Use Of Polydimethylsiloxane Research Articles

Rapid response, superior stable, and durable pressure sensor with rGO/CNC interdigital electrode

The development of pressure sensors with swift responsiveness and exceedingly high stability is an inevitable requirement for wearable electronic devices. Herein, we fabricated a high performance pressure sensor through the encapsulation of an interdigital electrode with employing polydimethylsiloxane (PDMS). The pressure sensor comprised self-assembled multifunctional reduced graphene oxide/cellulose nanocrystalline (rGO/CNC) composite film with interdigital electrode (RCI), and involves the use of PDMS to enhance the robustness and pressure sensitivity of the pressure sensor. The sensing enhancement is reflected in minimal conductive attenuation, under 30 min ultrasonic with a ΔR/R0 < 0.1 % in the initial phase and an impressive response time of 51 ms. Due to the outstanding performance, a smart glove that is integrated with the RCI sensor not only performs well timely feedback on human motions, but also achieves intelligent recognitions of various gestures assisted by neural network algorithms (the accuracy up to 99.1 %). Furthermore, this study offers an innovative decoupling method that effectively separates contact interface resistance and body resistance. The developed piezoresistive sensor and decoupling method are meaningful and valuable to long-term intelligent health management and human–machine interactions applications.

Advancing diagnostics and disease modeling: current concepts in biofabrication of soft microfluidic systems

Soft microfluidic systems play a pivotal role in personalized medicine, particularly in in vitro diagnostics tools and disease modeling. These systems offer unprecedented precision and versatility, enabling the creation of intricate three-dimensional (3D) tissue models that can closely emulate both physiological and pathophysiological conditions. By leveraging innovative biomaterials and bioinks, soft microfluidic systems can circumvent the current limitations involving the use of polydimethylsiloxane (PDMS), thus facilitating the development of customizable systems capable of sustaining the functions of encapsulated cells and mimicking complex biological microenvironments. The integration of lab-on-a-chip technologies with soft nanodevices further enhances disease models, paving the way for tailored therapeutic strategies. The current research concepts underscore the transformative potential of soft microfluidic systems, exemplified by recent breakthroughs in soft lithography and 3D (bio)printing. Novel applications, such as multi-layered tissues-on-chips and skin-on-a-chip devices, demonstrate significant advancements in disease modeling and personalized medicine. However, further exploration is warranted to address challenges in replicating intricate tissue structures while ensuring scalability and reproducibility. This exploration promises to drive innovation in biomedical research and healthcare, thus offering new insights and solutions to complex medical challenges and unmet needs.

Properties of Superhydrophobic and Acid–Alkali-Resistant Polyester Fabric Produced Using Plasma Processing

During the processes of production, storage, transportation and use of hazardous chemicals, acid–alkali corrosive liquid spatter and leakage would cause serious casualties. In order to protect the lives and health of staff, the surface of fabrics should be treated to obtain hydrophobicity and acid–alkali resistance. In this paper, polyester fabric was used as the base cloth, and polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE) micro-powder were used as the functional materials to fabricate waterproof and breathable fabric with good acid–alkali resistance using a method of plasma pretreatment-impregnation- and plasma-induced crosslinking. The effects of PDMS, PTFE powder and plasma-induced crosslinking on the surface and physical and chemical properties of fabric were investigated. It was found that the use of PDMS and PTFE powder had little effect on the mechanical and wearing comfort properties. However, it could significantly improve the acid–alkali resistance, as the liquid repellent rate of the treated fabric surface was higher than 80%, and the penetration index was lower than 2%.

