysis. To address this issue, we presented a simple and robust glass fiber-induced droplet coalescence method. The hydrophilic glass fiber embedded in the microchannels can induce the deformation of droplets and trigger the coalescence. Serial addition of reagents with controlled volumes was performed by this method without the requirement for an external power source.

  11. Nucleation and droplet growth at high pressure

    NASA Astrophysics Data System (ADS)

    Luijten, Carlo Cornelis Maria

    Homogeneous nucleation, the first stage of droplet formation in the absence of foreign particles, usually takes place in the presence of one or more supercritical carrier gases. The present work aimed at a systematic investigation of the effects of carrier gas pressure on nucleation and droplet growth. Using the so-called nucleation pulse method, nucleation and droplet growth can be separated in time, which facilitates quantitative study of these processes using Constant Angle Mie Scattering and light extinction. The method was implemented in a modified shock tube, using gas dynamic principles to create the pulse. In this way, nucleation and growth rates were measured as a function of temperature, pressure, and composition. Composition measurement at high pressure was achieved along two different routes. Water vapour concentrations were determined using a commercial humidity sensor, after calibration with total pressure as an independent parameter. Gas chromatography was used to determine hydrocarbon concentrations, after pressure reduction of the mixture over a thermostatic capillary tube. Using the above analysis techniques, nucleation and droplet growth experiments were performed for several vapour-gas mixtures, at pressures between 1 and 40 bar. Mixtures with a varying degree of interaction were selected, to allow for a systematic investigation of carrier gas influence. Besides these binary mixtures, the first quantitative nucleation and growth rates for- multicomponent-natural gas were obtained. Theoretical models for both nucleation and droplet growth were adapted to take into account the presence of a carrier gas, under condition of small carrier gas solubility. The main effects involved are the increase of saturated vapour density and decrease of surface tension with pressure. On the basis of our experiments, these effects were demonstrated to play important and counteracting roles in high pressure nucleation. Using Density Functional Theory, both effects

  12. A DROPLET MODEL OF QUIESCENT PROMINENCE DOWNFLOWS

    SciTech Connect

    Haerendel, G.; Berger, T.

    2011-04-20

    Observations of quiescent prominences with the Solar Optical Telescope on the Hinode satellite have revealed the ubiquitous existence of downflows forming coherent thin and highly structured vertically oriented threads with velocities between 10 and 20 km s{sup -1}. Their widths range between 300 and 500 km. They are often initiated at the top of the visible prominence, but sometimes also at intermediate level. We propose that the downflows are made of plasma packets that squeeze themselves through the dominantly horizontal field under the action of gravity. Their origin is assumed to be hot plasma supplied from either inside or the immediate vicinity of the prominence and condensing at its top. Under compression and further cooling, the matter overflows to the flanks of the prominence dragging its magnetic field with it. Under the increasing action of gravity, vertical structures are forming which eventually disconnect from the field of the inflow channel thus forming finite plasma packets. This process is reminiscent of water flowing over a mountain ridge and breaking up into a multitude of droplets. Like water droplets being subject to air drag, the falling plasma droplets experience a drag force by the horizontal prominence field and assume a steady vertical velocity. This happens via the excitation of Alfven waves. Lateral confinement by the prominence field determines their spatial extent. The small scales of the droplets and the directional balance of their internal tangled magnetic fields can explain the absence of appreciable vertical components in magnetic field measurements. On the basis of the observed width and vertical speed of the downflows and by adopting a prominence field of about 8 G, we derive central density and temperature of the droplets, which turn out to be quite consistent with known prominence characteristics. In the formulation of the drag force a dimensionless 'magnetic drag coefficient' has been introduced with a value well below unity.

  13. Engineering plant membranes using droplet interface bilayers

    PubMed Central

    Barlow, N. E.; Smpokou, E.; Macey, R.; Gould, I. R.; Turnbull, C.; Flemming, A. J.; Brooks, N. J.; Ces, O.; Barter, L. M. C.

    2017-01-01

    Droplet interface bilayers (DIBs) have become widely recognised as a robust platform for constructing model membranes and are emerging as a key technology for the bottom-up assembly of synthetic cell-like and tissue-like structures. DIBs are formed when lipid-monolayer coated water droplets are brought together inside a well of oil, which is excluded from the interface as the DIB forms. The unique features of the system, compared to traditional approaches (e.g., supported lipid bilayers, black lipid membranes, and liposomes), is the ability to engineer multi-layered bilayer networks by connecting multiple droplets together in 3D, and the capability to impart bilayer asymmetry freely within these droplet architectures by supplying droplets with different lipids. Yet despite these achievements, one potential limitation of the technology is that DIBs formed from biologically relevant components have not been well studied. This could limit the reach of the platform to biological systems where bilayer composition and asymmetry are understood to play a key role. Herein, we address this issue by reporting the assembly of asymmetric DIBs designed to replicate the plasma membrane compositions of three different plant species; Arabidopsis thaliana, tobacco, and oats, by engineering vesicles with different amounts of plant phospholipids, sterols and cerebrosides for the first time. We show that vesicles made from our plant lipid formulations are stable and can be used to assemble asymmetric plant DIBs. We verify this using a bilayer permeation assay, from which we extract values for absolute effective bilayer permeation and bilayer stability. Our results confirm that stable DIBs can be assembled from our plant membrane mimics and could lead to new approaches for assembling model systems to study membrane translocation and to screen new agrochemicals in plants.

  14. An interface tracking model for droplet electrocoalescence.

    SciTech Connect

    Erickson, Lindsay Crowl

    2013-09-01

    This report describes an Early Career Laboratory Directed Research and Development (LDRD) project to develop an interface tracking model for droplet electrocoalescence. Many fluid-based technologies rely on electrical fields to control the motion of droplets, e.g. microfluidic devices for high-speed droplet sorting, solution separation for chemical detectors, and purification of biodiesel fuel. Precise control over droplets is crucial to these applications. However, electric fields can induce complex and unpredictable fluid dynamics. Recent experiments (Ristenpart et al. 2009) have demonstrated that oppositely charged droplets bounce rather than coalesce in the presence of strong electric fields. A transient aqueous bridge forms between approaching drops prior to pinch-off. This observation applies to many types of fluids, but neither theory nor experiments have been able to offer a satisfactory explanation. Analytic hydrodynamic approximations for interfaces become invalid near coalescence, and therefore detailed numerical simulations are necessary. This is a computationally challenging problem that involves tracking a moving interface and solving complex multi-physics and multi-scale dynamics, which are beyond the capabilities of most state-of-the-art simulations. An interface-tracking model for electro-coalescence can provide a new perspective to a variety of applications in which interfacial physics are coupled with electrodynamics, including electro-osmosis, fabrication of microelectronics, fuel atomization, oil dehydration, nuclear waste reprocessing and solution separation for chemical detectors. We present a conformal decomposition finite element (CDFEM) interface-tracking method for the electrohydrodynamics of two-phase flow to demonstrate electro-coalescence. CDFEM is a sharp interface method that decomposes elements along fluid-fluid boundaries and uses a level set function to represent the interface.

  15. Droplet Epitaxy Image Contrast in Mirror Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Kennedy, S. M.; Zheng, C. X.; Jesson, D. E.

    2017-01-01

    Image simulation methods are applied to interpret mirror electron microscopy (MEM) images obtained from a movie of GaAs droplet epitaxy. Cylindrical symmetry of structures grown by droplet epitaxy is assumed in the simulations which reproduce the main features of the experimental MEM image contrast, demonstrating that droplet epitaxy can be studied in real-time. It is therefore confirmed that an inner ring forms at the droplet contact line and an outer ring (or skirt) occurs outside the droplet periphery. We believe that MEM combined with image simulations will be increasingly used to study the formation and growth of quantum structures.

  16. Retreat behavior of a charged droplet for electrohydrodynamic inkjet printing

    NASA Astrophysics Data System (ADS)

    Yudistira, Hadi Teguh; Nguyen, Vu Dat; Tran, Si Bui Quang; Kang, Tae Sam; Park, Jung Keun; Byun, Doyoung

    2011-02-01

    The charged droplet retreat phenomenon in electrohydrodynamic inkjet printing is experimentally observed and theoretically explained. If the charge concentration of a droplet generated from a nozzle is high enough, Coulomb fission is generated a second time and the main droplet retreats to the meniscus on the nozzle. The retreat phenomenon is due to interactions between the charged droplet, the meniscus, and charges on the substrate. The Rayleigh limit is used to give a theoretical estimate of the amount of charge on the droplet and the meniscus during the retreat.

  17. Stability of a pendant droplet in gas metal arc welding

    SciTech Connect

    Murray, P.E.

    1998-07-01

    The authors develop a model of metal transfer in gas metal arc welding and compute the critical mass of a pendant droplet in order to ascertain the size and frequency of droplets detaching from the consumable metal electrode. These results are used to predict the mode of metal transfer for a range of voltage and current encompassing free flight transfer, and the transition between globular and spray transfer. This model includes an efficient method to compute the stability of a pendant droplet and the location of the liquid bridge connecting the primary droplet and the residual liquid remaining after detachment of the primary droplet.

  18. A soft microchannel decreases polydispersity of droplet generation.

    PubMed

    Pang, Yan; Kim, Hyoungsoo; Liu, Zhaomiao; Stone, Howard A

    2014-10-21

    We study the effect of softness of the microchannel on the process of droplet generation in two-phase flows in a T-junction microchannel. One side of the microchannel has a flexible thin PDMS layer, which vibrates naturally while droplets are generated; the deformation frequency coincides with the frequency of droplet formation. Furthermore, we compare the polydispersity of water-in-oil droplets formed with a microchannel with one soft wall with those formed in a conventional rigid microchannel. We show that deformation of the soft wall reduces the polydispersity in the droplet size.

  19. Experimental Study of Supercooled Large Droplet Impingement Effects

    NASA Technical Reports Server (NTRS)

    Papadakis, M.; Rachman, A.; Wong, S. C.; Hung, K. E.; Vu, G. T.

    2003-01-01

    Typically, ice accretion results from small supercooled droplets (droplets cooled below freezing), usually 5 to 50 microns in diameter, which can freeze upon impact with an aircraft surface. Recently, ice accretions resulting from supercooled large droplet (SLD) conditions have become a safety concern. Current ice accretion codes have been extensively tested for Title 14 Code of Federal Regulations Part 25, Appendix C icing conditions but have not been validated for SLD icing conditions. This report presents experimental methods for investigating large droplet impingement dynamics and for obtaining small and large water droplet impingement data.

  20. Optical heterodyne measurement of cloud droplet size distributions.

    PubMed

    Gollub, J P; Chabay, L; Flygare, W H

    1973-12-01

    Optical heterodyne spectra of laser light quasi-elastically scattered by falling water droplets (1-10-micro radius) in a diffusion cloud chamber were used to determine the droplet size distribution. The rate of fall depends on radius in a known way, thus yielding a heterodyne spectrum manifesting a distribution of Doppler shifts. This spectrum, in conjunction with the calculated Mie scattering intensity as a function of droplet radius, provides a direct measure of the droplet size distribution for droplets large enough that Brownian motion is negligible. The experiments described in this paper demonstrate the technique and establish the potential for further more quantitative studies of size distributions.

  1. The liquid droplet radiator in space: A parametric approach

    NASA Astrophysics Data System (ADS)

    Buckner, Gerald L.; Tuttle, Ronald F.

    The Liquid Droplet Radiator (LDR) consists of a column or sheet of liquid droplets moving through space from a droplet generator to a collector. The droplets carry the waste heat generated by a space power system and radiate this waste heat directly to space during their flight. The liquid droplets are collected at a lower temperature, reheated and pumped to the generator and reused to remove waste heat from the thermodynamic power cycle. A parametric analysis is given of a cylindrical LDR to estimate its performance and operating characteristics using a new pump specific mass term.

  2. Spreading of Impacting Droplets on Wettability-Patterned Surfaces

    NASA Astrophysics Data System (ADS)

    Elsharkawy, Mohamed; Russo, Antonio; Asinari, Pietro; Megaridis, Constantine

    2016-11-01

    Droplet collision on solid surfaces is a long-studied field that has focused mostly on droplets striking uniform-wettability surfaces. As of now, very few studies exist that analyzed droplet impact on non-uniform (spatially) wettability surfaces. More importantly, no model exists for predicting droplet impact behavior on spatially non-uniform surfaces. Using photolithograhically-produced surfaces, we study droplet impact on axially-symmetric, non-uniform wettability surfaces. We expand upon previously presented models for uniform-wettability surfaces, and predict the maximum spreading diameter of droplets impacting on symmetric patterns on varying wettability surfaces. The present model is expanded to account for n annular regions of different wettabilities, and calculate the corresponding maximum spreading diameter. In addition, within the model we explore the concept of a wettability contrast barrier that must be overcome by the impacting droplets in order to continue their spreading phase. We show under which conditions a droplet can successfully overcome this barrier, and under which conditions it cannot. The model put forth makes strong use of the previously-reported droplet impact model of Passandideh-Fard et al. It draws upon geometric assumptions, such as cylindrical shape for the expanding liquid and spherical cap for the impacting droplet. The work is fundamental in nature, but offers valuable insight that helps understand droplet impact dynamics on non-uniform wettability surfaces.

  3. Hydrodynamics of Leidenfrost droplets in one-component fluids

    NASA Astrophysics Data System (ADS)

    Xu, Xinpeng; Qian, Tiezheng

    2013-04-01

    Using the dynamic van der Waals theory [Phys. Rev. E10.1103/PhysRevE.75.036304 75, 036304 (2007)], we numerically investigate the hydrodynamics of Leidenfrost droplets under gravity in two dimensions. Some recent theoretical predictions and experimental observations are confirmed in our simulations. A Leidenfrost droplet larger than a critical size is shown to be unstable and break up into smaller droplets due to the Rayleigh-Taylor instability of the bottom surface of the droplet. Our simulations demonstrate that an evaporating Leidenfrost droplet changes continuously from a puddle to a circular droplet, with the droplet shape controlled by its size in comparison with a few characteristic length scales. The geometry of the vapor layer under the droplet is found to mainly depend on the droplet size and is nearly independent of the substrate temperature, as reported in a recent experimental study [Phys. Rev. Lett.10.1103/PhysRevLett.109.074301 109, 074301 (2012)]. Finally, our simulations demonstrate that a Leidenfrost droplet smaller than a characteristic size takes off from the hot substrate because the levitating force due to evaporation can no longer be balanced by the weight of the droplet, as observed in a recent experimental study [Phys. Rev. Lett.10.1103/PhysRevLett.109.034501 109, 034501 (2012)].

  4. Rapid and continuous magnetic separation in droplet microfluidic devices

    SciTech Connect

    Brouzes, Eric; Kruse, Travis; Kimmerling, Robert; Strey, Helmut H.

    2014-12-03

    Here, we present a droplet microfluidic method to extract molecules of interest from a droplet in a rapid and continuous fashion. We accomplish this by first marginalizing functionalized super-paramagnetic beads within the droplet using a magnetic field, and then splitting the droplet into one droplet containing the majority of magnetic beads and one droplet containing the minority fraction. We quantitatively analysed the factors which affect the efficiency of marginalization and droplet splitting to optimize the enrichment of magnetic beads. We first characterized the interplay between the droplet velocity and the strength of the magnetic field and its effect on marginalization. We found that marginalization is optimal at the midline of the magnet and that marginalization is a good predictor of bead enrichment through splitting at low to moderate droplet velocities. Finally, we focused our efforts on manipulating the splitting profile to improve the enrichment provided by asymmetric splitting. We designed asymmetric splitting forks that employ capillary effects to preferentially extract the bead-rich regions of the droplets. Our strategy represents a framework to optimize magnetic bead enrichment methods tailored to the requirements of specific droplet-based applications. We anticipate that our separation technology is well suited for applications in single-cell genomics and proteomics. In particular, our method could be used to separate mRNA bound to poly-dT functionalized magnetic microparticles from single cell lysates to prepare single-cell cDNA libraries.

  5. Rapid and continuous magnetic separation in droplet microfluidic devices

    DOE PAGES

    Brouzes, Eric; Kruse, Travis; Kimmerling, Robert; ...

    2014-12-03

    Here, we present a droplet microfluidic method to extract molecules of interest from a droplet in a rapid and continuous fashion. We accomplish this by first marginalizing functionalized super-paramagnetic beads within the droplet using a magnetic field, and then splitting the droplet into one droplet containing the majority of magnetic beads and one droplet containing the minority fraction. We quantitatively analysed the factors which affect the efficiency of marginalization and droplet splitting to optimize the enrichment of magnetic beads. We first characterized the interplay between the droplet velocity and the strength of the magnetic field and its effect on marginalization.more » We found that marginalization is optimal at the midline of the magnet and that marginalization is a good predictor of bead enrichment through splitting at low to moderate droplet velocities. Finally, we focused our efforts on manipulating the splitting profile to improve the enrichment provided by asymmetric splitting. We designed asymmetric splitting forks that employ capillary effects to preferentially extract the bead-rich regions of the droplets. Our strategy represents a framework to optimize magnetic bead enrichment methods tailored to the requirements of specific droplet-based applications. We anticipate that our separation technology is well suited for applications in single-cell genomics and proteomics. In particular, our method could be used to separate mRNA bound to poly-dT functionalized magnetic microparticles from single cell lysates to prepare single-cell cDNA libraries.« less

  6. An experimental study on Rosensweig instability of a ferrofluid droplet

    NASA Astrophysics Data System (ADS)

    Chen, Ching-Yao; Cheng, Z.-Y.

    2008-05-01

    We experimentally investigate the interfacial morphologies of Rosensweig instability on an extremely thin layer of ferrofluid droplets under a constant perpendicular magnetic field. Striking patterns consisting of numerous subscale droplets that developed from Rosensweig instability are observed. For a dry plate, on which surface tension dominates, the breaking pattern of subscale droplets can be characterized by a dimensionless magnetic Bond number Bom. In general, a more pronounced instability, which is evident by a greater number of breaking subscale droplets N, arises with a higher Bom. For a magnetic Bond number that is larger than a critical value, we identify a new mode of interfacial breakup pattern, where the central droplet is torn apart with major mass loss. In addition, we found that the volume fractions of breaking subscale droplets are strongly affected by the height variation of the initial fluid surface and appear unevenly distributed with dominance of a central droplet. On the other hand, for a prewetted plate, a nearly flat fluid surface is achieved due to a smaller contact angle, which then leads to virtually evenly distributed subscale droplets. A global size for all breaking subscale droplets is observed regardless of their initial diameters. The number of breaking subscale droplets (N) and the diameter of the initial droplet (D) can be approximated by a quadratic proportionality of N ˜D2.

  7. Liquid droplet radiator program at the NASA Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Presler, A. F.; Coles, C. E.; Diem-Kirsop, P. S.; White, K. A., III

    1985-01-01

    The NASA Lewis Research Center and the Air Force Rocket Propulsion Laboratory (AFRPL) are jointly engaged in a program for technical assessment of the Liquid Droplet Radiator (LDR) concept as an advanced high performance heat ejection component for future space missions. NASA Lewis has responsibility for the technology needed for the droplet generator, for working fluid qualification, and for investigating the physics of droplets in space; NASA Lewis is also conducting systems/mission analyses for potential LDR applications with candidate space power systems. For the droplet generator technology task, both micro-orifice fabrication techniques and droplet stream formation processes have been experimentally investigated. High quality micro-orifices (to 50 micron diameter) are routinely fabricated with automated equipment. Droplet formation studies have established operating boundaries for the generation of controlled and uniform droplet streams. A test rig is currently being installed for the experimental verification, under simulated space conditions, of droplet radiation heat transfer performance analyses and the determination of the effect radiative emissivity of multiple droplet streams. Initial testing has begun in the NASA Lewis Zero-Gravity Facility for investigating droplet stream behavior in microgravity conditions. This includes the effect of orifice wetting on jet dynamics and droplet formation. Results for both Brayton and Stirling power cycles have identified favorable mass and size comparisons of the LDR with conventional radiator concepts.

  8. Droplet-driven transports on superhydrophobic-patterned surface microfluidics.

    PubMed

    Xing, Siyuan; Harake, Ryan S; Pan, Tingrui

    2011-11-07

    Droplet-based transport phenomena driven by surface tension have been explored as an automated pumping source for a number of chemical and biological applications. In this paper, we present a comprehensive theoretical and experimental investigation of unconventional droplet-based motions on a superhydrophobic-patterned surface microfluidic (S(2)M) platform. The S(2)M surfaces are monolithically fabricated using a facile two-step laser micromachining technique on regular polydimethylsiloxane (PDMS) chemistry. Unlike the traditional droplet-driven pumps built on an enclosed microfluidic network, the S(2)M network pins the liquid-solid interface of droplets to the lithographically defined wetting boundary and establishes a direct linkage between the volumetric and hydraulic measures. Moreover, diverse modes of droplet motions are theoretically determined and experimentally characterized in a bi-droplet configuration, among which several unconventional droplet-driven transport phenomena are first demonstrated. These include big-to-small droplet merging, droplet balancing, as well as bidirectional transporting, in addition to the classic small-to-big droplet transition. Furthermore, multi-stage programmable bidirectional pumping has been implemented on the S(2)M platform, according to the newly established droplet manipulation principle, to illustrate its potential use for automated biomicrofluidic and point-of-care diagnostic applications.

