Static Contact Angle Measurements Research Articles

Highly Hydrophobic Films of Engineered Silk Proteins by a Simple Deposition Method.

Molecular engineering of protein structures offers a uniquely versatile route for novel functionalities in materials. Here, we describe a method to form highly hydrophobic thin films using genetically engineered spider silk proteins. We used structurally engineered protein variants containing ADF3 and AQ12 spider silk sequences. Wetting properties were studied using static and dynamic contact angle measurements. Solution conditions and the surrounding humidity during film preparation were key parameters to obtain high hydrophobicity, as shown by contact angles in excess of 120°. Although the surface layer was highly hydrophobic, its structure was disrupted by the added water droplets. Crystal-like structures were found at the spots where water droplets had been placed. To understand the mechanism of film formation, different variants of the proteins, the topography of the films, and secondary structures of the protein components were studied. The high contact angle in the films demonstrates that the conformations that silk proteins take in the protein layer very efficiently expose their hydrophobic segments. This work reveals a highly amphiphilic nature of silk proteins and contributes to an understanding of their assembly mechanisms. It will also help in designing diverse technical uses for recombinant silk.

Transparent and anti-fouling perfluoropolyether coating with superior wear resistance

Perfluoropolyether (PFPE) siloxanes can be used as anti-fouling coating materials due to their simple large-scale preparation, transparency and omniphobic properties, but their wear resistance needs to be enhanced dramatically. Herein, we designed and synthesized a series of high-purity PFPE-siloxanes with different average molecular weights of PFPE chains and different numbers of trimethoxysilane groups. Then, these PFPE-siloxanes were coated on glass plates in a one-step dip coating process. The influence of the average molecular weight of PFPE chains and the number of trimethoxysilanes on the wear resistance of these PFPE films were investigated by the measurement of static contact angle and sliding angle of water, morphology and relative elemental content on the surface after different times of reciprocating friction. The film prepared from the PFPE-siloxanes combining a longer PFPE chain with more trimethoxysilane terminal groups possessed not only good transparency and excellent antifouling properties, but also presented superior wear resistance and anti-fingerprint properties. The surface wetting characteristic and morphology barely changed after 9000 times of friction with hard rubber under a 255 kPa pressure. The PFPE-siloxanes with excellent antifouling property and transparency make them as preferred candidates for engineering application fields.

Silica-based consolidants: Enhancement of chemical-physical properties of Vicenza stone in heritage buildings

Natural stones interact with the environment and undergo several chemical and physical weathering processes that cause the progressive loss of cohesion and degradation/disintegration of the material in the longer term. So, in order to retain the integrity of the historical patrimony and its undeniable impact on society, innovative materials and methodologies have been used in stone conservation field in recent years, also using a more environmentally-friendly approach. In this study, the interaction of three inorganic silica-based consolidant compounds with a valuable artistic calcareous rock, Vicenza stone, is discussed. This specific lithotype results to be still scarcely investigated, despite its high historical relevance and intrinsic features, especially porosity, which make it extensively susceptible to degradation. In particular, a colloidal suspension of silica made by particles with an average diameter of 10–20 nm, and two alkaline silicate solutions (lithium silicate and sodium silicate) are evaluated. An extensive characterization of both treated and untreated Vicenza stone samples was achieved by means of chemical–physical and morphological investigations (water absorption, open porosity, capillary absorption, ultrasonic pulse velocity and static contact angle measurements, Hg intrusion porosimetry, color evaluation, FTIR spectroscopy and SEM analyses). FTIR analyses revealed that all the consolidants exhibited a moderate penetration within the substrate, anyway a significant surface interaction with the stone, especially in the case of alkaline silicates, is proved by the results of SEM analyses, capillary absorption, static contact angle and color change. The improvement of the surface properties after treatments represents an essential and preliminary assumption to enhance the durability performance of Vicenza stone.

