Mufang Li

Stretchable conductive polyurethane elastomer in situ polymerized with multi-walled carbon nanotubes

The development of the wearable sensors for healthcare related applications requires mechanically stretchable, electrically conductive and biologically compatible elastomers. We have fabricated a conductive polyurethane (PU) elastomer by in situ polymerization with surface hydroxyl-modified Multi-Walled Carbon Nanotubes (MWNTs). The FT-IR and Raman spectroscopy results indicated that the successful incorporation of the MWNTs into PU macromolecules. The good dispersion of MWNTs in PU/MWNT elastomers was confirmed by transmission electron microscopy (TEM) and Raman spectroscopy. Thermogravimetric analysis (TGA) suggested improved thermal stability of the in situ polymerized PU/MWNT elastomers. The in situ polymerization with MWNTs led to a significant increase in the conductivity of PU/MWNT elastomers. The stretching facilitated the orientation of the MWNTs and further enhanced the conductivity of PU/MWNT elastomers. The in situ polymerized PU/MWNT elastomers were employed as electrodes to construct a pressure sensor demonstrating good sensitivity and consistency.

Hierarchically Three-Dimensional Nanofiber Based Textile with High Conductivity and Biocompatibility As a Microbial Fuel Cell Anode

Microbial fuel cells (MFCs) encompass complex bioelectrocatalytic reactions that converting chemical energy of organic compounds to electrical energy. Improving the anode configuration is thought to be a critical step for enhancing MFCs performance. In present study, a hierarchically structured textile polypyrrole/poly(vinyl alcohol-co-polyethylene) nanofibers/poly(ethylene terephthalate) (referred to PPy/NFs/PET) is shown to be excellent anode for MFCs. This hierarchical PPy/NFs/PET anode affords an open porous and three-dimensional interconnecting conductive scaffold with larger surface roughness, facilitating microbial colonization and electron transfer from exoelectrogens to the anode. The mediator-less MFC equipped with PPy/NFs/PET anode achieves a remarkable maximum power density of 2420 mW m(-2) with Escherichia coli as the microbial catalyst at the current density of 5500 mA m(-2), which is approximately 17 times higher compared to a reference anode PPy/PET (144 mW m(-2)). Considering the low cost, low weight, facile fabrication, and good winding, this PPy/NFs/PET textile anode promises a great potential for high-performance and cost-effective MFCs in a large scale.

The woven fiber organic electrochemical transistors based on polypyrrole nanowires/reduced graphene oxide composites for glucose sensing

Novel woven fiber organic electrochemical transistors based on polypyrrole (PPy) nanowires and reduced graphene oxide (rGO) have been prepared. SEM revealed that the introduction of rGO nanosheets could induce the growth and increase the amount of PPy nanowires. Moreover, it could enhance the electrical performance of fiber transistors. The hybrid transistors showed high on/off ratio of 102, fast switch speed, and long cycling stability. The glucose sensors based on the fiber organic electrochemical transistors have also been investigated, which exhibited outstanding sensitivity, as high as 0.773 NCR/decade, with a response time as fast as 0.5s, a linear range of 1nM to 5μM, a low detection concentration as well as good repeatability. In addition, the glucose could be selectively detected in the presence of ascorbic acid and uric acid interferences. The reliability of the proposed glucose sensor was evaluated in real samples of rabbit blood. All the results indicate that the novel fiber transistors pave the way for portable and wearable electronics devices, which have a promising future for healthcare and biological applications.

Hydrogel degradation triggered by pH for the smart release of antibiotics to combat bacterial infection

Here we developed a hydrogel that could be triggered by a change in pH to degrade and smartly release antibiotics to combat a bacterial infection; use of this hydrogel could reduce the inappropriate and disproportionate use of antibiotics.

A facile route to the production of polymeric nanofibrous aerogels for environmentally sustainable applications

Mesoporous polymeric aerogels with high compressibility and durability have attracted great attention due to their environmentally sustainable applications. However, it is still challenging to develop polymeric aerogels in a simple, low-cost and mass produced way. Herein, we report a strategy to prepare a high porosity polymeric nanofibrous aerogel (referred to as NFA) by direct freeze-drying of the poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous suspension. It is noteworthy that this process is free of gelation and any solvent exchange. In addition, the PVA-co-PE nanofibers were mass-produced from our production line, based on a high throughput Melt-Extrusion-Phase-Separation technique. Additionally, the network of the NFA aerogels can be tuned by the host–guest assembly of the nanofibers and the foreign PVA nano-lamellae from disordered/ordered cellular to a leaf-like structure. Further modification of the NFA by gaseous methyltrichlorosilane (MTS) led to covalently bonded siloxane nanoparticles formed on the surface, thereby facilely realizing the nanofibrous aerogel from hydrophilic to hydrophobic as well as achieving excellent resilience. The corresponding hydrophobic aerogel (designated as HNFA) possessed a slightly larger density of 11.1 mg cm−3 with an almost unchanged porosity of 99% and meso–macroporous pores of 5–100 nm compared with the NFA (8.3 mg cm−3). They are demonstrated as good thermal insulators (0.033–0.044 W m−1 K−1), high-performance air filters (99.2% filtration efficiency with 64 Pa pressure drop), organic pollutants absorbers (2500–5329% weight gain) and continuous water/oil separators. Therefore, this study opens up a new approach for simple and large-scale preparation of polymeric aerogels for versatile applications.