  9. Rapid and continuous magnetic separation in droplet microfluidic devices

    PubMed Central

    Brouzes, Eric; Kruse, Travis; Kimmerling, Robert; Strey, Helmut H.

    2015-01-01

    We present a droplet microfluidic method to extract molecules of interest from a droplet in a rapid and continuous fashion. We accomplish this by first marginalizing functionalized super-paramagnetic beads within the droplet using a magnetic field, and then splitting the droplet into one droplet containing the majority of magnetic beads and one droplet containing the minority fraction. We quantitatively analysed the factors which affect the efficiency of marginalization and droplet splitting to optimize the enrichment of magnetic beads. We first characterized the interplay between the droplet velocity and the strength of the magnetic field and its effect on marginalization. We found that marginalization is optimal at the midline of the magnet and that marginalization is a good predictor of bead enrichment through splitting at low to moderate droplet velocities. Finally, we focused our efforts on manipulating the splitting profile to improve the enrichment provided by asymmetric splitting. We designed asymmetric splitting forks that employ capillary effects to preferentially extract the bead-rich regions of the droplets. Our strategy represents a framework to optimize magnetic bead enrichment methods tailored to the requirements of specific droplet-based applications. We anticipate that our separation technology is well suited for applications in single-cell genomics and proteomics. In particular, our method could be used to separate mRNA bound to poly-dT functionalized magnetic microparticles from single cell lysates to prepare single-cell cDNA libraries. PMID:25501881

  10. Vibration-Induced Droplet Atomization --- An Experimental Investigation.

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1997-11-01

    The atomization of a liquid droplet placed on a vibrating membrane starts with the development of Faraday free surface waves. As the excitation amplitude increases, the waves grow in amplitude and ultimately begin to eject smaller secondary droplets from the wave crests. The rate of droplet ejection can be large enough to completely drain the primary droplet, an event we call bursting. The evolution of the droplet ejection process depends on a coupled system dynamic between the droplet and the membrane. When droplets are ejected the resonant frequency of the system increases. This changes the acceleration felt by the droplet and, in turn, the rate of droplet ejection. Depending on the excitation frequency and amplitude, various types of bursting or droplet ejection processes may occur. In the present experiments, the high acceleration needed to attain ejection (typically 300g) is achieved by driving a light-weight membrane near its resonant frequency (nominally 1000 Hz). The resonant characteristics and the acceleration during the ejection process for various droplet sizes and excitation amplitudes are investigated using a surface-mounted microfabricated accelerometer and a laboratory computer system.

  11. Interaction between microfluidic droplets in a Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Sarig, Itai; Starosvetsky, Yuli; Gat, Amir

    2015-11-01

    Various fluidic systems, such as chemical and biological lab-on-a-chip devices, involve motion of multiple droplets within an immersing fluid in narrow micro-channels. Modeling the dynamics of such systems requires calculation of the forces of interaction between the moving droplets. These forces are commonly approximated by superposition of dipoles solutions, which requires an assumption of sufficiently large distance between the droplets. In this work we obtain exact solutions for two droplets, and a droplet within a droplet, located within a moving immersing fluid and without limitation on the distance between the droplets. This is achieved by solution of the Laplace equation for the pressure in a bi-polar coordinate system, Fourier method and transformation and calculation of the force in a Cartesian coordinate system. Our results are validated with numerical computations, experimental data and with the existing dipole-based models. We utilize the results to calculate the dynamics of a droplet within a droplet, and of two close droplets, located within an immersing fluid with oscillating speed. The obtained results may be used to study the dynamics of dense droplet lattices, common to many current micro-fluidic systems.

  12. Nonaffine heterogeneities and droplet fluctuations in an equilibrium crystalline solid

    SciTech Connect

    Das, Tamoghna; Sengupta, Surajit; Rao, Madan

    2010-10-15

    We show, using molecular-dynamics simulations, that a two-dimensional Lennard-Jones solid exhibits droplet fluctuations characterized by nonaffine deviations from local crystallinity. The fraction of particles in these droplets increases as the mean density of the solid decreases and approaches {approx_equal}20% of the total number in the vicinity of the fluid-solid phase boundary. We monitor the geometry, local equation of state, density correlations, and Van Hove functions of these droplets. We provide evidence that these nonaffine heterogeneities should be interpreted as being droplet fluctuations from nearby metastable minima. The local excess pressure of the droplets plotted against the local number density shows a van der Waal loop with distinct branches corresponding to fluidlike compact and stringlike glassy droplets. The distinction between fluidlike and glassy droplets disappears above a well-defined temperature.

  13. Effective doping of low energy ions into superfluid helium droplets.

    PubMed

    Zhang, Jie; Chen, Lei; Freund, William M; Kong, Wei

    2015-08-21

    We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 10(4) ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 10(5)/droplet, is measured using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies.

  14. Supersonic laser-induced jetting of aluminum micro-droplets

    NASA Astrophysics Data System (ADS)

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-05-01

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10-100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  15. Magnetohydrodynamic actuation of droplets for millimetric planar fluidic systems

    SciTech Connect

    Ahmadi, A. McDermid, C. M.; Markley, L.

    2016-01-04

    In this work, a magnetohydrodynamic method is proposed for the actuation of droplets in small-scale planar fluidic systems, providing an alternative to commonly used methods such as electrowetting-on-dielectric. Elementary droplet-based operations, including transport, merging, and mixing, are demonstrated. The forces acting on millimetric droplets are carefully investigated, with a primary focus on the magnetic actuation force and on the unbalanced capillary forces that arise due to hysteresis. A super-hydrophobic channel is 3D printed to guide the droplets, with thin wires installed as contact electrodes and permanent magnets providing a static magnetic field. It is shown that droplet motion is enhanced by increasing the droplet size and minimizing the electrode contact surface. The effects of channel geometry on threshold voltage and minimum moveable droplet volume are characterized. Finally, the presence of electrolysis is investigated and mitigating strategies are discussed.

  16. Image processing system to analyze droplet distributions in sprays

    NASA Technical Reports Server (NTRS)

    Bertollini, Gary P.; Oberdier, Larry M.; Lee, Yong H.

    1987-01-01

    An image processing system was developed which automatically analyzes the size distributions in fuel spray video images. Images are generated by using pulsed laser light to freeze droplet motion in the spray sample volume under study. This coherent illumination source produces images which contain droplet diffraction patterns representing the droplets degree of focus. The analysis is performed by extracting feature data describing droplet diffraction patterns in the images. This allows the system to select droplets from image anomalies and measure only those droplets considered in focus. Unique features of the system are the totally automated analysis and droplet feature measurement from the grayscale image. The feature extraction and image restoration algorithms used in the system are described. Preliminary performance data is also given for two experiments. One experiment gives a comparison between a synthesized distribution measured manually and automatically. The second experiment compares a real spray distribution measured using current methods against the automatic system.

  17. Sorting and Manipulation of Magnetic Droplets in Continuous Flow

    NASA Astrophysics Data System (ADS)

    Al-Hetlani, Entesar; Hatt, Oliver J.; Vojtíšek, Martin; Tarn, Mark D.; Iles, Alexander; Pamme, Nicole

    2010-12-01

    We report the rapid on-chip generation and subsequent manipulation of magnetic droplets in continuous flow. Magnetic droplets were formed using aqueous-based ferrofluid as the dispersed phase and fluorocarbon oil as the continuous phase. Droplet manipulation was demonstrated with simple permanent magnets using two microfluidic platforms: (i) flow focusing droplet generation followed by their splitting into daughter droplets containing different amounts of magnetic nanoparticles, and (ii) droplet generation at a T-junction and their downstream deflection across a chamber for sorting based on the applied magnetic field and magnetite loading of the droplet. Both systems show great potential for performing a wide range of high throughput continuous flow processes including sample dilution, cell sorting and screening, and microparticle fabrication.

  18. Supersonic laser-induced jetting of aluminum micro-droplets

    SciTech Connect

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-05-04

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10–100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  19. Electrically Charged Droplets in Microgravity - Impact and Trajectories

    NASA Astrophysics Data System (ADS)

    Brandenbourger, Martin; Caps, Hervé; Vitry, Youen; Dorbolo, Stéphane

    2017-03-01

    In this work, the interaction between electrically charged droplets in microgravity is considered. During the 22 s of microgravity brought by a parabolic flight, water droplets with a radius r ∈ [0.41 - 0.97] mm were released one in front of the other. A high-speed camera allowed studying their interaction in the focal plane. The trajectories of the droplets are well adjusted by a punctual charge model. In some experiments, a physical contact between the charged droplets was observed. These collisions are studied via a phase diagram comparing the droplet Weber number, We, and the collision parameter, χ. By comparing these collisions to experiments involving neutral droplets, we deduce how the collision diagram is affected by electric charges. In particular, we show that the criterion for an impact between two droplets is no more χ < 1.

  20. Increased evaporation kinetics of sessile droplets by using nanoparticles.

    PubMed

    Nguyen, Tuan A H; Nguyen, Anh V

    2012-12-11

    The effect of nanoparticles on the evaporation of a sessile droplet into air is still controversial. Unlike insoluble surfactants which reduce the droplet evaporation rate, here we show that the presence of nanoparticles and the increase of their concentration lead to an increase in the overall rate of diffusive evaporation and, consequently, a decrease of the droplet lifetime. The nanoparticles accumulating at the droplet edge due to the well-known coffee-ring effect pin the three-phase contact line for an extended time and maintain a large air-water interface area, leading to the increased evaporation rate. We provide a full analytical prediction for the lifetime of a sessile droplet evaporating by the combined pinned-receding mode. A master equation and a master diagram for the droplet lifetime of the combined mode are obtained and experimentally validated, and explain the effect of nanoparticles on increasing the global evaporation rate and decreasing the droplet lifetime.

  1. Evaporation dynamics of water droplets on inclined surfaces

    NASA Astrophysics Data System (ADS)

    Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

    2016-11-01

    When a water droplet is gently placed on a flat substrate, particularly which is tilted at an inclined angle, usually there are advancing and receding angles inside the droplet formed by inclination under gravitational force. Evaporation dynamics of an nonspherical inclined droplet at inclinations would deviate from that of a spherical droplet. Here we study on evaporation dynamics rates of inclined droplets by measuring mass changes with time and their lifetimes. We find that the lifetime of an evaporating inclined droplets becomes longer as the gravitational influence becomes stronger. The lifetime depends on the pinning-depinning transitions and the depinning onset times, which are changed by the gravitational influence. This The dependence inclination-induced evaporation behavior would be useful important in understanding evaporation dynamics of inclined droplets. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1D1A1B01007133).

  2. Viscoelastic droplet dynamics in a Y-shaped capillary channel

    NASA Astrophysics Data System (ADS)

    Wang, Yuli; Do-Quang, Minh; Amberg, Gustav

    2016-03-01

    Non-Newtonian droplet dynamics commonly exist in microfluidic systems. We report simulations of viscoelastic (VE) droplets traveling in a two dimensional capillary bifurcation channel. A numerical system combining phase field method, VE rheology, and Stokes flow equations is built. As a generic microfluidic two-phase problem, we study how a non-Newtonian droplet that approaches a channel bifurcation will behave. We identify conditions for when a droplet will either split into two or be directed into one of the branches. In particular, we study the importance of the non-Newtonian properties. Our results reveal two different non-Newtonian mechanisms that can enhance splitting and non-splitting of droplets with respect to Newtonian droplets, depending on the size of droplet and capillary number.

  3. Image-based analysis of droplets in microfluidics.

    PubMed

    Zantow, Miné; Dendere, Ronald; Douglas, Tania S

    2013-01-01

    In order to design a microfluidic device that can produce monodispersed encapsulated enzymes as droplets, it is essential to be able to evaluate the system during its development. An automated method to determine the size of the droplets as well as a method to tag and track droplets as they move in the system is desirable for system evaluation. We apply the Hough transform for circles to determine droplet size. Most of the droplets in the images are detected, and the best results are obtained at 20x magnification. We also test the ability of the ImageJ 'particle tracker' plugin to determine the behaviour of the droplets as they move in microfluidic systems. It is effective in tracking droplets that travel less than 50 pixels between frames.

  4. Effective doping of low energy ions into superfluid helium droplets

    SciTech Connect

    Zhang, Jie; Chen, Lei; Freund, William M.; Kong, Wei

    2015-08-21

    We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 10{sup 4} ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 10{sup 5}/droplet, is measured using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies.

  5. Lysozyme pattern formation in evaporating droplets

    NASA Astrophysics Data System (ADS)

    Gorr, Heather Meloy

    Liquid droplets containing suspended particles deposited on a solid, flat surface generally form ring-like structures due to the redistribution of solute during evaporation (the "coffee ring effect"). The forms of the deposited patterns depend on complex interactions between solute(s), solvent, and substrate in a rapidly changing, far from equilibrium system. Solute self-organization during evaporation of colloidal sessile droplets has attracted the attention of researchers over the past few decades due to a variety of technological applications. Recently, pattern formation during evaporation of various biofluids has been studied due to potential applications in medical screening and diagnosis. Due to the complexity of 'real' biological fluids and other multicomponent systems, a comprehensive understanding of pattern formation during droplet evaporation of these fluids is lacking. In this PhD dissertation, the morphology of the patterns remaining after evaporation of droplets of a simplified model biological fluid (aqueous lysozyme solutions + NaCl) are examined by atomic force microscopy (AFM) and optical microscopy. Lysozyme is a globular protein found in high concentration, for example, in human tears and saliva. The drop diameters, D, studied range from the micro- to the macro- scale (1 microm -- 2 mm). In this work, the effect of evaporation conditions, solution chemistry, and heat transfer within the droplet on pattern formation is examined. In micro-scale deposits of aqueous lysozyme solutions (1 microm < D < 50 microm), the protein motion and the resulting dried residue morphology are highly influenced by the decreased evaporation time of the drop. The effect of electrolytes on pattern formation is also investigated by adding varying concentrations NaCl to the lysozyme solutions. Finally, a novel pattern recognition program is described and implemented which classifies deposit images by their solution chemistries. The results presented in this Ph

  6. A Droplet-Based High-Throughput SERS Platform on a Droplet-Guiding-Track-Engraved Superhydrophobic Substrate.

    PubMed

    Shin, Sera; Lee, Jaehong; Lee, Sanggeun; Kim, Hyunchul; Seo, Jungmok; Kim, Dayeong; Hong, Juree; Lee, Soonil; Lee, Taeyoon

    2017-02-01

    A novel droplet-based surface-enhanced Raman scattering (SERS) sensor for high-throughput real-time SERS monitoring is presented. The developed sensors are based on a droplet-guiding-track-engraved superhydrophobic substrate covered with hierarchical SERS-active Ag dendrites. The droplet-guiding track with a droplet stopper is designed to manipulate the movement of a droplet on the superhydrophobic substrate. The superhydrophobic Ag dendritic substrates are fabricated through a galvanic displacement reaction and subsequent self-assembled monolayer coating. The optimal galvanic reaction time to fabricate a SERS-active Ag dendritic substrate for effective SERS detection is determined, with the optimized substrate exhibiting an enhancement factor of 6.3 × 10(5) . The height of the droplet stopper is optimized to control droplet motion, including moving and stopping. Based on the manipulation of individual droplets, the optimized droplet-based real-time SERS sensor shows high resistance to surface contaminants, and droplets containing rhodamine 6G, Nile blue A, and malachite green are successively controlled and detected without spectral interference. This noble droplet-based SERS sensor reduces sample preparation time to a few seconds and increased detection rate to 0.5 µL s(-1) through the simple operation mechanism of the sensor. Accordingly, our sensor enables high-throughput real-time molecular detection of various target analytes for real-time chemical and biological monitoring.

  7. Stem cell niche engineering through droplet microfluidics.

    PubMed

    Allazetta, Simone; Lutolf, Matthias P

    2015-12-01

    Stem cells reside in complex niches in which their behaviour is tightly regulated by various biochemical and biophysical signals. In order to unveil some of the crucial stem cell-niche interactions and expedite the implementation of stem cells in clinical and pharmaceutical applications, in vitro methodologies are being developed to reconstruct key features of stem cell niches. Recently, droplet-based microfluidics has emerged as a promising strategy to build stem cell niche models in a miniaturized and highly precise fashion. This review highlights current advances in using droplet microfluidics in stem cell biology. We also discuss recent efforts in which microgel technology has been interfaced with high-throughput analyses to engender screening paradigms with an unparalleled potential for basic and applied biological studies.

  8. Helium anion formation inside helium droplets

    NASA Astrophysics Data System (ADS)

    Jabbour Al Maalouf, Elias; Reitshammer, Julia; Ribar, Anita; Scheier, Paul; Denifl, Stephan

    2016-07-01

    The formation of He∗- is examined with improved electron energy resolution of about 100 meV utilizing a hemispherical electron monochromator. The work presented provides a precise determination of the three previously determined resonance peak positions that significantly contribute to the formation of He∗- inside helium nanodroplets in the energy range from 20 eV to 29.5 eV. In addition, a new feature is identified located at 27.69 ± 0.18 eV that we assign to the presence of O2 as a dopant inside the droplet. With increasing droplet size a small blue shift of the resonance positions is observed. Also for the relatively low electron currents used in the present study (i.e., 15-70 nA) a quadratic dependence of the He∗- ion yield on the electron current is observed.

  9. Mechanism of supercooled droplet freezing on surfaces.

    PubMed

    Jung, Stefan; Tiwari, Manish K; Doan, N Vuong; Poulikakos, Dimos

    2012-01-10

    Understanding ice formation from supercooled water on surfaces is a problem of fundamental importance and general utility. Superhydrophobic surfaces promise to have remarkable 'icephobicity' and low ice adhesion. Here we show that their icephobicity can be rendered ineffective by simple changes in environmental conditions. Through experiments, nucleation theory and heat transfer physics, we establish that humidity and/or the flow of a surrounding gas can fundamentally switch the ice crystallization mechanism, drastically affecting surface icephobicity. Evaporative cooling of the supercooled liquid can engender ice crystallization by homogeneous nucleation at the droplet-free surface as opposed to the expected heterogeneous nucleation at the substrate. The related interplay between droplet roll-off and rapid crystallization is also studied. Overall, we bring a novel perspective to icing and icephobicity, unveiling the strong influence of environmental conditions in addition to the accepted effects of the surface conditions and hydrophobicity.

  10. Acid droplet generation in SRM exhaust clouds

    NASA Technical Reports Server (NTRS)

    Dingle, A. N.

    1983-01-01

    A free energy analysis is applied to the co-condensation/evaporation of H2O and HCl vapors on wettable particles in open air in order to model droplet nucleation in solid rocket motor (SRM) exhaust clouds. Formulations are defined for the free energy change, the drop radius, the saturation ratio, the total number of molecules, and the mean molecular radius in solution, as well as the molecular volume and the concentration range. The free energy release in the phase transition for the AL2O3 nuclei in the SRM exhaust is examined as a function of the HCl molefraction and nucleating particle radius, based on Titan III launch exhaust cloud conditions 90 sec after ignition. The most efficient droplet growth is determined to occur at an HCl molefraction of 0.082 and a particle radius of 0.0000013 cm, i.e. a molality of 5.355.

  11. Vaporization of droplets in premixing chambers

    NASA Technical Reports Server (NTRS)

    Yule, A. J.; Chigier, N. A.

    1980-01-01

    Detailed measurements were made of the structures of turbulent fuel sprays vaporizing in heated airstreams. The measurements show the size dependent vaporization and dispersion of the droplets and the important influence of the large eddies in the turbulence. The measurements form a data base for the development of models of fuel spray vaporization. Two laser techniques were specially developed for the investigation. A laser tomography technique converts line-of-sight light scattering measurements into time averaged 'point' measurements of droplet size distribution and volume concentration. A laser anemometer particle sizing technique was further developed to permit accurate measurements of individual particle sizes and velocities, with backscatter collection of light. The experiments are combined with heat transfer models to analyze the performance of miniature thermocouples in liquid sprays.

  12. Form factors for Russian doll droplet models

    NASA Astrophysics Data System (ADS)

    Wilemski, G.; Obeidat, A.; Hrahsheh, F.

    2013-05-01

    Molecular dynamics (MD) simulations of nanodroplets containing water and nonane show them to be nonspherical and strongly phase separated. A simple, but realistic model for these "Russian doll" structures is a spherical nonane lens that partially wets a spherical water droplet. This document contains an analytical calculation of the particle form factor P(q) needed to analyze experimental measurements of small angle neutron and x-ray scattering from aerosols of particles with this type of structure. In addition, an exact formulation of the particle form factor is developed for cylindrically symmetric droplets with otherwise arbitrary scattering length density functions. This result will be useful to calculate P(q) directly from MD simulation results. We compare results using both formulations and find excellent agreement between them.

