Droplet Technique Research Articles

A novel application of inverse gas chromatography for estimating contact angles in porous media

HypothesisSurface wettability is a critical factor in multi-phase flow within porous media, a processes essential in various applications e.g. in the energy sector. Traditional methods for assessing wettability of porous media by contact angle measurements, such as sessile droplet and micro-CT techniques, are limited by interface pinning, sample size or resolution impacting precision and accuracy. We hypothesized that using smaller and unconstrained probes, specifically gas molecules, to retrieve interactions along a representative sample size via inverse gas chromatography (IGC) could provide a more accurate determination of contact angles. MethodWe propose a procedure to relate IGC results with macro-scale wettability descriptions, such as the Young equation. To test the effectiveness of IGC method, glass bead samples with varying wettability, modified through a silanization process, were prepared. Contact angles for a distilled water-air-sample system were measured using the sessile droplet method and micro-CT for comparative analysis. IGC was employed to determine the surface energy components of these samples, which were then used in the extended Young-Dupré equation to calculate the contact angles. FindingsThe contact angle ranges determined by IGC and micro-CT for untreated glass beads, the most hydrophilic samples, showed great alignment. This consistency is attributed to the chemical amorphous nature of the untreated beads reflected in the assumption that dispersive and specific energetic components of surface sites are uncorrelated, on which the proposed analysis is based. For treated samples, where the silanization process creates correlations between surface energetic components, the alignment between IGC and micro-CT results was less precise. This study successfully demonstrated that IGC, a molecular-scale probe-based technique, can effectively determine the contact angle range, a macroscopic property, for amorphous samples. Future work should incorporate correlations between energetic components of surface detected by IGC to extend this method's applicability to a wider material range.

Experimental study of vegetable oil droplets vaporization under low temperature conditions such as those found in diesel engine cold parts

This paper presents an analysis of three vegetable oil droplets vaporization process in the range temperature from 473 to 723 K corresponding to low temperature conditions found in diesel engine cold parts. This process is analyzed for a droplet evaporating in a hot environment at atmospheric pressure using the fiber-suspended droplet technique well used in the literature, and analyzing the droplet normalized square diameter and temperature evolution surrounding the droplet when vaporizing. The main difference between those already studied in literature is the range temperature which varies between 473 and 723 K in which vegetable oils vaporizing problems leading to deposits formation in the cold regions of diesel engines especially in direct injection. This presents a scientific challenge for resolving deposit formation. The findings reveal that vegetable oil droplets experience expansion and heating for temperatures below 623 K: no other changes are observed. Between temperatures of 623 and 683 K, an increase in temperature, expansion, and an inconsistent vaporization is observed. This is followed by a phase of low and constant vaporization. From 683 K, vegetable oils experience an initial stage of heating and expansion, which is accompanied by a phenomenon of puffing and bursting. Finally, in the last phase, residue formation occurs. Puffing and bursting phenomena manifest once the temperature reaches 683 K, indicating the emergence of substantial quantities of light compounds including carboxylic acids, aromatics, acrolein, ketene, and fatty acids. These compounds are formed through the thermal degradation and polymerization of vegetable oils. This process causes deposits to form in the colder areas of diesel engines.

A polynomial temperature profile model for suspended droplet evaporation over a wide range of ambient pressures and convection conditions

The suspended droplet technique has been widely applied in experimental droplet evaporation studies, but heat conduction caused by support fiber can change the evaporation characteristics. In the present study, a novel theoretical model is proposed to investigate the effect of a suspender on droplet heating and evaporation. Considering the vortex circulation inside the droplet and the heat diffusion along the support fiber, the temperature distribution is assumed to exhibit a polynomial profile. The effects of pressure on the thermodynamic and transport properties are also accounted for. The simulation results are consistent with previous experimental data over a wide range of ambient pressures and convection conditions. The performance of the new model is further compared with that of other models in terms of computational efficiency and accuracy. The new model requires an order of magnitude less CPU time than does the effective thermal conductivity model to preserve the key features of the temperature distribution accurately. In addition, a dual effect of the fiber diameter on the evaporation rate is demonstrated. With increasing fiber diameter, the evaporation rate increases and then decreases. There are two different patterns that can depict heat transfer between the suspended droplets and the fibers: an “immersed area pattern” and a “fiber temperature pattern”. A switchover in the two patterns is responsible for the dual effect, which occurs at a threshold fiber diameter related to the environment.

