Liquid Polydimethylsiloxane Research Articles

Effective capillary pressure and permeability of a granular material during imbibition in a closed column

We present a method to determine the effective capillary pressure and permeability of a column packed with a granular material by means of imbibition experiments using a closed column and measuring both the liquid uptake and pressure differential that develops ahead of the liquid front. The method is based on finding an intermediate range of pressure differential values, where a Washburn approximation is no longer valid but a recently obtained effective description accurately reproduces the experimental results. To determine this intermediate range of pressures we calculate the goodness of fit corresponding to both the Washburn pressure-solution, valid at short times, and the implicit pressure-solution, which includes the non-linear dependence of the pressure on the liquid uptake and is compatible with finely divided solids. Using a closed column also allow us to compare the effective capillary pressure with the maximum advancing pressure measured using Bartell’s static method. We perform experiments using liquid polydimethylsiloxane, and glass beads or lactose powder. We show that an effective description of the liquid imbibition is possible and determine the corresponding capillary pressure and permeability that characterize the granular system. We observe that the heterogeneity of the system reduces the characterization range. However, it was possible to characterize lactose powder columns, where the heterogeneity leads to spontaneous bubbling and static measurements are not possible.

Multifunctional Hard Yet Flexible Coatings Fabricated Using a Universal Step-by-Step Strategy.

Hard yet flexible coatings with multi‐functionalities are useful for foldable displays and marine industries but rare. In this study, a highly cross‐linked multifunctional hybrid coating with ceramic‐like hardness and polymer‐like flexibility is reported. The coating is prepared via a step‐by‐step strategy, where two types of epoxy‐oligosiloxane nanoclusters are first synthesized by sol‐gel chemistry, and amine‐terminated curing agents are used to cross‐link them at room temperature. The coating is highly transparent (>92% transmittance), hard (6‐7H), and flexible (10 mm bending diameter) because of the unique combination of siloxane nanoclusters and polymer networks. Meanwhile, since the coating contains fouling‐resistant telomer and low‐surface‐tension liquid lubricant polydimethylsiloxane (PDMS), it exhibits excellent anti‐biofouling and self‐cleaning properties. The results indicate that the mechanical and antifouling properties of the coating can be easily tuned and prove that the step‐by‐step strategy is a promising and universal method. The novel coatings can meet the needs of applications in foldable displays, marine industries, and other fields.

Influence of laser processing conditions for the manufacture of microchannels on ultrahigh molecular weight polyethylene coated with PDMS and PAA

<abstract> <p>Ultrahigh molecular weight polyethene (UHMWPE) is employed as a bearing material in a range of applications due to its improved elasticity, compatibility, and impact resistance, processing conditions for a suitable surface texture are necessary. Surface texture processing on microchannels using lasers is always associated with the effect of heat damage on the polymer specimen surface. This study aims to explore the use of polydimethylsiloxane (PDMS) and polyacrylic acid (PAA) in the form of liquid gel coatings in order to reduce heat damage to surfaces during the laser processing of ultrahigh molecular weight polyethene (UHMWPE). First, PDMS and PAA were coated on the surface of the UHMWPE material specimen, and then texturing was performed using a laser diode and cleaned using the ultrasonic method. Second, the dimensions and texture profiles of all the samples from this study were measured using a confocal microscope and open source software. In addition, the effect of adding liquid gel on the surface at 150 µm thickness and laser power parameters was determined. The results show that the PDMS and PAA liquid gel layers help regulate the dimensional bulge of the fabricated microchannels at laser powers below 6 watts, compared to those produced without the coating.</p> </abstract>

The Design and Fabrication of Water-Resistant Sticky Mosquito Polypropylene Net and Its Application in Capturing Mosquitoes

In this work, inspired by the structure of spider web, the water-resistant sticky polypropylene (PP) net was fabricated for capturing mosquitoes here. The waterresistant pre-glue was first obtained through mixing liquid polydimethylsiloxane (PDMS), solid polytetrafluoroethylene (PTFE) microparticles and tetraethyl silicate (TEOS), where TEOS was used as cross linker to enhance adhesion strength. The sticky mosquitoes PP net was obtained through heating the PP net painted with the water-resistant pre-glue uniformly on the two sides of PP net at 60°C for 2 days. This sticky mosquitoes PP net works well in sticking mosquitoes even in the humid air.