Sustainability of Water Sprinkling Effect of Water-Retaining Ceramic Block

In recent years, heat management by a temperature reduction effect, such as a water sprinkling effect, is strongly desired because of suppression of global warming. In this study, in order to evaluate the sustainability of the water sprinkling effect of pavement blocks, we attempted to clarify the evaporation performance from the inside of the blocks by the viewpoint of wettability. Specifically, the wettabilities were analyzed by measurement of static and dynamic contact angles and of the pavement blocks with different surface porous spaces. Water evaporation properties were measured from the fully water-containing block. As a result of sustainability of water evaporation, the ceramic block, which has a small porous space and a slow water absorption rate, was capable of transport water from the wetting sand to the inside, and had the ability to transport the inside water to the evaporation surface. In order to maintain the water sprinkling effect of the paving block, the water diffusion behavior for maintaining the sustainability of water evaporation on the surface layer is important, and the water inside the block is diffused to the surface. It was found from these results that it is necessary to absorb moisture from the external environment on the block surface.

Cu-loaded polyurethane to reduce ureteral stent microbes adherence and regulation of the inflammation response to RAW264.7

Introduction: Ureteral stents blocked with encrustation are a common clinical complication and affect bacteria colonization and inflammatory response. In this study, different concentrations of copper (0.25, 0.5, 1, 1.5, and 2 g/L) were immobilized on polyurethane (PU) that showed functionalization of microbe resistance and regulation of the inflammation response to RAW264.7.Methods: X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and static water contact angles were used to analyze the surface characterization. Proteus mirabilis resistance test and adhesion of cells by SEM were carried out to evaluate the antibacterial property of Cu-bearing samples. Cell cytotoxicity assay and apoptosis were used to obtain acceptable concentrations of PU-Cu. The morphology of cells was used to observe the occurrence of pseudopodia after contact with PU-Cu. Would healing assay and Transwell invasion assay were carried out to observe the migration and recovery of macrophages. IL-6 and IL-10 were used to evaluate the secretion of pro-/anti-inflammatory cytokines.Results: X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and static water contact angle measurement were used to confirm successful immobilization of Cu on PU. Plate counting assay and observation of adhered cells by SEM demonstrated that the antibacterial performance of PU-Cu against Proteus mirabilis increased with the amount of Cu loading in a dependent manner. Furthermore, the CCK-8 assay and apoptosis test suggested an acceptable cytotoxicity of PU-Cu at concentrations of 0.25, 0.5, and 1 g/L. The morphology of cells observed by SEM showed reduced occurrence of pseudopodia after contact with PU-Cu. Wound healing and transwell invasion assays manifested that migration and recovery of macrophages were improved by PU-Cu. ELISA of IL-6 and IL-10 demonstrated that PU-Cu could regulate inflammatory cytokines toward anti-inflammatory functionalization.

Directional transport and coalescence behavior on Titanium-Tantalum alloy surface: Insights from experiment and molecular dynamics simulation

Friction and wear of artificial joints are severe problems. By designing a structure for directional transporting lubricant onto the Ti-Ta alloy surface, the friction or wear can be effectively reduced. Herein, molecular dynamics (MD) simulation and experiment were employed to study the directional transport and coalescence behavior of droplets on wedge-shape structure Ti-5Ta (wt%) alloy surface. Results show that water droplets can be continuously transported. Moreover, the experimental results of static and dynamic contact angle measurement show that the experiment agrees well with the MD simulation. Finally, the anti-gravity directional transport was achieved on a tilting Ti-5Ta (wt%) alloy surface. This work provides insights for reducing friction and extending service life of artificial joints in the medical field.

A mechanochemically created durable dynamic superhydrophilic‐like surface

Superhydrophilicity (superwettability) is generally defined as either a static water contact angle near 0° or water completely wetting the surface. Here, we show that there is a superhydrophilic‐like surface that has a large static water contact angle but demonstrates superhydrophilicity in its dynamic water contact performance. We found that polyethylene terephthalate (PET) surfaces showed such behavior following mechanical abrasion with sandpaper. We have evaluated the wettability of the abraded PET surfaces by using static water contact angle (SWCA) measurements and the dynamic water contact performance (DWCP) of impacting droplets, the latter including water sprays, water immersion, anti‐fogging and water droplet impact tests. The water was found to completely wet the abraded PET surfaces on spraying or immersion, although the measured SWCA was as high as 70°, similar to that of the unabraded PET surface. For the abraded PET surface, both the water layer thickness on water immersion and the subsequent drying time were similar to those of an especially coated superhydrophilic layer on the unabraded surface. Accordingly, superhydrophilicity may be determined by the process used to measure it.