Recent Progress in Droplet Structure Machining for Advanced Optics.

The development of optical and photonic applications using soft-matter droplets holds great scientific and application importance. The machining of droplet structures is expected to drive breakthroughs in advancing frontier applications. This review highlights recent advancements in micro-nanofabrication techniques for soft-matter droplets, encompassing microfluidics, laser injection, and microfluidic 3D printing. The principles, advantages, and weaknesses of these technologies are thoroughly discussed. The review introduces the utilization of a phase separation strategy in microfluidics to assemble complex emulsion droplets and control droplet geometries by adjusting interfacial tension. Additionally, laser injection can take full advantage of the self-assembly properties of soft matter to control the spontaneous organization of internal substructures within droplets, thus providing the possibility of high-precision customized assembly of droplets. Microfluidic 3D printing demonstrates a 3D printing-based method for machining droplet structures. Its programmable nature holds promise for developing device-level applications utilizing droplet arrays. Finally, the review presents novel applications of soft-matter droplets in optics and photonics. The integration of processing concepts from microfluidics, laser micro-nano-machining, and 3D printing into droplet processing, combined with the self-assembly properties of soft materials, may offer novel opportunities for processing and application development.

Enrichment of different taxa of the enigmatic candidate phyla radiation bacteria using a novel picolitre droplet technique.

The candidate phyla radiation (CPR) represents a distinct monophyletic clade and constitutes a major portion of the tree of life. Extensive efforts have focused on deciphering the functional diversity of its members, primarily using sequencing-based techniques. However, cultivation success remains scarce, presenting a significant challenge, particularly in CPR-dominated groundwater microbiomes characterized by low biomass. Here, we employ an advanced high-throughput droplet microfluidics technique to enrich CPR taxa from groundwater. Utilizing a low-volume filtration approach, we successfully harvested a microbiome resembling the original groundwater microbial community. We assessed CPR enrichment in droplet and aqueous bulk cultivation for 30days using a novel CPR-specific primer to rapidly track the CPR fraction through the cultivation attempts. The combination of soil extract and microbial-derived necromass provided the most supportive conditions for CPR enrichment. Employing these supplemented conditions, droplet cultivation proved superior to bulk cultivation, resulting in up to a 13-fold CPR enrichment compared to a 1- to 2-fold increase in bulk cultivation. Amplicon sequencing revealed 10 significantly enriched CPR orders. The highest enrichment in CPRs was observed for some unknown members of the Parcubacteria order, Cand. Jorgensenbacteria, and unclassified UBA9983. Furthermore, we identified co-enriched putative host taxa, which may guide more targeted CPR isolation approaches in subsequent investigations.

The inhibition of YAP Signaling Prevents Chronic Biliary Fibrosis in the Abcb4-/- Model by Modulation of Hepatic Stellate Cell and Bile Duct Epithelium Cell Pathophysiology.