Chemically and electrostatically double-crosslinked composite underwater adhesive

A hydrophobic composite underwater adhesive was constructed through simultaneously mixing liquid polydimethylsiloxane (PDMS), micro particle polytetrafluoroethylene (PTFE) and tetraethyl silicate (TEOS) together according to the different mass ratio of component and subsequently heating crosslinking reaction. The electrostatic interaction between hydrogen atoms charged partially positively in PDMS and fluorine atoms charged partially negatively in PTFE contribute the adhesive captivity of PDMS/PTFE while the crosslinking reaction of TEOS with PDMS will enhance further effectively mechanical properties of adhesives. The adhesive ability and sustainable time to various substrate were evaluated systematically.

Buckling Behaviors at the Interface of Liquid–Solid Systems

Buckling patterns are universal in organs of living organisms. Moreover, the functional realization of these organs is precisely dependent on the deformation of buckling structures, which is also related to the effect of interfacial interaction between liquid and solid surfaces. However, the detection of synergistic reaction between the buckling pattern and the effect of liquid–solid interface is absent. Herein, an experimental simulation of buckling behaviors at the solid–liquid interface, that is, by depositing Au atoms on liquid polydimethylsiloxane (PDMS) is developed. Buckling patterns can be directly created at the interface of Au atoms film and liquid PDMS. Furthermore, it is demonstrated that the orientation of buckling structures can be strictly controlled depending on the frame edges placed on the surface of the liquid PDMS before the deposition. Various ordered buckling patterns, such as parallel wrinkles pattern, magnetic‐field‐lines‐like buckling pattern, and bionic patterns, can be prepared depending on this buckling behavior. The experimental simulation of the buckling behavior at the liquid–solid interface is well promoted, which may be further helpful in understanding the effect of interfacial interaction between liquid and solid surfaces.

Use of liquid lithography to form in vitro intestinal crypts with varying microcurvature surrounding the stem cell niche

Objective. The role of the crypt microarchitecture and surrounding tissue curvature on intestinal stem/proliferative cell physiology is unknown. The utility of liquid lithography in creating polydimethylsiloxane (PDMS) micropillar stamps with controlled tip curvature was assessed. Using these stamps, the impact of microcurvature at the crypt base on intestinal cell and cytoskeletal behavior was studied. Approach. An SU-8 master mold as a support, polyols of varying surface energies as sacrificial liquids, and liquid PDMS as the solidifiable material were combined using liquid lithography to form PDMS micropillar arrays. Vapor phase deposition of organosilane onto the master mold was used to modify the surface energy of the master mold to shape the micropillar tips. Collagen was molded using the micropillar arrays forming a scaffold for culture of human primary colonic epithelial cells. Cell proliferation and cytoskeletal properties were assessed using fluorescent stains. Main results. Liquid lithography using low surface energy polyols (<55 dynes cm−1) generated convex-tipped PDMS micropillars, while polyols with higher surface energies (>55 dynes cm−1) yielded concave-tipped PDMS micropillars. Gradients of octyltrichlorosilane deposition across a master mold with an array of microwells yielded a PDMS micropillar array with a range of tip curvatures. Human primary colonic epithelial cells cultured on micropillar-molded collagen scaffolds demonstrated a stem/proliferative cell compartment at the crypt base. Crypts with a convex base demonstrated significantly lower cell proliferation at the crypt base than that of cells in crypts with either flat or concave bases. Crypts with a convex base also displayed higher levels of G-actin activity compared to that of crypts with flat or concave bases. Significance. Liquid lithography enabled creation of arrays of in vitro colonic crypts with programmable curvature. Primary cells at the crypt base sensed and responded to surface curvature by altering their proliferation and cytoskeletal properties.

