Preparation And Properties Of Transparent Ultra-sensitive Wearable Sensors Based On AgNW/Ti₃C₂T_xMXene

In recent years,wearable sensors have attracted more and more attention due to their portability and the real-time monitoring of human body signals.When wearable sensors are attached on the surface of the human body,it can detect some essential signals that allow doctors and users to understand the one's health status in real-time,and it can also record the daily activities so that the users can control their exercise.Besides,wearable sensors have a broad application prospect,and they can be used in human-computer interaction,virtual reality,flexible display,and many other fields.Generally,wearable sensors have low sensitivity and opacity,which limit their application field.Therefore,it is still a challenge to fabricate wearable sensors with both high transmittance and high sensitivity.Here,transparent wearable sensors with high sensitivity were fabricated by using silver nanowires(AgNW)and Ti₃C₂T_x MXene.As-prepared wearable sensors could detect the daily activities and physiological signals of the human body.There were two reasons for choosing AgNW and Ti₃C₂T_x MXene as sensing materials.First,AgNW has a high length-to-diameter ratio,high conductivity,low percolation threshold,and excellent flexibility,which makes it suitable as the conductive material for transparent wearable sensors.Second,Ti₃C₂T_x MXene,as an emerging two-dimensional conductive material,has high conductivity,and as-prepared monolayer Ti₃C₂T_x MXene has a high optical transmittance.By combining two high conductive and transparent materials to build a unique microstructure,the thickness of the sensing material layer can be reduced effectively.Therefore,the transmittance and sensitivity of as-prepared wearable sensors could be improved tremendously.This paper mainly includes the following two aspects:(1)AgNW was spin-coated on the surface of PDMS film,and then spin-coated a layer of PDMS to encapsulate the conductive network.Due to the excellent biocompatibility of PDMS film,the wearable sensors showed high transmittance,and no adverse reactions carried out when it was attached to the surface of human skin.Also,the sandwich structure was used to wrap the AgNW conductive layer,and it can effectively protect the conductive network and improve the stability of the as-prepared wearable sensor.Moreover,the transmittance and sensitivity of the sensors could be adjusted effectively by changing the number of AgNW spin-coating.When the number of AgNW spin-coating was six times,the sensors had a high transmittance of 72.2%and could be stretched up to 147%without breaking.With 15%applied strain,the resistance increases 5.17 times,which had a noticeable change.(2)AgNW and Ti₃C₂T_x MXene were deposited on the surface of PDMS film by combining spin-coating and spray-coating,respectively.Then,PDMS was spin-coated and cured on the surface of the conductive layer.The as-prepared sandwich structure could effectively improve the stability of wearable sensors and avoid water and air oxidation to damage the conductive network.By adjusting the spraying time of Ti₃C₂T_xMXene,the sensitivity and stretch range of the sensors could be adjusted adequately.Therefore,transparent sensors could be applied in the broader range.The AgNW/Ti₃C₂T_x MXene based wearable sensors have a transmittance of 89%and could also be used to measure very minimal strain.The resistance was increased by 2.2%at 0.025%strain and 198%at 1%strain,and it could be found that the sensors had a very high sensitivity.The as-prepared wearable sensors had a fast response of 54 ms,and the fast response allowed the wearable sensors to detect signals in real-time.High transmittance,high sensitivity,and adjustable stretching range made AgNW/Ti₃C₂T_x MXene based wearable sensors had excellent development potential in wearable electronics and flexible display.