The Study Of A Self-powered Wearable Device For Perspiration Analysis Based On Piezo-Biosensing Unit Matrix Of Enzyme/ZnO Nanoarrays

The emerging multifunctional flexible sensor(e.g.electronic-skin)for establishing body-electric interaction is one of the most important subjects that many researchers are focusing on.A variety of new multifunctional flexible electronic-skins(skin-implanted,organic-patched or skin-surface devices)accompanying with body activities have been studied for future medical care,such as detecting blood glucose,blood pressure,arterial stiffening,heart rate,electrolyte balance,body temperature,breathing rate and etc..These wearable electronic-skins and other flexible biosensors can achieve real-time detection of personal physiological metabolic indicators,and they can realize continuous detection of personal health status as a new personalized medicine technique.And diverse wearable non-invasive perspiration-analysis biosensors have been developed for accurate measurement of the physiological state,which can avoid the inconvenience for the traditional invasive blood sampling approach.Nowadays,an attractive research has been reported that a fully integrated multiplexed biosensor array system can extract the complex available information from different biomarkers in the perspiration secretion.For the further development of wearable non-invasive perspiration-analysis biosensors,the next generation of device requires the following distinct features.The device needs to be designed as mechanically flexible and has conformable integration with body through working on the skin surface or alongside the organic/tissue(not like pocket medical electronics).The device also needs to include multi-functional biosensor arrays,which can simultaneously and selectively measure different analytes(such as glucose,lactate,sodium ions,potassium ions,skin temperature and etc.).The third key difficulty in the device design is the flexible power supply for driving individual biosensors.The traditional bulky battery is not suitable for the wearable skin-like device and the distribution of power units needs to be solved.In human perspiration,biological molecules and inorganic salts contain a wealth of physiological information,and non-invasive monitoring on the human body can be achieved through the analysis of perspiration composition.In this paper,a self-powered wearable non-invasive electronic-skin for perspiration analysis basing on piezo-biosensing unit matrix of enzyme/ZnO nanoarrays has been presented.The enzymes modified on the surface of ZnO nanowires include LOx(lactate oxidase),GOx(glucose oxidase),uricase and urease.The electronic-skin can detect lactate,glucose,uric acid and urea in the perspiration through actively outputting piezoelectric signal.The electronic-skin can be attached on the forehead of a runner,and real-time/continuously monitor his physiological state.This research approach may probably point out the developing orientation of novel self-powered multifunctional electronic-skin.The details are as follows:(1)Fabrication of Self-Powered Wearable Non-Invasive Electronic-Skin:A seed-assisted hydrothermal method was used to synthesize vertically-aligned ZnO nanowire arrays on Ti substrate.Horizontally-aligned ZnO nanowire arrays(overwhelmed down)were the core materials in the device.The fabrication process(depositing interdigital electrode pattern),including photolithography and electron-beam evaporation processes,is similar to the previous report.A ZnO nanowire(length:～12 μm)could cross the electrode couple(distance:5 μm).The distance between neighboring electrode couples was 20μm,ensuring the same c-axis direction of all ZnO nano wires.(2)Sweat detecting analysis:The piezo-biosensing performance arises from the coupling effect between the surface enzymatic reaction(LOx and lactate,GOx and glucose,uricase and uric acid,urease and urea)and the piezoelectric characteristic of ZnO nanowire.The four piezo-biosensing units in the electronic-skin are modified with the LOx,GOx,uricase and urease,respectively.The enzymatic reactions can enhance the surface carrier density of ZnO nanowire,thus strengthening the piezo-screening effect and decreasing the piezoelectric impulse.(3)Application of Non-Invasive Electronic-Skin perspiration detection:We attach the wearable sweat analysis electronic-skin on different positions of the runner’s skin for monitoring the physiological state,through finger pressing or joint bending to provide a stable and continuous force for the device.And every unit of piezoelectric biosensor can generate piezoelectric biosensing signal.Then we selected a tester to perform an actual sweat detection analysis of the self-powered wearable sweat analysis electronic skin.Attaching the electronic skin to the runner’s forehead and making him run on the treadmill and then select the different stages of sweat samples for analysis.