  13. Swimming droplets driven by a surface wave

    NASA Astrophysics Data System (ADS)

    Ebata, Hiroyuki; Sano, Masaki

    2015-02-01

    Self-propelling motion is ubiquitous for soft active objects such as crawling cells, active filaments, and liquid droplets moving on surfaces. Deformation and energy dissipation are required for self-propulsion of both living and non-living matter. From the perspective of physics, searching for universal laws of self-propelled motions in a dissipative environment is worthwhile, regardless of the objects' details. In this article, we propose a simple experimental system that demonstrates spontaneous migration of a droplet under uniform mechanical agitation. As we vary control parameters, spontaneous symmetry breaking occurs sequentially, and cascades of bifurcations of the motion arise. Equations describing deformable particles and hydrodynamic simulations successfully describe all of the observed motions. This system should enable us to improve our understanding of spontaneous motions of self-propelled objects.

  14. Droplets of Trapped Quantum Dipolar Bosons

    NASA Astrophysics Data System (ADS)

    Macia, A.; Sánchez-Baena, J.; Boronat, J.; Mazzanti, F.

    2016-11-01

    Strongly interacting systems of dipolar bosons in three dimensions confined by harmonic traps are analyzed using the exact path integral ground-state Monte Carlo method. By adding a repulsive two-body potential, we find a narrow window of interaction parameters leading to stable ground-state configurations of droplets in a crystalline arrangement. We find that this effect is entirely due to the interaction present in the Hamiltonian without resorting to additional stabilizing mechanisms or specific three-body forces. We analyze the number of droplets formed in terms of the Hamiltonian parameters, relate them to the corresponding s -wave scattering length, and discuss a simple scaling model for the density profiles. Our results are in qualitative agreement with recent experiments showing a quantum Rosensweig instability in trapped Dy atoms.

  15. Dancing droplets: Chemical space, substrates, and control

    NASA Astrophysics Data System (ADS)

    Cira, Nate; Benusiglio, Adrien; Prakash, Manu

    2015-11-01

    Previously we showed that droplets of propylene glycol and water display remarkable properties when placed on clean glass due to an interplay between surface tension and evaporation. (Cira, Benusiglio, Prakash: Nature, 2015). We showed that these mechanisms apply to a range of two-component mixtures of miscible liquids where one component has both higher surface tension and higher vapor pressure on a variety of high energy surfaces. We now show how this rule can be cheated using a simple trick. We go on to demonstrate applications for cleaning, and show how this system works on substrates prepared only with sunlight. We finish by demonstrating active control of droplets, allowing access to a host of new possibilities.

  16. Engineering particle morphology with microfluidic droplets

    NASA Astrophysics Data System (ADS)

    Kang, Zhanxiao; Kong, Tiantian; Lei, Leyan; Zhu, Pingan; Tian, Xiaowei; Wang, Liqiu

    2016-07-01

    The controlled generation of microparticles with non-spherical features is of increasing importance. Such particles are useful for fundamental studies in areas such as self-assembly, as well as biomedical applications from drug carriers to photonic devices. We propose a simple model that captures the dominating factors controlling the size and morphology of non-spherical particles from phase separated droplets. The validity of our model is verified by comparing the generated non-spherical microparticles by droplet microfluidics. This simple relationship between the dominating factors and the final morphologies enables the production of non-spherical particles with well-defined shapes and tightly-controlled dimensions for a variety of applications from drug delivery vehicles to structural materials.

  17. Single droplet combustion of sunflower oil

    SciTech Connect

    Araya, K.; Tsunematsu, S.

    1987-01-01

    When sunflower oil (or plant oil, in general) was used as diesel engine fuel, the ignitability at low temperatures was much poorer than for No. 2 diesel oil. In addition, unburned carbon accumulated in the combustion chamber when the engine was idling. The research reported in this paper was conducted to investigate the causes of these problems. A single fuel droplet set at the tip of a combustion thread was inserted into an electric furnace and ignited. The behavior of the combustion was observed and analyzed by a high speed rotary video camera. The fuels studied were sunflower oil, No. 2 diesel oil, sunflower oil methyl ester and fish oil methyl ester. As a result, even if the droplet size of sunflower oil was the same as that of No. 2 diesel oil, its ignition delay was much longer than No. 2 diesel oil. This may be the main cause of poor ignitability of sunflower oil at low temperatures.

  18. ``Coffee-ring'' patterns of polymer droplets

    NASA Astrophysics Data System (ADS)

    Biswas, Nupur; Datta, Alokmay

    2013-02-01

    Dried droplets of polymer solutions carries the self-assembly behavior of polymer molecules by forming various patterns. Pattern formation is a consequence of deposition of molecules depending on motion of the contact line during the drying process. The contact line motion depends on initial polymer concentrations and hence entanglement. Thus depending on entanglement the patterns represent the `particle' like or `collective' behavior of polymer molecules.

  19. Droplet-model predictions of charge moments

    SciTech Connect

    Myers, W.D.

    1982-04-01

    The Droplet Model expressions for calculating various moments of the nuclear charge distribution are given. There are contributions to the moments from the size and shape of the system, from the internal redistribution induced by the Coulomb repulsion, and from the diffuseness of the surface. A case is made for the use of diffuse charge distributions generated by convolution as an alternative to Fermi-functions.

  20. Metal Slurry Droplet and Spray Combustion

    DTIC Science & Technology

    1993-09-15

    Thermophoresis on the Oxide Condensation 156 ii Appendix E Numerical Modeling of a Slurry Droplet Containing a Spherical Particle...Williams [110]. Thermophoresis can cause the condensed particles to move outwards, from the radius of condensation. However, convection would drive the...Here, the thermophoresis effect may drive the condensed particles outwards. However, since the bulk flow in the outer zone is negative (towards the

  1. Computational Fluid Dynamics of rising droplets

    SciTech Connect

    Wagner, Matthew; Francois, Marianne M.

    2012-09-05

    The main goal of this study is to perform simulations of droplet dynamics using Truchas, a LANL-developed computational fluid dynamics (CFD) software, and compare them to a computational study of Hysing et al.[IJNMF, 2009, 60:1259]. Understanding droplet dynamics is of fundamental importance in liquid-liquid extraction, a process used in the nuclear fuel cycle to separate various components. Simulations of a single droplet rising by buoyancy are conducted in two-dimensions. Multiple parametric studies are carried out to ensure the problem set-up is optimized. An Interface Smoothing Length (ISL) study and mesh resolution study are performed to verify convergence of the calculations. ISL is a parameter for the interface curvature calculation. Further, wall effects are investigated and checked against existing correlations. The ISL study found that the optimal ISL value is 2.5{Delta}x, with {Delta}x being the mesh cell spacing. The mesh resolution study found that the optimal mesh resolution is d/h=40, for d=drop diameter and h={Delta}x. In order for wall effects on terminal velocity to be insignificant, a conservative wall width of 9d or a nonconservative wall width of 7d can be used. The percentage difference between Hysing et al.[IJNMF, 2009, 60:1259] and Truchas for the velocity profiles vary from 7.9% to 9.9%. The computed droplet velocity and interface profiles are found in agreement with the study. The CFD calculations are performed on multiple cores, using LANL's Institutional High Performance Computing.

  2. Droplet Microfluidic System with On-Demand Trapping and Releasing of Droplet for Drug Screening Applications.

    PubMed

    Courtney, Matthew; Chen, Xiaoming; Chan, Sarah; Mohamed, Tarek; Rao, Praveen P N; Ren, Carolyn L

    2017-01-03

    96-Well plate has been the traditional method used for screening drug compounds libraries for potential bioactivity. Although this method has been proven successful in testing dose-response analysis, the microliter consumption of expensive reagents and hours of reaction and analysis time call for innovative methods for improvements. This work demonstrates a droplet microfluidic platform that has the potential to significantly reduce the reagent consumption and shorten the reaction and analysis time by utilizing nanoliter-sized droplets as a replacement of wells. This platform is evaluated by applying it to screen drug compounds that inhibit the tau-peptide aggregation, a phenomena related to Alzheimer's disease. In this platform, sample reagents are first dispersed into nanolitre-sized droplets by an immiscible carrier oil and then these droplets are trapped on-demand in the downstream of the microfluidic device. The relative decrease in fluorescence through drug inhibition is characterized using an inverted epifluorescence microscope. Finally, the trapped droplets are released on-demand after each test by manipulating the applied pressures to the channel network which allows continuous processing. The testing results agree well with that obtained from 96-well plates with much lower sample consumption (∼200 times lower than 96-well plate) and reduced reaction time due to increased surface volume ratio (2.5 min vs 2 h).

  3. RNA interference silencing of a major lipid droplet protein affects lipid droplet size in Chlamydomonas reinhardtii.

    PubMed

    Moellering, Eric R; Benning, Christoph

    2010-01-01

    Eukaryotic cells store oils in the chemical form of triacylglycerols in distinct organelles, often called lipid droplets. These dynamic storage compartments have been intensely studied in the context of human health and also in plants as a source of vegetable oils for human consumption and for chemical or biofuel feedstocks. Many microalgae accumulate oils, particularly under conditions limiting to growth, and thus have gained renewed attention as a potentially sustainable feedstock for biofuel production. However, little is currently known at the cellular or molecular levels with regard to oil accumulation in microalgae, and the structural proteins and enzymes involved in the biogenesis, maintenance, and degradation of algal oil storage compartments are not well studied. Focusing on the model green alga Chlamydomonas reinhardtii, the accumulation of triacylglycerols and the formation of lipid droplets during nitrogen deprivation were investigated. Mass spectrometry identified 259 proteins in a lipid droplet-enriched fraction, among them a major protein, tentatively designated major lipid droplet protein (MLDP). This protein is specific to the green algal lineage of photosynthetic organisms. Repression of MLDP gene expression using an RNA interference approach led to increased lipid droplet size, but no change in triacylglycerol content or metabolism was observed.

  4. Droplet formation and ejection from a micromachined ultrasonic droplet generator: Visualization and scaling

    NASA Astrophysics Data System (ADS)

    Meacham, J. M.; Varady, M. J.; Degertekin, F. L.; Fedorov, A. G.

    2005-10-01

    Visualization and scaling of drop-on-demand and continuous-jet fluid atomization of water are presented to elucidate the fluid physics of the ejection process and characterize the modes of operation of a novel micromachined ultrasonic droplet generator. The device comprises a fluid reservoir that is formed between a bulk ceramic piezoelectric transducer and an array of liquid horn structures wet etched into (100) silicon. At resonance, the transducer generates a standing ultrasonic pressure wave within the cavity and the wave is focused at the tip of the nozzle by the horn structure. Device operation has been demonstrated by water droplet ejection from 5to10μm orifices at multiple resonant frequencies between 1 and 5MHz. The intimate interactions between focused ultrasonic pressure waves and capillary waves formed at the liquid-air interface located at the nozzle tip are found to govern the ejection dynamics, leading to different ejection modalities ranging from individual droplets to continuous jet. Specifically, we report the results of high-resolution stroboscopic optical imaging of the liquid-air interface evolution during acoustic pumping to elucidate the role of capillary waves in the droplet formation and ejection process. A basic understanding of the governing physics gained through careful visualization and scaling forms the basis for development of improved theoretical models for the droplet formation and ejection processes by accounting for key fluid mechanical features of the phenomena.

  5. Frost halos from supercooled water droplets

    PubMed Central

    Jung, Stefan; Tiwari, Manish K.; Poulikakos, Dimos

    2012-01-01

    Water freezing on solid surfaces is ubiquitous in nature. Even though icing/frosting impairs the performance and safety in many processes, its mechanism remains inadequately understood. Changing atmospheric conditions, surface properties, the complexity of icing physics, and the unorthodox behavior of water are the primary factors that make icing and frost formation intriguing and difficult to predict. In addition to its unquestioned scientific and practical importance, unraveling the frosting mechanism under different conditions is a prerequisite to develop “icephobic” surfaces, which may avoid ice formation and contamination. In this work we demonstrate that evaporation from a freezing supercooled sessile droplet, which starts explosively due to the sudden latent heat released upon recalescent freezing, generates a condensation halo around the droplet, which crystallizes and drastically affects the surface behavior. The process involves simultaneous multiple phase transitions and may also spread icing by initiating sequential freezing of neighboring droplets in the form of a domino effect and frost propagation. Experiments under controlled humidity conditions using substrates differing up to three orders of magnitude in thermal conductivity establish that a delicate balance between heat diffusion and vapor transport determines the final expanse of the frozen condensate halo, which, in turn, controls frost formation and propagation. PMID:23012410

  6. Gold metal liquid-like droplets.

    PubMed

    Smirnov, Evgeny; Scanlon, Micheál D; Momotenko, Dmitry; Vrubel, Heron; Méndez, Manuel A; Brevet, Pierre-Francois; Girault, Hubert H

    2014-09-23

    Simple methods to self-assemble coatings and films encompassing nanoparticles are highly desirable in many practical scenarios, yet scarcely any examples of simple, robust approaches to coat macroscopic droplets with continuous, thick (multilayer), reflective and stable liquid nanoparticle films exist. Here, we introduce a facile and rapid one-step route to form films of reflective liquid-like gold that encase macroscopic droplets, and we denote these as gold metal liquid-like droplets (MeLLDs). The present approach takes advantage of the inherent self-assembly of gold nanoparticles at liquid-liquid interfaces and the increase in rates of nanoparticle aggregate trapping at the interface during emulsification. The ease of displacement of the stabilizing citrate ligands by appropriate redox active molecules that act as a lubricating molecular glue is key. Specifically, the heterogeneous interaction of citrate stabilized aqueous gold nanoparticles with the lipophilic electron donor tetrathiafulvalene under emulsified conditions produces gold MeLLDs. This methodology relies exclusively on electrochemical reactions, i.e., the oxidation of tetrathiafulvalene to its radical cation by the gold nanoparticle, and electrostatic interactions between the radical cation and nanoparticles. The gold MeLLDs are reversibly deformable upon compression and decompression and kinetically stable for extended periods of time in excess of a year.

  7. Electrofreezing of water droplets under electrowetting fields.

    PubMed

    Carpenter, Katherine; Bahadur, Vaibhav

    2015-02-24

    Electrofreezing is the electrically induced nucleation of ice from supercooled water. This work studies ice nucleation in electrowetted water droplets, wherein there is no electric field inside the droplet resting on a dielectric layer. Instead, there is an interfacial electric field and charge buildup at the solid-liquid interface. This situation is in contrast to most previous electrofreezing studies, which have used bare electrodes, involve current flow, and have a volumetric electric field inside the liquid. Infrared and high-speed visualizations of static water droplets are used to analyze surface electrofreezing. Ultrahigh electric fields of up to 80 V/μm are applied, which is one order of magnitude higher than in previous studies. The results facilitate an in-depth understanding of various mechanisms underlying electrofreezing. First, it is seen that interfacial electric fields alone can significantly elevate freezing temperatures by more than 15 °C, in the absence of current flow. Second, the magnitude of electrofreezing induced temperature elevation saturates at high electric field strengths. Third, the polarity of the interfacial charge does not significantly influence electrofreezing. Overall, it is seen that electrofreezing nucleation kinetics is primarily influenced by the three-phase boundary and not the solid-liquid interface. Through careful electrofreezing measurements on dielectric layers with pinholes to allow current flow, the individual role of electric fields and electric currents on electrofreezing is isolated. It is seen that both the electric field and the electric current influence electrofreezing; however, the physical mechanisms are very different.

  8. A frictional sliding algorithm for liquid droplets

    NASA Astrophysics Data System (ADS)

    Sauer, Roger A.

    2016-12-01

    This work presents a new frictional sliding algorithm for liquid menisci in contact with solid substrates. In contrast to solid-solid contact, the liquid-solid contact behavior is governed by the contact line, where a contact angle forms and undergoes hysteresis. The new algorithm admits arbitrary meniscus shapes and arbitrary substrate roughness, heterogeneity and compliance. It is discussed and analyzed in the context of droplet contact, but it also applies to liquid films and solids with surface tension. The droplet is modeled as a stabilized membrane enclosing an incompressible medium. The contact formulation is considered rate-independent such that hydrostatic conditions apply. Three distinct contact algorithms are needed to describe the cases of frictionless surface contact, frictionless line contact and frictional line contact. For the latter, a predictor-corrector algorithm is proposed in order to enforce the contact conditions at the contact line and thus distinguish between the cases of advancing, pinning and receding. The algorithms are discretized within a monolithic finite element formulation. Several numerical examples are presented to illustrate the numerical and physical behavior of sliding droplets.

  9. Droplet position control in digital microfluidic systems.

    PubMed

    Bhattacharjee, Biddut; Najjaran, Homayoun

    2010-02-01

    Research on so called digital microfluidic systems (DMS) capable of manipulating individual microdroplets on a cell-based structure has enormously increased in the past few years, mainly due to the demand of the technology-dependent biomedical applications. Significant research in this area has been related to the simulation and modeling of droplet motion, demonstration of different drop actuation techniques on laboratory-scale prototypes, and droplet routing and scheduling for more efficient assay procedures. This paper introduces the basics of the control analysis and design of a DMS, which is a relatively unexplored area in digital microfluidics. This paper starts with a discussion on a simplified dynamic model of droplet motion in a planar array of cells, and continues with more complicated dynamic models that are necessary to realize the structure of an appropriate closed-loop control system for the DMS. The control analysis and design includes both the transient and steady-state responses of the DMS under external driving forces. The proposed control analysis and design approach is implemented into SIMULINK models to demonstrate the performance of the DMS through simulation using the system parameters previously reported in the literature.

  10. Droplet-based pyrosequencing using digital microfluidics.

    PubMed

    Boles, Deborah J; Benton, Jonathan L; Siew, Germaine J; Levy, Miriam H; Thwar, Prasanna K; Sandahl, Melissa A; Rouse, Jeremy L; Perkins, Lisa C; Sudarsan, Arjun P; Jalili, Roxana; Pamula, Vamsee K; Srinivasan, Vijay; Fair, Richard B; Griffin, Peter B; Eckhardt, Allen E; Pollack, Michael G

    2011-11-15

    The feasibility of implementing pyrosequencing chemistry within droplets using electrowetting-based digital microfluidics is reported. An array of electrodes patterned on a printed-circuit board was used to control the formation, transportation, merging, mixing, and splitting of submicroliter-sized droplets contained within an oil-filled chamber. A three-enzyme pyrosequencing protocol was implemented in which individual droplets contained enzymes, deoxyribonucleotide triphosphates (dNTPs), and DNA templates. The DNA templates were anchored to magnetic beads which enabled them to be thoroughly washed between nucleotide additions. Reagents and protocols were optimized to maximize signal over background, linearity of response, cycle efficiency, and wash efficiency. As an initial demonstration of feasibility, a portion of a 229 bp Candida parapsilosis template was sequenced using both a de novo protocol and a resequencing protocol. The resequencing protocol generated over 60 bp of sequence with 100% sequence accuracy based on raw pyrogram levels. Excellent linearity was observed for all of the homopolymers (two, three, or four nucleotides) contained in the C. parapsilosis sequence. With improvements in microfluidic design it is expected that longer reads, higher throughput, and improved process integration (i.e., "sample-to-sequence" capability) could eventually be achieved using this low-cost platform.

  11. Dynamics of nanoscale droplets on moving surfaces.

    PubMed

    Ritos, Konstantinos; Dongari, Nishanth; Borg, Matthew K; Zhang, Yonghao; Reese, Jason M

    2013-06-11

    We use molecular dynamics (MD) simulations to investigate the dynamic wetting of nanoscale water droplets on moving surfaces. The density and hydrogen bonding profiles along the direction normal to the surface are reported, and the width of the water depletion layer is evaluated first for droplets on three different static surfaces: silicon, graphite, and a fictitious superhydrophobic surface. The advancing and receding contact angles, and contact angle hysteresis, are then measured as a function of capillary number on smooth moving silicon and graphite surfaces. Our results for the silicon surface show that molecular displacements at the contact line are influenced greatly by interactions with the solid surface and partly by viscous dissipation effects induced through the movement of the surface. For the graphite surface, however, both the advancing and receding contact angles values are close to the static contact angle value and are independent of the capillary number; i.e., viscous dissipation effects are negligible. This finding is in contrast with the wetting dynamics of macroscale water droplets, which show significant dependence on the capillary number.

  12. Decreasing luminescence lifetime of evaporating phosphorescent droplets

    NASA Astrophysics Data System (ADS)

    van der Voort, D. D.; Dam, N. J.; Sweep, A. M.; Kunnen, R. P. J.; van Heijst, G. J. F.; Clercx, H. J. H.; van de Water, W.