Elucidation of the methylene blue adsorption mechanism at the interface of powder pumice and aqueous solution by electro-kinetic and static contact angle measurements

Elucidation of the methylene blue adsorption mechanism at the interface of powder pumice and aqueous solution by electro-kinetic and static contact angle measurements

"THE SURFACE ENERGY OF COATING LAYERS USED FOR VIOLINS VARNISHING "

Numerous studies on new and historical violins have highlighted the importance of coatings for the acoustics of the musical instrument. The purpose of this paper is to present the results regarding the surface energy of resonant wood, spruce and maple in two states: lacquered and unvarnished. The method is based on static contact angle measurements of sessile drops. The obtained results highlight large differences in surface energy depending on the wood section (radial versus longitudinal), surface (lacquered versus unvarnished), wood species. Thus, although the surfaces are polar for both unpainted and lacquered samples, it can be seen that there is a tendency to increase the contact angle after applying the surface treatment (applying the varnish). In the case of spruce wood cut in the longitudinal direction, the contact angle increases by about 31% in the case of the lacquered surface. For maple wood, the increase is 10%. For radially cut spruce wood samples, it is observed that the contact angle is higher than 90°, the surface having a hydrophobic character, a characteristic that is not found in maple wood. The application of the varnish on the radial surface diminishes the hydrophobic characteristics of the spruce wood. In maple wood, the difference between the longitudinal and radial samples is very small (2%).

Preparation of transparent photoluminescence plastic concrete integrated with lanthanide aluminate

A simple strategy was presented for potential industrial preparation of persistent afterglow lightweight plastic concrete toward smart hard surfaces. Rare-earth activated aluminate (REA) pigment nanoparticles (NPs) were integrated into plastic bar. The transparency of the prepared plastic bar can be achieved by consistent distribution of REA NPs in the plastic fluid. Unsaturated polyester resin (bulk material) was mixed with silica nanoparticles (filler) and REA NPs (luminescent agent) using methyl ethyl ketone peroxide as hardener. The curing process was accomplished for a few minutes at room temperature. The diameters of REA NPs were reported in the range of 6–11 nm. The phosphor-concrete composite can be industrially applied onto a variety of hard surfaces. The photoluminescent plastic concrete showed an emission band at 515 nm upon excitation at 372 nm. Persistent photoluminescence was detected for pigment concentrations higher than 1%, whereas fluorescence emission was monitored for pigment concentrations equal to 1%. Photochromism was observed for the prepared plastic concrete as different colors were detected under different light conditions, including colorless under daytime light, green underneath UV rays, and greenish-yellow under darkness as proved by luminescence spectra and CIE Lab parameters. The static contact angle measurements proved good superhydrophobic activity. An improved UV protection and photostability were detected. The photoluminescent hard composite concrete displayed highly durability and reversible persistent afterglow emission. The morphology, elemental composition and hardness features of the prepared plastic concrete were investigated.

Understanding the Surface Condition of Silicone Rubber Nanocomposite Due to Corona Aging Using AFM Imaging and LIBS Spectroscopy

Silicone rubber insulators undergo degradation when they are exposed to corona discharges. The present study explores the surface degradation behavior of silicone rubber alumina nanocomposites due to corona aging using high-frequency ac voltage. The electric field distribution on the sample surface during corona aging is simulated using COMSOL. The change in silicone rubber functional group is studied using Fourier transform infrared (FTIR) spectroscopy analysis. The influence of corona aging time on the surface roughness recovery of silicone rubber nano alumina composites is studied using an atomic force microscopy (AFM). The elemental distribution behavior and change in the emission spectra persistence time are analyzed during recovery period of corona-aged silicone rubber nanocomposites using laser-induced breakdown spectroscopy (LIBS) technique. The addition of alumina nanofiller to the silicone rubber improves the resistance to aging due to corona discharge. Loss and recovery of hydrophobic property of silicone rubber due to corona aging were determined using static contact angle measurement. The results show a direct correlation between the contact angle and the surface roughness recovery characteristics. They indicate that the nanocomposite having a 5 wt% alumina content exhibits the highest resistance to corona discharge with least surface damage. Furthermore, fast recovery was observed in the first few hours after corona aging, and most samples eventually regained their properties after about 8 h of recovery time.