Primary sclerosing cholangitis (PSC) represents a chronic liver disease characterized by poor prognosis and lacking causal treatment options. Yes-associated protein (YAP) functions as a critical mediator of fibrogenesis; however, its therapeutic potential in chronic biliary diseases such as PSC remains unestablished. The objective of this study is to elucidate the possible significance of YAP inhibition in biliary fibrosis by examining the pathophysiology of hepatic stellate cells (HSC) and biliary epithelial cells (BEC). Human liver tissue samples from PSC patients were analyzed to assess the expression of YAP/connective tissue growth factor (CTGF) relative to non-fibrotic control samples. The pathophysiological relevance of YAP/CTGF in HSC and BEC was investigated in primary human HSC (phHSC), LX-2, H69, and TFK-1 cell lines through siRNA or pharmacological inhibition utilizing verteporfin (VP) and metformin (MF). The Abcb4-/- mouse model was employed to evaluate the protective effects of pharmacological YAP inhibition. Hanging droplet and 3D matrigel culture techniques were utilized to investigate YAP expression and activation status of phHSC under various physical conditions. YAP/CTGF upregulation was observed in PSC patients. Silencing YAP/CTGF led to inhibition of phHSC activation and reduced contractility of LX-2 cells, as well as suppression of epithelial-mesenchymal transition (EMT) in H69 cells and proliferation of TFK-1 cells. Pharmacological inhibition of YAP mitigated chronic liver fibrosis in vivo and diminished ductular reaction and EMT. YAP expression in phHSC was effectively modulated by altering extracellular stiffness, highlighting YAP's role as a mechanotransducer. In conclusion, YAP regulates the activation of HSC and EMT in BEC, thereby functioning as a checkpoint of fibrogenesis in chronic cholestasis. Both VP and MF demonstrate effectiveness as YAP inhibitors, capable of inhibiting biliary fibrosis. These findings suggest that VP and MF warrant further investigation as potential therapeutic options for the treatment of PSC.

Understanding the formation of particle bands and fingering patterns during evaporation of a sessile droplet containing colloids

Sessile droplets containing dispersed colloids evaporate on substrates leaving distinct deposition patterns. Applications using the droplets technique require a critical understanding of the complex particle dynamics that affect the deposition pattern. The fingering-like pattern formed when surfactant-laden droplets containing dispersed colloids evaporate is not yet well understood. The lateral imbalanced capillary meniscus forces (CMFs) between particles moving along the Marangoni vortex (MV) cluster particles into bands that deposit to form the fingering-like pattern. This work investigates the effect of particle shape, particle, and surfactant concentration on the phenomenon. Further, the importance of the contact angle and contact line (CL) dynamics of the droplet is also discussed. The results demonstrate that manipulating these parameters can control the band formation and the resulting deposition pattern. The findings of this work would be pivotal for a critical understanding of particle self-assembly and pattern morphologies of evaporating surfactant-laden droplets.

Simulation of a metal pellet spraying generator driven by micro-air pressure

Molten metal droplet techniques are one of the important technologies for printing micro-metal parts. At present, the equipment developed for this technology faces some challenges, such as the requirement for a micro-oxygen environment during operation and a complicated manufacturing process. Consequently, a micro-air-pressure driven metal pellet spraying (MPS) 3D printing generator was designed and manufactured using the drop-on-demand technique, which uses simple and low-cost equipment in an atmospheric environment. A 2D axisymmetric model has been proposed to study the mechanism of droplet generation by using a micro-pneumatic MPS generator. In addition, a proprietary pneumatic MPS generator was also used to conduct droplet generation experiments. The validity of the proposed model was verified through the simulation results of the droplet pattern and droplet diameter, which were in good agreement with the experimental ones. The analysis shows that in the droplet injection forming process, surface tension is dominant for low viscosity liquids at a very small Ohnesorge number (Oh < 0.01). The surface tension was conducive to the maintenance of the molten form of the projectile. During droplet injection, the phenomenon of oblate–prolate oscillation occurs due to the non-uniform distribution of pressure inside the droplet. This phenomenon exerts an influence on the accuracy of the droplet flight trajectory and deposition position. This study serves as a good reference for selecting the suitable settings for producing metal droplets using the MPS generator.

Microfluidic Droplet-Assisted Fabrication of Vessel-Supported Tumors for Preclinical Drug Discovery.