    2016-12-01

    Laser-induced phosphorescence has been used extensively to study spray dynamics. It is important to understand the influence of droplet evaporation in the interpretation of such measurements, as it increases luminescence quenching. By suspending a single evaporating n-heptane droplet in an acoustic levitator, the properties of lanthanide-complex europium-thenoyltrifluoroacetone-trioctylphosphine oxide (Eu-TTA-TOPO) phosphorescence are determined through high-speed imaging. A decrease was found in the measured phosphorescence decay coefficient (780 → 200 μs) with decreasing droplet volumes (10-9 → 10-11 m3) corresponding to increasing concentrations (10-4 → 10-2 M). This decrease continues up to the point of shell-formation at supersaturated concentrations. The diminished luminescence is shown not to be attributable to triplet-triplet annihilation, quenching between excited triplet-state molecules. Instead, the pure exponential decays found in the measurements show that a non-phosphorescent quencher, such as free TTA/TOPO, can be attributable to this decay. The concentration dependence of the phosphorescence lifetime can therefore be used as a diagnostic of evaporation in sprays.

  13. Lattice Boltzmann Simulations of Evaporating Droplets with Nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhao, Mingfei; Yong, Xin

    2016-11-01

    Elucidating the nanoparticle dynamics in drying droplets provides fundamental hydrodynamic insight into the evaporation-induced self-assembly, which is of great importance to materials printing and thin film processing. We develop a free-energy-based multiphase lattice Boltzmann model coupled with Lagrangian particle tracking to simulate evaporating particle-laden droplets on a solid substrate with specified wetting behavior. This work focuses on the interplay between the evaporation-driven advection and the self-organization of nanoparticles inside the droplet and at the droplet surface. For static droplets, the different parameters, fluid-particle interaction strength and particle number, governing the nanoparticle-droplet dynamics are systematically investigated, such as particle radial and circumferential distribution. We clarify the effect of nanoparticle presence on the droplet surface tension and wetting behavior. For evaporating droplets, we observe how droplet evaporation modulates the self-assembly of nanoparticles when the droplet has different static contact angles and hysteresis windows. We also confirm that the number of nanoparticles at the liquid-vapor interface influences the evaporation flux at the liquid-vapor interface.

  14. Droplet ejection and sliding on a flapping film

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Doughramaji, Nicole; Betz, Amy Rachel; Derby, Melanie M.

    2017-03-01

    Water recovery and subsequent reuse are required for human consumption as well as industrial, and agriculture applications. Moist air streams, such as cooling tower plumes and fog, represent opportunities for water harvesting. In this work, we investigate a flapping mechanism to increase droplet shedding on thin, hydrophobic films for two vibrational cases (e.g., ± 9 mm and 11 Hz; ± 2 mm and 100 Hz). Two main mechanisms removed water droplets from the flapping film: vibrational-induced coalescence/sliding and droplet ejection from the surface. Vibrations mobilized droplets on the flapping film, increasing the probability of coalescence with neighboring droplets leading to faster droplet growth. Droplet departure sizes of 1-2 mm were observed for flapping films, compared to 3-4 mm on stationary films, which solely relied on gravity for droplet removal. Additionally, flapping films exhibited lower percentage area coverage by water after a few seconds. The second removal mechanism, droplet ejection was analyzed with respect to surface wave formation and inertia. Smaller droplets (e.g., 1-mm diameter) were ejected at a higher frequency which is associated with a higher acceleration. Kinetic energy of the water was the largest contributor to energy required to flap the film, and low energy inputs (i.e., 3.3 W/m2) were possible. Additionally, self-flapping films could enable novel water collection and condensation with minimal energy input.

  15. Series of Two Droplets on Fiber Approaching Ignition

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber-Supported Droplet Combustion (FSDC) uses two droplets positioned on the fiber wire, instead of the usual one. Two droplets more closely simulates the environment in engines, which ignite many fuel droplets at once. The behavior of the burning was also unexpected -- the droplets moved together after ignition, generating quite a bit of data for understanding the interaction of fuel droplets while they burn. Because FSDC is backlit (the bright glow behind the drops), you carnot see the glow of the droplets while they burn -- instead, you see them shrink! The small blobs left on the wire after the burn are the beads used to center the fuel droplet on the wire. This image was taken on STS-94, July 12, 1997, MET:10/19:13 (approximate). FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations planned for the International Space Station. (251KB JPEG, 1350 x 1523 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300179.html

  16. In vitro characterization of perfluorocarbon droplets for focused ultrasound therapy.

    PubMed

    Schad, Kelly C; Hynynen, Kullervo

    2010-09-07

    Focused ultrasound therapy can be enhanced with microbubbles by thermal and cavitation effects. However, localization of treatment is difficult as bioeffects can occur outside of the target region. Spatial control of bubbles can be achieved by ultrasound-induced conversion of liquid perfluorocarbon droplets to gas bubbles. This study was undertaken to determine the acoustic parameters for bubble production by droplet conversion and how it depends on the acoustic conditions and droplet physical parameters. Lipid-encapsulated droplets containing dodecafluoropentane were manufactured with sizes ranging from 1.9 to 7.2 microm in diameter and diluted to a concentration of 8 x 10(6) droplets mL(-1). The droplets were sonicated in vitro with a focused ultrasound transducer and varying frequency and exposure under flow conditions through an acoustically transparent vessel. The sonications were 10 ms in duration at frequencies of 0.578, 1.736 and 2.855 MHz. The pressure threshold for droplet conversion was measured with an active transducer operating in pulse-echo mode and simultaneous measurements of broadband acoustic emissions were performed with passive acoustic detection. The results show that droplets cannot be converted at low frequency without broadband emissions occurring. However, the pressure threshold for droplet conversion decreased with increasing frequency, exposure and droplet size. The pressure threshold for broadband emissions was independent of the droplet size and was 2.9, 4.4 and 5.3 MPa for 0.578, 1736 and 2.855 MHz, respectively. In summary, we have demonstrated that droplet conversion is feasible for clinically relevant sized droplets and acoustic exposures.

  17. Large Diameter, Radiative Extinction Experiments with Decane Droplets in Microgravity

    NASA Technical Reports Server (NTRS)

    Easton, John; Tien, James; Dietrich, Daniel

    1999-01-01

    The extinction of a diffusion flame is of fundamental interest in combustion science. Linan, Law, and Chung and Law analytically and experimentally determined an extinction boundary in terms of droplet diameter and pressure for a single droplet due to Damkohler, or blowoff, extinction. More recently, other researchers demonstrated extinction due to finite rate kinetics in reduced gravity for free droplets of heptane. Chao modeled the effect of radiative heat loss on a quasi-steady spherically symmetric single droplet burning in the absence of buoyancy. They determined that for increasing droplet diameter, a second limit can be reached such that combustion is no longer possible. This second, larger droplet diameter limit arises due to radiative heat loss, which increases with increasing droplet and flame diameter. This increase in radiative heat loss arises due to an increase in the surface area of the flame. Recently, Marchese modeled fuel droplets with detailed chemistry and radiative effects, and compared the results to other work. The modeling also showed the importance of radiative loss and radiative extinction Experiments examined the behavior of a large droplet of decane burning in reduced gravity onboard the NASA Lewis DC-9 aircraft, but did not show a radiative extinction boundary due to g-jitter (Variations in gravitational level and direction) effects. Dietrich conducted experiments in the reduced gravity environment of the Space Shuttle. This work showed that the extinction diameter of methanol droplets increased when the initial diameter of the droplets was large (in this case, approximately 5 mm). Theoretical results agreed with these experimental results only when the theory included radiative effects . Radiative extinction was experimentally verified by Nayagam in a later Shuttle mission. The following work focuses on the combustion and extinction of a single fuel droplet. The goal is to experimentally determine a large droplet diameter limit that

  18. Inertial migration of deformable droplets in a microchannel

    SciTech Connect

    Chen, Xiaodong; Xue, Chundong; Hu, Guoqing E-mail: sunjs@nanoctr.cn; Zhang, Li; Jiang, Xingyu; Sun, Jiashu E-mail: sunjs@nanoctr.cn

    2014-11-15

    The microfluidic inertial effect is an effective way of focusing and sorting droplets suspended in a carrier fluid in microchannels. To understand the flow dynamics of microscale droplet migration, we conduct numerical simulations on the droplet motion and deformation in a straight microchannel. The results are compared with preliminary experiments and theoretical analysis. In contrast to most existing literature, the present simulations are three-dimensional and full length in the streamwise direction and consider the confinement effects for a rectangular cross section. To thoroughly examine the effect of the velocity distribution, the release positions of single droplets are varied in a quarter of the channel cross section based on the geometrical symmetries. The migration dynamics and equilibrium positions of the droplets are obtained for different fluid velocities and droplet sizes. Droplets with diameters larger than half of the channel height migrate to the centerline in the height direction and two equilibrium positions are observed between the centerline and the wall in the width direction. In addition to the well-known Segré-Silberberg equilibrium positions, new equilibrium positions closer to the centerline are observed. This finding is validated by preliminary experiments that are designed to introduce droplets at different initial lateral positions. Small droplets also migrate to two equilibrium positions in the quarter of the channel cross section, but the coordinates in the width direction are between the centerline and the wall. The equilibrium positions move toward the centerlines with increasing Reynolds number due to increasing deformations of the droplets. The distributions of the lift forces, angular velocities, and the deformation parameters of droplets along the two confinement direction are investigated in detail. Comparisons are made with theoretical predictions to determine the fundamentals of droplet migration in microchannels. In

  19. Polarimetric Retrievals of Cloud Droplet Number Concentrations

    NASA Astrophysics Data System (ADS)

    Sinclair, K.; Cairns, B.; Hair, J. W.; Hu, Y.; Hostetler, C. A.

    2014-12-01

    Cloud droplet number concentration (CDNC) is one of the most significant microphysical properties of liquid clouds and is essential for the understanding of aerosol-cloud interaction. It impacts radiative forcing, cloud evolution, precipitation, global climate and, through observation, can be used to monitor the cloud albedo effect, or the first indirect effect. The IPCC's Fifth Assessment Report continues to consider aerosol-cloud interactions as one of the largest uncertainties in radiative forcing of climate. The SABOR experiment, which was a NASA-led ship and air campaign off the east coast of the United States during July and August of 2014, provided an opportunity for the Research Scanning Polarimeter (RSP) to develop and cross-validate a new approach of sensing CDNC with the High Spectral Resolution Lidar (HSRL). The RSP is an airborne prototype of the Aerosol Polarimetry Sensor (APS) that was on-board the Glory satellite. It is a scanning sensor that provides high-precision measurements of polarized and full-intensity radiances at multiple angles over a wide spectral range. The distinctive feature of the polarimetric technique is that it does not make any assumption of the liquid water profile within the cloud. The approach involves (1) estimating the droplet size distribution from polarized reflectance observations in the rainbow, (2) using polarized reflectance to estimate above cloud water vapor and total reflectance to find how much near infra-red light is being absorbed in clouds, (3) finding cloud physical thickness from the absorption and cloud top pressure retrievals assuming a saturated mixing ratio for water vapor and (4) determining the cloud droplet number concentration from the physical thickness and droplet size distribution retrievals. An overview of the polarimetric technique will be presented along with the results of applying the new approach to SABOR campaign data. An analysis of the algorithm's performance when compared with the HSRL

  20. Evaporation of Droplets on Superhydrophobic Surfaces: Surface Roughness and Small Droplet Size Effects

    NASA Astrophysics Data System (ADS)

    Chen, Xuemei; Ma, Ruiyuan; Li, Jintao; Hao, Chonglei; Guo, Wei; Luk, B. L.; Li, Shuai Cheng; Yao, Shuhuai; Wang, Zuankai

    2012-09-01

    Evaporation of a sessile droplet is a complex, nonequilibrium phenomenon. Although evaporating droplets upon superhydrophobic surfaces have been known to exhibit distinctive evaporation modes such as a constant contact line (CCL), a constant contact angle (CCA), or both, our fundamental understanding of the effects of surface roughness on the wetting transition remains elusive. We show that the onset time for the CCL-CCA transition and the critical base size at the Cassie-Wenzel transition exhibit remarkable dependence on the surface roughness. Through global interfacial energy analysis we reveal that, when the size of the evaporating droplet becomes comparable to the surface roughness, the line tension at the triple line becomes important in the prediction of the critical base size. Last, we show that both the CCL evaporation mode and the Cassie-Wenzel transition can be effectively inhibited by engineering a surface with hierarchical roughness.

  1. Evaporation of droplets on superhydrophobic surfaces: surface roughness and small droplet size effects.

    PubMed

    Chen, Xuemei; Ma, Ruiyuan; Li, Jintao; Hao, Chonglei; Guo, Wei; Luk, B L; Li, Shuai Cheng; Yao, Shuhuai; Wang, Zuankai

    2012-09-14

    Evaporation of a sessile droplet is a complex, nonequilibrium phenomenon. Although evaporating droplets upon superhydrophobic surfaces have been known to exhibit distinctive evaporation modes such as a constant contact line (CCL), a constant contact angle (CCA), or both, our fundamental understanding of the effects of surface roughness on the wetting transition remains elusive. We show that the onset time for the CCL-CCA transition and the critical base size at the Cassie-Wenzel transition exhibit remarkable dependence on the surface roughness. Through global interfacial energy analysis we reveal that, when the size of the evaporating droplet becomes comparable to the surface roughness, the line tension at the triple line becomes important in the prediction of the critical base size. Last, we show that both the CCL evaporation mode and the Cassie-Wenzel transition can be effectively inhibited by engineering a surface with hierarchical roughness.

  2. Research study of droplet sizing technology leading to the development of an advanced droplet sizing system

    NASA Technical Reports Server (NTRS)

    Hess, C. F.; Smart, A. E.; Espinosa, V. E.

    1985-01-01

    An instrument to measure the size and velocity of droplets was developed. The instrument uses one of two techniques, as appropriate. In the first technique two small laser beams of one color identify the center of a larger laser beam of a different color. This defines a region of almost uniform intensity where the light scattered by the individual droplets can be related to their size. The first technique uses the visibility of a Doppler burst and validates it against the peak intensity of the signal's pedestal. Results are presented for monodisperse, bimodal, trimodal, and polydisperse sprays produced by the Berglund-Liu droplet generator and a pressure nozzle. Size distributions of a given spray obtained using three different size ranges show excellent self-consistency in the overlapping region. Measurements of sprays of known characteristics exhibit errors in the order of 10%. The principles of operation and design criteria of the instrument are discussed in great detail.

  3. Experimental Study of Unsupported Nonane fuel Droplet Combustion in Microgravity

    NASA Technical Reports Server (NTRS)

    Callahan, B. J.; Avedisian, C. T.; Hertzog, D. E.; Berkery, J. W.

    1999-01-01

    Soot formation in droplet flames is the basic component of the particulate emission process that occurs in spray combustion. The complexity of soot formation motivates a one-dimensional transport condition which has obvious advantages in modeling. Recent models of spherically symmetric droplet combustion have made this assumption when incorporating such aspects as detailed chemistry and radiation. Interestingly, spherical symmetry does not necessarily restrict the results because it has been observed that the properties of carbon formed in flames are not strongly affected by the nature of the fuel or flaming configuration. What is affected, however, are the forces acting on the soot aggregates and where they are trapped by a balance of drag and thermophoretic forces. The distribution of these forces depends on the transport conditions of the flame. Prior studies of spherical droplet flames have examined the droplet burning history of alkanes, alcohols and aromatics. Data are typically the evolution of droplet, flame, extinction, and soot shell diameters. These data are only now just beginning to find their way into comprehensive numerical models of droplet combustion to test proposed oxidation schemes for fuels such as methanol and heptane. In the present study, we report new measurements on the burning history of unsupported nonane droplets in a convection-free environment to promote spherical symmetry. The far-field gas is atmospheric pressure air at room temperature. The evolution of droplet diameter was measured using high speed cine photography of a spark-ignited, droplet within a confined volume in a drop tower. The initial droplet diameters varied between 0.5 mm and 0.6 mm. The challenge of unsupported droplets is to form, deploy and ignite them with minimal disturbance, and then to keep them in the camera field of view. Because of the difficulty of this undertaking, more sophisticated diagnostics for studying soot than photographic were not used. Supporting

  4. Hands-off preparation of monodisperse emulsion droplets using a poly(dimethylsiloxane) microfluidic chip for droplet digital PCR.

    PubMed

    Tanaka, Hironari; Yamamoto, Shunsuke; Nakamura, Arichika; Nakashoji, Yuta; Okura, Naoaki; Nakamoto, Norimitsu; Tsukagoshi, Kazuhiko; Hashimoto, Masahiko

    2015-04-21

    A fully autonomous method of creating highly monodispersed emulsion droplets with a low sample dead volume was realized using a degassed poly(dimethylsiloxane) (PDMS) microfluidic chip possessing a simple T-junction channel geometry with two inlet reservoirs for oil and water to be loaded and one outlet reservoir for the collection of generated droplets. Autonomous transport of oil and water phases in the channel was executed by permeation of air confined inside the outlet reservoir into the degassed PDMS. The only operation required for droplet creation was simple pipetting of oil and aqueous solutions into the inlet reservoirs. Long-lasting fluid transport in the current system enabled us to create ca. 51,000 monodispersed droplets (with a coefficient of variation of <3% for the droplet diameter) in 80 min with a maximum droplet generation rate of ca. 12 Hz using a PDMS chip that had been degassed overnight. With multiple time-course measurements, the reproducibility in the current method of droplet preparation was confirmed, with tunable droplet sizes achieved simply by changing the cross-sectional dimensions of the microchannel. Furthermore, it was verified that the resultant droplets could serve as microreactors for digital polymerase chain reactions. This hands-free technique for preparing monodispersed droplets in a very facile and inexpensive fashion is intended for, but not limited to, bioanalytical applications and is also applicable to material syntheses.

  5. Formation of droplets of alternating composition in microfluidic channels and applications to indexing of concentrations in droplet-based assays.

    PubMed

    Zheng, Bo; Tice, Joshua D; Ismagilov, Rustem F

    2004-09-01

    For screening the conditions for a reaction by using droplets (or plugs) as microreactors, the composition of the droplets must be indexed. Indexing here refers to measuring the concentration of a solute by addition of a marker, either internal or external. Indexing may be performed by forming droplet pairs, where in each pair the first droplet is used to conduct the reaction, and the second droplet is used to index the composition of the first droplet. This paper characterizes a method for creating droplet pairs by generating alternating droplets, of two sets of aqueous solutions in a flow of immiscible carrier fluid within PDMS and glass microfluidic channels. The paper also demonstrates that the technique can be used to index the composition of the droplets, and this application is illustrated by screening conditions of protein crystallization. The fluid properties required to form the steady flow of the alternating droplets in a microchannel were characterized as a function of the capillary number Ca and water fraction. Four regimes were observed. At the lowest values of Ca, the droplets of the two streams coalesced; at intermediate values of Ca the alternating droplets formed reliably. At even higher values of Ca, shear forces dominated and caused formation of droplets that were smaller than the cross-sectional dimension of the channel; at the highest values of Ca, coflowing laminar streams of the two immiscible fluids formed. In addition to screening of protein crystallization conditions, understanding of the fluid flow in this system may extend this indexing approach to other chemical and biological assays performed on a microfluidic chip.

  6. Dynamics of concentric and eccentric compound droplets suspended in extensional flows

    NASA Astrophysics Data System (ADS)

    Qu, Xiaofeng; Wang, Yechun

    2012-12-01

    The motion, deformation, and stability of compound droplets in extensional flows are investigated numerically via a three-dimensional spectral boundary element method. We examine the droplet stability under the influences of the capillary number, the inner droplet size and the relative magnitude of the surface tension of the two interfaces composing the compound droplet. The influence of viscosity on the droplet deformation is also discussed. We conclude that a compound droplet with a larger inner droplet and/or smaller inner surface tension is less stable and cannot withstand strong flow. For moderate viscosity ratios, a compound droplet with a more viscous "shell" exhibits larger deformation at steady state. In addition, for an eccentric compound droplet, both the inner and outer droplets tend to migrate away from its original location due to the asymmetry of the problem. The initial location of the inner droplet also influences the droplet stability as well as the migration velocity of the compound droplet.

  7. Droplet fusion by alternating current (AC) field electrocoalescence in microchannels.

    PubMed

    Chabert, Max; Dorfman, Kevin D; Viovy, Jean-Louis

    2005-10-01

    We present a system for the electrocoalescence of microfluidic droplets immersed in an immiscible solvent, where the undeformed droplet diameters are comparable to the channel diameter. The electrodes are not in direct contact with the carrier liquid or the droplets, thereby minimizing the risk of cross-contamination between different coalescence events. Results are presented for the coalescence of buffered aqueous droplets in both quiescent and flowing fluorocarbon streams, and on-flight coalescence is demonstrated. The capillary-based system presented here is readily amenable to further miniaturization to any lab-on-a-chip application where the conductivity of the droplets is much greater than the conductivity of the stream containing them, and should aid in the further application of droplet microreactors to biological analyses.

