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1.
In this work, the nanoscale footprints of self-driven liquid gallium droplet movement on a GaAs (001) surface will be presented and analyzed. The nanoscale footprints of a primary droplet trail and ordered secondary droplets along primary droplet trails are observed on the GaAs surface. A well ordered nanoterrace from the trail is left behind by a running droplet. In addition, collision events between two running droplets are investigated. The exposed fresh surface after a collision demonstrates a superior evaporation property. Based on the observation of droplet evolution at different stages as well as nanoscale footprints, a schematic diagram of droplet evolution is outlined in an attempt to understand the phenomenon of stick-slip droplet motion on the GaAs surface. The present study adds another piece of work to obtain the physical picture of a stick-slip self-driven mechanism in nanoscale, bridging nano and micro systems. 相似文献
2.
Thermodynamics of contact angle phenomena is strongly affected by the presence of thin liquid films. However, at present, studies for CO 2/brine/mineral systems only consider the films apart from contact angles. In this paper, molecular dynamics (MD) simulations have been performed to simultaneously investigate the interrelationship between water film thicknesses and water contact angles. Two types of contact angles were considered namely Young’s contact angle (no water film is present) and contact angle with film (a stable film is present). The results showed that as Young’s contact angle increased, film thickness decreased which leading to increasing of contact angle with film. The effects of CO 2-mineral pre-contact have also been investigated and it has been found that on mediate hydrophilic surfaces (Q 3), water films were present when CO 2 droplets were placed above the surfaces, however, water films were absent when CO 2 droplets directly contact with the surfaces. This phenomenon implies that water films on mineral surfaces have a possibility to rupture and a film rupture mechanism for CO 2 adhesion on hydrated mineral surfaces was proposed. These results may provide new information on interactions among CO 2, water/brine and mineral to better understand the behaviour of CO 2 during geologic sequestration. 相似文献
3.
Water droplets on bare silicon surfaces are studied to examine the wetting behaviour as a function of the surface energy and to parameterise water–silicon interactions in order to recover the hydrophobic behaviour measured by experiments. Two different wetting regimes characterised by a critical interaction strength value are observed. At a threshold value of the water–silicon interaction parameter, water molecules start penetrating into the first layer of silicon surface under thermally vibrating walls, resulting in two distinct wetting behaviours. Fixed (cold) silicon walls do not exhibit the two different wetting characteristics. Size effects are studied for nano-scale droplets, and line tension influence is observed depending on the surface wettability. Decrease in the droplet size increases the contact angle values for the low wetting cases, while contact angles decrease for smaller droplets on the high wetting surfaces. Considering the line tension effects and droplet size, ? Si–O for water–silicon interactions to recover the hydrophobic behaviour of silicon surfaces is estimated to be 12.5% of the value predicted using the Lorentz–Berthelot mixing rule. 相似文献
4.
<正> Natural surfaces with super hydrophobic properties often have micro or hierarchical structures.In this paper, the wettingbehaviours of a single droplet on biomimetic micro structured surfaces with different roughness parameters are investigated.Atheoretical model is proposed to study wetting transitions.The results of theoretical analysis are compared with those of experimentindicating that the proposed model can effectively predict the wetting transition.Furthermore, a numerical simulationbased on the meso scale Lattice Boltzmann Method (LBM) is performed to study dynamic contact angles, contact lines, andlocal velocity fields for the case that a droplet displays on the micro structured surface.A spherical water droplet with r_s= 15 μmfalls down to a biomimetic square-post patterned surface under the force of gravity with an initial velocity of 0.01 m·s~(-1) and aninitial vertical distance of 20 μm from droplet centre to the top of pots.In spite of a higher initial velocity, the droplet can stillstay in a Cassie state; moreover, it reaches an equilibrium state at t≈17.5 ms, when contact angle is 153.16° which is slightlylower than the prediction of Cassie-Baxter's equation which gives θ_(CB)=154.40°. 相似文献
5.
