Gas permeation through rubbery polymer nano-corrugated membranes

A Gemini basic ionic liquid and functionalized cellulose nanocrystal-based mixed matrix membrane for CO2/N2 separation

Owing to the adverse environmental impact, carbon capture and separation have gained tremendous interest throughout the globe. Herein, a CO2/N2 gas separative mixed matrix membrane containing amine functionalized cellulose nanocrystals and a Gemini basic ionic liquid has been developed, which exhibits the highest permeance of 21 033 GPU and moderate selectivity of 21.3.

Polydimethylsiloxane/Magnesium Oxide Nanosheet Mixed Matrix Membrane for CO2 Separation Application

Carbon dioxide (CO₂) concentration is now 50% higher than in the preindustrial period and efforts to reduce CO₂ emission through carbon capture and utilization (CCU) are blooming. Membranes are one of the attractive alternatives for such application. In this study, a rubbery polymer polydimethylsiloxane (PDMS) membrane is incorporated with magnesium oxide (MgO) with a hierarchically two-dimensional (2D) nanosheet shape for CO₂ separation. The average thickness of the synthesized MgO nanosheet in this study is 35.3 ± 1.5 nm. Based on the pure gas separation performance, the optimal loading obtained is at 1 wt.% where there is no observable significant agglomeration. CO₂ permeability was reduced from 2382 Barrer to 1929 Barrer while CO₂/N₂ selectivity increased from only 11.4 to 12.7, and CO₂/CH₄ remained relatively constant when the MMM was operated at 2 bar and 25 °C. Sedimentation of the filler was observed when the loading was further increased to 5 wt.%, forming interfacial defects on the bottom side of the membrane and causing increased CO₂ gas permeability from 1929 Barrer to 2104 Barrer as compared to filler loading at 1 wt.%, whereas the CO₂/N₂ ideal selectivity increased from 12.1 to 15.0. Additionally, this study shows that there was no significant impact of pressure on separation performance. There was a linear decline of CO₂ permeability with increasing upstream pressure while there were no changes to the CO₂/N₂ and CO₂/CH₄ selectivity.

Fabrication and characterization of a flexible and disposable impedance-type humidity sensor based on polyaniline (PAni)

This work presents a highly sensitive, economical, flexible, and disposable humidity sensor developed with a facile fabrication process. The sensor was fabricated on cellulose paper using polyemaraldine salt, a form of polyaniline (PAni), via the drop coating method. A three-electrode configuration was employed to ensure high accuracy and precision. The PAni film was characterized using various techniques including ultraviolet-visible (UV-vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The humidity sensing properties were evaluated through electrochemical impedance spectroscopy (EIS) in a controlled environment. The sensor exhibits a linear response with R 2 = 0.990 for impedance over a wide range of (0%-97%) relative humidity (RH). Further, it displayed consistent responsiveness, a sensitivity of 1.1701 Ω/%RH, acceptable response (≤220 s)/recovery (≤150 s), excellent repeatability, low hysteresis (≤2.1%) and long-term stability at room temperature. The temperature dependence of the sensing material was also studied. Due to its unique features, cellulose paper was found to be an effective alternative to conventional sensor substrates according to several factors including compatibility with the PAni layer, flexibility and low cost. These unique characteristics make this sensor a promising option for use in specific healthcare monitoring, research activities, and industrial settings as a flexible and disposable humidity measurement tool.

Tuning the Transport Properties of Gases in Porous Graphene Membranes with Controlled Pore Size and Thickness

Porous graphene membranes have emerged as promising alternatives for gas‐separation applications due to their atomic thickness enabling ultrahigh permeance, but they suffer from low gas selectivity. Whereas decreasing the pore size below 3 nm is expected to increase the gas selectivity due to molecular sieving, it is rather challenging to generate a large number of uniform small pores on the graphene surface. Here, a pore‐narrowing approach via gold deposition onto porous graphene surface is introduced to tune the pore size and thickness of the membrane to achieve a large number of small pores. Through the systematic approach, the ideal combination is determined as pore size below 3 nm, obtained at the thickness of 100 nm, to attain high selectivity and high permeance. The resulting membrane shows a H2/CO2 separation factor of 31.3 at H2 permeance of 2.23 × 105 GPU (1 GPU = 3.35 × 10−10 mol s−1 m−2 Pa−1), which is the highest value reported to date in the 105 GPU permeance range. This result is explained by comparing the predicted binding energies of gas molecules with the Au surface, −5.3 versus −21 kJ mol−1 for H2 and CO2, respectively, increased surface–gas interactions and molecular‐sieving effect with decreasing pore size.

