Polydimethylsiloxane Membrane Research Articles

Enhancing butanol separation efficiency in pervaporation with ZIF-8 porous liquid infused mixed matrix membranes

Separating butanol/water mixtures via distillation is notably energy-intensive and costly, highlighting the urgent need for more efficient alternatives. This study introduces a novel approach using mixed matrix membranes (MMMs) infused with Zeolitic Imidazolate Framework-8 (ZIF-8) transformed into its porous liquid (PL) form, aimed at enhancing the separation efficiency of butanol/water mixtures through pervaporation (PV). We selected ZIF-8 for its hydrophobic nature and high surface area, which are critical for improving both flux and selectivity in membrane-based separation processes. The study details the synthesis of ZIF-8-PL, its characterization through techniques such as Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), and the fabrication of the MMMs. Our results demonstrate that ZIF-8-PL-based membranes at 55°C with a 30 wt% PL loading significantly enhance biobutanol-selective PV efficiency. Specifically, these membranes show an improvement in flux of approximately 102% and an increase in separation factor by 64% when compared to unmodified polydimethylsiloxane (PDMS) membranes. This significant enhancement highlights the effectiveness of PL-based fillers in advancing MMM performance for biofuel separation, providing a promising route to optimize energy efficiency and cost-effectiveness in industrial scale applications.

Splay aligned liquid crystal network photoactuators for integrated microfluidic pumps

As lab-on-a-chip devices aim to incorporate complex and multi-step microfluidic workflows, active fluid control within these platforms is critical. We use a splay aligned liquid crystal network (LCN) photoactuator, capable of deformation upon blue light illumination, as a stimuli responsive material to create integrated fluidic elements. After optimization of the manufacturing parameters, a well-defined actuator material is attained. Illumination with a 455 nm light emitting diode (LED) at 41 mW cm−2 achieves deflection of a 3 × 8 × 0.05 mm LCN film by 380 µm, generating forces of 1.1 mN. The actuator response is stable over time and scalable by light intensity, temperature, and size of the LCN film. By combining with a polydimethylsiloxane (PDMS) membrane, integration into a microfluidic chip is demonstrated and fluid movement of 77 nL in a 2 s stroke is attained. In a pumping setup, the LCN film functions as pumping membrane and two passive PDMS check valves complete the integrated micropump. Constant pumping rates of 0.1 µL min−1 are achieved. An advantage of this micropump setup lies in the non-contact actuation method, which allows for easy integration into microfluidic chips, without the need for chip-to-world connections. Furthermore, with the simple manufacturing procedure and the low operating power, important requirements for application in point-of-care settings are fulfilled.

Effects of Solvents on the Material Properties of Screen‐printed Electrodes and a PDMS Dielectric for Dielectric Elastomer Transducers

Dielectric elastomer transducers (DETs), namely highly stretchable dielectric membranes sandwiched between two compliant electrodes, allow to develop sensors, actuators, and generator systems. DET performance is strongly influenced by the material properties of dielectric and electrodes, as well as the type of manufacturing process. For instance, when manufacturing the electrodes via screen‐printing, significant amounts of solvents are needed to adjust the printing materials viscosity, but they potentially alter DET properties. The investigation of this effect, however, is largely unexplored. Addressing this issue, this paper investigates the influence of various solvents on a DET consisting of a polydimethylsiloxane (PDMS) membrane with PDMS/carbon black electrodes. Physical and chemical interactions between dielectric and solvents are characterized by infrared‐spectroscopy (IR), optical investigations, and light microscopy. Different solvents used for screen‐printing are analyzed in terms of their effects on the electrode electrical resistance, screen‐print image, and breakdown strength. Even though the solvent strongly affects the electrodes electrical resistance (ranging from ∽22 kΩ to >MΩ), it does not modify the breakdown strength of the pure dielectric (113 V/µm). In the IR, no chemical ageing was found. The obtained results provide systematic guidelines for the choice of solvents in DET electrode manufacturing.This article is protected by copyright. All rights reserved.