  8. Phase rainbow refractometry for accurate droplet variation characterization.

    PubMed

    Wu, Yingchun; Promvongsa, Jantarat; Saengkaew, Sawitree; Wu, Xuecheng; Chen, Jia; Gréhan, Gérard

    2016-10-15

    We developed a one-dimensional phase rainbow refractometer for the accurate trans-dimensional measurements of droplet size on the micrometer scale as well as the tiny droplet diameter variations at the nanoscale. The dependence of the phase shift of the rainbow ripple structures on the droplet variations is revealed. The phase-shifting rainbow image is recorded by a telecentric one-dimensional rainbow imaging system. Experiments on the evaporating monodispersed droplet stream show that the phase rainbow refractometer can measure the tiny droplet diameter changes down to tens of nanometers. This one-dimensional phase rainbow refractometer is capable of measuring the droplet refractive index and diameter, as well as variations.

  9. Investigation of critical burning of fuel droplets. [monopropellants

    NASA Technical Reports Server (NTRS)

    Faeth, G. M.; Chanin, S.

    1974-01-01

    The steady combustion characteristics of droplets were considered in combustion chamber environments at various pressures, flow conditions, and ambient oxidizer concentrations for a number of hydrocarbon fuels. Using data obtained earlier, predicted gasification rates were within + or - 30% of measurements when the correction for convection was based upon average properties between the liquid surface and the flame around the droplet. Analysis was also completed for the open loop response of monopropellant droplets, based upon earlier strand combustion results. At the limit of large droplets, where the effect of flame curvature is small, the results suggest sufficient response to provide a viable mechanism for combustion instability in the frequency and droplet size range appropriate to practical combustors. Calculations are still in progress for a broader range of droplet sizes, including conditions where active combustion effects are small.

  10. Droplet deposition and momentum transfer in annular flow

    SciTech Connect

    Fore, L.B.; Dukler, A.E.

    1995-09-01

    Entrainment and deposition in gas-liquid annular upflow are known to account for as much as 20% of the pressure gradient, through droplet accelerations in the core region. Momentum is transferred from the core when droplets decelerate upon impact with the liquid film. It is usually assumed that all of this momentum is transferred to the film, essentially driving the film upward in conjunction with interfacial friction. New data, obtained for annular gas-liquid upflow in a 5.08-cm-ID tube, are used in a momentum balance analysis to determine the mechanism of momentum transfer from depositing droplets. Measurements include the liquid film thickness, wall shear stress, pressure gradient, entrained liquid fraction, droplet deposition rate, droplet centerline axial velocity, and mass-average drop size for two gas-liquid systems. This analysis supports the idea that large droplets displace the film locally and decelerate primarily at the wall, effectively transferring negligible momentum to the liquid film.

  11. Generation and mixing of subfemtoliter aqueous droplets on demand.

    PubMed

    Tang, Jianyong; Jofre, Ana M; Kishore, Rani B; Reiner, Joseph E; Greene, Mark E; Lowman, Geoffrey M; Denker, John S; Willis, Christina C C; Helmerson, Kristian; Goldner, Lori S

    2009-10-01

    We describe a novel method of generating monodisperse subfemtoliter aqueous droplets on demand by means of piezoelectric injection. Droplets with volumes down to 200 aL are generated by this technique. The droplets are injected into a low refractive index perfluorocarbon so that they can be optically trapped. We demonstrate the use of optical tweezers to manipulate and mix droplets. For example, using optical tweezers we bring two droplets, one containing a calcium sensitive dye and the other calcium chloride, into contact. The droplets coalesce with a resulting reaction time of about 1 ms. The monodispersity, manipulability, repeatability, small size, and fast mixing afforded by this system offer many opportunities for nanochemistry and observation of chemical reactions on a molecule-by-molecule basis.

  12. Effects of induced vibration modes on droplet sliding phenomena

    NASA Astrophysics Data System (ADS)

    Mejia, Jose Eduardo; Alvarado, Jorge; Yao, Chun-Wei; Dropwise Condensation Collaboration; Engineered Surfaces Collaboration

    2016-11-01

    An analytical and experimental investigation has been undertaken to understand the effects of induced vibration modes on droplet sliding phenomena. A mathematical model has been postulated which is capable of estimating accurately droplet sliding angles when using hydrophobic and hydrophilic surfaces. The model, which takes into account equilibrium contact angle, contact angle hysteresis, and droplet volume, has been validated using experimental data. The model has been modified to be able to estimate droplet sliding angle when different modes of vibrations are imposed on the surfaces. Experimental results to date reveal that when resonance modes of vibrations are imposed, the droplet sliding angles decrease considerably. The results also indicate that the modified model can be used effectively to relate imposed resonance frequencies to the critical sliding angle of droplets. LSAMP sponsored NSF Fellowship.

  13. Spontaneous electrical charging of droplets by conventional pipetting

    PubMed Central

    Choi, Dongwhi; Lee, Horim; Im, Do Jin; Kang, In Seok; Lim, Geunbae; Kim, Dong Sung; Kang, Kwan Hyoung

    2013-01-01

    We report that a droplet dispensed from a micropipette almost always has a considerable electrical charge of a magnitude dependent on the constituents of the droplet, on atmospheric humidity and on the coating material of pipette tip. We show that this natural electrification of a droplet originates from the charge separation between a droplet and pipette tip surface by contact with water due to the ionization of surface chemical groups. Charge on a droplet can make it difficult to detach the droplet from the pipette tip, can decrease its surface tension, can affect the chemical characteristics of solutions due to interactions with charged molecules, and can influence the combination and localization of charged bio-molecules; in all cases, the charge may affect results of experiments in which any of these factors is important. Thus, these findings reveal experimental parameters that should be controlled in experiments that use micropipettes. PMID:23784001

  14. Droplet networks with incorporated protein diodes show collective properties.

    PubMed

    Maglia, Giovanni; Heron, Andrew J; Hwang, William L; Holden, Matthew A; Mikhailova, Ellina; Li, Qiuhong; Cheley, Stephen; Bayley, Hagan

    2009-07-01

    Recently, we demonstrated that submicrolitre aqueous droplets submerged in an apolar liquid containing lipid can be tightly connected by means of lipid bilayers to form networks. Droplet interface bilayers have been used for rapid screening of membrane proteins and to form asymmetric bilayers with which to examine the fundamental properties of channels and pores. Networks, meanwhile, have been used to form microscale batteries and to detect light. Here, we develop an engineered protein pore with diode-like properties that can be incorporated into droplet interface bilayers in droplet networks to form devices with electrical properties including those of a current limiter, a half-wave rectifier and a full-wave rectifier. The droplet approach, which uses unsophisticated components (oil, lipid, salt water and a simple pore), can therefore be used to create multidroplet networks with collective properties that cannot be produced by droplet pairs.

  15. Combustion of interacting droplet arrays in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Dietrich, Daniel L.; Haggard, John B.

    1993-01-01

    This research program involves the study of one and two dimensional arrays of droplets in a buoyant-free environment. The purpose of the work is to extend the database and theories that exist for single droplets into the regime where droplet interactions are important. The eventual goal being to use the results of this work as inputs to models on spray combustion where droplets seldom burn individually; instead the combustion history of a droplet is strongly influenced by the presence of the neighboring droplets. The emphasis of the present investigation is experimental, although comparison will be made to existing theoretical and numerical treatments when appropriate. Both normal gravity and low gravity testing will be employed, and the results compared. The work to date will be summarized in the next section, followed by a section detailing the future plans.

  16. Vapor mediated droplet interactions - models and mechanisms (Part 2)

    NASA Astrophysics Data System (ADS)

    Benusiglio, Adrien; Cira, Nate; Prakash, Manu

    2014-11-01

    When deposited on clean glass a two-component binary mixture of propylene glycol and water is energetically inclined to spread, as both pure liquids do. Instead the mixture forms droplets stabilized by evaporation induced surface tension gradients, giving them unique properties such as negligible hysteresis. When two of these special droplets are deposited several radii apart they attract each other. The vapor from one droplet destabilizes the other, resulting in an attraction force which brings both droplets together. We present a flux-based model for droplet stabilization and a model which connects the vapor profile to net force. These simple models capture the static and dynamic experimental trends, and our fundamental understanding of these droplets and their interactions allowed us to build autonomous fluidic machines.

  17. Compound Droplet Levitation for Lab-on-a-Chip

    NASA Astrophysics Data System (ADS)

    Black, James; Neitzel, G. Paul

    2016-11-01

    A fluid transport mechanism utilizing thermocapillarity has been previously shown to successfully levitate and translate both microliter- and nanoliter-volume droplets of silicone oil. The surface flow required to drive levitation and transport has not been achieved for aqueous droplets, and encapsulation of samples within a layer of silicone oil is necessary. A droplet-on-demand generator capable of producing nanoliter-volume compound droplets has been developed and previously reported. The work presented here discusses efforts to demonstrate the applicability of this microfluidic transport mechanism to lab-on-a-chip systems. We elaborate on translation speeds of single-phase, nanoliter-volume, silicone-oil droplets. Compound droplets of varying compositions of oil and water are then generated, captured, levitated, and merged to explore the composition limits thereof. Work supported by NSF and NASA.

  18. Single-molecule emulsion PCR in microfluidic droplets.

    PubMed

    Zhu, Zhi; Jenkins, Gareth; Zhang, Wenhua; Zhang, Mingxia; Guan, Zhichao; Yang, Chaoyong James

    2012-06-01

    The application of microfluidic droplet PCR for single-molecule amplification and analysis has recently been extensively studied. Microfluidic droplet technology has the advantages of compartmentalizing reactions into discrete volumes, performing highly parallel reactions in monodisperse droplets, reducing cross-contamination between droplets, eliminating PCR bias and nonspecific amplification, as well as enabling fast amplification with rapid thermocycling. Here, we have reviewed the important technical breakthroughs of microfluidic droplet PCR in the past five years and their applications to single-molecule amplification and analysis, such as high-throughput screening, next generation DNA sequencing, and quantitative detection of rare mutations. Although the utilization of microfluidic droplet single-molecule PCR is still in the early stages, its great potential has already been demonstrated and will provide novel solutions to today's biomedical engineering challenges in single-molecule amplification and analysis.

  19. Droplet microfluidics--a tool for single-cell analysis.

    PubMed

    Joensson, Haakan N; Andersson Svahn, Helene

    2012-12-03

    Droplet microfluidics allows the isolation of single cells and reagents in monodisperse picoliter liquid capsules and manipulations at a throughput of thousands of droplets per second. These qualities allow many of the challenges in single-cell analysis to be overcome. Monodispersity enables quantitative control of solute concentrations, while encapsulation in droplets provides an isolated compartment for the single cell and its immediate environment. The high throughput allows the processing and analysis of the tens of thousands to millions of cells that must be analyzed to accurately describe a heterogeneous cell population so as to find rare cell types or access sufficient biological space to find hits in a directed evolution experiment. The low volumes of the droplets make very large screens economically viable. This Review gives an overview of the current state of single-cell analysis involving droplet microfluidics and offers examples where droplet microfluidics can further biological understanding.

  20. Bi-Component Droplet Combustion in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Shaw, B. D.

    2003-01-01

    This research deals with reduced-gravity combustion of bi-component droplets initially in the mm size range or larger. The primary objectives of the research are to study the effects of droplet internal flows, thermal and solutal Marangoni stresses, and species volatility differences on liquid species transport and overall combustion phenomena (e.g., gas-phase unsteadiness, burning rates, sooting, radiation, and extinction). The research program utilizes a reduced-gravity environment so that buoyancy effects are rendered negligible. Use of large droplets also facilitates visualization of droplet internal flows, which is important for this research. In the experiments, droplets composed of low- and high-volatility species are burned. The low-volatility components are initially present in small amounts. As combustion of a droplet proceeds, the liquid surface mass fraction of the low-volatility component will increase with time, resulting in a sudden and temporary decrease in droplet burning rates as the droplet rapidly heats to temperatures close to the boiling point of the low-volatility component. This decrease in burning rates causes a sudden and temporary contraction of the flame. The decrease in burning rates and the flame contraction can be observed experimentally. Measurements of burning rates as well as the onset time for flame contraction allow effective liquid-phase species diffusivities to be calculated, e.g., using asymptotic theory. It is planned that droplet internal flows will be visualized in flight and ground-based experiments. In this way, effective liquid species diffusivities can be related to droplet internal flow characteristics. This program is a continuation of extensive ground based experimental and theoretical research on bi-component droplet combustion that has been ongoing for several years. The focal point of this program is a flight experiment (Bi-Component Droplet Combustion Experiment, BCDCE). This flight experiment is under

  1. Grooved organogel surfaces towards anisotropic sliding of water droplets.

    PubMed

    Zhang, Pengchao; Liu, Hongliang; Meng, Jingxin; Yang, Gao; Liu, Xueli; Wang, Shutao; Jiang, Lei

    2014-05-21

    Periodic micro-grooved organogel surfaces can easily realize the anisotropic sliding of water droplets attributing to the formed slippery water/oil/solid interface. Different from the existing anisotropic surfaces, this novel surface provides a versatile candidate for the anisotropic sliding of water droplets and might present a promising way for the easy manipulation of liquid droplets for water collection, liquid-directional transportation, and microfluidics.

  2. Directional electrostatic accretion process employing acoustic droplet formation

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    1996-01-01

    The present invention is directed to an apparatus for manufacturing a free standing solid metal part. In the present invention metal droplets are produced from a free surface pool of molten metal is when an acoustic wave impacts an acoustic lens that is contiguous with the free standing pool of molten metal. The metal droplets are then charged and deflected toward a target. The build up of the metal droplets combine to form the free standing solid metal part.

  3. Bi-Component Droplet Combustion in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Shaw, Benjamin D.

    2004-01-01

    This research deals with reduced-gravity combustion of bi-component droplets initially in the mm size range or larger. The primary objectives of the research are to study the effects of droplet internal flows, thermal and solutal Marangoni stresses, and species volatility differences on liquid species transport and overall combustion phenomena (e.g., gas-phase unsteadiness, burning rates, sooting, radiation, and extinction). The research program utilizes a reduced gravity environment so that buoyancy effects are rendered negligible. Use of large droplets also facilitates visualization of droplet internal flows, which is important for this research. In the experiments, droplets composed of low- and high-volatility species are burned. The low-volatility components are initially present in small amounts. As combustion of a droplet proceeds, the liquid surface mass fraction of the low-volatility component will increase with time, resulting in a sudden and temporary decrease in droplet burning rates as the droplet rapidly heats to temperatures close to the boiling point of the low-volatility component. This decrease in burning rates causes a sudden and temporary contraction of the flame. The decrease in burning rates and the flame contraction can be observed experimentally. Measurements of burning rates as well as the onset time for flame contraction allow effective liquid-phase species diffusivities to be calculated, e.g., using asymptotic theory. It is planned that droplet internal flows will be visualized in flight and ground-based experiments. In this way, effective liquid species diffusivities can be related to droplet internal flow characteristics. This program is a continuation of extensive ground-based experimental and theoretical research on bi-component droplet combustion that has been ongoing for several years. The focal point of this program is a flight experiment (Bi-Component Droplet Combustion Experiment, BCDCE). This flight experiment is under

  4. Instabilities, motion and deformation of active fluid droplets

    NASA Astrophysics Data System (ADS)

    Whitfield, Carl A.; Hawkins, Rhoda J.

    2016-12-01

    We consider two minimal models of active fluid droplets that exhibit complex dynamics including steady motion, deformation, rotation and oscillating motion. First we consider a droplet with a concentration of active contractile matter adsorbed to its boundary. We analytically predict activity driven instabilities in the concentration profile, and compare them to the dynamics we find from simulations. Secondly, we consider a droplet of active polar fluid of constant concentration. In this system we predict, motion and deformation of the droplets in certain activity ranges due to instabilities in the polarisation field. Both these systems show spontaneous transitions to motility and deformation which resemble dynamics of the cell cytoskeleton in animal cells.

  5. Dynamics of droplet entrapment in a constricted microchannel

    NASA Astrophysics Data System (ADS)

    Nekouei, Mehdi; Bithi, Swastika; Vanapalli, Siva

    2016-11-01

    Droplet migration and clogging in confined geometries is a problem of fundamental importance in oil recovery and droplet microfluidics. A confined droplet flowing through a conduit can either be arrested at the constriction or squeeze through it. The dynamics of the trapped and squeezed states are expected to depend on capillary number, drop size, viscosity ratio. Although there have been a number of studies on the dynamics of droplets passing through a constriction, investigations of dynamics of trapped droplets in constricted microchannels is lacking. In this work, we performed three-dimensional simulations of droplet trapping and squeezing process in a constricted microchannel. We also conducted experiments to validate the key results of the simulations. We investigated the impact of different system parameters on the onset of droplet immobilization at the constriction. We found that the continuous phase flows through the corners of the droplet, i.e. gutter flows to play an important role in determining the transition between trapping and squeezing. Therefore we evaluated the effect of different system parameters on gutter flows and found that the hydrodynamic resistance of gutters depends on the viscosity, size and confinement of the droplet.

  6. Droplet evaporation dynamics on a superhydrophobic surface with negligible hysteresis.

    PubMed

    Dash, Susmita; Garimella, Suresh V

    2013-08-27

    We report on experiments of droplet evaporation on a structured superhydrophobic surface that displays very high contact angle (CA ∼ 160 deg), and negligible contact angle hysteresis (<1 deg). The droplet evaporation is observed to occur in a constant-contact-angle mode, with contact radius shrinking for almost the entire duration of evaporation. Experiments conducted on Teflon-coated smooth surface (CA ∼ 120 deg) as a baseline also support an evaporation process that is dominated by a constant-contact-angle mode. The experimental results are compared with an isothermal diffusion model for droplet evaporation from the literature. Good agreement is observed for the Teflon-coated smooth surface between the analytical expression and experimental results in terms of the total time for evaporation, transient volume, contact angle, and contact radius. However, for the structured superhydrophobic surface, the experiments indicate that the time taken for complete evaporation of the droplet is greater than the predicted time, across all droplet volumes. This disparity is attributed primarily to the evaporative cooling at the droplet interface due to the high aspect ratio of the droplet and also the lower effective thermal conductivity of the substrate due to the presence of air gaps. This hypothesis is verified by numerically evaluating the temperature distribution along the droplet interface. We propose a generalized relation for predicting the instantaneous volume of droplets with initial CA > 90 deg, irrespective of the mode of evaporation.

  7. Printing microstructures in a polymer matrix using a ferrofluid droplet

    NASA Astrophysics Data System (ADS)

    Abdel Fattah, Abdel Rahman; Ghosh, Suvojit; Puri, Ishwar K.

    2016-03-01

    We print complex curvilinear microstructures in an elastomer matrix using a ferrofluid droplet as the print head. A magnetic field moves the droplet along a prescribed path in liquid polydimethylsiloxane (PDMS). The droplet sheds magnetic nanoparticle (MNP) clusters in its wake, forming printed features. The PDMS is subsequently heated so that it crosslinks, which preserves the printed features in the elastomer matrix. The competition between magnetic and drag forces experienced by the ferrofluid droplet and its trailing MNPs highlight design criteria for successful printing, which are experimentally confirmed. The method promises new applications, such as flexible 3D circuitry.

  8. Cross-Interface Emulsification for Generating Size-Tunable Droplets.

    PubMed

    Xu, Peng; Zheng, Xu; Tao, Yi; Du, Wenbin

    2016-03-15

    We report cross-interface emulsification (XiE), a simple method for the generation of monodisperse droplets of controllable volumes from picoliter to nanoliter. A device is set up in which a fused-silica capillary is vibrating across the surface of the continuous phase (mineral oil) in a reservoir, and the flow of the dispersed phase (aqueous solution) in the capillary is segmented into monodisperse droplets at the air/oil interface. We find that the volume of droplets is mainly dominated by the flow rate and vibrating frequency and not significantly influenced by other factors, such as the viscosity of the continuous phase and dispersed phase, the inner diameter of the capillary (20-100 μm), or the shape of the tip (tapered or flat). These features reflect high robustness, flexibility, and precision of XiE for on-demand volume control of droplets. The droplets automatically assemble into planar monolayer droplet arrays (PMDA) in flat-bottomed microwells of 96-well plates, offering excellent convenience for imaging of droplets. As a representative application, we carry out digital loop-mediated isothermal amplification using PMDAs with multivolume droplets for the absolute quantification of nucleic acids. Our results demonstrate that XiE is simple and controllable for the production of monodisperse size-tunable droplets, and it offers opportunities for common laboratories, even without microfabrication facilities, to perform digital quantification, single cell analysis, and other biochemical assays with high throughput.