Corrosion Properties of DLC Film in Weak Acid and Alkali Solutions

As an important joint material, tantalum (Ta) needs to be studied intensively in terms of wear and corrosion resistance. Two films of Ta/Ti/DLC (diamond-like carbon) (referred to as TD film) and Ta/Ti/TiN/Ti/DLC (referred to as TTTD film) were prepared by magnetron sputtering technology, and their electrochemical corrosion performance in lactic acid and sodium bicarbonate solutions was also investigated. The morphology observation, electrochemical corrosion experiment, and static contact angle measurement were carried out using a scanning electron microscope, electrochemical workstation, and a contact angle meter. This paper mainly discusses and analyzes the corrosion influencing factors and corrosion mechanisms of these two films under two different environments. The 20-day immersion experiments show that the TD film in both solutions results in severe surface corrosion due to its loose structure and many internal defects. In contrast, the surface of the TTTD film with a dense structure, a multilayer structure, and a thicker thickness is not corroded under the same conditions. The electrochemical corrosion experiments show that the corrosion resistance of the TD film is worse than that of the Ta substrate, while the TTTD film has the strongest corrosion resistance, improving the corrosion resistance of the Ta substrate. Although the TD film had a higher sp3 content than the TTTD film, it does not provide protection to the Ta substrate due to increased structural defects in the TD film. The results of the contact angle show that the contact angle of the TTTD film is smaller than that of the TD film in both solutions. However, the TTTD film has the lowest roughness and the densest structure, and thus the TTTD film is more resistant to corrosion. It is finally concluded that the surface morphology and internal structure of the films are the main factors affecting corrosion resistance. This provides an important reference for the application of DLC film in weak alkaline and weak acid environments.

An in-depth evaluation of sample and measurement induced influences on static contact angle measurements

Static contact angle measurements are one of the most popular methods to analyze the wetting behavior of materials of any kind. Although this method is readily applicable without the need of sophisticated machinery, the results obtained for the very same material may vary strongly. The sensitivity of the measurement against environmental conditions, sample preparation and measurement conduction is a main factor for inconsistent results. Since often no detailed measurement protocols exist alongside published data, contact angle values as well as elaborated wetting studies do not allow for any comparison. This paper therefore aims to discuss possible influences on static contact angle measurements and to experimentally demonstrate the extent of these effects. Sample storage conditions, cleaning procedures, droplet volume, water grade and droplet application as well as the influence of evaporation on the static contact angle are investigated in detail. Especially sample storage led to differences in the contact angle up to 60%. Depending on the wetting state, evaporation can reduce the contact angle by 30–50% within 10 min in dry atmospheres. Therefore, this paper reviews an existing approach for a climate chamber and introduces a new measuring setup based on these results. It allows for the observation of the wetting behavior for several minutes by successfully suppressing evaporation without negatively affecting the surface prior to measurement by exposure to high humidity environments.

Wetting and Adhesion of a Polymer Melt on Porous Self‐Assembled Polymer Substrates by Breath Figure Templating

AbstractThis study addresses the wetting and adhesion of a low molecular mass poly(n‐butyl acrylate) homopolymer melt, used as a weak acrylic adhesive, on two types of textured polymer films prepared by the breath figure templating method. The first film is a polystyrene homopolymer honeycomb‐like structure with well‐defined porous structure and long‐range ordering. The second is a disordered poly(n‐butyl acrylate)‐block‐polystyrene diblock copolymer film featuring a broad distribution of pore diameters. Static contact angle measurements show that porous films repel better the polymer melt than the corresponding nontextured films. Contact angles and spreading of polymer melt droplets on these textured surfaces reveals a Cassie‐Baxter state on the ordered porous film and a partial Wenzel state on the disordered porous films. In addition, probe tack results show that the textured surfaces tend to induce cavitation. The correlation between the wetting and adhesion highlights the major role of melt insertion into the pores, which is primarily controlled by the pores’ dimensions.