Mechanical Activation, Mineral Powders, Chemical Modification, Solid-Phase Reactivity, Polyorganosiloxanes

Mechanochemical reactivity of nonfunctional organosilicon polymers with the most typical structure (linear, cyclolinear, three-dimensional) was studied: polyphenylsiloxane (PPS), polyvinylsiloxane (PVS), polydimethylsiloxane liquid (PMS-6) and dimethylsiloxane rubber (SKTN).

A novel technique to fabricate magnetic polydimethylsiloxane micropillar

AbstractIn past decades, polymeric micropillars have been employed in many complex functional micro‐devices, such as micro‐fluids, micro‐sensors, tunable wetting surfaces, and substrate structures. This paper presents a novel technique to fabricate high‐aspect‐ratio magnetic polydimethylsiloxane (PDMS) micropillars that can move under gradient magnetic fields. First, a drop of Fe3O4 superparamagnetic nanoparticles was dispersed in acetone solution, sonicated, and poured over a pre‐etch silicon mold with deep micro‐holes. Second, we quickly attracted Fe3O4 nanoparticles in micro‐holes with a strong permanent magnet at the silicon mold's backside. Third, we used a soft lithography process to force the PDMS liquid to flow into the micro‐holes by sequencing the air in a vacuum chamber, baked in a hot plate, and then peeled off in ethanol solution and dried in a CO2 dryer machine. The diameters of PDMS magnetic micropillars were from 1 μm, 2 μm to 10 μm, and the heights were 30 μm and 50 μm. We observed 1 μm micropillar with 50 aspect ratio could deflect its end up to 12 μm under a gradient magnetic field of 5 mT/mm. The magnetic micropillar end movement in an ethanol solution was validated, which broads the application to micro‐fluidics and other liquid microdevices. The energy‐dispersive X‐ray spectroscopy also examined the iron percentage in PDMS micropillars. They were in a range of 42% to 81.4%; with the median value was 59.6% that is the highest value reported in the literature, to our best knowledge.

Enhancing the Yield Stress in Liquid Polydimethylsiloxane to Allow Its 3D Printing: Hydrogels as Removable Fillers

AbstractFor manufacturing parts of very soft materials by liquid deposition modeling (e.g., to mimic living soft tissues), formulations of 3D‐printable polydimethylsiloxane have been developed, with the aim of increasing the yield stress of the liquid and reducing the final mechanical modulus. In the present work, suspensions of solid‐like hydrogel particles, which are easily 3D‐printable, are prepared in order to generate yield stress, and the suspended phase is removed after manufacturing by taking advantage of the thermo‐reversibility of the hydrogel behavior, resulting in porosity, which reduces the final rigidity. The reported approach is even more efficient than a previous approach based on emulsion formulations.

Измерение пробивного напряжения вязких жидкостей

The national standards on measuring the breakdown voltage of liquid dielectrics are considered, in particular, the measurement procedure and the measuring cell main parameters. The breakdown voltage of PDMS-1000, PDMS-12500 and PDMS-30000 liquids produced by various manufacturers was measured, and the main problems faced in carrying out measurements were identified. It is shown, using the example of polydimethylsiloxane liquid dielectrics, that after breakdown of viscous liquids, a channel is produced in them, which consists of gas bubbles held by the surface tension force, due to which the channel may in many cases persist for a long time. Theoretical calculations confirmed by an experiment were performed, based on which the velocity of air bubbles in polydimethylsiloxane liquids can be estimated. A conclusion has been drawn about the necessity to increase the time intervals between individual measurements, as well as the time interval before the start of measurements after pouring the test liquid into the measurement cell. It is shown that visual control of the interelectrode region and a special method of mixing the liquid are also necessary. It can be stated based on the accomplished study that the existing standards for breakdown voltage measurements in viscous liquids need to be refined.

Supercooling suppression of phase change liquid metal–polydimethylsiloxane soft composites

Supercooling is suppressed in liquid metal polydimethylsiloxane composites for the first time.