Mechanochemically robust hydrophobic fabric using an aqueous emulsion of amine-terminated polydimethylsiloxane

Polydimethylsiloxane (PDMS) is a highly reliable thermosetting polymer with exceptional chemical and mechanical resistance, as well as remarkable water repellency and adhesive performance. Its unique features make it the preferred choice for fluorine-free hydrophobic coatings. However, the use of PDMS requires organic solvents that are toxic and environmentally hazardous. In this study, an emulsion composed of amine-terminated polydimethylsiloxane (PDMS-NH2) in an environmentally friendly solvent, water, was prepared. Subsequently, glutaraldehyde (GA) was added and crosslinked to generate a hydrophobic PDMS–GA emulsion. The PDMS–GA emulsion is a low-viscosity solution that can infiltrate different types of fabrics (cotton, nylon, and polyester) or paper with numerous intertwined fibers. After dipping the fabrics and paper into the prepared PDMS–GA emulsion, they were washed in an aqueous solution containing dispersed kaolin particles and dried to yield a rough structure. As a result, a hydrophobic surface with a water contact angle of 151.2° was achieved. Furthermore, after exposure to strongly acidic or alkaline solutions (pH 1–13) and washing six times with water, the hydrophobic fabric remained chemically stable. Additionally, it withstood ten tape peeling tests, proving its mechanical durability. Crucially, the hydrophobic treatment method does not involve fluorine and uses eco-friendly water as the solvent. Therefore, this is a convenient way to apply waterproof coatings to functional textiles that require water resistance and are expected to have great industrial applications.

Inexpensive and rapid fabrication of PDMS microfluidic devices for biological testing applications using low cost commercially available 3D printers

Polydimethylsiloxane (PDMS) elastomers have been extensively used in the development of microfluidic devices, capable of miniaturizing biomolecular and cellular assays to the microlitre and nanolitre range, thereby increasing the throughput of experimentation. PDMS has been widely used due to its optical clarity and biocompatibility, among other desirable physical and chemical properties. Despite the widespread use of PDMS in microfluidic devices, the fabrication process typically via soft lithography technology requires specialized facilities, instruments, and materials only available in a limited number of laboratories. To expand microfluidic research capabilities to a greater scientific population, we developed and characterized a simple and robust method of fabricating relatively inexpensive PDMS microfluidic devices using readily available reagents and commercially available three-dimensional (3D) printers. The moulds produced from the 3D printers resolve designed microfluidic channel features accurately with high resolution (>100 µm). The critical physical and chemical post-processing modifications we outline here are required to generate functional and optically clear microfluidic devices.

Microfluidic System for Cell Mixing and Particle Focusing Using Dean Flow Fractionation

Recent developments in the field of additive manufacturing processes have led to tremendous technological progress and opened directions for the field of microfluidics. For instance, new flexible materials for 3D printing allow the substitution of polydimethylsiloxane (PDMS) in microfluidic prototype development. Three-dimensional-printed microfluidic components open new horizons, in particular for the automated handling of biological cells (e.g., eukaryotic cells or bacteria). Here, we demonstrate how passive mixing and passive separation processes of biological cells can be realized using 3D printing concepts for rapid prototyping. This technique facilitates low-cost experimental setups that are easy to modify and adopt for specific detection and diagnostic purposes. In particular, printing technologies based on fused deposition modeling and stereolithography are used and their realization is discussed. Additive technologies enable the fabrication of multiplication mixers, which overcome shortcomings of current pillar or curve-based techniques and enable efficient mixing, also of biological cells without affecting viability. Using standard microfluidic components and state-of-the art 3D printing technologies, we realize a separation system based on Dean flow fragmentation without the use of PDMS. In particular, we describe the use of a 3D-printed helix for winding a capillary for particle flow and a new chip design for particle separation at the outlet. We demonstrate the functionality of the system by successful isolation of ~12 µm-sized particles from a particle mixture containing large (~12 µm, typical size of eukaryotic cells) and small (~2 µm, typical size of bacteria or small yeasts) particles. Using this setup to separate eukaryotic cells from bacteria, we could prove that cell viability is not affected by passage through the microfluidic systems.

A New Perspective on SPME and SPME Arrow: Formaldehyde Determination by On-Sample Derivatization Coupled with Multiple and Cooling-Assisted Extractions.