Mitigated CH4 release of anaerobic waste fermentation is enabled through effluent degassing system equipped with a polydimethylsiloxane membrane contactor

In this study, first, a fed-batch biogas fermenter was established using anaerobic digester sludge treating secondary sludge from a municipal wastewater treatment plant and operated for 120 days on glycerol as the sole substrate. Then, the prefiltered effluent of the anaerobic digester unit was loaded subsequently into a stirred-tank coupled with a hollow-fibre, polydimethylsiloxane (PDMS) gas-liquid membrane contactor and a dissolved methane sensor for studying the gas recovery process under continuous biogas supply, consisting of CH4 and CO2 in different proportions (70/30 CH4/CO2 vol.%; 50/50 CH4/CO2 vol.%; 30/70 CH4/CO2 vol.%.). Experiments showed that besides the actual composition of the internal biogas, the ratio (0.5-2) of sweep gas (N2) and effluent (liquid) volumetric flow rates (G/L) could be a crucial operating factor with influence on the degassing efficiency attainable by the 1 m2 PDMS membrane module. Results were compared to the performance of the same PDMS membrane module working with synthetic anaerobic digester effluents, indicating the dissolved methane recoveries observed with the synthetic effluents (>50%) considerably surpassed those with the real effluent (<20%) where the dissolved methane concentrations, at G/L of 1, were in the range of 12.4 to 17.3 mg L−1.

Mechanical analysis of PDMS films based on different hyperelastic numerical constitutive models

PDMS(polydimethylsiloxane) is widely employed as a substrate material in flexible electronic devices, necessitating its ability to undergo camber deformation while maintaining excellent ductility and flexibility. Understanding the mechanical behavior of PDMS is imperative for its practical applications. Consequently, to numerically investigate the tensile behavior of PDMS, two commonly used hyperelastic constitutive models, the Mooney-Rivlin model and the 3-term Ogden model, have been employed to describe its mechanical characteristics. The material coefficients were determined by fitting the uniaxial tensile experimental data. Subsequently, separate finite element models were developed for the PDMS membrane and the Cu-PDMS composite layer structure. The numerical findings demonstrate that both the Mooney-Rivlin model and the 3-term Ogden model adequately fit the experimental data. Nevertheless, in comparison to the 3-term Ogden model, the PDMS stress distribution exhibits higher values at the same tensile rate, consequently resulting in the fracture of the Cu layer first.

Hydrophobic enrichment-induced augmentation of NH2-UiO-66 particle interactions for enhanced pervaporation performance of polydimethylsiloxane membrane

BackgroundIn this research, we aimed to improve the hydrophobic property of NH2-UiO-66 particles by palmitoyl chloride (PC) modification. PC-UiO-66 particles were mixed in the selective layer of PDMS (polydimethylsiloxane)-PVDF (Polyvinylidene fluoride) composite membrane for organo-selective pervaporation. MethodsWe effectively preserved conspicuous crystallinity and high porosity during a conversion from hydrophilic to hydrophobic MOF, as confirmed by XRD and BET studies. The successful incorporation of palmitoyl long alkyl chains into PC-UiO-66 was verified through FTIR, XPS, and EDS studies. PC-UiO-66 particles exhibited an excellent dispersion in PDMS matrix due to a strong interfacial polymer-MOF interaction observed in FESEM and AFM studies. An organophilic pervaporation separation performance of pristine PDMS, NH2-UiO-66/PDMS, and PC-UiO-66/PDMS membranes coated on PVDF support was evaluated for ethanol/water, IPA/water, and 1,5 PDO/IPA feed solution. Significant findingsThe results demonstrated that adding PC-UiO-66 particles significantly improved the separation performance of PC-UiO-66/PDMS membranes, achieving the highest selectivity compared to pristine PDMS and NH2-UiO-66/PDMS membranes.

The nature of PDMS affects the results of the immunoassays carried out in microfluidic channels

Due to various physical or biochemical processes, the nature of polydimethylsiloxane (PDMS) could affect the sensitivity and accuracy of immunoassays performed in microfluidic channels. An appropriate PDMS membrane with high adsorption properties and low background noise allows more sensitive detection of biomarkers. Here, we explored the unusual correlation between membrane surface properties and the signal-to-noise ratio (SNR) of immunoassay, developed a microfluidic-based versatile point-of-care (MVP) detection system on PDMS membrane to simultaneously detect multiple vitamins from multiple human serums. Compared with conventional enzyme-linked immunosorbent assay (ELISA) and Roche electroluminescence method, the MVP detection system exhibits a lower consumption of sample and reagents (10 µL per test), a lower limit of detection (LOD: 6.15 ng/mL), a higher SNR (33.49 dB) and multiplexed ability (seven samples and two targets in one assay). Our MVP detection system can quantitatively detect folic acid (FA) and vitamin D3 (VD3) from human serums and shows good consistency with ELISA and Roche electroluminescence methods. The R square values of FA and VD3 detections are 0.94 and 0.91, respectively. The MVP system is more cost-effective than utilizing conventional methods for a single detection (about 0.04 USD for each target) because of the straightforward design of our detection instruments, their superior anti-interference capabilities, and the low cost of routine instrument maintenance.

