High-Performance Dielectric Elastomer Nanogenerator for Efficient Energy Harvesting and Sensing via Alternative Current Method

Electrospun cellulose acetate nanofibrous composites for multi-responsive shape memory actuators and self-powered pressure sensors

Soft actuators and sensors have attracted extensive scientific interest attributed to their great potential applications in various fields, but the integration of actuating and sensing functions in one material is still a big challenge. Here, we developed an electrospun cellulose acetate (CA)/carbon nanotube nanofiborous composite with both functional applications as multi-responsive shape memory actuators and triboelectric nanogenerator (TENG) based sensors. Attributed to excellent thermo- and light-induced shape memory performance, the CA nanofiborous composites showed high heavy-lift capability as light driven actuators, able to lift burdens 1050 times heavier than their own weight. The CA nanofiborous membranes based TENG exhibited high output performance with open-circuit voltage, short-circuit density, and instantaneous power density about 103.2 V, 7.93 mA m^-2 and 0.74 W m^-2, respectively. The fabricated TENG based pressure sensor exhibited a high sensitivity of 3.03 V kPa^-1 below 6.8 kPa and 0.11 V kPa^-1 in the pressure range from 6.8 to 65 kPa, which can be effectively used to monitor human motion state and measure wind velocity. It is expected that the electrospun composites with actuating and sensing functions will show prosperous applications prospects in soft robotics.

Supramolecular Elastomers with Excellent Dielectric Properties and High Recyclability Based on the Coordinative Bond

The enhancement in dielectric properties and self-healing ability for dielectric materials has been a challenging subject these years. Herein, a series of self-healed dielectric elastomers by combining the ferric ions and carboxyl-containing poly(sulfone siloxane)s is reported. Experimental results indicate the excellent dielectric properties of obtained elastomers, as the dielectric constant up to 12.8. SEM micrographs exhibit that carboxyl groups and ferric ions can aggregate together to generate clusters, which further result in interfacial polarization. Besides, high polarity dipole units including sulfonyl units and carboxyl groups contribute to dipole polarization. The overlay of the two mentioned polarization eventually results in the high dielectric property. The dielectric constant obviously increases with the contents of carboxyl groups and ferric ions. Moreover, the samples are feasible for recycling and reprocessing with high self-healing efficiency, owing to the reversibility of the coordination bond. A self-healing efficiency of 92.1% in tensile strength of the obtained samples can be reached after 2 h treatment at 60 °C. And the elastomers can also conveniently recover most mechanical properties after solution treatment. This work may offer a promising method for preparing dielectric elastomers with high dielectric properties and self-healing ability.

A Stretchable Expanded Polytetrafluorethylene-Silicone Elastomer Composite Electret for Wearable Sensor

Soaring developments in wearable electronics raise an urgent need for stretchable electrets. However, achieving soft electrets simultaneously possessing excellent stretchability, longevity, and high charge density is still challenging. Herein, a facile approach is proposed to prepare an all-polymer hybrid composite electret based on the coupling of elastomer and ePTFE membrane. The composite electrets are fabricated via a facile casting and thermal curing process. The obtained soft composite electrets exhibit constantly high surface potential (-0.38 kV) over a long time (30 days), large strain (450%), low hysteresis, and excellent durability (15,000 cycles). To demonstrate the applications, the stretchable electret is utilized to assemble a self-powered flexible sensor based on the electrostatic induction effect for the monitoring of human activities. Additionally, output signals in the pressure mode almost two orders of magnitude larger than those in the strain mode are observed and the sensing mechanism in each mode is investigated.