Formaldehyde (FA) is a toxic compound and a human carcinogen. Regulating FA-releasing substances in commercial goods is a growing and interesting topic: worldwide production sectors, like food industries, textiles, wood manufacture, and cosmetics, are involved. Thus, there is a need for sensitive, economical, and specific FA monitoring tools. Solid-phase microextraction (SPME), with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBHA) on-sample derivatization and gas chromatography, is proposed for FA monitoring of real-life samples. This study reports the use of polydimethylsiloxane (PDMS) as a sorbent phase combined with innovative commercial methods, such as multiple SPME (MSPME) and cooling-assisted SPME, for FA determination. Critical steps, such as extraction and sampling, were evaluated in method development. The derivatization was performed at 60 °C for 30 min, followed by 15 min sampling at 10 °C, in three cycles (SPME Arrow) or six cycles (SPME). The sensitivity was satisfactory for the method's purposes (LOD-LOQ at 11-36 ng L-1, and 8-26 ng L-1, for SPME and SPME Arrow, respectively). The method's linearity ranges from the lower LOQ at trace level (ng L-1) to the upper LOQ at 40 mg L-1. The precision range was 5.7-10.2% and 4.8-9.6% and the accuracy was 97.4% and 96.3% for SPME and SPME Arrow, respectively. The cooling MSPME set-up applied to real commercial goods provided results of quality comparable to previously published data.

Mechanobiological Analysis of Nanoparticle Toxicity.

Nanoparticles (NPs) are commonly used in healthcare and nanotherapy, but their toxicity at high concentrations is well-known. Recent research has shown that NPs can also cause toxicity at low concentrations, disrupting various cellular functions and leading to altered mechanobiological behavior. While researchers have used different methods to investigate the effects of NPs on cells, including gene expression and cell adhesion assays, the use of mechanobiological tools in this context has been underutilized. This review emphasizes the importance of further exploring the mechanobiological effects of NPs, which could reveal valuable insights into the mechanisms behind NP toxicity. To investigate these effects, different methods, including the use of polydimethylsiloxane (PDMS) pillars to study cell motility, traction force production, and rigidity sensing contractions, have been employed. Understanding how NPs affect cell cytoskeletal functions through mechanobiology could have significant implications, such as developing innovative drug delivery systems and tissue engineering techniques, and could improve the safety of NPs for biomedical applications. In summary, this review highlights the significance of incorporating mechanobiology into the study of NP toxicity and demonstrates the potential of this interdisciplinary field to advance our knowledge and practical use of NPs.

Development and evaluation of microwave microfluidic devices made of polydimethylsiloxane

A transparent, optically observable microfluidic device for microwave-induced chemical reactions using 24.125 GHz ISM band incorporating was developed. The microfluidic channels can pass through gaps in the post-wall waveguide. The post-wall waveguide allows microwave irradiation to be applied to designed area of the microfluidic channel. In this study, Polydimethylsiloxane (PDMS), commonly used in microfluidic devices, was used as the microwave waveguide material. A glass plate sputtered with indium tin oxide was used to shield microwave leakage to the top and bottom. 4 W of microwave input power was used to heat ethylene glycol, which is used as a solvent in chemical synthesis, in the channels of the fabricated device, and a temperature rise to 100 °C was observed in 70 s. We believe that the use of PDMS as a waveguide material will facilitate observation during microwave irradiation using optics and combination with other microreactors.

Improving Sustainability of the Griess Reaction by Reagent Stabilization on PDMS Membranes and ZnNPs as Reductor of Nitrates: Application to Different Water Samples.