Tuning the Transport Properties of Gases in Porous Graphene Membranes with Controlled Pore Size and Thickness

Porous graphene membranes have emerged as promising alternatives for gas-separation applications due to their atomic thickness enabling ultrahigh permeance, but they suffer from low gas selectivity. Whereas decreasing the pore size below 3 nm is expected to increase the gas selectivity due to molecular sieving, it is rather challenging to generate a large number of uniform small pores on the graphene surface. Here, a pore-narrowing approach via gold deposition onto porous graphene surface is introduced to tune the pore size and thickness of the membrane to achieve a large number of small pores. Through the systematic approach, the ideal combination is determined as pore size below 3 nm, obtained at the thickness of 100 nm, to attain high selectivity and high permeance. The resulting membrane shows a H₂ /CO₂ separation factor of 31.3 at H₂ permeance of 2.23 × 10⁵ GPU (1 GPU = 3.35 × 10^-10  mol s^-1 m^-2 Pa^-1 ), which is the highest value reported to date in the 10⁵ GPU permeance range. This result is explained by comparing the predicted binding energies of gas molecules with the Au surface, -5.3 versus -21 kJ mol^-1 for H₂ and CO₂ , respectively, increased surface-gas interactions and molecular-sieving effect with decreasing pore size.

Structural and Functional Properties of Fluorinated Silica Hybrid Barrier Layers on Flexible Polymeric Foil

The reported work was focused on sol–gel-derived organically modified and fluorinated silica coatings deposited on elastic polymeric foil. The structure and topography of the coatings were tested by infrared spectroscopy and microscopic studies. The functional properties were determined using thermal analysis, surface analysis, and oxygen permeability tests. The barrier feature of the investigated materials against oxygen was correlated with the properties of the coatings. The hybrid (organic–inorganic) structure of the coatings was proven, demonstrating the presence of a silica network modified with alkyl and fluoroalkyl groups since precursors with the isooctyl group or different lengths of the fluoroalkyl chains were used for the syntheses. The coatings were free of defects and had a smooth surface except for the sample containing the longest fluoroalkyl chain (perfluorododecyl group), which showed a wrinkle-like surface. The hydrophobic character of the coatings increased, whereas the oxygen permeation coefficient values decreased (reaching a fourfold lower coefficient in comparison to the bare substrate) with a higher content of the fluorinated carbon atoms in the structure. The results were enriched by the information from the thermomechanical analysis as well as nanoindentation and scratch tests giving values of the glass transition temperature, thermal expansion coefficient, coatings adhesion, and hardness of the investigated systems.

Integrating Microstructured Electrospun Scaffolds in an Open Microfluidic System for in Vitro Studies of Human Patient-Derived Primary Cells

Recent studies have suggested that microenvironmental stimuli play a significant role in regulating cellular proliferation and migration, as well as in modulating self-renewal and differentiation processes of mammary cells with stem cell (SCs) properties. Recent advances in micro/nanotechnology and biomaterial synthesis/engineering currently enable the fabrication of innovative tissue culture platforms suitable for maintenance and differentiation of SCs in vitro. Here, we report the design and fabrication of an open microfluidic device (OMD) integrating removable poly(ε-caprolactone) (PCL) based electrospun scaffolds, and we demonstrate that the OMD allows investigation of the behavior of human cells during in vitro culture in real time. Electrospun scaffolds with modified surface topography and chemistry can influence attachment, proliferation, and differentiation of mammary SCs and epigenetic mechanisms that maintain luminal cell identity as a function of specific morphological or biochemical cues imparted by tailor-made fiber post-treatments. Meanwhile, the OMD architecture allows control of cell seeding and culture conditions to collect more accurate and informative in vitro assays. In perspective, integrated systems could be tailor-made to mimic specific physiological conditions of the local microenvironment and then analyze the response from screening specific drugs for more effective diagnostics, long-term prognostics, and disease intervention in personalized medicine.

The Role of Surfaces in Gas Transport Through Polymer Membranes

This paper describes a procedure to measure the permeability P, diffusivity D, and rate of adsorption k₁, thus determining the solubility S and rate of desorption k₂ of He, N₂, O₂, CH₄, and CO₂ on a polydimethylsiloxane (PDMS) membrane. The described procedure is able to determine experimentally all the physical quantities that characterize the gas transport process through a thin rubber polymer membrane. The experiments were carried out at room temperature and at a transmembrane pressure of 1 atm. The results are in good agreement with the available data in the literature and offer an evaluation of k₁ and k₂.