Design, Fabrication And Performance Study Of Ionic Hydrogel-based Self-powered Sensors

In recent years,as the wearable sensing devices play a more and more important role in improving individual health and quality of life,they have been widely studied.Among others,ionic hydrogel is considered as one of the most promising wearable sensor materials because of its tissue-like mechanical properties,excellent biocompatibility,high transparency,etc.The exisiting ionic hydrogel-based sensors are mostly resistive and capacitive sensors.Due to the different signal tranport carriers between the ionic hydrogel-based sensors and external electronic circuits,the ionic hydrogel-based sensors are generally required to be powered by AC supply.The use of commercial battery will induce the occurrence of electrochemical reactions on the surfaces of metal electrodes,leading to lack of chemical and sensing stability for resulting ionic sensors.Therefore,for achieving the wearable applications of ionic sensors,a commercial battery and a DC-AC conversion circuit should be introduced for the steady operation of them,which limits the miniaturization,lightweight and wearable comfort of the sensors.In order to solve the above problems,this paper puts forward two new designing strategies of self-powered ionic sensors(SPI-sensors).Their sensing performances and mechanisms have been systematically studied,and the resulting SPI-sensors can be used for the the real-time monitoring of motion and temperature of human body.The main research results are shown as follows:1.We present a new strategy for designing high-performance self-powered ionic hydrogel-based sensors for wearable applications by simply replacing the metal electrodes of ionic sensors with the battery electrodes.The strategy can not only maintain a stable ion concentration within ionic sensors due to the insertion/extraction of ions on two battery electrodes during the signal transmission,but also endow the sensors with self-powering capacity.The as-prepared self-powered ionic hydrogel-based sensors show ultrawide sensing range(0.01%?2000%),high sensitivity(8.9),ultrahigh charge and discharge stability(10000times),which is superior to the existing ionic sensors.Besides,the self-powered ionic hydrogel-based sensors can precisely monitor the full-range human motions in real time,and simultaneously can be used as a power source for other wearable devices.The resulting SPI-sensors show great potential in the applications such as human-computer interaction,motion and health monitoring of human bodies,etc.2.Inspired by the receptors of the human sensing system,we present a novel yet versatile strategy towards designing humanlike bionic SPI-sensors.The bionic SPI-sensors can be integrated readily by sandwiching an ionic diode between two ionic hydrogels,in which the ionic diode severs as artificial cell membrane,and two ionic hydrogels function as the extracellular and intracellular electrolytes,respectively.The bionic SPI-sensors show high pressure identification range(> 90 N),large strain sensing range(> 400%),high detection resolutions of pressure(0.1 N),wide temperature identification range(0?-100?),and can sense the temperature variation precisely in a safe non-contact mode.Besides,the bionic self-powered ion sensor can not only monitor the bending of human joints,subtle vibration of vocal cords and pulse in real time,but also detect the radiation temperature around the heat source.This work opens up a new path for constructing multifunctional self-powered ionic sensors capable of recreating human sensory functions.