A new approach based on the use of polydimethylsiloxane (PDMS) membranes doped with Griess reagents for in situ determination of and - in real samples is proposed. The influence of some doping compounds, on the properties of the PDMS membranes, such as tetraethyl orthosilicate (TEOS), or/and ionic liquids (OMIM PF6) has been studied. Membrane characterization was performed. To apply the procedure to determination, dispersed Zn nanoparticles (ZnNPs) were employed. The analytical responses were the absorbance or the RGB components from digital images. Good precision (RSD < 8%) and detection limit of 0.01 and 0.5 mgL−1 for and , respectively, were achieved. The approach was satisfactory when applied to the determination of and in drinking waters, irrigation and river waters, and waters from canned and fresh vegetables. The results obtained were statistically comparable with those by using nitrate ISE or UV measurement. This approach was transferred satisfactory to 96 wells for multianalysis. This study enables the improvement in the on-site determination of and in several matrices. It is a sustainable alternative over the reagent derivatizations in solution and presents several advantages such as being versatile, simplicity, low analysis time, cost, and energy efficiency. The response can be detected visually or by portable instruments such as smartphone.

Birefringent tissue-mimicking phantom for polarization-sensitive optical coherence tomography imaging.

.Significance: Tissue birefringence is an important parameter to consider when designing realistic, tissue-mimicking phantoms. Options for suitable birefringent materials that can be used to accurately represent tissue scattering are limited.Aim: To introduce a method of fabricating birefringent tissue phantoms with a commonly used material—polydimethylsiloxane (PDMS)—for imaging with polarization-sensitive optical coherence tomography (PS-OCT).Approach: Stretch-induced birefringence was characterized in PDMS phantoms made with varying curing ratios, and the resulting phantom birefringence values were compared with those of biological tissues.Results: We showed that, with induced birefringence levels up to , PDMS can be used to resemble the birefringence levels in weakly birefringent tissues. We demonstrated the use of PDMS in the development of phantoms to mimic the normal and diseased bladder wall layers, which can be differentiated by their birefringence levels.Conclusions: PDMS allows accurate control of tissue scattering and thickness, and it exhibits controllable birefringent properties. The use of PDMS as a birefringent phantom material can be extended to other birefringence imaging systems beyond PS-OCT and to mimic other organs.

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

&lt;abstract&gt; &lt;p&gt;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.&lt;/p&gt; &lt;/abstract&gt;

Оптоакустический генератор ультразвука на основе структуры с таммовским плазмоном и органическим активным слоем

Currently, a new class of ultrasound generators is being actively developed, based on the conversion of optical energy of laser radiation into ultrasonic mechanical vibrations. It was shown theoretically that an efficient optoacoustic generator can be realized using a structure with a Tamm plasmon as an active medium. This article discusses the improvement of such an optoacoustic generator by adding a layer of organic material (polydimethylsiloxane), which has an extremely high coefficient of thermal expansion. Modeling of the properties of the structure was carried out, which showed that the use of polydimethylsiloxane as an additional layer of the structure of an optoacoustic transducer is expedient at frequencies up to 50 MHz. It was also shown that the addition of an organic layer leads to an increase in the efficiency of optoacoustic conversion by 4 orders of magnitude.

Polydimethylsiloxane chemistry for the fabrication of microfluidics—Perspective on its uniqueness, limitations and alternatives

Polydimethylsiloxane (PDMS) is the benchmark for the fabrication of microfluidic devices. Fluidic chips can be produced by several methods, including soft lithography, peel and print, and stamping. Modified PDMS precursors and other polymer chemistries have been explored therefor. However, in many cases the use of PDMS may be adopted, by default, without necessarily questioning if it is the most ideal material for the intended outcome. Here, the focus is to generate critical awareness around the uniqueness and limitations of the PDMS chemistry as it relates to its use in the fabrication of microfluidic devices. Materials based on PDMS are compared and contrasted with the relatively few alternatives for which data was found related to their use in microfluidics as potential PDMS substitutes. We evaluate where we are in terms of designing next-generation materials for microfluidic applications. Additionally, we intend this article to aid the microfluidics researcher by highlight the most important structure/property relationships that can serve as guidelines in materials selection for microfluidics.