Fabrication of Ultrahydrophobic Epoxy Coating Modified by SiO2-PDMS for Corrosion Protection and Self-Cleaning

In this work, ordinary epoxy coatings were modified by hydrophobic nanoSiO2 and hydroxyl PDMS to construct ultrahydrophobic epoxy coatings for corrosion protection and self-cleaning of phosphatized Q235 carbon steel. Ordinary epoxy polymer coating was fabricated via polyaddition reaction between E44 (bisphenol A epoxy resin oligomer) and DDM (4,4-diaminodiphenyl methane). The microscopic morphologies of coatings showed that many SiO2 nanoparticles were presented on the surface of ultrahydrophobic epoxy coating. Through static water contact angle measurement, the modified epoxy coating displayed ultrahydrophobicity with a water contact angle of approximately 150°. However, adding too much nanoSiO2 caused cracks on the modified epoxy coating, which deteriorated the corrosion resistance of the coating. According to the corrosion test results, the modified coating added with 6.7 wt% hydrophobic nanoSiO2 and chemically modified with hydroxyl PDMS showed the best corrosion protection performance, which was reflected by the high impedance of approximately 109 Ω·cm2 after 50 d immersion in 3.5 wt% NaCl (aq.). Besides, the coating also presented good self-cleaning performance. The coating extracted from the slurry still remained clean without any contamination.

Surface modification of polycarbonate urethane by grafting polyethylene glycol and bivalirudin drug for improving hemocompatibility

AbstractAs the clinical demand for blood‐contacting materials increases, higher requirements are placed on their physicochemical properties, durability and hemocompatibility in vivo. In this work, a multiple functionalized material was developed through a facile modification process. Herein, polycarbonate urethane (PCU) surface was co‐modified with polyethylene glycol (PEG) and bivalirudin (BVLD). PCU provides excellent physical and mechanical properties, PEG and BVLD, especially BVLD, enable the surface with outstanding anticoagulant capacity. Specifically, PCU surface was first treated with hexamethylene diisocyanate to introduce active isocyanate groups onto the surface, followed by hydroxy‐PEG grafting to improve the hydrophilicity. Finally, BVLD was immobilized on the surface via Michael addition reaction to improve antithrombotic properties. Attenuated total reflection Fourier transforms infrared spectroscopy and UV spectrophotometers were used to confirm the modified surfaces. The hydrophilicity was characterized by static water contact angle measurement, the morphology of the modified surfaces was observed by scanning electron microscopy. Blood compatibility of the modified surfaces was characterized by the hemolysis rate, platelet adhesion assay and cell culture test. The results showed that the BVLD immobilized surface has excellent anticoagulant properties, good fibrin‐bound thrombin inhibition, and good resistance against non‐specific adhesion of proteins. Hence, the co‐modification with PEG and BVLD was proved an encouraging strategy for improving hemocompatibility.

Influence of Sharklet-Inspired Micropatterned Polymers on Spatio-Temporal Variations of Marine Biofouling.

This article aims to show the influence of surface characteristics (microtopography, chemistry, mechanical properties) and seawater parameters on the settlement of marine micro- and macroorganisms. Polymers with nine microtopographies, three distinct mechanical properties, and wetting characteristics are immersed for one month into two contrasting coastal sites (Toulon and Kristineberg Center) and seasons (Winter and Summer). Influence of microtopography and chemistry on wetting is assessed through static contact angle and captive air bubble measurements over 3-weeks immersion in artificial seawater. Microscopic analysis, quantitative flow cytometry,metabarcoding based on the ribulose biphosphate carboxylase (rbcL) gene amplification, and sequencing are performed to characterize the settled microorganisms. Quantification of macrofoulers is done by evaluating the surface coverage and the type of organism. It is found that for long static in situ immersion, mechanical properties and non-evolutive wettability have no major influence on both abundance and diversity of biofouling assemblages, regardless of the type of organisms. The apparent contradiction with previous results, based on model organisms, may be due to the huge diversity of marine environments, both in terms of taxa and their size. Evolutive wetting properties with wetting switching back and forth over time have shown to strongly reduce the colonization by macrofoulers.