  9. Flight behavior of charged droplets in electrohydrodynamic inkjet printing

    NASA Astrophysics Data System (ADS)

    Yudistira, Hadi Teguh; Nguyen, Vu Dat; Dutta, Prashanta; Byun, Doyoung

    2010-01-01

    Flight behaviors of charged droplets are presented for electrohydrodynamic (EHD) inkjet printing. Three different kinds of EHD spraying techniques, pulsed dc, ac, and single potential (SP) ac, have been investigated and both conductive and dielectric target surfaces were considered. Experimental results show that the flight paths of charged droplets may deviate from their regular straight route, i.e., directly from the nozzle to the substrate. Depending on the droplet charge and applied electric field, droplets may deflect, reflect, or retreat to the meniscus. We can solve these drawbacks by SP EHD printing.

  10. Droplet microfluidics for high-throughput biological assays.

    PubMed

    Guo, Mira T; Rotem, Assaf; Heyman, John A; Weitz, David A

    2012-06-21

    Droplet microfluidics offers significant advantages for performing high-throughput screens and sensitive assays. Droplets allow sample volumes to be significantly reduced, leading to concomitant reductions in cost. Manipulation and measurement at kilohertz speeds enable up to 10(8) samples to be screened in one day. Compartmentalization in droplets increases assay sensitivity by increasing the effective concentration of rare species and decreasing the time required to reach detection thresholds. Droplet microfluidics combines these powerful features to enable currently inaccessible high-throughput screening applications, including single-cell and single-molecule assays.

  11. Combustion and micro-explosion of multicomponent droplets

    SciTech Connect

    Wang, C.H.

    1983-01-01

    An experimental investigation of the gasification, combustion, and micro-explosion of droplets of miscible multicomponent fuel mixtures and water/oil emulsions in hot, oxidizing, pressurized environments is described. The experiment involves generating a stream of droplets of uniform and controllable size, spacing, and velocity by the ink-jet printing technique, injecting them into the continuously flowing combustion environment produced by a flat-flame burner, and examining the subsequent combustion processes using high-speed photography. Results show that the gasification mechanism of miscible multicomponent droplets consist of an initial phase of transient adjustment of the droplet surface layer such that it becomes more concentrated with the less volatile component, and a second phase of liquid-phase-diffusion-limited steady-state combustion with the fractional gasification rate of the constituents being equal to their respective initial mass fractions in the mixture. Micro-explosion of miscible multicomponent droplets is found to be favored with an unstable droplet generation mode, with increasing the system pressure, and with light alcohol addition. The internal bubble growth process is a relatively slow one, occupying about 10% of the droplet lifetime. Micro-explosion of water/oil emulsion droplets occurs under both normal and high pressure environments. Results also show that prior to the onset of micro-explosion in the nominally opaque droplet becomes transparent, indicating deterioration of the emulsion structure. Results and insights on the ignition, extinction, and soot formation characteristics are also documented.

  12. Spreading dynamics of droplet on an inclined surface

    NASA Astrophysics Data System (ADS)

    Shen, Chaoqun; Yu, Cheng; Chen, Yongping

    2016-06-01

    A three-dimensional unsteady theoretical model of droplet spreading process on an inclined surface is developed and numerically analyzed to investigate the droplet spreading dynamics via the lattice Boltzmann simulation. The contact line motion and morphology evolution for the droplet spreading on an inclined surface, which are, respectively, represented by the advancing/receding spreading factor and droplet wetted length, are evaluated and analyzed. The effects of surface wettability and inclination on the droplet spreading behaviors are examined. The results indicate that, dominated by gravity and capillarity, the droplet experiences a complex asymmetric deformation and sliding motion after the droplet comes into contact with the inclined surfaces. The droplet firstly deforms near the solid surface and mainly exhibits a radial expansion flow in the start-up stage. An evident sliding-down motion along the inclination is observed in the middle stage. And the surface-tension-driven retraction occurs during the retract stage. Increases in inclination angle and equilibrium contact angle lead to a faster droplet motion and a smaller wetted area. In addition, increases in equilibrium contact angle lead to a shorter duration time of the middle stage and an earlier entry into the retract stage.

  13. Dynamic response of vaporizing droplet to pressure oscillation

    NASA Astrophysics Data System (ADS)

    Yuan, Lei; Shen, Chibing; Zhang, Xinqiao

    2017-02-01

    Combustion instability is a major challenge in the development of the liquid propellant engines, and droplet vaporization is viewed as a potential mechanism for driving instabilities. Based on the previous work, an unsteady droplet heating and vaporization model was developed. The model and numerical method are validated by experimental data available in literature, and then the oscillatory vaporization of n-Heptane droplet exposed to unsteady harmonic nitrogen atmosphere was numerically investigated over a wide range of amplitudes and frequencies. Also, temperature variations inside the droplet were demonstrated under oscillation environments. It was found that the thermal wave is attenuated with significantly reduced wave intensities as it penetrates deep into droplet from the ambient gas. Droplet surface temperature exhibits smaller fluctuation than that of the ambient gas, and it exhibits a time lag with regard to the pressure variation. Furthermore, the mechanism leading to phase lag of vaporization rate with respect to pressure oscillation was unraveled. Results show that this phase lag varies during the droplet lifetime and it is strongly influenced by oscillation frequency, indicating droplet vaporization is only capable of driving combustion instability in some certain frequency domains. Instead, the amplitude of the oscillation does not have very significant effects. It is noteworthy that thermal inertia of the droplet also plays a considerable role in determining the phase lag.

  14. Tuning of the droplet motion in interconnected microfluidic devices

    NASA Astrophysics Data System (ADS)

    Hu, Guoqing; Song, Kui; Zhang, Li

    2010-11-01

    The problem of controlling the droplet motions in multiphase flows on the microscale has gained increasing attention because the droplet-based microfluidic devices provide great potentials for chemical/biological applications such as drug discovery, chemical kinetics study, material synthesis, and DNA/cell assays. It is critical to understand the relevant physics on droplet hydrodynamics and thus control the generation, motion, splitting, and coalescence of droplets in complex microfluidic networks. The operation of those applications sometimes requires the arrival of droplets from different branch microchannels at a designated location within a transit time. We propose a simple design for interconnected microfluidic devices that implement the feedback mechanism to synchronize the droplet motion via a passive way. Numerical simulations using the Volume of Fluid (VOF) algorithm are conducted to investigate the time-dependent dynamics of droplets in both gas-liquid and liquid-liquid systems. An analytical mode based on the electronic-hydraulic analogy is also developed to describe the transit behavior of the droplet traffic. Both the numerical and theoretical results agree well with the corresponding experimental results. Furthermore, we optimize the microfluidic networks to control the motion of a series of droplets.

  15. Dynamic interactions of Leidenfrost droplets on liquid metal surface

    NASA Astrophysics Data System (ADS)

    Ding, Yujie; Liu, Jing

    2016-09-01

    Leidenfrost dynamic interaction effects of the isopentane droplets on the surface of heated liquid metal were disclosed. Unlike conventional rigid metal, such conductive and deformable liquid metal surface enables the levitating droplets to demonstrate rather abundant and complex dynamics. The Leidenfrost droplets at different diameters present diverse morphologies and behaviors like rotation and oscillation. Depending on the distance between the evaporating droplets, they attract and repulse each other through the curved surfaces beneath them and their vapor flows. With high boiling point up to 2000 °C, liquid metal offers a unique platform for testing the evaporating properties of a wide variety of liquid even solid.

  16. Electric field mediated spraying of miniaturized droplets inside microchannel.

    PubMed

    Timung, Seim; Chaudhuri, Joydip; Borthakur, Manash Pratim; Mandal, Tapas Kumar; Biswas, Gautam; Bandyopadhyay, Dipankar

    2016-10-17

    We report a facile and noninvasive way to disintegrate a microdroplet into a string of further miniaturized ones under the influence of an external electrohydrodynamic field inside a microchannel. The deformation and breakup of the droplet was engendered by the Maxwell's stress originating from the accumulation of induced and free charges at the oil-water interface. While at smaller field intensities, for example less than 1 MV/m, the droplet deformed into a plug, at relatively higher field intensities, e.g. ∼1.16 MV/m, a pair of droplets having opposite surface charge was formed. The charged droplets showed an interesting periodic bridging and breakup during their translation motion across the channel. For even higher field intensities, for example more than 1.2 MV/m, the entire droplet underwent dielectrophoresis toward one of the electrodes before experiencing a strong attractive force from the other electrode to deform into a shape of a Taylor cone. With progress in time, mimicking the electrospraying phenomenon, the cone tip periodically ejected a string of miniaturized water droplets to form a microemulsion inside the channel. The frequency and size of the droplet ejection could be tuned by varying the applied field intensity. A water droplet of ∼214 μm diameter could continuously eject droplets of size ∼10 μm or even smaller to form a microemulsion inside the channel.

  17. Sessile multidroplets and salt droplets under high tangential electric fields

    PubMed Central

    Xie, Guoxin; He, Feng; Liu, Xiang; Si, Lina; Guo, Dan

    2016-01-01

    Understanding the interaction behaviors between sessile droplets under imposed high voltages is very important in many practical situations, e.g., microfluidic devices and the degradation/aging problems of outdoor high-power applications. In the present work, the droplet coalescence, the discharge activity and the surface thermal distribution response between sessile multidroplets and chloride salt droplets under high tangential electric fields have been investigated with infrared thermography, high-speed photography and pulse current measurement. Obvious polarity effects on the discharge path direction and the temperature change in the droplets in the initial stage after discharge initiation were observed due to the anodic dissolution of metal ions from the electrode. In the case of sessile aligned multidroplets, the discharge path direction could affect the location of initial droplet coalescence. The smaller unmerged droplet would be drained into the merged large droplet as a result from the pressure difference inside the droplets rather than the asymmetric temperature change due to discharge. The discharge inception voltages and the temperature variations for two salt droplets closely correlated with the ionization degree of the salt, as well as the interfacial electrochemical reactions near the electrodes. Mechanisms of these observed phenomena were discussed. PMID:27121926

  18. Droplet Mobility Manipulation on Porous Media Using Backpressure.

    PubMed

    Vourdas, N; Pashos, G; Kokkoris, G; Boudouvis, A G; Stathopoulos, V N

    2016-05-31

    Wetting phenomena on hydrophobic surfaces are strongly related to the volume and pressure of gas pockets residing at the solid-liquid interface. In this study, we explore the underlying mechanisms of droplet actuation and mobility manipulation when backpressure is applied through a porous medium under a sessile pinned droplet. Reversible transitions between the initially sticky state and the slippery states are thus incited by modulating the backpressure. The sliding angles of deionized (DI) water and ethanol in DI water droplets of various volumes are presented to quantify the effect of the backpressure on the droplet mobility. For a 50 μL water droplet, the sliding angle decreases from 45 to 0° when the backpressure increases to ca. 0.60 bar. Significantly smaller backpressure levels are required for lower surface energy liquids. We shed light on the droplet actuation and movement mechanisms by means of simulations encompassing the momentum conservation and the continuity equations along with the Cahn-Hilliard phase-field equations in a 2D computational domain. The droplet actuation mechanism entails depinning of the receding contact line and movement by means of forward wave propagation reaching the front of the droplet. Eventually, the droplet skips forward. The contact line depinning is also corroborated by analytical calculations based on the governing vertical force balance, properly modified to incorporate the effect of the backpressure.

  19. Optical influence of oil droplets on cone photoreceptor sensitivity.

    PubMed

    Wilby, David; Roberts, Nicholas W

    2017-03-17

    Oil droplets are spherical organelles found in the cone photoreceptors of vertebrates. They are generally assumed to focus incident light into the outer segment, and thereby improve light catch because of the droplets' spherical lens-like shape. However, using full-wave optical simulations of physiologically realistic cone photoreceptors from birds, frogs and turtles we find that pigmented oil droplets actually drastically reduce the transmission of light into the outer segment integrated across the full visible wavelength range of each species. Only transparent oil droplets improve light catch into the outer segments, and any enhancement is critically dependent on the refractive index, diameter of the oil droplet, and diameter and length of the outer segment. Furthermore, oil droplets are not the only optical elements found in cone inner segments. The ellipsoid, a dense aggregation of mitochondria situated immediately prior to the oil droplet, mitigates the loss of light at oil droplet surface. We describe a framework for integrating these optical phenomena into simple models of receptor sensitivity and the relevance of these observations to evolutionary appearance and loss of oil droplets is discussed.

  20. Scaling Laws for Inter-droplet Ice Bridging

    NASA Astrophysics Data System (ADS)

    Nath, Saurabh; Ahmadi, Farzad; Boreyko, Jonathan

    2016-11-01

    In this work, we study the dynamics of an ice bridge growing from a frozen droplet towards its neighboring supercooled liquid droplet. Experiments were done on a Peltier stage inside a humidity chamber with deposited or condensed droplets where the substrate temperature and ambient humidity could be controlled. Following a quasi-steady diffusion-driven model, we develop scaling laws to show how the growth rate depends on the substrate temperature, droplet sizes and inter-droplet distances over and above other environmental parameters such as air temperature and humidity. The growth rate as well as the success or failure of an ice bridge to connect to its neighboring liquid droplet depend on a nondimensional number called the separation parameter S*, defined as the ratio of the initial inter-droplet spacing to the diameter of the evaporating liquid droplet. It is shown that the maximum value of S* for connection scales as 1 as long as frozen drop is larger than the liquid droplet. For the converse case of a larger water drop, there are at least three separate regimes of critical S*, depending on whether the water drop is a puddle, a spherical cap or if the frozen drop is a puddle.

  1. The Burning of Large N-Heptane Droplets in Microgravity

    NASA Technical Reports Server (NTRS)

    Manzello, Samuel L.; Choi, Mun Young; Kazakov, Andrei; Dryer, Frederick L.; Dobashi, Ritsu; Hirano, Toshisuke; Ferkul, Paul (Technical Monitor)

    2000-01-01

    Experimental results are presented on the burning and sooting behavior of large n-heptane droplets in air at atmospheric pressure under microgravity conditions. The experiments were performed at the Japanese Microgravity Center (JAMIC) 10 sec dropshaft in Hokkaido, Japan. Soot volume fraction, burning rate, flame standoff and luminosity were measured for droplets of 2.6 mm and 2.9 mm in initial diameter. These are the largest droplets for which soot volume fraction measurements have ever been performed. Previous measurements of soot volume fractions for n-heptane droplets, confined to smaller droplet sizes of less than 1.8 mm, indicated that maximum soot volume fraction increased monotonically with initial droplet size. The new results demonstrate for the first time that sooting tendency is reduced for large droplets as it has been speculated previously but never confirmed experimentally. The lower soot volume fractions for the larger droplets were also accompanied by higher burning rates. The observed phenomenon is believed to be caused by the dimensional influence on radiative heat losses from the flame. Numerical calculations confirm that soot radiation affects the droplet burning behavior.

  2. Synchronized reinjection and coalescence of droplets in microfluidics.

    PubMed

    Lee, Manhee; Collins, Jesse W; Aubrecht, Donald M; Sperling, Ralph A; Solomon, Laura; Ha, Jong-Wook; Yi, Gi-Ra; Weitz, David A; Manoharan, Vinothan N

    2014-02-07

    Coalescence of two kinds of pre-processed droplets is necessary to perform chemical and biological assays in droplet-based microfluidics. However, a robust technique to accomplish this does not exist. Here we present a microfluidic device to synchronize the reinjection of two different kinds of droplets and coalesce them, using hydrostatic pressure in conjunction with a conventional syringe pump. We use a device consisting of two opposing T-junctions for reinjecting two kinds of droplets and control the flows of the droplets by applying gravity-driven hydrostatic pressure. The hydrostatic-pressure operation facilitates balancing the droplet reinjection rates and allows us to synchronize the reinjection. Furthermore, we present a simple but robust module to coalesce two droplets that sequentially come into the module, regardless of their arrival times. These re-injection and coalescence techniques might be used in lab-on-chip applications requiring droplets with controlled numbers of solid materials, which can be made by coalescing two pre-processed droplets that are formed and sorted in devices.

  3. Microfluidic droplet sorting using integrated bilayer micro-valves

    NASA Astrophysics Data System (ADS)

    Chen, Yuncong; Tian, Yang; Xu, Zhen; Wang, Xinran; Yu, Sicong; Dong, Liang

    2016-10-01

    This paper reports on a microfluidic device capable of sorting microfluidic droplets utilizing conventional bilayer pneumatic micro-valves as sorting controllers. The device consists of two micro-valves placed symmetrically on two sides of a sorting area, each on top of a branching channel at an inclined angle with respect to the main channel. Changes in transmitted light intensity, induced by varying light absorbance by each droplet, are used to divert the droplet from the sorting area into one of the three outlet channels. When no valve is activated, the droplet flows into the outlet channel in the direction of the main channel. When one of the valves is triggered, the flexible membrane of valve will first be deflected. Once the droplet leaves the detection point, the deflected membrane will immediately return to its default flattened position, thereby exerting a drawing pressure on the droplet and deviating it from its original streamline to the outlet on the same side as the valve. This sorting method will be particularly suitable for numerous large-scale integrated microfluidic systems, where pneumatic micro-valves are already used. Only few structural modifications are needed to achieve droplet sorting capabilities in these systems. Due to the mechanical nature of diverting energy applied to droplets, the proposed sorting method may induce only minimal interference to biological species or microorganisms encapsulated inside the droplets that may accompany electrical, optical and magnetic-based techniques.

  4. Sessile multidroplets and salt droplets under high tangential electric fields

    NASA Astrophysics Data System (ADS)

    Xie, Guoxin; He, Feng; Liu, Xiang; Si, Lina; Guo, Dan

    2016-04-01

    Understanding the interaction behaviors between sessile droplets under imposed high voltages is very important in many practical situations, e.g., microfluidic devices and the degradation/aging problems of outdoor high-power applications. In the present work, the droplet coalescence, the discharge activity and the surface thermal distribution response between sessile multidroplets and chloride salt droplets under high tangential electric fields have been investigated with infrared thermography, high-speed photography and pulse current measurement. Obvious polarity effects on the discharge path direction and the temperature change in the droplets in the initial stage after discharge initiation were observed due to the anodic dissolution of metal ions from the electrode. In the case of sessile aligned multidroplets, the discharge path direction could affect the location of initial droplet coalescence. The smaller unmerged droplet would be drained into the merged large droplet as a result from the pressure difference inside the droplets rather than the asymmetric temperature change due to discharge. The discharge inception voltages and the temperature variations for two salt droplets closely correlated with the ionization degree of the salt, as well as the interfacial electrochemical reactions near the electrodes. Mechanisms of these observed phenomena were discussed.

  5. Organic films on atmospheric aerosol particles, fog droplets, cloud droplets, raindrops, and snowflakes

    NASA Astrophysics Data System (ADS)

    Gill, P. S.; Graedel, T. E.; Weschler, C. J.

    1983-05-01

    If surface-active organic molecules are present as surface films, the transfer of gases into the atmospheric water system could be impeded, evaporation could be slowed, and the aqueous chemical reactions could be influenced. The results of new measurements of the surface tension of aqueous solutions of common atmospheric organic compounds (beta-pinene, n-hexanol, eugenol, and anethole) are reported, and it is shown that the compounds produce films with properties similar to those of the better known surfactants. It is concluded that organic films are probably common on atmospheric aerosol particles and that they may occur under certain circumstances on fog droplets, cloud droplets, and snowflakes. If they are present, they will increase the lifetimes of aerosol particles, fog droplets, and cloud droplets, both by inhibiting water vapor evaporation and by reducing the efficiency with which these atmospheric components are scavenged. It is thought likely that the transport of gaseous molecules into and out of the aqueous solution will be impeded by factors of several hundred or more when organic films are present.

  6. Influence of droplet size and velocity on droplet impact process on waxy leaf surfaces

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A custom-designed system consisting of two high-speed digital cameras, a uniform-size droplet generator, a constant-speed linear track unit, light sources and a 3-dimensional (3-D) image analytical program was used to investigate the impact processes. Leaves of Dracaena deremensis, Euphorbia pulche...