Optical fibres have received considerable attention as high-density sensor arrays suitable for both in vitro and in vivo measurements of biomolecules and biological processes in living organisms and/or nano-environments. The fibre surface was chemically modified by exposure to a selective etchant that preferentially erodes the fibre cores relative to the surrounding cladding material, thus producing a regular pattern of cylindrical wells of approximately 2.5 μm in diameter and 2.5 μm deep. The surface hydrophobicity of the etched and non-etched optical fibres was analysed using the sessile pico-drop method. The surface topography was characterised by atomic force microscopy (AFM), while the surface chemistry was probed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Six taxonomically different bacterial strains showed a consistent preference for attachment to the nano-scale smoother ( R q = 273 nm), non-etched fibre surfaces (water contact angle, θ = 106° ± 4°). In comparison, the surfaces of the etched optical fibres (water contact angle, θ = 96° ± 10°) were not found to be amenable to bacterial attachment. Bacterial attachment on the non-etched optical fibre substrata varied among different strains. 相似文献
6.
Abstract The adhesion of Klebsormidium flaccidum, Stichococcus bacillaris and Chlorella cf. mirabilis, three strains of green microalgae isolated from biofilms on façade coatings were investigated in a parallel plate flow chamber. The model surfaces tested were glass slides, and ?CH 3 (mediated by octadecyltrichlorosilane [OTS] and hexamethyldisilazane [HMDZ] modification) and -NH 2 (aminopropyltriethoxysilane [APS] modification) terminated self-assembled monolayers. Algal physicochemical properties were evaluated by the microbial adhesion to solvents (MATS) assay and by contact angle measurements. The model surfaces were characterised by X-ray photoelectron spectroscopy analysis and by contact angle measurements. Predicted adhesion trends were then compared to in vitro measurements. The adhesion strength of the three algal strains followed the trend: APS > OTS > HMDZ > glass. The adhesion process thus seemed to be mediated by hydrophobic and electrostatic interactions, and was shown to be influenced by the algal culture age and the initial contact time. 相似文献
7.
The line tension for a Lennard–Jones (LJ) fluid on a (9, 3) solid of varying strength was calculated using Monte Carlo simulations. A new perturbation method was used to determine the interfacial tension between liquid–vapour, solid–liquid and solid–vapour phases for this system to determine the Young's equation contact angle. Cylindrical and spherical nanodroplets were simulated for comparison. The contact angles from the cylindrical drops and Young's equation agree very well over the range of surface strengths and cylindrical drop sizes, except on a very weak surface. Tolman length effects were not observable for cylindrical drops. This shows that quite small systems can reproduce macroscopic contact angles. For spherical droplets, a deviation between the contact angle of spherical droplets and Young's equation was evident, but decreased with increasing interaction strengths to be negligible for contact angles less than 90°. Linear fitting of the contact angle data for varying droplet sizes showed no clear effect by line tension on contact angle. All calculated line tension values have a magnitude less than 4 × 10 ? 12 J/m with both negative and positive signs. The best estimate of line tension for this system of LJ droplets was 1 × 10 ? 13 J/m, which is smaller than the reported estimations in the literature, and is too small to be conclusively positive or negative in value. 相似文献
8.
The retention patterns of five taxonomically different marine bacteria after attachment on two types of glass surfaces, as-received and chemically etched, have been investigated. Contact angle measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray fluorescence spectroscopy (XRF) and X-ray photoelectron spectrometry (XPS) were employed to investigate the impact of nanometer scale surface roughness on bacterial attachment. Chemical modification of glass surfaces resulted in a ~1 nm decrease in the average surface roughness ( R a) and the root-mean-squared roughness ( Rq ) and in a ~8 nm decrease in the surface height and the peak-to-peak ( R max) and the 10-point average roughness ( Rz ). The study revealed amplified bacterial attachment on the chemically etched, nano-smoother glass surfaces. This was a consistent response, notwithstanding the taxonomic affiliation of the selected bacteria. Enhanced bacterial attachment was accompanied by elevated levels of secreted extracellular polymeric substances (EPS). An expected correlation between cell surface wettability and the density of the bacterial attachment on both types of glass surfaces was also reported, while no correlation could be established between cell surface charge and the bacterial retention pattern. 相似文献
9.
