In order to remit the membrane wetting in membrane distillation (MD), polytetrafluoroethylene (PTFE) flat membrane with low surface free energy and high water contact angle (WCA) was prepared by a simple heat setting process. Membrane morphology evolution, such as breakage of fibrils and fusion of PTFE resin, and its influence on membrane characters including pore size, porosity and roughness were discussed. The effect of the heat setting process on the membrane wetting was evaluated by the membrane wetting time (MWT) in a static absorption experiment (SAE) and sweep gas membrane distillation (SGMD). The results show that the crystallinity decreases with increasing the heat setting temperature and time, which leads to low surface free energy and therefore low adsorbing capacity of penetrating agent and the long wetting time in the static absorption experiment and SGMD. In addition, pore size increases firstly and then decreases due to the breakage of fibrils and fusion of PTFE resin, respectively, which further affects the permeate flux . Therefore, we propose that the anti-fouling property and separation performance of PTFE flat membrane in SGMD can be well handled and hope that such a PTFE flat membrane would be potentially useful in seawater desalination .
Biomaterials for cell replacement therapy could facilitate the delivery, function, and retrieval of transplanted therapeutic cells. However, the limited capacity to accommodate a sufficient quantity of cells in biomedical devices has hindered the success of clinical application, resulting from the suboptimal spatial organization of cells and insufficient permeation of nutrients in the materials. Herein, through the immersion-precipitation phase transfer (IPPT) process from polyether sulfone (PES), we develop planar asymmetric membranes with a hierarchical pore architecture spanning from nanopores (∼20 nm) in the dense skin and open-ended microchannel arrays with gradient pore size increasing vertically from microns to ∼100 μm. The nanoporous skin would be an ultrathin diffusion barrier, while the microchannels could support high-density cell loading by acting as separate chambers allowing uniform distribution of cells in the scaffold. Alginate hydrogel could permeate into the channels and form a sealing layer after gelation, which could slow down the invasion of host immune cells into the scaffold. The hybrid thin-sheet encapsulation system (∼400 μm thick) could protect allogeneic cells over half-year after intraperitoneal (IP) implantation in immune-competent mice. Such structural membranes and plastic–hydrogel hybrids of thin dimensions could find important applications in cell delivery therapy.
Wang Dan,Liu Jinfang,Yang Shuqi,Ji Xin,Wang Yuliang,Omoniyi Ahmed Olalekan,Zhang Jianfu,Su Zhongmin
Water-based polymer films can be readily deposited onto a wide range of metallic materials as an environmentally friendly coating through the demulsification-induced fast solidification(DIFS) method. However, there is still a lack of in-depth understanding of the demulsification process of the water-based emulsions and their deposition processes. Herein, we demonstrate that the build-up process of the commercial water-based micron-scale waterborne polyurethane, polyvinyl acetate, polyurethane acrylate, and natural rubber polymer films is affected by the collective effect of electric field and ion diffusion exerted by anode-cathode electrode pairs, applied voltage, conduction time, electrode distance, and emulsion species. A structural investigation of as-prepared polymer films allows us to propose two new structure build-up models. During a flat film deposition, isolated islands are formed first and grow on the substrate surface, and eventually, their mutual coalescence forms the final layer. Whereas, for a convex layer formation, the layer is first formed in the middle of the substrate and then grows toward the sides of the convex structure of the substrate. The results presented in this work expand the understanding of the mechanism of the DIFS process and may provide some new insights into structure-oriented multifunctional material design.
危险品化学品经营许可证（带存储）