Molecular dynamics simulation and experimental verification of influence of crosslinking reaction process parameters on oxygen permeability of PDMS membranes

Sufficient oxygen permeability of the substrate is the key to ensuring the reliability of the Continuous Liquid Interface Production process. Polydimethylsiloxane (PDMS), as a cost-effective material with good gas permeability, holds potential for applications as oxygen-permeable windows in constrained substrates. Therefore, it is of great significance to investigate how to enhance the oxygen permeability of PDMS. In this study, the program code for the crosslinking reaction between the prepolymer and curing agent was developed. Molecular dynamics simulations were employed to investigate the effects of the process parameters on the diffusion coefficient of oxygen. Validation experiments were conducted by measuring the oxygen permeability of the substrate. The research findings reveal that process parameters, including crosslinking time, crosslinking temperature, and the mass ratio of prepolymers to curing agents, influence the diffusion coefficient of oxygen in PDMS membranes. Increasing the crosslinking time leads to an increase in the number of crosslinking points, hindering polymer chain mobility and limiting the increase in free volume, thereby decreasing the oxygen diffusion coefficient. An optimal crosslinking temperature of 348 K enhances the probability of jump channel formation between cavities, resulting in the maximum oxygen diffusion coefficient. The oxygen diffusion coefficient of PDMS membranes increases with rising mass ratio.

A highly efficient cell culture method using oxygen-permeable PDMS-based honeycomb microwells produces functional liver organoids from human induced pluripotent stem cell-derived carboxypeptidase M liver progenitor cells.

Recent advancements in bioengineering have introduced potential alternatives to liver transplantation via the development of self-assembled liver organoids, derived from human-induced pluripotent stem cells (hiPSCs). However, the limited maturity of the tissue makes it challenging to implement this technology on a large scale in clinical settings. In this study, we developed a highly efficient method for generating functional liver organoids from hiPSC-derived carboxypeptidase M liver progenitor cells (CPM+ LPCs), using a microwell structure, and enhanced maturation through direct oxygenation in oxygen-permeable culture plates. We compared the morphology, gene expression profile, and function of the liver organoidwith those of cells cultured under conventional conditions using either monolayer or spheroid culture systems. Our results revealed that liver organoids generated using polydimethylsiloxane-based honeycomb microwells significantly exhibited enhanced albumin secretion, hepatic marker expression, and cytochrome P450-mediated metabolism. Additionally, the oxygenated organoids consisted of both hepatocytes and cholangiocytes, which showed increased expression of bile transporter-related genesas well as enhanced bile transport function. Oxygen-permeable polydimethylsiloxane membranes may offer an efficient approach to generating highly mature liver organoids consisting of diverse cell populations.

Mixed matrix membranes of polydimethylsiloxane with activated carbon for ABE separation

AbstractThe demand for the large‐scale biofuels production is very high. The use of ethanol and butanol in flex‐fuel vehicles have already been achieved, but still need improvement to decrease the gasoline‐dependence. In addition to it, the preparation of ethanol and butanol by eco‐friendly routes are still a challenge. The use of ABE route, in which acetone, butanol, and ethanol are prepared by fermentation of 5 or 6 carbon sugars, requires higher yields and better separation performance. The goal of this work was to evaluate the use of pervaporation through asymmetric activated carbon (AC) dispersed polymethylsiloxane membranes for the separation of ABE aqueous solution with 1 wt% total organics. The amount of the filler was varied from 0 to 3 wt%. Membranes were characterized by scanning electronic microscopy, Fourier transformed infrared spectroscopy, swelling in solvents, thermogravimetric analysis, and differential scanning calorimetry. Membrane with 1 wt% of AC membrane showed different behaviors both in thermal resistance, which was increased, and also in pervaporation separation index (PSI). In this condition, membrane total flux, separation factor, and PSI for ethanol were 13.2, 2.6, and 19.9 g m−2 h−1, so that sorption behavior and diffusion rates were changed. Thus, it was possible to modulate membrane properties.

An Ultrasoft and Flexible PDMS-Based Balloon-Type Implantable Device for Controlled Drug Delivery.