We have found that the antibody A2, a marker for the capsule of steroidogenic lipid droplets, reacts with an intermediate filament-associated protein, P 200, in 3T3-L1 preadipocytes. Supporting evidence came from the colocalization pattern of P 200 with vimentin in double label experiments. The association of P 200 with vimentin was further confirmed by its copurification with vimentin after high salt extraction and colocalization of these two proteins in high salt-extracted and vinblastine-treated cells. In preadipocytes this protein was distributed on the vimentin filament network. At the early stage of adipose conversion, this protein was found to encircle nascent lipid droplets ranging from 0.1 to 0.2 μm, accompanied with a decreased distribution on the vimentin filament system. This infers a possible translocation of P 200 from the vimentin filaments to the droplet surface. Meanwhile, the vimentin filaments remained in a normal distribution in the cytoplasm and were apparently not associated with the nascent droplet. The association of vimentin filaments to droplet surfaces became prominent in lipid droplets larger than 0.2 μm, forming a typical vimentin cage. Immunogold staining also confirmed the translocation of P 200 immunoreactivity from the droplet surface to the vimentin cage. The relocation of P 200 from the cytoplasmic vimentin filaments to the droplet surface prior to the formation of the vimentin cage, as well as the reorganization of this protein in the vimentin cage, suggests a stabilizing role in the lipid droplet formation and an inducing function of this protein in the formation of the vimentin cage. J. Cell. Biochem. 67:84–91, 1997. © 1997 Wiley-Liss, Inc. 相似文献
10.
Few leafhopper species are known to be ant-attended. Evidence is presented that unequivocally demonstrates that Dalbulus quinquenotatus is a myrmecophile. In a greenhouse study, the behavior of D. quinquenotatus and four Dalbulus species not associated with ants was observed in the absence and presence of the pavement ant, Tetramorium caespitum. D. quinquenotatus is readily contacted by tending ants and responds to stroking on the abdomen from ants' antennae by excreting and holding honeydew droplets until droplets are removed by ants. Nonattended Dalbulus species avoid contact with ants by walking, jumping, or flying away when approached. D. quinquenotatus excretes three to six times the volume of honeydew as do two nonattended species, D. maidis and D. gelbus. Droplets of D. quinquenotatus are about 23% larger in diameter and excreted two to four times more frequently than for the other species. D. quinquenotatus takes about 0.15 s to form honeydew droplets on the anal tube, then holds the droplet an average of 0.28 s before expelling it when ants are absent. In the presence of ants, D. quinquenotatus holds the droplet an average of 1.31 s, which gives ants time to harvest the droplet. Nonattended species, however, immediately expel droplets from the anal tube after droplet formation. This ant-leafhopper mutualism apparently has evolved due to the ability of D. quinquenotatus to have extensive physical contact with ants and excrete large amounts of honeydew. D. chiapensis, a possible descendent of D. quinquenotatus, may secondarily have lost its mutualistic relationship with ants. 相似文献
11.
Appropriate droplet size and the preferred sex and age of insects for insecticides used in topical application were investigated to standardize the method of testing the susceptibility of Stenotus rubrovittatus (Matsumura). The overflow of acetone droplets applied on the notum of the thorax of S. rubrovittatus adults occurred when the droplet size exceeded 0.20 μl per insect, and the overflow occurred more frequently in males than in females. No effect of acetone solution on mortality was observed at less than 0.20 μl droplet size per insect within 72 h after treatment. The LD 50 values and relative potencies of fenitrothion 24 and 48 h after treatment were almost the same in each sex. The fenitrothion susceptibility of males was twice higher than that of females. The fenitrothion susceptibility increased with age after emergence. However, there were small differences in LD 50 values and relative potencies between 4–7 and 8–11 days after emergence because the females 4–11 days after emergence had a small difference in body weight. These results led us to conclude that the recommended size of acetone droplets per insect is less than 0.20 μl and that it is suitable to use S. rubrovittatus females 4–11 days after emergence for topical application. 相似文献
12.