Concurrent filtration and inactivation of bacteria using poly(vinyl alcohol-co-ethylene) nanofibrous membrane facilely modified using chitosan and graphene oxide

Integrating multiple nanoscale components with antibacterial properties into a single membrane filter is indispensable for efficient application in water treatment. Herein, we prepare a poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membrane (NFM) decorated using chitosan (CS) and graphene oxide (GO), via a melt-phase-separated nanofiber/CS-GO suspension coating technique. As indicated by morphology and structure analysis, CS and GO have tight physical attachment to the surface of the nanofibers throughout the PVA-co-PE layer, with diminished pore size and contact angle. Compared to commercial PVDF membrane, NFMs exhibit enhanced retention rate of pigmented nanoparticles and bacterial cells and higher and more stable water flux due to their relatively small thickness and high stacking density. The performance for inactivation of bacteria is also improved by employing NFM. Particularly after CS/GO modification, the inactivation rate of the membrane is increased to the range of 97.8–99.5% against E. coli and S. aureus with superior repetitive-use performance. These results can be attributed to the enhancement effect of the nanofiber network on the activity of the hydroxyl groups in PVA-co-PE, NH3+ in chitosan and the 2D structure of graphene oxide. The present membranes have much potential for use in long-term water treatment with high efficiency and stability.

Affinity functionalization of PVA-co-PE nanofibrous membrane with Ni(II)-chelated ligand for bovine hemoglobin adsorption

We report that poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membrane was surface functionalized by iminodiacetic acid (IDA) and then chelated by Ni(II) ions for hemoglobin adsorption. The results indicated that bovine hemoglobin (BHb) adsorption on Ni(II)-chelated PVA-co-PE nanofibrous membrane was better described by the Langmuir model. The experimental maximum adsorption capacity value was 66 mg g−1. The method performed in this study provides an exploratory research for the large-scale purification of BHb and other proteins.

Reinforcement of Polyethylene Terephthalate via Addition of Carbon-Based Materials

Abstract Polyethylene terephthalate is one of the most important engineering thermoplastic materials and polymers. Based on its processing and thermal treatments, PET possesses an amorphous (transparent) or a semicrystalline (opaque and white) form. Nowadays, much attention has been paid to the addition of carbon-based materials to PET polymer. Carbon-based materials including carbon nanotubes, carbon fiber, and graphene have extraordinary thermal conductivity and mechanical and electrical properties, thus finding applications as additives to various structural and functional materials. When they are incorporated into a PET polymer matrix, the resulting composites have significantly different electrical, mechanical, and physical–chemical properties than the original.

Natural alginate fiber-based actuator driven by water or moisture for energy harvesting and smart controller

Many idle green resources exist in nature, including water and moisture, which are ubiquitous but have no great value. In this work, we, for the first time, innovatively twisted a gel-state natural alginate fiber prepared by wet spinning to obtain a fiber-based actuator that shows remarkable performance under water and moisture stimulation. Owing to the excellent swelling and contraction properties in response to water, the twisted alginate fiber-based actuator underwent a rapid reversible rotational motion with a rotation speed of 13 000 rpm and a revolution of over 400 turns. Moreover, the shape, as well as the performance, of the twisted fiber remained stable, even after 400 cycles. The excellent driving performance, simple preparation, low-cost production, and the industrialization development trend render the natural alginate fiber-based actuator a new type of green-energy material as a viable replacement for the existing torsional fiber-based actuators made of GO and nanotube materials. In addition, we designed the twisted fiber into a hydro-generator, a smart rainy curtain, breathable fabric, and a smart crane, which have great application prospects in future intelligent systems.

A novel PU/PVA-co-PE composite nanofiber membrane for water filtration

Filter membranes with high efficiency and low energy consumption are gaining more attention owing to the increase in water pollution. To enhance the filtration performance, a novel spindle polyurethane (PU) / poly(vinyl alcoholco-ethylene) (PVA-co-PE) composite nanofiber membrane was prepared. It is the first time that the spindle composite nanofibers and nanofiber membranes are prepared based on the PU/PVA-co-PE/CAB (cellulose acetate butyrate) immiscible polymer blends. The effects of PU concentration on the morphology, size distribution, and hydrophilicity of PU/PVA-co-PE nanofiber membranes were analyzed. The pure PVA-co-PE nanofiber membrane and PU/PVA-co-PE composite nanofiber membranes were used to filtrate the nanoparticle suspension with scarlet pigments (50–300 nm). Due to the smaller pore size, looser structure, and larger porosity, the rejection rate and flux of spindle PU/PVA-co-PE composite nanofiber membranes are both higher than that of pure PVA-co-PE nanofiber membrane. When the basic weight of nanofiber layer is 6 g/m2, the rejection rate of all the PU/PVA-co-PE membranes are above 99%. This study provided a novel, facile, and high-throughput method to prepare spindle nanofiber membranes and indicated the advantage of spindle PU/PVA-co-PE composite nanofiber membranes in the application of water filtration.