High-fidelity in vitro tumor models are important for preclinical drug discovery processes. Currently, the most commonly used model for in vitro drug testing remains the two-dimensional (2D) cell monolayer. However, the natural in vivo tumor microenvironment (TME) consists of extracellular matrix (ECM), supporting stromal cells and vasculature. They not only participate in the progression of tumors but also hinder drug delivery and effectiveness on tumor cells. Here, we report an integrated engineering system to generate vessel-supported tumors for preclinical drug screening. First, gelatin-methacryloyl (GelMA) hydrogel was selected to mimic tumor extracellular matrix (ECM). HCT-116 tumor cells were encapsulated into individual micro-GelMA beads with microfluidic droplet technique to mimic tumor-ECM interactions in vitro. Then, normal human lung fibroblasts were mingled with tumor cells to imitate the tumor-stromal interaction. The tumor cells and fibroblasts reconstituted in the individual GelMA microbead and formed a biomimetic heterotypic tumor model with a core-shell structure. Next, the cell-laden beads were consociated into a functional on-chip vessel network platform to restore the tumor-tumor microenvironment (TME) interaction. Afterward, the anticancer drug paclitaxel was tested on the individual and vessel-supported tumor models. It was demonstrated that the blood vessel-associated TME conferred significant additional drug resistance in the drug screening experiment. The reported system is expected to enable the large-scale fabrication of vessel-supported heterotypic tumor models of various cellular compositions. It is believed to be promising for the large-scale fabrication of biomimetic in vitro tumor models and may be valuable for improving the efficiency of preclinical drug discovery processes.

Coating SiO2 nanoparticles with polyvinyl alcohol for interfacial tension alteration in the system CO2+polyethylen glycol+water

Interfacial tension (IFT) data were measured and correlated by a theoretical model for the system CO2/polyethylene glycol (PEG) (40 wt.%)+water (60 wt.%). The effect of both bare SiO2 nanoparticles (NPs) as well as their modified surface counterparts on the IFT alteration was investigated. SiO2 NPs were synthesized followed by coating with polyvinyl alcohol (PVA). IFT measurements based on a well-established pendant droplet technique were carried out in the presence of 0.00–0.05 wt.% NPs over the temperatures and pressures of 298–323 K and 0.1–4.0 MPa, respectively. The obtained results depict that IFT decreases with increasing pressure and increasing NPs concentration, and increases with increasing temperature. It was shown that increasing the SiO2 NPs concentration from 0.00 to 0.05 wt.% causes a 35.8% decrease at constant pressure and temperature of 3.0 MPa and 323 K, respectively. Increasing pressure from 2.0 to 4.0 MPa in the presence of 0.03 wt.% SiO2 NPs decreases the IFT of the system by 27% at a constant temperature of 313 K. Lower IFTs were observed (11.50–18.90%) when PVA-coated NPs were added to the fluid. Finally, the parameters of the employed theoretical model were determined using global and local parameters, the latter of which showed higher precisions in the representation of data.

Determination of UV Filters in Surface Water by VA‐DLLME‐SFOD Technique Coupled with GC‐MS/MS

AbstractA simple, rapid, and sensitive method is developed for the determination of UV filters in river waters by applying the vortex‐assisted dispersive liquid–liquid microextraction based on solidified floating organic droplet technique followed by the injector port silylation (IPS) in a gas chromatography‐tandem mass spectrometry system. Statistical experimental design methods including general factorial design, one factor at a time, and central composite face‐centered design are used for optimization purposes. Under optimized conditions, 460 µL of acetone and 30 µL of 2‐dodecanone are rapidly injected into a 10 mL water sample with 10% (w/v) NaCl at pH 2.5 and vortexed for 3 min. After centrifugation, 2 µL of the separated organic solvent is subjected to auto‐IPS with 1 µL of bis (trimethylsilyl) trifluoroacetamide containing 1% trimethylchlorosilane, at 260 °C for 4.5 min in programmable temperature vaporization mode. As a result of the validation studies, the intra‐day and inter‐day precision indicated as relative standard deviation are less than 12.4% and 18.8%, respectively. For all UV filters, detection limits are between 1.1 and 5.5 ng L−1 and limit of quantitation values are between 3.1 and 16.6 ng L−1. Successful recovery of extraction values (77.1%–107.4%) and good enrichment factors (231–350) are obtained.