Sialic acid biosensing by post-printing modification of PEDOT:PSS with pyridylboronic acid

ABSTRACT A poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based conducting polymer, which has biorecognition capabilities, has promising biosensing applications. Previously, we developed a facile method for post-printing chemical modification of PEDOT:PSS thin films from commercial sources. Molecular recognition elements were directly introduced into the PSS side chain by a two-step chemical reaction: introduction of an ethylenediamine linker via an acid chloride reaction of the sulfonate moiety, and subsequent receptor attachment to the linker via amine coupling. In this study, the same method was used to introduce 6-carboxypyridine-3-boronic acid (carboxy-PyBA) into the linker for specifically detecting N-acetylneuraminic acid (sialic acid, SA), as a cancer biomarker. The surface-modified PEDOT:PSS films were characterized by X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and static water contact angle and conductivity measurements. The specific interaction between PyBA and SA was detected by label-free reagent-free potentiometry. The SA-specific negative potential responses of modified PEDOT:PSS electrodes, which was ascribed to an SA carboxyl anion, were observed in a physiologically relevant SA range (1.6–2.9 mM) at pH 5, in a concentration-dependent manner even in the presence of 10% fetal bovine serum. The sensitivity was −2.9 mV/mM in 1–5 mM SA with a limit of detection of 0.7 mM. The sensing performances were almost equivalent to those of existing graphene-based electrical SA sensors. These results show that our chemical derivatization method for printing PEDOT:PSS thin films will have applications in SA clinical diagnostics.

Hemocompatible polydimethylsiloxane/polysulfone ultrathin composite membrane for extracorporeal membrane oxygenation

Although dense polydimethylsiloxane (PDMS) membranes, the first membranes used for extracorporeal membrane oxygenation (ECMO) system, exhibited biological inertness with no plasma leakage or air embolism occurred during oxygenation process, they also displayed low CO2/O2 exchange capacities due to the large membrane thickness making up for the low material mechanical strength. Herein, polydimethylsiloxane/polysulfone (PDMS/PSF) composite membranes were firstly synthesized with an ultra-thin PDMS dense layer coated on PSF porous substrate of excellent mechanical strength, then characterized by SEM, EDS, TGA, zeta potential and static contact angle measurements for structural and surface property analyses, and further evaluated for their CO2/O2 permeation and hemocompatibility performances as well as the influence of sterilization on the properties. Characterization results showed that an ultra-thin PDMS dense layer were successfully coated on PSF substrate and the composite membranes obtained demonstrated thermostability, surface electronegativity and hydrophobicity. Gas permeation analyses indicated that the composite membranes exhibited efficient CO2/O2 exchange capacity with an optimum CO2 permeability of ∼ 2700GPU at atmospheric pressure and a CO2/O2 selectivity of ∼ 6. Moreover, hemocompatibility analyses demonstrated that the PDMS/PSF composite membranes in current work displayed comparable blood compatibility to other membranes investigated. Meanwhile, autoclave was proved feasible for membrane sterilization with no adverse effects on the performances of PDMS/PSF composite membranes. These findings suggested that PDMS/PSF composite membranes showed great application potential in ECMO system, and provided basic data for further exploration and modifications.

Contamination and carryover free handling of complex fluids using lubricant-infused pipette tips

Cross-contamination of biological samples during handling and preparation, is a major issue in laboratory setups, leading to false-positives or false-negatives. Sample carryover residue in pipette tips contributes greatly to this issue. Most pipette tips on the market are manufactured with hydrophobic polymers that are able to repel high surface tension liquids, yet they lack in performance when low surface tension liquids and viscous fluids are involved. Moreover, hydrophobicity of pipette tips can result in hydrophobic adsorption of biomolecules, causing inaccuracies and loss in precision during pipetting. Here we propose the use of lubricant-infused surface (LIS) technology to achieve omniphobic properties in pipette tips. Using a versatile and simple design, the inner lumen of commercially available pipette tips was coated with a fluorosilane (FS) layer using chemical vapor deposition (CVD). The presence of FS groups on the tips is confirmed by x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) tests. After lubrication of the tips through a fluorinated lubricant, the omniphobicity and repellent behaviour of the tips drastically enhanced which are revealed via static and hysteresis contact angle measurements. The repellency of the lubricant-infused pipette tips against physical adsorption is investigated through pipetting a food coloring dye as well as human blood samples and are compared to the untreated tips. The results show significantly less amount carryover residue when the lubricant-infused tips are utilized compared to commercially available ones. We also demonstrate the lubricant-infused tips reduce bacteria contamination of the inner lumen by 3 to 6-log (over 99%, depending on the tip size) after pipetting up and down the bacteria solution.