The synthesis and properties of siloxane-urethane copolymers aqueous nanodispersion using hydroxyalkyl and hydrohxypolyester terminated polydimethylsiloxane

We synthesize siloxane-urethane copolymer aqueous dispersions by using hydroxypropyl terminated polydimethysiloxane (HAS) and hydrohxypolyester terminated polydimethylsiloxane (PES) as siloxane monomers and dimethylol propionic acid (DMPA) as intrachain emulsifier. The stable dispersions have the average sizes from 24 to 59 nm dependent on the reaction conditions. From the dispersions, the transparent films with the improved hydrophobicity are prepared. The water contacting angels of these films are enhanced by increasing the siloxane contents. In order to reveal the influences of the different chemical structures of siloxane, these films are also investigated about the UV-vis spectrum, tensile property, topography, and glass transition. It is obtained that the use of PES can obtain the films with better light transmission, around 95%. It is observed by atom force microscope that the as-synthesized siloxane-urethane copolymer films display less phase separation, agreeing well with the high transparency. Moreover, the rheological tests and model calculations are carried out to illustrate the effects of DMPA concentrations on the viscosities and correlation to the dispersion particle sizes. The as-synthesized aqueous nanodispersions promise to be used for the transparent coatings of hydrophobicity.

Modular Microphysiological System for Modeling of Biologic Barrier Function.

Microphysiological systems, also known as organs-on-chips, are microfluidic devices designed to model human physiology in vitro. Polydimethylsiloxane (PDMS) is the most widely used material for organs-on-chips due to established microfabrication methods, and properties that make it suitable for biological applications such as low cytotoxicity, optical transparency, gas permeability. However, absorption of small molecules and leaching of uncrosslinked oligomers might hinder the adoption of PDMS-based organs-on-chips for drug discovery assays. Here, we have engineered a modular, PDMS-free microphysiological system that is capable of recapitulating biologic barrier functions commonly demonstrated in PDMS-based devices. Our microphysiological system is comprised of a microfluidic chip to house cell cultures and pneumatic microfluidic pumps to drive flow with programmable pressure and shear stress. The modular architecture and programmable pumps enabled us to model multiple in vivo microenvironments. First, we demonstrate the ability to generate cyclic strain on the culture membrane and establish a model of the alveolar air-liquid interface. Next, we utilized three-dimensional finite element analysis modeling to characterize the fluid dynamics within the device and develop a model of the pressure-driven filtration that occurs at the glomerular filtration barrier. Finally, we demonstrate that our model can be used to recapitulate sphingolipid induced kidney injury. Together, our results demonstrate that a multifunctional and modular microphysiological system can be deployed without the use of PDMS. Further, the bio-inert plastic used in our microfluidic device is amenable to various established, high-throughput manufacturing techniques, such as injection molding. As a result, the development plastic organs-on-chips provides an avenue to meet the increasing demand for organ-on-chip technology.

Numerical study of a highly efficient light trapping nanostructure of perovskite solar cell on a textured silicon substrate

In this paper, a nanostructured perovskite solar cell (PSC) on a textured silicon substrate is examined, and its performance is analyzed. First, its configuration and the simulated unit cell are discussed, and its fabrication method is explained. In this proposed structure, poly-dimethylsiloxane (PDMS) is used instead of glass. It is shown that the use of PDMS dramatically reduces the reflection from the cell surface. Furthermore, the light absorption is found to be greatly increased due to the light trapping and plasmonic enhancement of the electric field in the active layer. Then, three different structures, are compared with the main proposed structure in terms of absorption, considering the imperfect fabrication conditions and the characteristics of the built PSC. The findings show that in the worst fabrication conditions considered structure (FCCS), short-circuit current density (Jsc) is 22.28 mA/cm2, which is 27% higher than that of the planar structure with a value of 17.51 mA/cm2. As a result, the efficiencies of these FCCSs are significant as well. In the main proposed structure, the power conversion efficiency (PCE) is observed to be improved by 32%, from 13.86% for the planar structure to 18.29%.