Effect of sodium citrate on asphaltene film at the oil–water interface

HypothesisSodium citrate (Na3Cit) has been proven to improve the oil sands extraction recovery, but its mechanism is still unclear. Here we hypothesize that the presence of Na3Cit affects the asphaltene behaviour at the oil–water interface, which enhances oil–water separation and, thereby, heavy oil recovery. ExperimentsNa3Cit-asphaltene interaction was first investigated on their interfacial shear rheology at one heptol-water interface. Na3Cit-asphaltene interaction was further revealed by measuring the interaction forces between two heptol-water interfaces using the atomic force microscopy droplet technique combined with the Stokes-Reynolds-Young-Laplace (SRYL) model. Interfacial properties were further illustrated through interfacial tension, zeta potential, Langmuir trough, and FE-SEM. FindingsNa3Cit was found to weaken the strength of the asphaltene film at the heptol-water interface. Moreover, Na3Cit could diminish the adhesion forces observed between two asphaltene-in-heptol droplets in high salinity solutions. Besides, Na3Cit also made the asphaltene-in-heptol droplet more negatively charged. These results collectively suggest that Na3Cit-asphaltene interaction results in a looser and more elastic asphaltene interfacial network with the slow formation and reduces the adhesion between two interfaces, all of which are most likely the consequence of increased electrostatic repulsion between asphaltene interfacial nanoaggregates. Our study provided new understandings of Na3Cit-asphaltene interactions at the interface.

Droplet microfluidics for double lipase immobilisation using TiO2 and alginate microbeads

A double immobilisation technique was developed for C. antarctica lipase (CALB) that improved its enzymatic activity and solved difficulties frequently observed in reactions catalysed by lipases. The first immobilisation consisted of CALB adsorption onto a TiO2 nanoparticle surface (CALB TiO2). The adsorption was carried out by an oriented monolayer formed by CALB’s hydrophilic amino acids and the TiO2 surface, leaving the CALB’s active site accessible for reaction. As a result, an increase in enzymatic activity was achieved. The Relative Enzymatic Activity ((REA) obtained was 289%. The second immobilisation consisted of CALBTiO2 entrapment into calcium alginate microbeads [(CALBTiO2)EDTA-Ca], obtained by an internal crosslinking ion-exchange mechanism and using microfluidic droplet technique. The microbiocatalyst obtained, (CALBTiO2)EDTA-Ca, retained a high enzymatic activity (REAt=0 = 232%) and stability (REAt=30days = 263%) at a size (diameter, Ø=8.9·104 nm) that enabled easier recovery than CALBTiO2 (Ø = 2.3·102 nm) or CALBFree (Ø=5.0 nm), and showed a favourable porosity for diffusion without releasing CALBTiO2. Although the microbeads showed CALBFree leaching, as demonstrated by the loss of REA after a mechanical resistant test, (CALBTiO2)EDTA-Ca maintained an almost constant REA.

Influence of Air Cold Plasma Modification on the Surface Properties of Paper Used for Packaging Production

In this study, the effect of air plasma on the surface properties of printed and coated cardboard was investigated. The material was activated by low-pressure cold plasma for 1, 10, 20, and 30 s. Wettability changes on the surface were examined by contact angle measurements using the sessile droplet technique. The differences in the surface free energy were calculated using the Lifshitz–van der Waals/acid–base and Contact Angle Hysteresis approaches. Optical profilometry was used for the surface roughness evaluation and an X-ray photoelectron spectroscopy analysis was performed to find changes in surface chemistry. Adhesive strength tests were carried out to estimate the adhesion changes after the material’s modification. It was found that the water and formamide contact angles increased after the plasma treatment while the diiodomethane contact angle did not change. As a result of the modification, the surface free energy also increased significantly and the surface roughness increased. The pull-off tests confirmed the improvement in the material’s surface properties. Moreover, it was demonstrated that the optimal effect can be obtained after just 10 s of the plasma process.

