No abstract

The development of energetic materials with both high energy and high safety has always been the focus of the field of energetic materials. In this paper, a low-current-sensitivity flexible energetic film composed of carbon nanofibers (CNFs)-coated Al/CuO metastable intermolecular composites (MICs) was prepared by a blow-spinning combined with controlled heat treatment technique. Hotspots can hardly generate in this kind of energetic film due to the increased electrical and thermal conductivity, leading to low sensitivity of MICs. It evenly stays at a high voltage (60 V) for 24 h without raising the temperature significantly. The energetic films keep the high energy release of MICs due to the additional violent reactions between CuO and CNFs as well as the light weight of CNFs, showing the heat release of 2864 J/g. In addition, the obtained films exhibit good mechanical properties and can maintain the structural integrity after 1000 cycles of repeated bending to a 6 mm curvature radius. The above characteristics reveal that energetic films presented in this paper have certain safety, high energy, and flexibility and have potential applications in transient electronics with flexible requirements such as micro-electromechanical system.

Electrothermal actuators (ETAs) have received great attention among soft actuators due to their simple structure and light weight. Since most of the application scenarios of ETAs are on soft robots, the current research on ETAs mainly focuses on the improvement of their max deformation. In fact, important application prospects of soft actuators lie in biological and medical aspects, such as smart wearable devices. This remind us to consider the issues of safety and comfort, which have been neglected for a long time. In this work, we report an ultralight, porous Nafion/Ag composite microfiber film actuator prepared by blow-spinning. Unlike most ETAs, it has porous fibrous structure and can achieve considerable deformation in a safe temperature range for the organisms (30-67 °C). The film actuator, with a low density (about 0.45 g cm-3), can bend in a short time (within 15 s) to an angle of about 91° and achieve a displacement of 11.2 mm when applied a low voltage (2.4 V). Owing to the processing method of blow-spinning, the film actuator presents a series of excellent characteristics, including softness, light weight and porosity, etc. To summarize, the Nafion/Ag composite microfiber film actuator shows great potential in soft robots and smart wearable devices due to their properties of low driven voltage, low weight and moderate working temperature range.