The State of Water in the Zoogley of the Tibetan Milk Fungus and the Effect of Liquid Polydimethylsiloxane on It

The State of Water in the Zoogley of the Tibetan Milk Fungus and the Effect of Liquid Polydimethylsiloxane on It

Role of in‐situ polymethyl‐methacrylate in addition type silicone rubber with specific reference to adhesion and damping properties

AbstractHerein, a strategy of embedding in‐situ polymethyl‐methacrylate (PMMA) domains in polydimethylsiloxane (PDMS) networks is proposed to enhance adhesive and damping properties of addition type silicone rubber (SR). PMMA domains improve the modulus of SR (at room temperature), which is stronger correlated to its adhesive performance, according to the Griffith criterion. Besides, the damping performance at high temperature is provided by the glass transition of thermoplastic PMMA. The PMMA/SR blends are obtained by the crosslink of PMMA and vinyl‐terminated polydimethylsiloxane (vi‐PDMS) liquid blends with polymethylhydrosiloxane, and the PMMA/vi‐PDMS liquid blends are prepared by in‐situ radical polymerization of methyl‐methacrylate (MMA) in vi‐PDMS with toluene as compatibilizer. Effects of disperse speed, compatibilizer content, and PMMA proportion on the morphologies and properties of PMMA/SR blends are studied. Small PMMA domains (around 800 nm) in PMMA/vi‐PDMS blends with narrow size distribution and well dispersion are formed at appropriate disperse speed (100–300 rpm) and abundant compatibilizer content (~100 wt% refers to vi‐PDMS). The blends with 20 wt% PMMA possess tensile strength over 8 MPa and lap shear strength over 5 MPa to stainless steel. And the blends with 50 wt% PMMA show good damping properties with tan δ over 0.15 at temperature range from −50 to 150°C. Tg‐PMMA moves slightly to lower temperature with less PMMA embedded, but Tg‐PDMS remained stable relatively.

Diphenylsiloxane–dimethylsiloxane copolymer: Optical functions from 191 to 1688 nm (0.735–6.491 eV) by spectroscopic ellipsometry

We report the optical functions of diphenylsiloxane-dimethylsiloxane (DPS-DMS) copolymer as determined from reflection spectroscopic ellipsometry (SE) and transmission ultraviolet-visible data, which were generated over 191–1688 nm from a commercial sample of DPS-DMS. This material is a random, linear copolymer terminated with silanol groups that is a liquid at room temperature and pressure. Both reflection and transmission measurements required special experimental considerations. The reflection SE measurements utilized the “rough-surface” method, wherein the liquid was poured onto a roughened (frosted) glass slide, which scatters the reflected light leaving only the reflection from the liquid surface. That is, there is effectively no substrate or material beneath the liquid that affects the ellipsometry measurements or that needs to be modeled. Transmission measurements were obtained via a dual cuvette approach to eliminate the effects of the cuvettes. The reflection data provided the refractive index across the entire spectral range as well as the extinction coefficient at ultraviolet wavelengths. The transmission measurements provided input for the extinction coefficients at visible and near infrared wavelengths, where the liquid is transparent or semitransparent. The reflected SE data were modeled using a Sellmeier dispersion model and six Gaussian oscillators plus a surface roughness layer. This produced a good fit with a mean squared error (MSE) of 2.41. For example, we obtained the following n(λ) values, where λ is the wavelength in nanometers: n(300) = 1.534, n(500) = 1.477, and n(1000) = 1.458. As expected, the refractive index of DPS-DMS is higher than that of liquid polydimethylsiloxane.

Plasma-induced Interfacial Crosslinking of Liquid Polydimethylsiloxane Films and Their Organic Solvent Permeation Performance

Polydimethylsiloxane (PDMS) has been extensively studied as a separation membrane due to the high permeability of gases and organic solvents. Here we report 60-nm-thick PDMS membranes prepared by i...

3D Printing Silicone Elastomer for Patient-Specific Wearable Pulse Oximeter.