Determination of the Partial Contributions to the Electrical Conductivity of TiO2-SiO2-Al2O3-MgO-CaO Slags: Role of the Experimental Processing Conditions

The electrical transport properties of molten TiO2–SiO2–Al2O3–MgO–CaO slags were determined as a function of temperature and oxygen partial pressure. To avoid the corrosion of crucible materials by this slag at ultra high temperatures, the pendant droplet technique was used inside a modified floating zone furnace. Electronic and ionic transference numbers were estimated using stepped-potential chronoamperometry experiments to quantify the contribution of the electronic/ionic conductivity to the total electric conductivity. The results show that these slags are mixed conductors, where current is carried by ionic and electronic carriers. The oxygen partial pressure dependence of the electronic transference numbers, t_e, indicated a semiconducting mechanism in the molten slag. The ratio of the different valences of the transition metal ions had a predominant effect on the t_e. The {{text{TiO}}_{2}} content also favoured electronic conduction, while the effect of temperature and structure was less noticeable within the temperature and composition range studied.

Droplet Microfluidics for High-Throughput Analysis of Antibiotic Susceptibility in Bacterial Cells and Populations.

ConspectusAntibiotic-resistant bacteria are an increasing concern both in everyday life and specialized environments such as healthcare. As the rate of antibiotic-resistant infections rises, so do complications to health and the risk of disability and death. Urgent action is required regarding the discovery of new antibiotics and rapid diagnosis of the resistance profile of an infectious pathogen as well as a better understanding of population and single-cell distribution of the resistance level. High-throughput screening is the major affordance of droplet microfluidics. Droplet screens can be exploited both to look for combinations of drugs that could stop an infection of multidrug-resistant bacteria and to search for the source of resistance via directed-evolution experiments or the analysis of various responses to a drug by genetically identical bacteria. In droplet techniques that have been used in this way for over a decade, aqueous droplets containing antibiotics and bacteria are manipulated both within and outside of the microfluidic devices. The diagnostics problem was approached by producing a series of microfluidic systems with integrated dilution modules for automated preparation of antibiotic concentration gradients, achieving the speed that allowed for high-throughput combinatorial assays. We developed a method for automated emulsification of a series of samples that facilitated measuring the resistance levels of thousands of individual cells encapsulated in droplets and quantifying the inoculum effect, the dependence of resistance level on bacterial cell count. Screening of single cells encapsulated in droplets with varying antibiotic contents has revealed a distribution of resistance levels within populations of clonally identical cells. To be able to screen bacteria from clinical samples, a study of fluorescent dyes in droplets determined that a derivative of a popular viability marker is more suitable for droplet assays. We have developed a detection system that analyzes the growth or death state of bacteria with antibiotics for thousands of droplets per second by measuring the scattering of light hitting the droplets without labeling the cells or droplets. The droplet-based microchemostats enabled long-term evolution of resistance experiments, which will be integrated with high-throughput single-cell assays to better understand the mechanism of resistance acquisition and loss. These techniques underlie automated combinatorial screens of antibiotic resistance in single cells from clinical samples. We hope that this Account will inspire new droplet-based research on the antibiotic susceptibility of bacteria.

Measurements of Liquid AISI 304L Steel Density and Surface Tension, and Influence of Surface‐Active Elements at High Temperatures

Within the framework of the welding of steel components in pressurized water reactors, the optimization of the weld pool penetration is a major issue. The thermal‐hydraulics of the molten steel pool can be driven by Marangoni flows at the free surface. To compute these flows, liquid steel's thermophysical properties such as density ρ and surface tension σ are required. Such properties for austenitic vessel steel AISI 304L at liquid state are scarce, and even not available above 1800 °C, due to technological issues. The viscometer temperature installation (VITI) is designed to implement sessile droplet (SD) and maximum bubble pressure (MBP) techniques. These techniques allow to determine original ρ and σ data for two grades of AISI 304L steel, namely 304LP1 and 304LP4—low and high sulfur content, at various temperatures. In particular, thanks to the innovative design of MBP configuration, original surface tension data are obtained from the melting point up to 2100 °C. For the first time, experimental evidence of the Sahoo et al.'s (1988) model at high temperature is provided, emphasizing the decisive role played by surface‐active elements such as sulfur and oxygen on surface tension, whose content evolution is assessed by dedicated chemical analyses.

