Polymeric membranes are widely applied in biomedical applications, including in vitro
organ models. In such models, they are mostly used as supports on which cells are cultured to create
functional tissue units of the desired organ. To this end, the membrane properties, e.g., morphology
and porosity, should match the tissue properties. Organ models of dynamic (barrier) tissues, e.g.,
lung, require flexible, elastic and porous membranes. Thus, membranes based on poly (dimethyl
siloxane) (PDMS) are often applied, which are flexible and elastic. However, PDMS has low cell
adhesive properties and displays small molecule ad- and absorption. Furthermore, the introduction
of porosity in these membranes requires elaborate methods. In this work, we aim to develop porous
membranes for organ models based on poly(trimethylene carbonate) (PTMC): a flexible polymer
with good cell adhesive properties which has been used for tissue engineering scaffolds, but not in
in vitro organ models. For developing these membranes, we applied evaporation-induced phase
separation (EIPS), a new method in this field based on solvent evaporation initiating phase separation,
followed by membrane photo-crosslinking. We optimised various processing variables for obtaining
form-stable PTMC membranes with average pore sizes between 5 to 8 µm and water permeance in
the microfiltration range (17,000–41,000 L/m2
/h/bar). Importantly, the membranes are flexible and are
suitable for implementation in in vitro organ models.

Development of porous and flexible ptmc membranes for in vitro organ models fabricated by evaporation-induced phase separation

The demand for new water resources has been increasing worldwide due to the growing global population and industrialization. Membranes play a central role in water purification processes with continuous technology improvements, new uses and cost reductions. Phase inversion is the most commonly used technique for preparing polymeric membranes. However, most commercial membranes are prepared from hydrophobic materials, which make them more susceptible to suffer the adsorption or deposition of molecules over their surface or inside their pores. This phenomenon, commonly termed as fouling, is one of the major operational problems in membrane processes. This review covers different membranes modification techniques to enhance permeability and to reduce fouling and the accumulation of microorganisms on membrane surface. The physicochemical properties of membrane surface can be tuned by grafting or coating to introduce functionalities like hydrophilic moieties or charged groups. Blending hydrophilic additives into the casting solution is another approach to increase membrane hydrophilicity and to improve water filtration performance. This review summarises the variety of porous materials that have been used to introduce inorganic nanoparticles into the casting solution. Porous carriers are used to introduce antimicrobial metals by preserving nanoparticle stability. Additionally, organic compounds, especially dendritic structures, have attracted considerable interest due to their highly branched structure, and their large number of terminal functional groups, which can also be used to enhance membrane properties. This work reviews the modification and functionalization techniques recently proposed to improve permeability and durability of the membranes used in pressure-driven separations.

A critical review of membrane modification techniques for fouling and biofouling control in pressure-driven membrane processes

https://hal.archives-ouvertes.fr/hal-03377885/document

Towards permanent hydrophilic PVDF membranes. Amphiphilic PVDF-b-PEG-b-PVDF triblock copolymer as membrane additive

https://hal.archives-ouvertes.fr/hal-02932005/document

Biobased polyhydroxyalkanoate (PHA) membranes: Structure/performances relationship

Fungal-derived carboxymethyl chitosan blended with polyvinyl alcohol as membranes for wound dressings.

By considering a mixture of poly(methyl methacrylate)–tetrahydrofuran–water (PMMA–THF–H2O), we report an experimental approach to tune the distribution of pores in polymer films formed via evaporation induced phase separation (EIPS). We show that the drying induced composition and microstructural changes that occur due to the evaporation of the solvent (THF) and the nonsolvent (H2O) delineate the ultimate polymer film morphology. The temporal evolution of the microstructure, the phase behavior and the change in the composition of the PMMA–THF–H2O mixture at air–solution (top surface) and solution–substrate (bottom surface) interfaces is monitored to provide insights into the origin of the pore distribution in the final polymer films. The effects of various parameters such as nonsolvent and polymer concentration in the casting solution, casting solution thickness, relative humidity and temperature on the final film morphology are investigated to correlate how the composition path (CP) change under various conditions ultimately dictates the film morphology. We show that depending on the change in the composition of the polymer solution (evolution of CP) and the water/PMMA ratio at the time of phase separation, the morphology of the final film formed varies as – (1) non porous i.e., dense film (2) a film with pores only at the bottom surface (3) an asymmetric film i.e., films with a top dense layer (non-porous) supported by porous sub-layers (4) a porous film with uniform pores distributed across the entire film thickness and (5) a film with pores only at the top surface. In addition, we show that the morphology of the PMMA film can also be tuned by varying the composition of low and high molecular weight PMMA in the casting solution. These porous PMMA structures, being biocompatible, are useful for applications in cell culture, drug delivery and wound dressing.

/pdf/tailoring-pore-distribution-in-polymer-films-via-evaporation-e1leh4vmsf.pdf

Tailoring pore distribution in polymer films via evaporation induced phase separation

We report a novel approach for the fabrication of porous polymer films and their self-folding behavior in response to water. In this approach, the poly(vinyl alcohol) (PVA) films of tunable porosity are prepared by direct casting of aqueous PVA solution into a nonsolvent, isopropyl alcohol (IPA). The method developed is simple, efficient and low-cost. The results presented provide a modular route to tune the distribution of pores across the film thickness by varying the volume of nonsolvent and the polymer solution. We show that asymmetric porous polymer films (which consist of pores across a certain thickness of the film in the plane perpendicular to its surface) as well as symmetric porous polymer films (which have pores across the entire film) can be fabricated by this versatile method. The percentage of pores in the polymer film calculated as , where tp is the thickness of the film across which the pores exist and ttotal is the total thickness of the film, can be tuned over a wide range. The emanated porous PVA films are found to show self-folding behaviour in response to water. Our results indicate that the pore architecture in the films significantly enhances the actuation speed. The self-folding originating due to the diffusion of water molecules across the film is observed to occur in a controlled and predictable manner for the films with 60% pores and above. A detailed study of the folding characteristics and actuation speed in relation to folding time is substantiated.

Rumiaya Pervin

Papers

Tailoring pore distribution in polymer films via evaporation induced phase separation

Engineering polymer film porosity for solvent triggered actuation.

Influence of initial composition of casting solution on morphology of porous thin polymer films produced via phase separation