Preparation And Application Of Graphene-based Flexible Wearable Sensor

Wearable devices have attracted wide attention because of their huge application potential in interactive entertainment,sports,medical health and other fields.Traditional wearable sensors,due to their inherent rigidity and mismatch of human-machine interface,have greatly restricted the real application.Flexible sensors have gradually emerged in many fields because of their good wearing comfort and excellent biocompatibility.But how to improve the detection sensitivity,adhesion and self-healing of the sensor still has not small challenges.Graphene has the advantages of high strength?125 GPa?,large specific surface area(2 630?g^-1),good conductivity and biocompatibility,and has become one of the first sensitive materials for preparing flexible sensors.In this paper,two different graphene-based hydrogel materials were prepared by a simple solution blending method and assembled into a flexible wearable sensor,and used to detect different amplitudes of human body movement and physiological parameters.The specific research contents are as follows:?1?Flexible and wearable sensor based on nanocomposite hydrogels has been proposed for monitoring the human large-scale,small-scale movements and several physiological signals.The nanocomposite hydrogel,prepared from graphene oxide?GO?,polyvinyl alcohol?PVA?and polydopamine?PDA?,exhibits excellent mechanical and electrical properties with tensile stress of 146.5 KPa,fracture strain of 2 580%,fracture energy of 2 390.86KJ m^-3,and the conductivity of 5 mS cm^-1.In addition,it possesses other merits including good self-healing with the electrical self-healing efficiency of 98%of its original resistance within 10 seconds,and strong self-adhesion onto a variety of surfaces of materials.This self-adhesive,self-healing,graphene-based conductive hydrogel can further assembled as wearable sensors to accurate and real-time detect the signals of human large-scale motions?including bending and stretching fingers joints,wrists joints,elbows joints,neck joints and knees joints?and small-scale motions?including swallowing,breathing and pulsing?through fracturing and recombination of reduced graphene oxide?rGO?electrical pathways in porous structures of hydrogel networks.Furthermore,the hydrogel can also be used as self-adhesive surface electrodes to detect human electrophysiological signals.Therefore,the hydrogel-based wearable sensor is expected to be used for long-term and continuous monitoring human body motion and detecting physiological parameters.?2?Another topic in this paper is to select an interpenetrating cross-linkednetwork hydrogel with good biocompatibility polyacrylamide?PAm?and sodium alginate?SA?as the flexible substrate,and use rGO partially reduced by PDA as the conductive Filler,the prepared PAm-prGO-SA hydrogel has excellent electrical conductivity,ultra-high toughness and good water retention properties.The results show that PAm-prGO-SA hydrogel has excellent electrical properties,its conductivity is as high as 12.99 S cm^-1,and the bending sensor response is 290%.At the same time,SA,GO and PDA have a large number of hydrophilic groups,so that the hydrogel has a good water retention performance.It keeps the water content above 90%in a short time.In addition,the synergy between the interpenetrating network composed of hydrogel and the interaction force between GO and each molecular chain makes the fracture energy of PAm-prGO-SA hydrogel up to4 754 KJ cm^-3.To a certain extent,the disadvantages of hydrogels in terms of tensile properties are improved.The PAm-prGO-SA hydrogel is assembled into a flexible wearable sensor that can accurately and effectively detect large movements of the human body,such as wrist,knee,and neck movements,and can also detect small strains of the human body?breathe?.Therefore,the sensor has great application potential in wearable devices in the medical and health field.