Obtaining water-repellent coatings based on expanded perlite materials

Superhydrophobic coatings are currently not widely used due to complex scaling problems, high cost and low environmental resistance. One solution is the use of organic coating technology. The paper shows the possibility of obtaining surface coatings with high water-repellent properties based on expanded perlite and regenerated adsorbent. The most effective surface treatment is polymethylhydrogensiloxane. In the work properties of obtained coatings were characterized by contact angles using the sessile droplet technique, optical and electron microscopy and IR-spectroscopy. With polymer content is more than 50 wt% for untreated and more than 40 wt% for the polymethylhydrogensiloxane treated perlite, the Cassie steady state and the water contact angle of more than 140° were reached. The resulting coatings are an example of a good microscale base coat for the further creation of superhydrophobic volumetric hierarchical coatings. It has been shown that the use of an adsorbent for used refined sunflower oil is as effective as the use of freshly ground expanded perlite.

Gram Negative Bacteria (Escherichia coli) Win Against Gram Positive Bacteria (Staphylococcus aureus) in The Same Media

Introduction: Biodiversity of the microorganism in Indonesia lead to the large amount of patient with infection. Human can get infected in two different place, with different kind of bacteria that cause the infection. This may lead to bacteremia without knowing which bacteria type whose causing it, either the Gram positive or Gram negative bacteria, whereas the treatment of this two types of bacteria are different. The aim of this study is to determine the doubling time of the Gram positive and Gram negative bacteria when they are grown in the same lesion and the kinds of bacteria that we need to eliminate first.Methods: Staphylococcus aureus and Escherichia coli bacteria were used as samples in this study. Bacterial culture in nutrient broth with 0.5 OD turbidity were mixed then incubated in incubator with 35˚C. Every one hour within 24 hour, 0.01 ml of bacterial culture was taken in serial dilutionover time, varying between 106 – 1012, . It was then planted in nutrient agar plate with droplets technique. After it had been incubated for 24 hours, we counted the Colony Forming Unit per ml (CFU/ml) to time, then the doubling time of the bacteria. The result were then compared between the Staphylococcus aureus and Escherichia coli group.Results: Two tailed t-test result of the doubling time between Staphylococcus aureus dan Escherichia coli was < 0,05 (p=0,000) wich means that there is significant difference of the doubling time between Staphylococcus aureus (24,35 ± 2,23 munites), and Escherichia coli (18,37 ± 0,50 minutes). When grown in the same media, Gram positive bacteria (Staphylococcus aureus) had slower doubling time than Gram negative bacteria (Escherichia coli) as much as 1.32 times.Conclusion: In bacteremia with two possible kinds of bacterial suspect, we need to eliminate the Gram negative bacteria first.

Study of Titanium-Silver Monolayer and Multilayer Films for Protective Applications in Biomedical Devices.

The search for coatings that extend the useful life of biomedical devices has been of great interest, and titanium has been of great relevance due to its innocuousness and low reactivity. This study contributes to the investigation of Ti/Ag films in different configurations (monolayer and multilayer) deposited by magnetron sputtering. The sessile droplet technique was applied to study wettability; greater film penetrability was obtained when Ag is the external layer, conferring high efficiency in cell adhesion. The morphological properties were characterized by SEM, which showed porous nuclei on the surface in the Ag coating and crystals embedded in the Ti film. The structural properties were studied by XRD, revealing the presence of TiO2 in the anatase crystalline phase in a proportion of 49.9% and the formation of a silver cubic network centered on the faces. Tafel polarization curves demonstrated improvements in the corrosion current densities of Ag/Ti/Ag/Ti/Ag/Ti/Ag/Ti and Ti/Ag compared to the Ag coating, with values of 0.1749, 0.4802, and 2.044 nA.m−2, respectively. Antimicrobial activity was evaluated against the bacteria Pseudomonas aeruginosa and Bacillus subtilis and the yeasts Candida krusei and Candida albicans, revealing that the Ti/Ag and Ag/Ti/Ag/Ti/Ag/Ti/Ag/Ti coatings exhibit promise in biomedical material applications.