Moisture self-regulating ionic skins with ultra-long ambient stability for self-healing energy and sensing systems

Dehydration has been a key limiting factor for the operation of conductive hydrogels in practical application. Here, we report self-healable ionic skins that can self-regulate their internal moisture level by capturing extenral moistures via hygroscopic ion-coordinated polymer backbones through antipolyelectrolyte effect. Results show the ionic skin can maintain its mechanical and electrical functions over 16 months in the ambient environment with high stretchability (fracture stretch ∼2216 %) and conductivity (23.5 mS/cm). The moisture self-regulating capability is further demonstrated by repeated exposures to harsh environments such as 200°C heating, freezing, and vacuum drying with recovered conductivity and stretchability. Their reversible ionic and hydrogen bonds also enable self-healing feature as a sample with the fully cut-through damage can restore its conductivity after 24 h at 40 % relative humidity. Utilizing the ionic skin as a building block, self-healing flexible piezoelecret sensors have been constructed to monitor physiological signals. Together with a facile transfer-printing process, a self-powered sensing system with a self-healable supercapacitor and humidity sensor has been successfully demonstrated. These results illustrate broad-ranging possibilities for the ionic skins in applications such as energy storage, wearable sensors, and human-machine interfaces

Design and Performance of a Low-Energy Gamma-Ray Trigger System for HERD

The High Energy cosmic-Radiation Detection (HERD) facility has been proposed as one of the main experiments on board the Chinese space station. HERD is scheduled to be installed around 2027 and to operate for at least 10 years. Its main scientific goals are the study of the cosmic ray spectrum and composition up to the PeV energy range, indirect dark matter detection, and all-sky gamma-ray observation above 100 MeV. HERD features a novel design in order to optimize its acceptance per weight, with a central 3D imaging calorimeter surrounded on top and on its four lateral sides by complementary subdetectors. A dedicated trigger, dubbed the ultra-low-energy gamma-ray (ULEG) trigger, is required to enable the detection of gamma rays down to ~100 MeV. The ULEG trigger design is based upon the search for energy deposition patterns on the tracker and the anticoincidence shield, compatible with the conversion of a gamma ray within the tracker volume and resulting in enough tracker hits to allow for a good-quality gamma-ray direction reconstruction. We describe the current status of the design of the ULEG trigger system. We also characterize its performance in detecting gamma rays as inferred from Monte Carlo studies