Polytetrafluoroethylene (PTFE) hollow fiber membranes are a promising candidate in highly contaminated wastewater treatment and management because PTFE is intrinsically chemically inert and hydrophobic. However, low water flux and fouling (contamination due to protein attachment and accumulation), both associated with low surface energy, pose great limits in filtration efficiency and the long-term use of PTFE hollow fiber membranes. Here we report a surface engineering approach/strategy of coating PTFEÂ hollow fiber membranes with polyvinyl alcohol/oxidized sodium alginate (PVA/OSA) double network (DN) hydrogels via N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTS) hydrolysis and grafting. The as-prepared PVA/OSA DN hydrogel coated PTFE hollow fiber membranes exhibited high efficiency in oil-water separation and excellent antifouling performance due primarily to the favorable interfacial electrostatic interaction and the hydration coating layer on the fiber surfaces. Moreover, the PVA/OSA DN hydrogel coatings remained high hydrophilicity and structural intergrity and operation stability after extensive time of soaking in strong acidic and alkaline solutions, all in great favor of the performance they were initially designed and intended for.
The Org-rectorite, which was used as a filler in the Rectorite/Epoxy nanocomposites, was prepared by the intercalation and exfoliation of rectorite with dodecyl-bis (2-hydroxyethyl)-methylazanium chloride as the organic cation exchange agent. The two curing agents methyl hexahydrophthalic anhydride (MHHPA) and m-phenylenediamine were employed at working temperature ranging from 70 °C to 190 °C. The samples were characterized by Fourier Transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) analysis. The results show that the d 001 (55.9 Å) of Rectorite/Epoxy composites cured with MHHPA at 70 °C was larger than the Org-rectorite (28.7 Å), and the Org-rectorite was exfoliated at 90 °C working temperature. While the d 001 of Rectorite/Epoxy composites cured with m-phenylenediamine at 70 °C and 90 °C were 40.9 Å and 42.1 Å , and were exfoliated at 140 °C. The apparent activation energy (Ea) of Rectorite/Epoxy composites cured with MHHPA and m-phenylenediamine were obtained to be 74.85 and 59.15 KJ/mol, respectively. The higher apparent activation energy (Ea) of MHHPA systems may be responsible for the lower exfoliation temperature.
Increasing interests in remote monitoring of vital signs through telecommunication, especially with wireless and mobile communication have enabled a new generation of information system for healthcare applications. The system may include miniature sensor nodes embedded with wireless communications and a mobile computer delivering information to remote locations. In this paper, we introduced an inexpensive and ultra-low power system for measuring ECG and heart rate in contact and contact-less manners. Existing monitoring system uses gel or electrodes for measuring ECG signals. However, in this study, we used unique electric potential EPIC sensors from Plessey's and infrared sensors. The prototype is capable of monitoring both heart rate and ECG signals with a hibernation mode, which would require less power to transmit the data. Our developed prototype can be used to monitor premature infants as their skins are sensitive and current system uses patches or gel to collect biomedical signals. The proposed prototype for monitoring vital signs has been tested in our lab. The results show that it can achieve low power consumption though a hibernation mode.
Numerical models were established to correlate with the experimentally measured properties of mesh conductors previously developed through a combined process of dip coating carbon nanotubes and inkjet printing poly 3,4-ethylenedioxythiophene: poly styrene sulfonate. The electroluminescent (EL) devices assembled with such mesh conductors as front electrodes were modeled by commercially available finite element method software COMSOL Multiphysics. The modeling results are in agreement with those from the experiments and suggest that an optimized fiber arrangement is the key for further improving the performance of EL devices based on mesh conductors.
Introducing ionic liquids as new structure-controlled additives, Polysulfone (PSf) membranes were prepared by the wet-phase-inversion using 1-(n-Octyl)-3-Methyl limidazolium Hexfluorophosphate [C 8 mim][PF 6 ] or 1-hexadecyl-3-methylimidazolium thiocyanate [C 16 mim][SCN] into the casting solution (PSF/NMP). Scanning electron microscope was utilized to visualize cross-sections and surfaces of the membranes to gain more better understanding the influence of different ionic liquids on the structure and seperation properties of the membrane. With increase of concentration of ionic liquid [C 16 mim][SCN] in casting solutions, the structures of the membranes changed from asymmetric finger pores to the spongy-finger-macrovoid structure of the pores. However, With increase of concentration of ionic liquid [C 8 mim][PF 6 ] in casting solutions, the structures of the membranes changed from asymmetric finger pores, lengthened macroporous pores, to the close macrovoid pores. Fininally, permeation properties of the membranes was investigated. The result indicated that at the 4:76 ratio of [C 16 mim][SCN]/NMP, the retention rate and solution flux of the prepared membrane are 97.1% for PEG10000 and 48.7 L· h -1 · m -2 . At the 4:76 ratio of [C 8 mim][PF 6 ]/NMP in the polymer solution, the retention rate of the membrane is 92.3% for PEG10000 and solution flux is 33.7 L· h -1 · m -2 . Meanwhile, the two ionic liquids were used as plasticizers, according the thermal properties of the membranes.
In this review, we demonstrated the recent advances in the fabrication strategies of graphene–biomacromolecule hybrid materials and their applications in the field of tissue engineering, such as implant materials, cell culture scaffolds, and regenerative medicine.
Poly(vinylidene fluoride) (PVDF) membranes with highly hydrophilic and antifouling properties are desirable for oily wastewater treatment. Herein, we report (1) a strategy of bulk modification of PVDF by in situ integration of PVDF and a particle-based double-network (PDN) hydrogel, poly-2-acrylamido-2-methylpropanesulfonate/polyacrylamide (PAMPS/PAAm), via a strong PDN and PVDF interpenetrating polymer network (PDN–PVDF IPN) to obtain a PVDF/PDN solution and (2) the subsequent casting of it into a microfiltration membrane via spray-assisted non-solvent-induced phase separation (SANIPS). The IPN structure modulates the surface segregation behavior of the highly hydrophilic and robust PDN hydrogel in the process of SANIPS, endowing the resulting PVDF/PDN membrane with excellent bulk mechanical properties and much enhanced wettability and thereby high oil/water emulsion separation efficiency and antifouling performance. Moreover, the PVDF/PDN membrane presented good chemical stability upon soaking in strongly acidic and alkaline solutions for an extensive time. Our work expands the research in phase-inversion-based antifouling oil/water separation materials.
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