Previous work has shown that organosilica-based xerogels have the potential to control biofouling. In this study, modifications of chemistry were investigated with respect to their resistance to marine slimes and to settlement of barnacle cyprids. Adhesion force measurements of bovine serum albumin (BSA)-coated atomic force microscopy (AFM) tips to xerogel surfaces prepared from aminopropylsilyl-, fluorocarbonsilyl-, and hydrocarbonsilyl-containing precursors, indicated that adhesion was significantly less on the xerogel surfaces in comparison to a poly(dimethylsiloxane) elastomer (PDMSE) standard. The strength of adhesion of BSA on the xerogels was highest on surfaces with the highest and the lowest critical surface tensions, γ C and surface energies, γ S, and duplicated the ‘Baier curve’. The attachment to and removal of cells of the diatom Navicula perminuta from a similar series of xerogel surfaces were examined. Initial attachment of cells was comparable on all of the xerogel surfaces, but the percentage removal of attached cells by hydrodynamic shear stress increased with γ C and increased wettability as measured by the static water contact angle, θ Ws, of the xerogel surfaces. The percentage removal of cells of Navicula was linearly correlated with both properties ( R 2 = 0.74 for percentage removal as a function of θ Ws and R 2 = 0.69 for percentage removal as a function of γ C). Several of the aminopropylsilyl-containing xerogels showed significantly greater removal of Navicula compared to a PDMSE standard. Cypris larvae of the barnacle B. amphitrite showed preferred settlement on hydrophilic/higher energy surfaces. Settlement was linearly correlated with θ Ws ( R 2 = 0.84) and γ C ( R 2 = 0.84). Hydrophilic xerogels should prove useful as coatings for boats in regions where fouling is dominated by microfouling (protein and diatom slimes). 相似文献
13.
Previous studies have shown that some polyphenols have anti-ice nucleation activity (anti-INA) against ice-nucleating bacteria that contribute to frost damage. In the present study, leaf disk freezing assay, a test of in vitro application to plant leaves, was performed for the screening of anti-INA, which inhibits the ice nucleation activity of an ice-nucleating bacterium Erwinia ananas in water droplets on the leaf surfaces. The application of polyphenols with anti-INA, kaempferol 7- O-β-glucoside and (–)-epigallocatechin gallate, to the leaf disk freezing assay by cooling at ?4–?6 °C for 3 h, revealed that both the compounds showed anti-INAs against E. ananas in water droplets on the leaf surfaces. Further, this assay also revealed that the extracts of five plant leaves showed high anti-INA against E. ananas in water droplets on leaf surfaces, indicating that they are the candidate resources to protect crops from frost damage. 相似文献
14.
The ability of encapsulation to protect hydrophilic–bioactive food compounds from harsh environments can be improved by strengthening the hydrophilic barriers of encapsulated food compounds in Ca-alginate microgel particles via the integration of oil into the microgels. This study introduces a one-step procedure to integrate water-in-oil (W/O) emulsion droplets directly into Ca-alginate microgels during the production using the impinging aerosols system. A water-in-oil-in-water (20 kg m−3 alginate solution) (W1/O/W2) double emulsion was prepared using a high speed homogeniser followed by a microfluidiser. The microstructure of the W1/O/W2 emulsion was analysed using optical and fluorescence microscopy. The mean diameters of the W1/O/W2 emulsion droplets and resultant microgels were in the range of 27.8–65.4 μm and 160–420 μm, respectively. Food dye was used as a proxy for a hydrophilic food compound and its release from the microgels was significantly decreased when it was encapsulated in the W/O emulsion droplets. Based on the numerical analysis, the presence of the W/O emulsion droplets in the gel network reduced the degree of gelation of the microgel because the diffusion rate of Ca2+ cation in the microgel is reduced. The degree of gelation of the W/O emulsion droplets encapsulated microgel is 0.6 when the diameter of the droplet is reduced to 77.5 μm and the concentration of CaCl2 solution is doubled to 22 kg m−3. The potentiality of the impinging aerosol system to produce Ca-alginate microgels to encapsulate hydrophilic compounds with improved barriers is presented in this work. 相似文献
15.