Non-biodegradable implants have undergone extensive investigation as drug delivery devices to enable advanced healthcare toward personalized medicine. However, fibroblast encapsulation is one of the major challenges in all non-biodegradable implants, besides other challenges such as high initial burst, risk of membrane rupture, high onset time, non-conformal contact with tissues, and tissue damage. To tackle such challenges, we propose a novel ultrasoft and flexible balloon-type drug delivery device for unidirectional and long-term controlled release. The ultrasoft balloon-type device (USBD) was fabricated by using selective bonding between 2 polydimethylsiloxane (PDMS) membranes and injecting a fluid into the non-bonded area between them. The balloon acted as a reservoir containing a liquid drug, and at the same time, the membrane of the balloon itself acted as the pathway for release based on diffusion. The release was modulated by tuning the thickness and composition of the PDMS membrane. Regardless of the thickness and composition, all devices exhibited zero-order release behavior. The longest zero-order release and nearly zero-order release were achieved for 30 days and 58 days at a release rate of 1.16 μg/day and 1.68 μg/day, respectively. Invivo evaluation was performed for 35 days in living rats, where the USBD maintained zero-order and nearly zero-order release for 28 days and 35 days, respectively. Thanks to the employment of ultrasoft and flexible membranes and device design, the USBD could achieve minimal tissue damage and foreign body responses. It is expected that the proposed device may provide a novel approach for long-term drug delivery with new therapeutic modalities.

Bioethanol production from cassava fermentation in pervaporation membrane bioreactor fed with high concentration sugar

Bioethanol production from cassava in a pervaporation membrane bioreactor consisted of fermentation coupled with polydimethylsiloxane (PDMS) membrane separation has been carried out. A cassava hydrolysate with a high sugar concentration of 448–492 gL-1 was prepared by repeating the liquefaction process and then fed to the bioreactor to overcome the fermentation broth volume expansion problem. The coupled system lasted as long as 248 h. The cell concentration, sugar consumption rate, ethanol productivity, and total ethanol production were 22 gL-1, 3.91 gL-1h−1, 1.47 gL-1h−1, and 365.1 gL-1, respectively. The average membrane flux and separation factors of the membrane were 645 gm-2h−1 and 5.3, respectively. A permeate vapor with as high as 21.5 wt% ethanol concentration downstream of the membrane was obtained. Fractional condensation was used downstream of the membrane to differentially refine and recover the ethanol from the permeate vapor. The ethanol concentration can be increased by 57.3 % with the fractional condensation method, with separation factor increased to 9.8–14.9. As much as 96.6 % of the permeated ethanol on the downstream of the membrane can be recovered as the product with high ethanol concentration.

Structural Performance and Evaluation of PDMS-Based Planar Membrane for Electromagnetic Vibration Energy Harvester (EM-VEH)

This paper discusses the performances of Polydimethylsiloxane (PDMS) membranes with the electromagnetic coils and magnetic arrangement as the supporting structure to generate electricity by capturing the energy from vibrating ambient source. The membrane attached to the permanent magnet moved according to the structure of the electromagnetic system. The study first designed the PDMS planar membrane to allow the vibration energy capturer to induce the coils efficiently. Membrane vibration from a loudspeaker with an operating frequency of 32 Hz was used as the vibration source. The generated energy stored in a storage circuit  using a 220 µF/25 Volt capacitor, while a 1.5 Volt LED was used as a tested load in the system. The results showed that the moving membrane attached with a 10 mm diameter magnet revealed an open circuit output voltage of 500 mV on the EM coil. An experiment within a 20-minute flashing LED load test produced an output voltage of 2.2 Volts. This study would benefit the development of vibration energy harvester used to supply a low electrical power for microdevices in an isolated area.

Effects of polydimethylsiloxane membrane surface treatments on human uterine smooth muscle cell strain response