Commercial pulse oximeters are used clinically to measure heart rate and blood oxygen saturation and traditionally made from rigid materials. However, these devices are unsuitable for continuous monitoring due to poor fit and mechanical mismatch. Soft materials that match the elastic properties of biological tissue provide improved comfort and signal-to-noise but typically require molding to manufacture, limiting the speed and ease of customizing for patient-specific anatomy. Here, freeform reversible embedding (FRE) 3D printing is used to create polydimethylsiloxane (PDMS) elastomer cuffs for use on the hand and foot. FRE enables printing liquid PDMS prepolymer in 3D geometries within a sacrificial hydrogel bath that provides support during cure. This serves as proof-of-concept for fabricating patient-specific pulse oximeters with pressure sensing, termed P3 -wearable. A sizing analysis establishes dimensional accuracy of FRE-printed PDMS compared to anatomical computer-aided design models. The P3 -wearable successfully outputs photoplethysmography (PPG) and pressure amplitude signals wirelessly to a tablet in real time and the PPG is used to calculate heart rate, blood oxygen content, and activity state. The results establish that FRE printing of PDMS can be used to fabricate patient-specific wearable devices and measure heart rate and blood oxygenation on par with commercial devices.

The role of charge states in the self-organization of detonation nanodiamonds nanoparticles

The self-organization of detonation nanodiamond particles in dielectric liquid polydimethylsiloxane has been studied by broadband dielectric spectroscopy. Frequency dependences of the conductivity and the complex modulus of dielectric permittivity were measured. The structure of nanodiamond suspensions has been studied by small-angle X-ray scattering as well. Electrophysical properties of detonation nanodiamond suspensions, namely conductivity and permittivity, strongly depend on the particle surface chemistry. The temperature dependences show the activation nature of polarization processes. The model explaining observed effects has been proposed.

In Situ Inkjet Printing of the Perovskite Single-Crystal Array-Embedded Polydimethylsiloxane Film for Wearable Light-Emitting Devices.

Metal halide perovskites are promising light-emitting materials for applications such as wearable lighting devices and flat panel displays because of their high photoluminescence efficiency, high color purity, and facile solution processability. However, the intrinsic ambient instability and crystal friability issues have fundamentally hindered the practical applications of perovskites. Here, we solve this problem through a liquid to liquid self-encapsulation inkjet-printing technique. Perovskite inks are directly inkjet-printed into the liquid polydimethylsiloxane (PDMS) precursor to in situ form the self-encapsulation perovskite single-crystal-embedded PDMS structure. We show that the space-confined effect of the liquid PDMS precursor can significantly retard the perovskite crystallization process and promote the embedded growth of perovskite single crystals in PDMS. Benefiting from the sealing function of PDMS, the printed perovskite single crystals show excellent ambient stability and flexibility. Furthermore, we demonstrate that wafer-scale air-stable and flexible perovskite fluorescent patterns can be produced in PDMS by direct inkjet printing, which is cost-effective and free of complex microfabrication processes. This method provides a facile approach to scalable fabrication of air-stable and wearable perovskite fluorescent patterns, which will be of great significance for potential application in perovskite light-emitting diode display.

Stretchable and conductive composites film with efficient electromagnetic interference shielding and absorptivity

The development of high-performance stretchable and electromagnetic interference (EMI) shielding materials is crucial to the rapidly growing industry of next-generation flexible electronics such as portable electronics and wearable devices. The common approach to EMI shielding is to increase the contents of conductive materials and improve the conductivity. However, this approach is limited by the worse stretchable property. An intrinsically stretchable conductive and EMI shielding thin film (thickness of 0.7 mm) based on functional adhesive (FA) composited by silver nanoparticles (Ag NPs), nickel nanoparticles (Ni NPs), and liquid polydimethylsiloxane (PDMS) is proposed in this paper. The FA is coated onto cured PDMS substrates to fabricate the film, achieving maximum tensile strain of 250% and EMI shielding effectiveness (SE) of 57.1 dB. Up to 35% absorptivity makes an important contribution to SE. This film can withstand more than 20000 stretching-releasing cycles at tensile strain of 0–100% and 0–150%, with no delamination, demonstrating its superior stretchability and repeatability. The mechanism of EMI shielding of silver and nickel nanoparticles is discussed. The durability of these films in terms of electrical and EMI SE properties are also tested. In addition, a device to change the output power of a transformer is constructed.