Wireless Rehabilitation Training Sensor Arrays Made with Hot Screen-Imprinted Conductive Hydrogels with a Low Percolation Threshold.

Herein, we propose a highly sensitive wireless rehabilitation training ball with a piezoresistive sensor array for patients with Parkinson's disease (PD). The piezoresistive material is a low percolation threshold conductive hydrogel which is formed with polypyrrole (PPy) nanofibers (NFs) as a conductive filler derived from a polydopamine (PDA) template. The proton acid doping effect and molecular template of PDA are essential for endowing PPy NFs with a high aspect ratio, leading to a low percolation threshold (∼0.78 vol %) and a low Young's 004Dodulus of 37.69 kPa and hence easy deformation. The piezoresistive sensor exhibited a static and dynamic stability of 10,000 s and 15,000 cycle times, respectively. This stability could be attributed to the increased hydrophilicity of conductive fillers, enhancing the interfacial strength between the conductive filler and the matrix. The interaction between the PDA-PPy NFs and the hydrogel matrix endows the hydrogel with toughness and ensures the stability of the device. Additionally, the microdome structure of the conductive hydrogel, produced by hot screen-imprinting, dramatically improves the sensitivity of the piezoresistive sensor (∼856.14 kPa-1). The microdome conductive hydrogel can distinguish a subtle pressure of 15.40 Pa compared to the control hydrogel without a microstructure. The highly sensitive piezoresistive sensor has the potential to monitor the hand-grip force, which is not well controlled by patients with PD. The rehabilitation training ball assembled with a sensor array on the surface and a wireless chip for communication inside is built and used to monitor the pressure in real time through the WeChat applet. Thus, this work has significantly broadened the application of hydrogel-based flexible piezoresistive sensors for human activity monitoring, which provides a promising strategy to realize next-generation electronics.

Facile preparation of stretchable and self-healable conductive hydrogels based on sodium alginate/polypyrrole nanofibers for use in flexible supercapacitor and strain sensors.

A series of multifunctional conductive hydrogels (denoted as SA-B-DAPPy) is developed by combining sodium alginate (SA) and dopamine functionalized polypyrrole (DAPPy) nanofibers with borax as a cross-linking agent. By modulation of the DAPPy weight ratio to 3.5 wt%, the conductivity of the hydrogel can reach a high value of 1.33 ± 0.012 S/m. Both borate interactions and hydrogen bonds within hydrogel frameworks can account for the satisfactory stretchability (more than 800%) and instantaneous self-healing ability. More significantly, the SA-B-DAPPy hydorgels can be easily fabricated as electrode component in the symmetric supercapacitor with SA-B-DAPPy//SA-B//SA-B-DAPPy configuration. Due to the self-healing of the electrode/electrolyte interface, the obtained all-in-one device can deliver superior areal specific capacitance of 587 mF/cm2 at current density of 1.0 mA/cm2, high energy density of 52.18 µWh/cm2 at power density of 800 µW/cm2, good capacitance retention of 80% after 2000 cycles, as well as integration characteristics. Furthermore, on account of high conductivity, a thin SA-B-DAPPy hydrogel film can be fabricated into the motion sensor to detect and distinguish various human movements. The sensor exhibits high gauge factor (GF) up to 10.23, and stable, repeatable response signals, which permit supersensitive for monitoring large-scale joints motions and subtle muscle movements.

Highly Active Multimetallic Palladium Nanoalloys Embedded in Conducting Polymer as Anode Catalyst for Electrooxidation of Ethanol.

Fabrication of multimetallic nanocatalysts with controllable composition remains a challenge for the development of low-cost electrocatalysts, and incorporating metal-based catalysts into active carbon nanoarchitectures represents an emerging strategy to improve the catalytic performance of electrocatalysts. Herein, a facile method developed for Pd nanoparticle (NP)-based multimetallic alloys incorporated on polypyrrole (Ppy) nanofibers by in situ nucleation and growth of NPs using colloidal radiolytic technique is described. Electrochemical measurement suggests that the as-prepared catalysts demonstrate dramatically enhanced electrocatalytic activity for ethanol oxidation in alkaline medium. The ultrasmall Pd30Pt29Au41/Ppy nanohybrids (∼8 nm) exhibit excellent electrocatalytic activity, which is ∼5.5 times higher than that of its monometallic counterparts (12 A/mg Pd, 5 times higher activity compared to that of Pd/C catalyst). Most importantly, the ternary nanocatalyst shows no obvious change in chemical structure and long-term stability, reflected in the 2% loss in forward current density during 1000 cycles. The superior catalytic activity and durability of the nanohybrids have been achieved due to the formation of Pt-Pd-Au heterojunctions with cooperative action of the three metals in the alloy composition, and the strong interactions between the Ppy nanofiber support with the metal NPs. The facile synthetic approach provides a new generation of polymer-supported metal alloy hybrid nanostructures as potential electrocatalysts with superior catalytic activity for fuel cell applications.

A high-throughput nanofibers mat-based micro-solid phase extraction for the determination of cationic dyes in wastewater.

This study used nanofibers mat (NFsM)-based micro-SPE (µ-SPE) in 96-well plate format as a novel high-throughput sample preparation technique prior to the determination of cationic dyes in wastewater using HPLC-DAD. P-Toluene sulfonate (PTS(-)) doped polypyrrole (PPy) functionalized NFsM (PTS-PPy NFsM) was optimized as SPE sorbent in aspects of PPy form (particles and NFsM) and its doped anions (Cl(-) and PTS(-)), which showed good extraction efficiency and adsorption capacity for cationic dyes (Auramine-O, Chrysoidine and Rhodamine-B). Under the optimal conditions, the limits of detection (LODs) were between 0.3 and 0.5µg/L, and the linearity was achieved in the concentration ranging from 1.0 to 150.0µg/L with correlation coefficients (R) between 0.992 and 0.999. Compared with the published SPE methods, this approach demonstrated its advantages such as shorter extraction time (0.3min per sample), lower requirement sorbent (2.0mg), lower volume of organic solvent (0.7mL), higher recovery (90.1-99.1%) and precision (RSDs<6.9%). With this developed method, we have successfully analyzed the dyeing industry wastewater, which meets the Discharge Standards of Water Pollutants for Dyeing and Finishing of Textile Industry in China. The concentrations of three analyzed cationic dyes were from 2.9 to 13.9µg/L. The NFsM-based µ-SPE technique is practically a high-throughput sample preparation procedure that can accurately assess the pollutants in the wastewater from dyeing industry.

Disks solid phase extraction based polypyrrole functionalized core-shell nanofibers mat.

A novel disks solid phase extraction (SPE) based on polypyrrole (PPy) functionalized core-shell electrospun nanofibers mat was proposed. The performance of the established disks SPE technique was evaluated in the extraction of trace polar analytes from environmental water samples. Disulphonated (acid yellow 9) and monosulphonated azo dyes (acid orange 7 and metanil yellow) were selected as typical model analytes. Under the optimum conditions, detection limits were 0.15-0.3 µg/L for all target analytes and the enrichment coefficients were 106-121. The recoveries of sulfonated azo dyes added to typical environmental water samples were 87.6-112.3%, suggesting that the interferences of the sample matrix did not affect the enrichment. Compared with existing methods, the device in this study showed higher recovery, lower detection limit and better precision. Moreover, the miniaturized disks SPE technique for sample preparation is simple and fast, with significantly reduced sorbent bed mass (2.5 mg) and eluent volume (500 µL). These results indicate that PPy nanofibers mat-based disks SPE may be a promising device that can effectively extract the polar species in water samples.