In the United States, 1 in 10 infants are born preterm. The majority of neonatal deaths and nearly a third of infant deaths are linked to preterm birth. Preterm birth is initiated when the quiescent state of the uterus ends prematurely, leading to contractions and parturition beginning as early as 32 weeks, though the origins are not well understood. To enable research and discovery of therapeutics with potential to better address preterm birth, the capability to study isolated cell processes of pregnant uterine tissue in vitro is needed. Our development of an in vitro model of the myometrium utilizing human uterine smooth muscle cells (uSMCs) responsible for contractions provides a methodology to examine cellular mechanisms of late-stage pregnancy potentially involved in preterm birth. We discuss culture of uSMCs on a flexible polydimethylsiloxane (PDMS) substrate functionalized with cationic poly-l-lysine (PLL), followed by extracellular matrix (ECM) protein coating. Previous work exploring uSMC behavior on PDMS substrates have utilized collagen-I coatings, however, we demonstrated the first exploration of human uSMC response to strain on fibronectin-coated flexible membranes, importantly reflecting the significant increase of fibronectin content found in the myometrial ECM during late-stage pregnancy. Using the model we developed, we conducted proof-of-concept studies to investigate the impact of substrate strain on uSMC cell morphology and gene expression. It was found that PLL and varied ECM protein coatings (collagen I, collagen III, and fibronectin) altered cell nuclei morphology and density on PDMS substrates. Additionally, varied strain rates applied to uSMC substrates significantly impacted uSMC gene expression of IL-6, a cytokine associated with instances of preterm labor. These results suggest that both surface and mechanical properties of in vitro systems impact primary human uSMC phenotype and offer uSMC culture methodologies that can be utilized to further the understanding of cellular pathways involved in the uterus under mechanical load.

Fabrication of a Magnetically Driven Cell-Stretching Device for Predefined Cell Alignment in Vitro

Various devices have been developed that use stretching silicone sheets to evaluate cellular mechanotransduction. However, few studies have explored predefined cell alignments using mechanical stimuli for engineering applications, including cell sheets and drug screenings. Therefore, we proposed a magnetically driven cell-stretching device for predefined cell alignment in vitro, which consisted mainly of a circular silicone membrane with a neodymium magnet and standard cell culture dish. As the proposed device was incorporated into a cell culture dish, there may be a small risk of contamination in long-term incubation experiments. The device was fabricated by assembling a polydimethylsiloxane membrane and silicone ring. The fabricated device showed that the membrane strain increased with increasing voltage application to the electromagnet, and indicated that cell alignment occurs when strain exceeds 0.8%. Following cyclic stimulation of cells adhered to a membrane for 4 h in a CO2 incubator with 1.05% strain at 0.1 Hz, cell alignment with the predefined direction increased by 20.4% compared to that before stimulation. The findings imply that the proposed device may be utilized for predefined cell alignment.

Homoporous polydimethylsiloxane membrane microfilter for ultrafast label-free isolation and recognition of circulating tumor cells in peripheral blood

The detection of circulating tumor cells (CTCs) in peripheral blood is a novel and accurate technique for the early diagnosis of cancers. However, this method is challenging because of the need for high collection efficiency due to the ultralow content and similar size of CTCs compared with other blood cells. To address the aforementioned issue, we proposed a homoporous polydimethylsiloxane (PDMS) membrane and its microfilter device to perform the ultrafast isolation and identification of CTCs directly from peripheral blood without any labeling treatment. The membrane pores can be homogenously controlled at a size of 6.3μm through the cross-linking time of PDMS during a filtration-coating strategy. Within only 10 s, the designed device achieved a retention rate greater than 70% for pancreatic cancer cells, and it exhibited excellent cell compatibility to support cell proliferation. The isolated CTCs on this membrane can be easily observed and identified using a fluorescence microscope.

A Semi-Automatic Environmental Monitoring Device for Mercury and Cobalt Ion Detection.

A syringe-based, semi-automatic environmental monitoring device is developed for on-site detection of harmful heavy metal ions in water. This portable device consists of a spring-embedded syringe and a polydimethylsiloxane (PDMS) membrane-based flow regulator for semi-automatic fix-and-release fluidic valve actuation, and a paper-based analytical device (PAD) with two kinds of gold nanoclusters (AuNCs) for sensitive Hg2+ and Co2+ ion detection, respectively. The thickness of the elastic PDMS membrane can be adjusted to stabilize and modulate the flow rates generated by the pushing force provided by the spring attached to the plunger. Also, different spring constants can drastically alter the response time. People of all ages can extract the fix-volume sample solutions and then release them to automatically complete the detection process, ensuring high reliability and repeatability. The PAD comprises two layers of modified paper, and each layer is immobilized with bovine serum albumin-capped gold nanoclusters (R-AuNCs) and glutathione-capped gold clusters (G-AuNCs), respectively. The ligands functionalized on the surface of the AuNCs not only can fine-tune the optical properties of the nanoclusters but also enable specific and simultaneous detection of Hg2+ and Co2+ ions via metallophilic Au+ -Hg2+ interaction and the Co2+ -thiol complexation effect, respectively. The feasibility of the device for detecting heavy metal ions at low concentrations in various environmental water samples is demonstrated. The Hg2+ and Co2+ ions can be seen simultaneously within 20 min with detection limits as low as 1.76 nm and 0.27 µm, respectively, lower than those of the regulatory restrictions on water by the US Environmental Protection Agency and the European Union. we expect this sensitive, selective, portable, and easy-to-use device to be valid for on-site multiple heavy metal ion pollution screenings in resource-constrained settings.