Most mammalian cells package neutral lipids into droplets that are surrounded by a monolayer of phospholipids and a specific set of proteins including the adipose differentiation-related protein (ADRP; also called adipophilin), which is found in a wide array of cell types, and the perilipins, which are restricted to adipocytes and steroidogenic cells. TIP47 was initially identified in a yeast two-hybrid screen for proteins that interact with the cytoplasmic tail of the mannose 6-phosphate receptor, yet its sequence is highly similar to the lipid droplet protein, ADRP, and more distantly related to perilipins. Hence, we hypothesized that TIP47 might be associated with lipid droplets. In HeLa cells grown in standard low lipid-containing culture media, immunofluorescence microscopy revealed that the cells had few lipid droplets; however, TIP47 and ADRP were found on the surfaces of the small lipid droplets present. When the cells were grown in media supplemented with physiological levels of fatty acids, the amount of neutral lipid stored in lipid droplets increased dramatically, as did the staining of TIP47 and ADRP surrounding these droplets. TIP47 was found primarily in the cytosolic fractions of HeLa cells and murine MA10 Leydig cells grown in low lipid-containing culture medium, while ADRP was undetectable in these fractionated cell homogenates. When HeLa and MA10 Leydig cells were lipid-loaded, significant levels of ADRP were found in the floating lipid droplet fractions and TIP47 levels remained constant, but the distribution of a significant portion of TIP47 shifted from the cytosolic fractions to the lipid droplet fractions. Thus, we conclude that TIP47 associates with nascent lipid droplets and can be classified as a lipid droplet-associated protein. 相似文献
16.
The present study evaluated the removal of Escherichia coli XL1-blue biofilms using periodic jets of carbon dioxide aerosols (a mixture of solid and gaseous CO 2) with nitrogen gas. The aerosols were generated by the adiabatic expansion of high-pressure CO 2 gas through a nozzle and used to remove air-dried biofilms. The areas of the biofilms were measured from scanning electron micrographs before and after applying the aerosols. The removal efficiency of the aerosol treatment was measured with various air-drying times of the biofilms before the treatment, surface materials, and durations of CO 2 aerosols in each 8-s aerosol–nitrogen cleaning cycle. Nearly 100% of the fresh biofilms were removed from the various surfaces very reliably within 90 s. This technique can be useful for removing unsaturated biofilms on solid surfaces and has potential applications for cleaning bio-contaminated surfaces. 相似文献
17.
This paper investigated the generation characteristics of nonspherical oil-in-water ( O/ W) droplets consisting of food-grade components using microchannel (MC) array devices that have many rectangular MCs with shallow
wells. The well height was designed to be twice the MC height. Two hydrophilic MC array devices made of surface-oxidized single-crystal
silicon with equivalent MC diameters of 3.2 and 8.4 μm were used. Refined soybean oil was used as the to-be-dispersed phase,
and a Milli-Q water solution of 1.0 wt% polyoxyethylene (20) sorbitan monolaurate (Tween20) was used as the continuous phase.
Highly uniform discoid droplets with diameters of 9.0 and 21.5 μm, heights of 4.6 and 9.8 μm, and coefficients of variation
of less than 4% were generated by simply forcing a to-be-dispersed phase via rectangular MCs into a well filled with a continuous
phase. The to-be-dispersed phase pressures necessary for droplet generation were less than 8 kPa. The detailed generation
process of the discoid droplets was analyzed using movie clips taken by a high-speed camera. Key phenomena during the detachment
process were considered to be rapid flow of the to-be-dispersed phase into the well and instantaneous pinch-off of the neck.
The effect of the to-be-dispersed phase velocity inside a rectangular MC ( U
d,MC) on the resultant droplet diameter and the droplet-generation rate was also analyzed. Size-controlled discoid droplets were
stably generated via the rectangular MC below the critical U
d,MC, and the droplet-generation rate became maximum at the critical U
d,MC. 相似文献
18.
Currently, much effort is being invested in novel formulations of bioactive molecules, such as emulsions, for pharmaceutical,
food, and cosmetic applications. Therefore, methods to produce emulsions with controlled-size droplets of uniform size distribution
have been developed. On this concern, a microfluidic device called the microchannel (MC) was used in this work for emulsification.