  7. Laser diagnostics for microgravity droplet studies

    NASA Technical Reports Server (NTRS)

    Winter, Michael

    1995-01-01

    An instrument has been designed, built, and tested for performing laser diagnostic measurements of droplet combustion in low-gravity-flight aircraft. Nonintrusive measurements are of particular importance for droplet combustion (the simplest example of non-premixed combustion) and transport in microgravity environments, where physical contact would introduce an unacceptable level of perturbations. The resolution of these diagnostics can also isolate transport to length scales much smaller than the droplet diameter. These techniques can be configured to instantaneously map an entire flow field in two and three dimensions, providing either qualitative or quantitative information on the distribution of a desired scalar or vector quantity. Detailing the gas-phase flow field and position of the flame front can be achieved using planar laser-induced fluorescence (PLIF) of OH or another flame front marker. An alternative approach is to obtain LIF from a diagnostic seed included in the liquid phase fuel; it would be consumed at the flame front. The main advantage to this approach is that it is easier to choose the wavelength of the molecular absorption which coincides with convenient laser wavelengths rather than finding lasers which can be configured to access OH. Our present method uses a nitrogen-pumped dye laser tuned to a sodium absorption and addition of small concentrations of NaCl to the fuel. Particle image velocimetry (PIV) is a laser-based technique which has recently had its practicality greatly enhanced by the development of high-resolution CCD cameras and the increase in speed and capacity of computer systems. With this technique, a seeded flow is illuminated with a double-pulsed laser sheet to generate a double exposure image on a film or CCD camera. Computer analysis of the image is used to determine the particle velocity vectors and, thus, the gas velocity within the plane of the laser sheet. Our current experiment uses PIV for measuring relative droplet

  8. Focusing of cylindrical liquid jets into droplets

    NASA Astrophysics Data System (ADS)

    Edwards, Kristen; McCleney, Amy; Bardet, Philippe

    2013-11-01

    Upward angled water jets discharging in quiescent air are studied experimentally with time varying forcing. The jets issue from a 2 mm diameter tube, while highly controllable forcing is accomplished with a magnetic linear motor coupled with an arbitrary waveform generator. In particular, regimes of jet focusing are generated at various injection rates. The jets result in large droplets that can be created at various elevations. This type of flow mimics the spray generated by an Archer fish. Actual forcing functions were monitored using LDT.

  9. Chiral partition functions of quantum Hall droplets

    SciTech Connect

    Cappelli, Andrea Viola, Giovanni; Zemba, Guillermo R.

    2010-02-15

    Chiral partition functions of conformal field theory describe the edge excitations of isolated Hall droplets. They are characterized by an index specifying the quasiparticle sector and transform among themselves by a finite-dimensional representation of the modular group. The partition functions are derived and used to describe electron transitions leading to Coulomb blockade conductance peaks. We find the peak patterns for Abelian hierarchical states and non-Abelian Read-Rezayi states, and compare them. Experimental observation of these features can check the qualitative properties of the conformal field theory description, such as the decomposition of the Hilbert space into sectors, involving charged and neutral parts, and the fusion rules.

  10. Quark matter droplets in neutron stars

    NASA Technical Reports Server (NTRS)

    Heiselberg, H.; Pethick, C. J.; Staubo, E. F.

    1993-01-01

    We show that, for physically reasonable bulk and surface properties, the lowest energy state of dense matter consists of quark matter coexisting with nuclear matter in the presence of an essentially uniform background of electrons. We estimate the size and nature of spatial structure in this phase, and show that at the lowest densities the quark matter forms droplets embedded in nuclear matter, whereas at higher densities it can exhibit a variety of different topologies. A finite fraction of the interior of neutron stars could consist of matter in this new phase, which would provide new mechanisms for glitches and cooling.

  11. Shear driven droplet shedding and coalescence on a superhydrophobic surface

    NASA Astrophysics Data System (ADS)

    Moghtadernejad, S.; Tembely, M.; Jadidi, M.; Esmail, N.; Dolatabadi, A.

    2015-03-01

    The interest on shedding and coalescence of sessile droplets arises from the importance of these phenomena in various scientific problems and industrial applications such as ice formation on wind turbine blades, power lines, nacelles, and aircraft wings. It is shown recently that one of the ways to reduce the probability of ice accretion on industrial components is using superhydrophobic coatings due to their low adhesion to water droplets. In this study, a combined experimental and numerical approach is used to investigate droplet shedding and coalescence phenomena under the influence of air shear flow on a superhydrophobic surface. Droplets with a size of 2 mm are subjected to various air speeds ranging from 5 to 90 m/s. A numerical simulation based on the Volume of Fluid method coupled with the Large Eddy Simulation turbulent model is carried out in conjunction with the validating experiments to shed more light on the coalescence of droplets and detachment phenomena through a detailed analysis of the aerodynamics forces and velocity vectors on the droplet and the streamlines around it. The results indicate a contrast in the mechanism of two-droplet coalescence and subsequent detachment with those related to the case of a single droplet shedding. At lower speeds, the two droplets coalesce by attracting each other with successive rebounds of the merged droplet on the substrate, while at higher speeds, the detachment occurs almost instantly after coalescence, with a detachment time decreasing exponentially with the air speed. It is shown that coalescence phenomenon assists droplet detachment from the superhydrophobic substrate at lower air speeds.

  12. The electroosmotic droplet switch: countering capillarity with electrokinetics.

    PubMed

    Vogel, Michael J; Ehrhard, Peter; Steen, Paul H

    2005-08-23

    Electroosmosis, originating in the double-layer of a small liquid-filled pore (size R) and driven by a voltage V, is shown to be effective in pumping against the capillary pressure of a larger liquid droplet (size B) provided the dimensionless parameter sigmaR(2)/epsilon|zeta|VB is small enough. Here sigma is surface tension of the droplet liquid/gas interface, epsilon is the liquid dielectric constant, and zeta is the zeta potential of the solid/liquid pair. As droplet size diminishes, the voltage required to pump electroosmotically scales as V approximately R(2)/B. Accordingly, the voltage needed to pump against smaller higher-pressure droplets can actually decrease provided the pump poresize scales down with droplet size appropriately. The technological implication of this favorable scaling is that electromechanical transducers made of moving droplets, so-called "droplet transducers," become feasible. To illustrate, we demonstrate a switch whose bistable energy landscape derives from the surface energy of a droplet-droplet system and whose triggering derives from the electroosmosis effect. The switch is an electromechanical transducer characterized by individual addressability, fast switching time with low voltage, and no moving solid parts. We report experimental results for millimeter-scale droplets to verify key predictions of a mathematical model of the switch. With millimeter-size water droplets and micrometer-size pores, 5 V can yield switching times of 1 s. Switching time scales as B(3)/VR(2). Two possible "grab-and-release" applications of arrays of switches are described. One mimics the controlled adhesion of an insect, the palm beetle; the other uses wettability to move a particle along a trajectory.

  13. Levitation-free vibrated droplets: resonant oscillations of liquid marbles.

    PubMed

    McHale, G; Elliott, S J; Newton, M I; Herbertson, D L; Esmer, K

    2009-01-06

    A spherical conducting droplet in an alternating electric field is known to undergo shape oscillations. When the droplet is supported by a substrate, the shape is no longer a complete sphere, but shape resonances are still observed. To obtain a completely spherical droplet, some kind of levitation is needed, unless the droplet is in microgravity, and this has previously been provided by gas films or magnetic or other external forces. In this work, we report observations of shape oscillations of a hydrophobic-powder-coated droplet of water. A droplet of water rolled on a hydrophobic powder self-coats such that the water becomes encapsulated as a liquid marble. When the powder is a spherical hydrophobic grain with a contact angle greater than 90 degrees , it adheres to the solid-water interface with more than half of its diameter projecting from the liquid, thus ensuring the encapsulated water does not come into contact with any substrate. These liquid marbles are highly mobile and can be regarded as completely nonwetting droplets possessing contact angles of 180 degrees . In this work, we show that they also provide a new mechanism equivalent to levitating droplets and provide droplets with small contact areas and completely mobile contact lines for studies of shape oscillations. Liquid marbles were created using hydrophobic lycopodium and droplets of water containing potassium chloride and were excited into motion using an electrowetting-on-dielectric configuration with applied frequency swept from 1 to 250 Hz. Both an up-and-down motion and an oscillation involving multiple nodes were observed and recorded using a high-speed camera. The resonant oscillation modes of small liquid marbles were fitted to the theory for vibrations of a free spherical volume of fluid. This work demonstrates the principle that oscillation modes of completely nonwetting droplets can be studied using a simple powder coating approach without the need for an active mechanism for levitation.

  14. Effect of viscosity on droplet-droplet collision outcome: Experimental study and numerical comparison

    NASA Astrophysics Data System (ADS)

    Gotaas, Cecilie; Havelka, Pavel; Jakobsen, Hugo A.; Svendsen, Hallvard F.; Hase, Matthias; Roth, Norbert; Weigand, Bernhard

    2007-10-01

    The influence of viscosity on droplet-droplet collision behavior at ambient conditions was studied experimentally and numerically. N-decane, monoethyleneglycol (MEG), diethyleneglycol (DEG), and triethyleneglycol were used as liquid phase providing viscosities in the range from 0.9to48mPas. Collision Weber numbers ranged approximately from 10 to 420. A direct numerical simulation code, based on the volume-of-fluid concept, was used for the simulations. Experimentally, observations of two droplet streams using a modified stroboscopic technique (aliasing method) were used to investigate the whole range of impact parameters during one experimental run. The experimental method has previously been verified for the water/air system [C. Gotaas et al., Phys. Fluids 19, 102105 (2007)]. In the present work, it was tested and validated for the n-decane/air system. Measured data agree well with those published in the literature. Well-defined regions of stretching separation and coalescence were identified, while reflexive separation regions were not found by using a single sinusoidal disturbance. However, the onset of reflexive separation was identified for MEG and DEG using an amplitude modulation technique. The results show that the criteria for onset of reflexive separation for viscous fluids provided by Y. I. Jiang et al. [J. Fluid Mech. 234, 177 (1992)] are not valid. This is consistent with the results given by K. D. Willis and M. Orme [Exp. Fluids 34, 28 (2003)]. A new empirical correlation for the onset of reflexive separation for high viscosity fluids is presented. The borders between coalescing and stretching separation were shifted toward higher Weber numbers with increasing viscosity. The lack of occurrence of reflexive separation for the single sinusoidal disturbance (small droplets), as well as the stretching separation boundary shift, can be explained by dissipation of collision kinetic energy in viscous flows inside the merged droplet after collision. Results

  15. Flocculation of deformable emulsion droplets. 1: Droplet shape and line tension effects

    SciTech Connect

    Denkov, N.D.; Petsev, D.N.; Danov, K.D.

    1995-12-01

    A simple theoretical model which allows the study of the configuration and the interaction energy of a doublet of flocculated Brownian droplets was recently proposed (Denkov et al., Phys, Rev. Lett. 71, 3226 (1993)). In this model the equilibrium film radius and thickness are determined by minimizing the total pair interaction energy which is presented as a sum of explicit expressions for the different contributions (van der Waals, electrostatic, steric, depletion, surface extension, etc.). In the present study this simplified model is numerically verified by comparison with the results stemming from the real shape of the interacting droplets. In order to determine the real configuration of two drops in contact the authors solve numerically the augmented Laplace equation of capillarity which accounts for the interaction between the droplets. Then the total interaction energy is alteratively calculated by integrating the energy density along the surfaces of the droplets. The numerical comparison shows that the equilibrium film radius and thickness, as well as the interaction energy calculated by means of the simplified model, are in very good agreement with the results from the more detailed (but more complex) approach. Numerical calculations of the equilibrium line tensions acting at the film periphery, a function of the droplet radius, are performed. The obtained results are relevant also to flocs containing more than two particles since the theory predicts pairwise additivity of the interaction energy in most cases. The results can be useful in gaining a deeper understanding of the processes of stabilization of flocculation in emulsions. Emulsions of great importance in many areas of human activity such as oil recovery.

  16. Surface Modification of Droplet Polymeric Microfluidic Devices for the Stable and Continuous Generation of Aqueous Droplets

    PubMed Central

    Subramanian, Balamurugan; Kim, Namwon; Lee, Wonbae; Spivak, David A.; Nikitopoulos, Dimitris E.; McCarley, Robin L.; Soper, Steven A.

    2012-01-01

    Droplet microfluidics performed in poly(methylmethacrylate), PMMA, microfluidic devices resulted in significant wall wetting by water droplets formed in a liquid-liquid segmented flow when using a hydrophobic carrier fluid, such as perfluorotripropylamine (FC-3283). This wall wetting led to water droplets with non-uniform sizes that were often trapped on the wall surfaces leading to unstable and poorly controlled liquid-liquid segmented flow. To circumvent this problem, we developed a two-step procedure to hydrophobically modify the surfaces of PMMA and other thermoplastic materials commonly used for making microfluidic devices. The surface modification route involved the introduction of hydroxyl groups by oxygen plasma treatment of the polymer surface followed by a solution phase reaction with heptadecafluoro-1,1,2,2–tetrahydrodecyl trichlorosilane dissolved in the fluorocarbon solvent FC-3283. This procedure was found to be useful for the modification of PMMA and other thermoplastic surfaces, including polycyclic olefin copolymer (COC) and polycarbonate (PC). Angle-resolved X-ray photoelectron spectroscopy indicated that the fluorination of these polymers took place with high surface selectivity. This procedure was used to modify the surface of a PMMA droplet microfluidic device (DMFD) and was shown to be useful to reduce the wetting problem during the generation of aqueous droplets in a perfluorotripropylamine (FC-3283) carrier fluid and could generate stable segmented flows for hours of operation. In the case of the PMMA DMFD, oxygen plasma treatment was carried out after the PMMA cover plate was thermally fusion bonded to the PMMA microfluidic chip. Because the appended chemistry to the channel wall created a hydrophobic surface, it will accommodate the use of other carrier fluids that are hydrophobic as well, such as hexadecane or mineral oils. PMID:21608975

  17. Surface modification of droplet polymeric microfluidic devices for the stable and continuous generation of aqueous droplets.

    PubMed

    Subramanian, Balamurugan; Kim, Namwon; Lee, Wonbae; Spivak, David A; Nikitopoulos, Dimitris E; McCarley, Robin L; Soper, Steven A

    2011-06-21

    Droplet microfluidics performed in poly(methyl methacrylate) (PMMA) microfluidic devices resulted in significant wall wetting by water droplets formed in a liquid-liquid segmented flow when using a hydrophobic carrier fluid such as perfluorotripropylamine (FC-3283). This wall wetting led to water droplets with nonuniform sizes that were often trapped on the wall surfaces, leading to unstable and poorly controlled liquid-liquid segmented flow. To circumvent this problem, we developed a two-step procedure to hydrophobically modify the surfaces of PMMA and other thermoplastic materials commonly used to make microfluidic devices. The surface-modification route involved the introduction of hydroxyl groups by oxygen plasma treatment of the polymer surface followed by a solution-phase reaction with heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane dissolved in fluorocarbon solvent FC-3283. This procedure was found to be useful for the modification of PMMA and other thermoplastic surfaces, including polycyclic olefin copolymer (COC) and polycarbonate (PC). Angle-resolved X-ray photoelectron spectroscopy indicated that the fluorination of these polymers took place with high surface selectivity. This procedure was used to modify the surface of a PMMA droplet microfluidic device (DMFD) and was shown to be useful in reducing the wetting problem during the generation of aqueous droplets in a perfluorotripropylamine (FC-3283) carrier fluid and could generate stable segmented flows for hours of operation. In the case of PMMA DMFD, oxygen plasma treatment was carried out after the PMMA cover plate was thermally fusion bonded to the PMMA microfluidic chip. Because the appended chemistry to the channel wall created a hydrophobic surface, it will accommodate the use of other carrier fluids that are hydrophobic as well, such as hexadecane or mineral oils.

  18. Temperature-Induced Coalescence of Colliding Binary Droplets on Superhydrophobic Surface

    PubMed Central

    Yi, Nan; Huang, Bin; Dong, Lining; Quan, Xiaojun; Hong, Fangjun; Tao, Peng; Song, Chengyi; Shang, Wen; Deng, Tao

    2014-01-01

    This report investigates the impact of droplet temperature on the head-on collision of binary droplets on a superhydrophobic surface. Understanding droplet collision is critical to many fundamental processes and industrial applications. There are many factors, including collision speed, collision angle, and droplet composition, that influence the outcome of the collision between binary droplets. This work provides the first experimental study of the influence of droplet temperature on the collision of binary droplets. As the droplet temperature increases, the possibility increases for the two droplets to coalesce after collision. The findings in this study can be extended to collision of droplets under other conditions where control of the droplet temperature is feasible. Such findings will also be beneficial to applications that involve droplet collision, such as in ink-jet printing, steam turbines, engine ignition, and spraying cooling. PMID:24603362

  19. Temperature-Induced Coalescence of Colliding Binary Droplets on Superhydrophobic Surface

    NASA Astrophysics Data System (ADS)

    Yi, Nan; Huang, Bin; Dong, Lining; Quan, Xiaojun; Hong, Fangjun; Tao, Peng; Song, Chengyi; Shang, Wen; Deng, Tao

    2014-03-01

    This report investigates the impact of droplet temperature on the head-on collision of binary droplets on a superhydrophobic surface. Understanding droplet collision is critical to many fundamental processes and industrial applications. There are many factors, including collision speed, collision angle, and droplet composition, that influence the outcome of the collision between binary droplets. This work provides the first experimental study of the influence of droplet temperature on the collision of binary droplets. As the droplet temperature increases, the possibility increases for the two droplets to coalesce after collision. The findings in this study can be extended to collision of droplets under other conditions where control of the droplet temperature is feasible. Such findings will also be beneficial to applications that involve droplet collision, such as in ink-jet printing, steam turbines, engine ignition, and spraying cooling.

  20. Temperature-induced coalescence of colliding binary droplets on superhydrophobic surface.

    PubMed

    Yi, Nan; Huang, Bin; Dong, Lining; Quan, Xiaojun; Hong, Fangjun; Tao, Peng; Song, Chengyi; Shang, Wen; Deng, Tao

    2014-03-07

    This report investigates the impact of droplet temperature on the head-on collision of binary droplets on a superhydrophobic surface. Understanding droplet collision is critical to many fundamental processes and industrial applications. There are many factors, including collision speed, collision angle, and droplet composition, that influence the outcome of the collision between binary droplets. This work provides the first experimental study of the influence of droplet temperature on the collision of binary droplets. As the droplet temperature increases, the possibility increases for the two droplets to coalesce after collision. The findings in this study can be extended to collision of droplets under other conditions where control of the droplet temperature is feasible. Such findings will also be beneficial to applications that involve droplet collision, such as in ink-jet printing, steam turbines, engine ignition, and spraying cooling.

  1. Sintering of viscous droplets under surface tension

    PubMed Central

    Vasseur, Jérémie; Llewellin, Edward W.; Schauroth, Jenny; Dobson, Katherine J.; Scheu, Bettina; Dingwell, Donald B.

    2016-01-01

    We conduct experiments to investigate the sintering of high-viscosity liquid droplets. Free-standing cylinders of spherical glass beads are heated above their glass transition temperature, causing them to densify under surface tension. We determine the evolving volume of the bead pack at high spatial and temporal resolution. We use these data to test a range of existing models. We extend the models to account for the time-dependent droplet viscosity that results from non-isothermal conditions, and to account for non-zero final porosity. We also present a method to account for the initial distribution of radii of the pores interstitial to the liquid spheres, which allows the models to be used with no fitting parameters. We find a good agreement between the models and the data for times less than the capillary relaxation timescale. For longer times, we find an increasing discrepancy between the data and the model as the Darcy outgassing time-scale approaches the sintering timescale. We conclude that the decreasing permeability of the sintering system inhibits late-stage densification. Finally, we determine the residual, trapped gas volume fraction at equilibrium using X-ray computed tomography and compare this with theoretical values for the critical gas volume fraction in systems of overlapping spheres. PMID:27274687

  2. Sintering of viscous droplets under surface tension

    NASA Astrophysics Data System (ADS)

    Wadsworth, Fabian B.; Vasseur, Jérémie; Llewellin, Edward W.; Schauroth, Jenny; Dobson, Katherine J.; Scheu, Bettina; Dingwell, Donald B.

    2016-04-01

    We conduct experiments to investigate the sintering of high-viscosity liquid droplets. Free-standing cylinders of spherical glass beads are heated above their glass transition temperature, causing them to densify under surface tension. We determine the evolving volume of the bead pack at high spatial and temporal resolution. We use these data to test a range of existing models. We extend the models to account for the time-dependent droplet viscosity that results from non-isothermal conditions, and to account for non-zero final porosity. We also present a method to account for the initial distribution of radii of the pores interstitial to the liquid spheres, which allows the models to be used with no fitting parameters. We find a good agreement between the models and the data for times less than the capillary relaxation timescale. For longer times, we find an increasing discrepancy between the data and the model as the Darcy outgassing time-scale approaches the sintering timescale. We conclude that the decreasing permeability of the sintering system inhibits late-stage densification. Finally, we determine the residual, trapped gas volume fraction at equilibrium using X-ray computed tomography and compare this with theoretical values for the critical gas volume fraction in systems of overlapping spheres.

  3. Investigation of critical burning of fuel droplets

    NASA Technical Reports Server (NTRS)

    Allison, C. B.; Canada, G. S.; Faeth, G. M.

