Air pollution caused by particulate matter and toxic gases is violating individual’s health and safety. Nanofibrous membrane, being a reliable filter medium for particulate matter, has been extensively studied and applied in the field of air purification. Among the different fabrication approaches of nanofibrous membrane, electrospinning is considered as the most favorable and effective due to its advantages of controllable process, high production efficiency, and low cost. The electrospun membranes, made of different materials and unique structures, exhibit good PM2.5 filtration performance and multi-functions, and are used as masks and filters against PM2.5. This review presents a brief overview of electrospinning techniques, different structures of electrospun nanofibrous membranes, unique characteristics and functions of the fabricated membranes, and summarization of the outdoor and indoor applications in PM filtration.

Tactile recognition is among the basic survival skills of human beings, and advances in tactile sensor technology have been adopted in various fields, bringing benefits such as outstanding performance in manipulating objects and general human−robot interactions. However, promoting enhanced perception of the existing tactile sensors is limited by their sensor array arrangement and wire-connected design. Here we present a wireless flexible magnetic tactile sensor (FMTS) consisting of a multidirection magnetized flexible film (perception module) and a contactless Hall sensor (signal receiving module). The flexible magnetic film is composed of NdFeB microparticles and soft silicone elastomer microparticles, and it transfers the unambiguous transduction of external force position and magnitude into magnetic signals. Benefiting from the specific magnetization arrangement and clustering algorithm, only one Hall sensor is needed in FMTS to perceive the magnitude and position of the contact spot simultaneously with super-resolution (2.1 mm average error) on a large area (3600 mm 2 ), and the effective working distance is also greatly extended (∼30 mm), allowing for the full softness and adaptability to diverse conditions. We anticipate that this design will promote the development of soft tactile sensors and their integration into human−robot interaction and humanoid robot perception.

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The hybrid aerial underwater vehicle (HAUV) merges the best of unmanned aerial vehicle (UAV) and unmanned underwater vehicle into one platform makes it possible to operate in both the air and water. Various possible applications of HAUV have aroused much research on it. However, the underwater endurance and operation depth of current HAUVs are still limited. This hinders the application and popularization of HAUV in rugged environments. This paper presented the design, fabrication, and testing of a novel concept HAUV, Nezha III. It is featured by its piston-driven underwater glide strategy and combination of an underwater glider and fixed-wing vertical takeoff and landing aircraft. In-depth design and evaluation of the amphibious wings with tradeoffs between aerodynamic and hydrodynamic performance in both fluids was conducted. The vehicle prototype was built, and field experiments, including domain transitions and underwater operations, were conducted in Qiandao Lake, China. Due to the experiment site constraints, the computational fluid dynamics technique evaluated horizontal flight performance with fixed wings. The experimental results show that the prototype can realize rotor flight and stable domain transitions. Moreover, this piston-driven underwater glide strategy extended the HAUV's underwater endurance over 24 h and operational depth to 25.5 m. To the best of our knowledge, Nezha III possesses the most extended underwater endurance among existing HAUVs.

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