This is a novel method for producing monodispersed emulsion droplets with very narrow droplet size distribution and low energy
input, due to the spontaneous droplet generation basically driven by the interfacial tension, unlike other conventional emulsification
processes. This technology provides the formulation of oil-in-water (O/W) emulsions containing lipophilic active molecules
with increased bioavailability, which may be readily absorbed by the human body. MC emulsification enables the preparation
of highly monodispersed O/W emulsions, which may be applied as enhancer on active molecules delivery systems, as well as in
foodstuff. In this study, formulations of O/W emulsions loaded with bioactive molecules, such as β-carotene and γ-oryzanol,
were prepared by the MC emulsification process. Refined soybean oil containing the dissolved lipophilic molecule and either
sugar ester or gelatin solution (1 wt.%) were used as the dispersed and continuous phases, respectively. The emulsification
process conducted using the asymmetric straight-through MC plate enabled the production of monodispersed O/W emulsions, resulting
in β-carotene-loaded O/W emulsions with average droplet size ( d
av) of 27.6 μm and coefficient of variation (CV) of 2.3% and γ-oryzanol-loaded droplets with d
av of 28.8 μm and CV of 3.8%. The highly monodisperse β-carotene-loaded droplets were physically stable throughout the storage
period observed, resulting in droplets with d
av 28.2 μm and CV of 2.9% after 4 months storage in darkness at 5 °C. Single micrometer-sized monodisperse emulsions loaded
with β-carotene were successfully formulated using the grooved MC emulsification, resulting in droplets with d
av of 9.1 μm and CV of 6.2%.
This work was funded by The Ministry of Agriculture, Forestry and Fisheries of Japan, through the Food Nanotechnology Project,
and the Japan Society for the Promotion of Science. 相似文献
19.
Expiratory droplets and droplet nuclei can be pathogen carriers for airborne diseases. Their transport characteristics were studied in detail in two idealized floor-supply-type ventilation flow patterns: Unidirectional-upward and single-side-floor, using a multiphase numerical model. The model was validated by running interferometric Mie imaging experiments using test droplets with nonvolatile content, which formed droplet nuclei, ultimately, in a class-100 clean-room chamber. By comparing the droplet dispersion and removal characteristics with data of two other ceiling-supply ventilation systems collected from a previous work, deviations from the perfectly mixed ventilation condition were found to exist in various cases to different extent. The unidirectional-upward system was found to be more efficient in removing the smallest droplet nuclei (formed from 1.5 mum droplets) by air extraction, but it became less effective for larger droplets and droplet nuclei. Instead, the single-side-floor system was shown to be more favorable in removing these large droplets and droplet nuclei. In the single-side-floor system, the lateral overall dispersion coefficients for the small droplets and nuclei (initial size =45 mum) were about an order of magnitude higher than those in the unidirectional-upward system. It indicated that bulk lateral airflow transport in the single-side-floor system was much stronger than the lateral dispersion mechanism induced mainly by air turbulence in the unidirectional-upward system. The time required for the droplets and droplet nuclei to be transported to the exhaust vent or deposition surfaces for removal varied with different ventilation flow patterns. Possible underestimation of exposure level existed if the perfectly mixed condition was assumed. For example, the weak lateral dispersion in the unidirectional ventilation systems made expiratory droplets and droplet nuclei stay at close distance to the source leading to highly nonuniform spatial distributions. The distance between the source and susceptible patients became an additional concern in exposure analysis. Relative significance of the air-extraction removal mechanism was studied. This can have impact to the performance evaluation of filtration and disinfection systems installed in the indoor environment. These findings revealed the need for further development in a risk-assessment model incorporating the effect of different ventilation systems on distributing expiratory droplets and droplet nuclei nonuniformly in various indoor spaces, such as buildings, aircraft cabins, trains, etc. 相似文献
20.
Ultrastructural and cell fractionation studies implicate lipid droplets in the storage of cholesterol and in the secretion of steroids. To evaluate the role of the lipid droplet in steroidogenesis, a discontinuous gradient centrifugation method has been developed for the isolation of both lipid droplet and non-lipid fractions from decapsulated rat adrenal homogenates. Steroids were extracted from the fractions with chloroform/methanol; the cholesterol ester, cholesterol and corticosterone in each extract were purified using a single chromatogram and the purified steroid and sterols were assayed fluorometrically. The lipid droplet fraction contained 85% of the esterified cholesterol and 32% of the free cholesterol found in whole gland extracts. Although adrenal lipid droplet fractions isolated from non-stimulated control animals contained 65–79% of the total corticosterone assayed in extracts of the whole gland, injections of ACTH did not increase corticosterone 1n this fraction. On the other hand, the corticosterone measured in non-lipid fraction extracts increased significantly following ACTH treatment. These results suggest that the synthesis/release mechanism for corticosterone is not associated with the lipid droplets but may involve specific components in the non-lipid fraction. The function of lipid droplet corticosterone is unknown. 相似文献
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