Mechanical Enhancement of the Strain‐Sensor Response in Dimers of Strongly Coupled Plasmonic Nanoparticles

AbstractDue to their particular optical and mechanical properties, plasmomechanical devices have become choice candidates in strain sensing applications. Using numerical simulation, a plasmomechanical system consisting of two gold nanoparticles with different shapes and separated by a small gap, deposited onto a deformable polydimethylsiloxane membrane, is investigated. With the aim of understanding the relationship between the plasmonic behavior of gold nanoparticles and induced mechanical deformations, mechanical extension ranging from 0% to 20% is applied to the polydimethylsiloxane membrane. In a first step, a mechanical calculation based on a hyperelastic model for polydimethylsiloxane shows that the interparticle spacing is enhanced nonlinearly by a percentage greater than the externally applied deformation, depending on the shape and size of the nanoparticles as well as the polydimethylsiloxane membrane thickness. Full optical simulation of the deformed nanosystems demonstrates that the plasmonic resonance wavelength is highly sensitive to the applied displacements and is enhanced compared to a basic approach where the gap deformation is taken as equal to the macroscopic applied deformation. The best figure of merit () is obtained for the disk–rod dimer near the strong coupling regime, larger than the values reported in the literature for localized nanoparticle systems.

Superhydrophobic and robust photothermal/electrothermal PVDF-a/CNT-s@PDMS membrane for crude oil removal and dye adsorption

Recently, the crude oil spill has brought inevitable harm to the global ecological environment. Due to the high-viscosity crude oil, it is wise to take advantage of the photothermal/electrothermal effects of the membrane to separate the crude oil from the water. However, the functional separation membrane always suffers from low photothermal/electrothermal effects and poor stability. Herein, the vinyl polyvinylidene fluoride/mercapto carbon nanotubes@vinyl-terminated polydimethylsiloxane (PVDF-a/CNT-s@PDMS) membrane with fast photothermal/electrothermal effects and organic absorption property was successfully prepared by electrospinning and multi-layer loading method. The prepared PVDF-a/CNT-s@PDMS membrane resisted a variety of liquids and had stable superhydrophobicity (WCA = 156°). Furthermore, the membrane maintained superhydrophobicity even suffer from water and milk under the applied voltage condition. After 100 wear resistance tests, the membrane maintained stable superhydrophobicity and the separation rate remained unchanged. The surface temperature of the membrane rapidly approached to the maximum temperature in 30 s, showing a rapid photothermal/electrothermal effects, and the average separation rate of crude oil was 1185 kg m−2 h−1·bar−1. Meanwhile, the membrane exhibited outstanding efficiency for separate immiscible oil-water mixtures. Importantly, the incorporation of the sulfhydryl group enhanced the special ability of the composite membrane to adsorb organic dyes from oil phase. Therefore, the PVDF-a/CNT-s@PDMS membrane has a wide range of potential application in the domain of oil-water separation.

Ultrathin polyorganosilica membranes synthesized by oxygen-plasma treatment of polysiloxanes for H2/CO2 separation

Oxygen plasma treatment of polydimethylsiloxane (PDMS) induces an ultrathin polyorganosilica (POSi) layer (<10 nm) on top of a PDMS membrane, leading to excellent H2/gas separation properties and providing a rapid and scalable way to fabricate robust silica membranes compared with conventional high-temperature and time-consuming sol-gel methods. Here, we thoroughly investigate POSi membranes derived from poly (dimethylsiloxane-co-methylhydroxidesiloxane) (poly (DMS-co-MHOS)) containing -SiOH groups that can be more easily converted to silica networks than the -SiCH3 in PDMS. The effect of the polysiloxane structure and plasma treatment conditions (including plasma generating powers, oxygen flowrate, chamber pressure, and treatment time) on the silica chemistry, structure, and H2/CO2 separation properties are systematically determined to derive structure/property relationships. An optimized membrane exhibits H2 permeance of 880 GPU and H2/CO2 selectivity of 67 at 150 °C, superior to state-of-the-art polymeric membranes. The membrane retains H2/CO2 selectivity as high as 46 when challenged with simulated syngas containing 2.8 mol% water vapor at 150 °C, demonstrating the potential of these POSi membranes for practical applications.