    1972-01-01

    Measurements were made on the burning of liquid hydrazine, MMH, and UDMH in a combustion gas environment. The experimental range of these tests involved gas temperatures of 1660-2530 K, oxygen concentrations of 0-42% by mass and droplet diameters (employing both droplets and porous spheres) of 0.11-1.91 cm. at atmospheric pressure. A simplified hybrid combustion theory was developed which was found to correlate the present results as well as the experimental measurements of other investigators. Measurements were also made of the monopropellant strand burning rates and liquid surface temperatures of a number of nitrate ester fuels and hydrazine at elevated pressures. The temperature measurements for the nitrate esters were found to be in good agreement with a theoretical model which allowed for gas solubility in the liquid phase at high pressures. Experimental results were also obtained on the burning rates and liquid surface temperatures of a number of paraffin and alcohol fuels burning in air pressures up to 72 atm. For these tests, the fuels were burned from porous spheres in a natural convection environment. Initial findings on a pressurized flat flame burner are also described as well as the design of an oscillatory combustion apparatus to test the response of burning liquid fuels.

  4. Droplet-Based Production of Liposomes

    NASA Technical Reports Server (NTRS)

    Ackley, Donald E.; Forster, Anita

    2009-01-01

    A process for making monodisperse liposomes having lipid bilayer membranes involves fewer, simpler process steps than do related prior methods. First, a microfluidic, cross junction droplet generator is used to produce vesicles comprising aqueous solution droplets contained in single layer lipid membranes. The vesicles are collected in a lipid-solvent mix that is at most partially soluble in water and is less dense than is water. A layer of water is dispensed on top of the solvent. By virtue of the difference in densities, the water sinks to the bottom and the solvent floats to the top. The vesicles, which have almost the same density as that of water, become exchanged into the water instead of floating to the top. As there are excess lipids in the solvent solution, in order for the vesicles to remain in the water, the addition of a second lipid layer to each vesicle is energetically favored. The resulting lipid bilayers present the hydrophilic ends of the lipid molecules to both the inner and outer membrane surfaces. If lipids of a second kind are dissolved in the solvent in sufficient excess before use, then asymmetric liposomes may be formed.

  5. Accelerating Yeast Prion Biology using Droplet Microfluidics

    NASA Astrophysics Data System (ADS)

    Ung, Lloyd; Rotem, Assaf; Jarosz, Daniel; Datta, Manoshi; Lindquist, Susan; Weitz, David

    2012-02-01

    Prions are infectious proteins in a misfolded form, that can induce normal proteins to take the misfolded state. Yeast prions are relevant, as a model of human prion diseases, and interesting from an evolutionary standpoint. Prions may also be a form of epigenetic inheritance, which allow yeast to adapt to stressful conditions at rates exceeding those of random mutations and propagate that adaptation to their offspring. Encapsulation of yeast in droplet microfluidic devices enables high-throughput measurements with single cell resolution, which would not be feasible using bulk methods. Millions of populations of yeast can be screened to obtain reliable measurements of prion induction and loss rates. The population dynamics of clonal yeast, when a fraction of the cells are prion expressing, can be elucidated. Furthermore, the mechanism by which certain strains of bacteria induce yeast to express prions in the wild can be deduced. Integrating the disparate fields of prion biology and droplet microfluidics reveals a more complete picture of how prions may be more than just diseases and play a functional role in yeast.

  6. Liquid quantum droplets of ultracold magnetic atoms

    NASA Astrophysics Data System (ADS)

    Ferrier-Barbut, Igor; Schmitt, Matthias; Wenzel, Matthias; Kadau, Holger; Pfau, Tilman

    2016-11-01

    The simultaneous presence of two competing inter-particle interactions can lead to the emergence of new phenomena in a many-body system. Among others, such effects are expected in dipolar Bose-Einstein condensates, subject to dipole-dipole interaction and short-range repulsion. Magnetic quantum gases and in particular Dysprosium gases, offering a comparable short-range contact and a long-range dipolar interaction energy, remarkably exhibit such emergent phenomena. In addition an effective cancellation of mean-field effects of the two interactions results in a pronounced importance of quantum-mechanical beyond mean-field effects. For a weakly dominant dipolar interaction the striking consequence is the existence of a new state of matter equilibrated by the balance between weak mean-field attraction and beyond mean-field repulsion. Though exemplified here in the case of dipolar Bose gases, this state of matter should appear also with other microscopic interactions types, provided a competition results in an effective cancellation of the total mean-field. The macroscopic state takes the form of so-called quantum droplets. We present the effects of a long-range dipolar interaction between these droplets.

  7. Locating the source of projectile fluid droplets

    NASA Astrophysics Data System (ADS)

    Varney, Christopher R.; Gittes, Fred

    2011-08-01

    The ill-posed projectile problem of finding the source height from spattered droplets of viscous fluid is a longstanding obstacle to accident reconstruction and crime-scene analysis. It is widely known how to infer the impact angle of droplets on a surface from the elongation of their impact profiles. However, the lack of velocity information makes finding the height of the origin from the impact position and angle of individual drops not possible. From aggregate statistics of the spatter and basic equations of projectile motion, we introduce a reciprocal correlation plot that is effective when the polar launch angle is concentrated in a narrow range. The vertical coordinate depends on the orientation of the spattered surface and equals the tangent of the impact angle for a level surface. When the horizontal plot coordinate is twice the reciprocal of the impact distance, we can infer the source height as the slope of the data points in the reciprocal correlation plot. If the distribution of launch angles is not narrow, failure of the method is evident in the lack of linear correlation. We perform a number of experimental trials, as well as numerical calculations and show that the height estimate is relatively insensitive to aerodynamic drag. Besides its possible relevance for crime investigation, reciprocal-plot analysis of spatter may find application to volcanism and other topics and is most immediately applicable for undergraduate science and engineering students in the context of crime-scene analysis.

  8. Droplet evaporation on a soluble substrate

    NASA Astrophysics Data System (ADS)

    Mailleur, Alexandra; Pirat, Christophe; Colombani, Jean; CNES Collaboration

    2015-11-01

    Stains left by evaporated droplets are ubiquitous in everyday life as well as in industrial processes. Whatever the composition of the evaporating liquid (colloidal suspensions, biological fluids...), the stains are mostly constituted by a deposit at the periphery of the dried drop, similar to a coffee stain (Deegan, 1997). All these studies have been carried with non-reacting solids. In this presentation, we focus on the behavior of a pure-water droplet evaporating on a soluble substrate which is more complex, since three phenomena are strongly interacting: the dissolution of the substrate, the diffusion/convection of the dissolved species into the drop and the evaporation of the liquid. NaCl and KCl single crystals have been chosen for this experimental study as they are fast-dissolving solids. We have observed that the dissolution induces a pinning of the triple line from the beginning of the evaporation, leading to a decrease of the contact angle in time. At the end of the evaporation, a peripheral deposit is always formed, proof of an outward flow inside the drop (coffee-ring effect). The authors would like to thank the CNES for the financial support.

  9. Helium anion formation inside helium droplets

    NASA Astrophysics Data System (ADS)

    Maalouf, Elias Jabbour Al; Reitshammer, Julia; Ribar, Anita; Scheier, Paul; Denifl, Stephan

    2016-07-01

    The formation of He∗- is examined with improved electron energy resolution of about 100 meV utilizing a hemispherical electron monochromator. The work presented provides a precise determination of the three previously determined resonance peak positions that significantly contribute to the formation of He∗- inside helium nanodroplets in the energy range from 20 eV to 29.5 eV. In addition, a new feature is identified located at 27.69 ± 0.18 eV that we assign to the presence of O2 as a dopant inside the droplet. With increasing droplet size a small blue shift of the resonance positions is observed. Also for the relatively low electron currents used in the present study (i.e., 15-70 nA) a quadratic dependence of the He∗- ion yield on the electron current is observed. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  10. Metastable Polymerization of Sickle Hemoglobin in Droplets

    PubMed Central

    Aprelev, Alexey; Weng, Weijun; Zakharov, Mikhail; Rotter, Maria; Yosmanovich, Donna; Kwong, Suzanna; Briehl, Robin W.; Ferrone, Frank A.

    2007-01-01

    Sickle cell disease arises from a genetic mutation of one amino acid in each of the two hemoglobin β chains, leading to the polymerization of hemoglobin in the red cell upon deoxygenation, and is characterized by vascular crises and tissue damage due to the obstruction of small vessels by sickled cells. It has been an untested assumption that, in red cells that sickle, the growing polymer mass would consume monomers until the thermodynamically well-described monomer solubility was reached. By photolyzing droplets of sickle hemoglobin suspended in oil we find that polymerization does not exhaust the available store of monomers, but stops prematurely, leaving the solutions in a supersaturated, metastable state typically 20% above solubility at 37°C, though the particular values depend on the details of the experiment. We propose that polymer growth stops because the growing ends reach the droplet edge, whereas new polymer formation is thwarted by long nucleation times, since the hemoglobin concentration is lowered by depletion of monomers into the polymers that have formed. This finding suggests a new aspect to the pathophysiology of sickle cell disease, namely, that cells deoxygenated in the microcirculation are not merely undeformable, but will actively wedge themselves tightly against the walls of the microvasculature by a ratchet-like mechanism driven by the supersaturated solution. PMID:17493634

  11. Droplet formation and scaling in dense suspensions

    PubMed Central

    Miskin, Marc Z.; Jaeger, Heinrich M.

    2012-01-01

    When a dense suspension is squeezed from a nozzle, droplet detachment can occur similar to that of pure liquids. While in pure liquids the process of droplet detachment is well characterized through self-similar profiles and known scaling laws, we show here the simple presence of particles causes suspensions to break up in a new fashion. Using high-speed imaging, we find that detachment of a suspension drop is described by a power law; specifically we find the neck minimum radius, rm, scales like near breakup at time τ = 0. We demonstrate data collapse in a variety of particle/liquid combinations, packing fractions, solvent viscosities, and initial conditions. We argue that this scaling is a consequence of particles deforming the neck surface, thereby creating a pressure that is balanced by inertia, and show how it emerges from topological constraints that relate particle configurations with macroscopic Gaussian curvature. This new type of scaling, uniquely enforced by geometry and regulated by the particles, displays memory of its initial conditions, fails to be self-similar, and has implications for the pressure given at generic suspension interfaces. PMID:22392979

  12. Droplet migration in a Hele-Shaw cell: Effect of the lubrication film on the droplet dynamics

    NASA Astrophysics Data System (ADS)

    Ling, Yue; Fullana, Jose-Maria; Popinet, Stéphane; Josserand, Christophe

    2016-06-01

    Droplet migration in a Hele-Shaw cell is a fundamental multiphase flow problem which is crucial for many microfluidics applications. We focus on the regime at low capillary number and three-dimensional direct numerical simulations are performed to investigate the problem. In order to reduce the computational cost, an adaptive mesh is employed and high mesh resolution is only used near the interface. Parametric studies are performed on the droplet horizontal radius and the capillary number. For droplets with an horizontal radius larger than half the channel height, the droplet overfills the channel and exhibits a pancake shape. A lubrication film is formed between the droplet and the wall and particular attention is paid to the effect of the lubrication film on the droplet velocity. The computed velocity of the pancake droplet is shown to be lower than the average inflow velocity, which is in agreement with experimental measurements. The numerical results show that both the strong shear induced by the lubrication film and the three-dimensional flow structure contribute to the low mobility of the droplet. In this low-migration-velocity scenario, the interfacial flow in the droplet reference frame moves toward the rear on the top and reverses direction moving to the front from the two side edges. The velocity of the pancake droplet and the thickness of the lubrication film are observed to decrease with capillary number. The droplet velocity and its dependence on capillary number cannot be captured by the classic Hele-Shaw equations, since the depth-averaged approximation neglects the effect of the lubrication film.

  13. Acoustic droplet vaporization is initiated by superharmonic focusing

    PubMed Central

    Shpak, Oleksandr; Verweij, Martin; Vos, Hendrik J.; de Jong, Nico; Lohse, Detlef; Versluis, Michel

    2014-01-01

    Acoustically sensitive emulsion droplets composed of a liquid perfluorocarbon have the potential to be a highly efficient system for local drug delivery, embolotherapy, or for tumor imaging. The physical mechanisms underlying the acoustic activation of these phase-change emulsions into a bubbly dispersion, termed acoustic droplet vaporization, have not been well understood. The droplets have a very high activation threshold; its frequency dependence does not comply with homogeneous nucleation theory and localized nucleation spots have been observed. Here we show that acoustic droplet vaporization is initiated by a combination of two phenomena: highly nonlinear distortion of the acoustic wave before it hits the droplet and focusing of the distorted wave by the droplet itself. At high excitation pressures, nonlinear distortion causes significant superharmonics with wavelengths of the order of the droplet size. These superharmonics strongly contribute to the focusing effect; therefore, the proposed mechanism also explains the observed pressure thresholding effect. Our interpretation is validated with experimental data captured with an ultrahigh-speed camera on the positions of the nucleation spots, where we find excellent agreement with the theoretical prediction. Moreover, the presented mechanism explains the hitherto counterintuitive dependence of the nucleation threshold on the ultrasound frequency. The physical insight allows for the optimization of acoustic droplet vaporization for therapeutic applications, in particular with respect to the acoustic pressures required for activation, thereby minimizing the negative bioeffects associated with the use of high-intensity ultrasound. PMID:24449879

  14. Tunable Superomniphobic Surfaces for Sorting Droplets by Surface Tension

    NASA Astrophysics Data System (ADS)

    Movafaghi, Sanli; Wang, Wei; Metzger, Ari; Williams, Desiree; Williams, John; Kota, Arun

    2016-11-01

    Manipulation of liquid droplets on super-repellent surfaces (i.e., surfaces that are extremely repellent to liquids) has been widely studied because droplets exhibit high mobility on these surfaces due to the ultra-low adhesion, which leads to minimal sample loss and contamination. Although droplet manipulation has been demonstrated using electric fields, magnetic fields, guiding tracks and wettability gradients, to the best of our knowledge, there are no reports of droplet manipulation methods that can sort droplets by surface tension on super-repellent surfaces. In this work, we utilized tunable superomniphobic surfaces (i.e., surfaces that are extremely repellent to virtually all liquids) to develop a simple device with precisely tailored solid surface energy domains that, for the first time, can sort droplets by surface tension. Droplet sorting occurs on our device entirely due to a balance between the work done by gravity and the work expended due to adhesion, without the need for any external energy input. Our device can be fabricated easily in a short time and is particularly useful for in-the-field and on-the-go operations, where complex analysis equipment is unavailable. We envision that our methodology for droplet sorting will enable inexpensive and energy-efficient analytical devices for personalized point-of-care diagnostic platforms and lab-on-a-chip systems.

  15. Dynamic effects induced transition of droplets on biomimetic superhydrophobic surfaces.

    PubMed

    Jung, Yong Chae; Bhushan, Bharat

    2009-08-18

    Superhydrophobic surfaces have considerable technological potential for various applications because of their extreme water-repellent properties. Dynamic effects, such as the bouncing and vibration of a droplet, can destroy the composite solid-air-liquid interface. The impact pressure of a bouncing droplet and the inertia force of a vibrating droplet affect the transition from a solid-air-liquid interface to a solid-liquid interface. Therefore, it is necessary to study the dynamic effect of droplets under various system parameters (impact velocity and frequency and amplitude of vibration). A new model for the prediction of the wetting and dewetting process during droplet vibration based on the relationship between the adhesion force and the inertia force of a droplet is proposed. To investigate whether micro-, nano-, and hierarchical structures can resist the destabilizing factors responsible for the transition, a study of bouncing and vibration of a water droplet is systematically conducted on various surfaces. The physics of wetting phenomena for water droplet studies is of fundamental importance in the geometrical design of superhydrophobic surfaces.

  16. Droplets sliding down inclined planes: unexpected dynamics on elastomer plates

    NASA Astrophysics Data System (ADS)

    Hourlier-Fargette, Aurelie; Antkowiak, Arnaud; Neukirch, Sebastien

    2016-11-01

    Droplet dynamics on an angled surface results from a competition between the weight of the droplet, capillary forces, and viscous dissipation inside the drop. The motion of droplets on stiff surfaces has been investigated for a long time, both experimentally and theoretically, while recent studies have shown the interesting physics underlying the sliding of droplets on soft surfaces. We focus on the dynamics of water-glycerol mixture droplets sliding down vertical plates of silicone elastomers, highlighting an unexpected behavior: the droplet dynamics on such a surface includes two regimes with different constant speeds. These results contrast with those found in the literature for droplets sliding on materials such as treated glass. We investigate the universality of this behavior on various elastomers, and study in detail the two regimes and the sharp transition observed between them. Different candidates can be responsible for the sudden speed change: bistability, chemical interaction with the substrate, softness of the material, etc. Our experiments to clarify the role of each of them reveal an unexpected link between microscopic phenomena at the scale of the polymer matrix and the macroscopic dynamics of a droplet.

  17. Droplet impact on liquid films in the presence of surfactants

    NASA Astrophysics Data System (ADS)

    Jais, Khadijah; Yip, Natalie; Che, Zhizhao; Matar, Omar

    2016-11-01

    In this study of droplet impact on liquid films, surfactants are added to the droplet, the liquid film or both, and the effects of different surfactant concentrations are investigated using high-speed imaging. The results show that surfactants suppress partial coalescence, due to damping of the capillary waves. Rebounding occurs more frequently when surfactants are added, as the surfactant molecules resist the drainage of the intervening air layer. When the droplet deforms the surfactant film, there is an uneven distribution of surfactant molecules along the interface, resulting in a surface tension gradient and a Marangoni stress. The Marangoni stress acts to even out the surface tension gradient and to aid rebounding. Surfactant droplet ruptures the film with a much lower surfactant concentration, leaving an apparent dry region on the substrate at the impact point. This is likely due to Marangoni stresses where the film pulls the droplet apart. As the film thickness is increased, a Worthington jet is formed, with secondary droplet(s) ejected from the jet only when surfactants are present. This study reveals that the presence of surfactants can significantly alter the impact process of droplets on liquid films. EPSRC UK Programme Grant MEMPHIS (EP/K003976/1).

  18. Length Scale of Leidenfrost Ratchet Switches Droplet Directionality

    SciTech Connect

    Agapov, Rebecca L; Boreyko, Jonathan B; Briggs, Dayrl P; Srijanto, Bernadeta R; Retterer, Scott T; Collier, Pat; Lavrik, Nickolay V

    2014-01-01

    Arrays of tilted pillars with characteristic heights spanning from hundreds of nanometers to tens of micrometers were created using wafer level processing and used as Leidenfrost ratchets to control droplet directionality. Dynamic Leidenfrost droplets on the ratchets with nanoscale features were found to move in the direction of the pillar tilt while the opposite directionality was observed on the microscale ratchets. This remarkable switch in the droplet directionality can be explained by varying contributions from the two distinct mechanisms controlling droplet motion on Leidenfrost ratchets with nanoscale and microscale features. In particular, asymmetric wettability of dynamic Leidenfrost droplets upon initial impact appears to be the dominant mechanism determining their directionality on tilted nanoscale pillar arrays. By contrast, asymmetric wetting does not provide a strong enough driving force compared to the forces induced by asymmetric vapour flow on arrays of much taller tilted microscale pillars. Furthermore, asymmetric wetting plays a role only in the dynamic Leidenfrost regime, for instance when droplets repeatedly jump after their initial impact. The point of crossover between the two mechanisms coincides with the pillar heights comparable to the values of the thinnest vapor layers still capable of cushioning Leidenfrost droplets upon their initial impact. The proposed model of the length scale dependent interplay between the two mechanisms points to the previously unexplored ability to bias movement of dynamic Leidenfrost droplets and even switch their directionality.

  19. Controlled Lateral Positioning of Microparticles Inside Droplets Using Acoustophoresis.

    PubMed

    Fornell, Anna; Nilsson, Johan; Jonsson, Linus; Periyannan Rajeswari, Prem Kumar; Joensson, Haakan N; Tenje, Maria

    2015-10-20

    In this paper, we utilize bulk acoustic waves to control the position of microparticles inside droplets in two-phase microfluidic systems and demonstrate a method to enrich the microparticles. In droplet microfluidics, different unit operations are combined and integrated on-chip to miniaturize complex biochemical assays. We present a droplet unit operation capable of controlling the position of microparticles during a trident shaped droplet split. An acoustic standing wave field is generated in the microchannel, and the acoustic forces direct the encapsulated microparticles to the center of the droplets. The method is generic, requires no labeling of the microparticles, and is operated in a noncontact fashion. It was possible to achieve 2+-fold enrichment of polystyrene beads (5 μm in diameter) in the center daughter droplet with an average recovery of 89% of the beads. Red blood cells were also successfully manipulated inside droplets. These results show the possibility to use acoustophoresis in two-phase systems to enrich microparticles and open up the possibility for new droplet-based assays that are not performed today.

  20. Dispersion and evaporation of droplets amended with adjuvants on soybeans

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased use of adjuvants to improve pesticide spray application efficiency is hindered by a lack of knowledge to enhance droplet adhesion. Dispersion and evaporation of single 300 µm droplets amended with four different spray adjuvants deposited at four different soybean plant locations were inves...