Thermal and Manufacturing Design Considerations for Silicon-Based Embedded Microchannel Three-Dimensional-Manifold Coolers (EMMC)—Part 3: Addressing Challenges in Laser Micromachining-Based Manufacturing of Three-Dimensional-Manifolded Microcooler Devices

Abstract Laser machining is an inexpensive and fast alternative to conventional microfabrication techniques and has the capability to produce complicated three-dimensional (3D), hierarchical structures. It is especially important while performing rapid prototyping and quick design studies of extreme heat flux cooling devices. One of the major issues plaguing the use of laser micromachining to manufacture commercially usable devices, is the formation of debris during cutting and the difficulty in removing these debris efficiently after the machining process. For silicon substrates, this debris can interfere with surrounding components and cause problems during bonding with other substrates by preventing uniform conformal contact. This study delves deep into the challenges faced and methods to overcome them during laser micromachining-based manufacturing of such complicated 3D-manifolded microcooler structures. Specifically, this work summarizes several postprocess techniques that can be employed for complete debris removal during etching of silicon samples using an Nd/YVO4 ultraviolet (UV) laser, detailing the advantages and drawbacks of each approach. A method that was found to be particularly promising to achieve very smooth surfaces with almost complete debris removal was the use of polydimethylsiloxane (PDMS) as a high-rigidity protective coating. In the process, a novel technique to strip PDMS from silicon surface was also developed. The result of this study is valuable to the microfabrication industry where smooth and clean substrate surfaces are highly desirable and it will significantly improve the process of using UV lasers to create microstructures for commercial applications as well as in a research environment.

Characterization of Shear Strain on PDMS: Numerical and Experimental Approaches

Polydimethylsiloxane (PDMS) is one of the most popular elastomers and has been used in different fields, especially in biomechanics research. Among the many interesting features of this material, its hyperelastic behavior stands out, which allows the use of PDMS in various applications, like the ones that mimic soft tissues. However, the hyperelastic behavior is not linear and needs detailed analysis, especially the characterization of shear strain. In this work, two approaches, numerical and experimental, were proposed to characterize the effect of shear strain on PDMS. The experimental method was implemented as a simple shear testing associated with 3D digital image correlation and was made using two specimens with two thicknesses of PDMS (2 and 4 mm). A finite element software was used to implement the numerical simulations, in which four different simulations using the Mooney–Rivlin, Yeoh, Gent, and polynomial hyperelastic constitutive models were performed. These approaches showed that the maximum value of shear strain occurred in the central region of the PDMS, and higher values emerged for the 2 mm PDMS thickness. Qualitatively, in the central area of the specimen, the numerical and experimental results have similar behaviors and the values of shear strain are close. For higher values of displacement and thicknesses, the numerical simulation results move further away from experimental values.

Nanostars—decorated microfluidic sensors for surface enhanced Raman scattering targeting of biomolecules

Novel localised surface plasmon resonance-based sensors exploitable as diagnostic devices through surface enhanced Raman scattering (SERS) represent a powerful solution for the analysis of liquid samples. In this work, we developed a rapid, versatile, low-cost and time-saving strategy combining advanced (3D-printing) and traditional manufacturing (replica molding) processes to prototype polymeric microfluidic devices, integrating all the components into a single portable platform. Microfluidics provide multiplexed capability, adequate miniaturization and robustness, handling simplicity, reliability, as well as low sample and reagents consumption, while the use of polydimethylsiloxane as supporting substrate drastically reduces the final cost. To introduce SERS capability, plasmonic features were incorporated functionalizing substrates with gold nanoparticles (NPs), engineered in terms of shape, size and surface chemistry to play with plasmonic properties as well as to guarantee reproducibility to the NPs immobilization step and consequently to the SERS effect for signal enhancing. To assess the feasibility of the measurements for molecules optical targeting, SERS-microfluidic systems were synergically coupled with a portable fiber-based set-up and Raman spectra of rhodamine 6 G at different concentrations were acquired. To further demonstrate the potentiality of developed SERS-based substrates as point-of-care devices, Raman analysis were successfully implemented on aqueous solutions of amyloid-β 1–42 (Aβ), considered the main biomarkers for Alzheimer’s disease.