Flexible piezoresistive pressure sensors have been attracted a lot of attention due to their simple mechanism, easy fabrication, and convenient signal acquisition and analysis. Herein, a new flexible piezoresistive sensor based on microstructured electrospun rough polyurethane (PU) nanofibers film is assembled. The microstructured PU film with tiny bumps is prepared in one step via electrospinning technology, which imparts a microstructured rough upper surface and a smooth lower surface. With this unique microstructure, we have made it possible for PU/Ag films to serve as sensing layers for piezoresistive sensors by introducing a silver conductive layer on the surface of electrospun PU film. The fabricated piezoresistive pressure sensor delivers high sensitivity (10.53 kPa−1 in the range of 0–5 kPa and 0.97 kPa−1 in the range of 6–15 kPa), fast response time (60 ms), fast recovery time (30 ms), and long-time stability (over 10,000 cycles). This study presents a fabrication strategy to prepare the microstructured PU nanofiber film using electrospinning technology directly, and the as-developed sensor shows promise in applications such as wrist pulse measurement, finger movement monitoring, etc., proving its great potential for monitoring human activities.
Flexible piezoelectric devices could be widely used as important components in the future of electronic skin, foldable screens, robotics, and more. Herein, an integrated flexible piezoelectric device based on polyurethane/silver nanowire (PU/AgNW) electrodes and a piezoelectric polyurethane/polyvinylidene fluoride-trifluoroethylene [PU/P(VDF-TrFE)] layer was assembled directly through the continuous electrospinning method. The sheet resistance of the PU/AgNW electrode is 1.4 Ω sq−1 without tensile strain, and the integrated device exhibits high flexibility, high water-vapor permeability, and excellent work stability. Furthermore, both the PU/AgNW electrode and the piezoelectric device perform with excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), attributed to the incorporation of the silver nanowires. The cross-section SEM image shows a uniform structure of the device, which implies a good connection between electrode layers and the piezoelectric layer. The open-circuit output voltage, short-circuit output current and power density of the device can reach up to 47.9 V, 31.8 μA, and 35.3 μw cm−2, respectively. This study presents a fabrication strategy for both flexible conductive electrodes and piezoelectric devices, and it shows a promising application for monitoring human-activity and harvesting energy from ambient environments.
With
the fast growth of wearable intelligent devices, flexible
sensors with a broad strain sensing range and high sensitivity are
in urgent demand. Furthermore, the sensitivity of flexible wearable
electronic devices to various signal capture depends on multiple interfacial
bond interactions and a microstructure. However, a flexible sensor
without multiple interfacial bonds has poor mechanical properties,
low sensitivity/conductivity, and single sensing function to limit
commercial sensor application. In this work, the novel dip-coating
technique was used to design a flexible sensor based on polyvinyl
alcohol with multiple interfacial bond interactions and a microcrack
structure. Interestingly, the sensor exhibits high sensitivity with
gauge factor > 100, a high conductivity of 356 mS m–1, impressive thermal sensitivity (0.01071 °C–1), a large strain of 344.5%, and excellent wear-resistance and durability.
Possible sensing mechanisms under multiple stimuli have been presented.
Moreover, flexible sensors with multiple signal monitoring can monitor
real-time full-range human body motion and physical signal collection,
providing a promising strategy to develop this sensor with outstanding
performance in flexible sensor and sporting applications.
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