Research On The Performance Of Flexible Thermoelectric Devices And The Application In The Detection Of Lactic Acid

Lactic acid is an important metabolite in the human body.As a biochemical indicator of various diseases and symptoms,lactic acid testing plays a very important role in clinical analysis.At the same time,it has been widely used in sports medicine to determine the status and fitness of athletes.Among them,the sweat lactic acid test as a non-invasive in vitro test will not cause any wound or even infection,so it has broad prospects in various applications.The traditional way of supplying energy for these devices is to use energy storage devices.The energy is usually provided by conventional batteries.But these energy devices need to be recharged regularly.In addition,it’s hard to integrate batteries for the small,thin and stretchable biomedical devices,and replacing the battery will cause some symptoms which need a long-time healing process,such as inflammation and internal bleeding.With the continuous exploration of new environmental energy,various energy collectors have been invented.They are considered to be an expansion of batteries to provide long-term power supplement and even completely replace batteries to power various sensors.Among them,thermoelectric generators can continuously use various heat sources and convert them into electrical energy,including the heat energy that is usually ignored in the human body and the environment.The thermoelectric generator does not require any moving parts and almost does not require maintenance,which makes its application more reliable and widespread.The feasibility of thermoelectric generators has been successfully demonstrated in various fields.They can realize the self-powered operation of a variety of wearable biomedical devices without any external power supply.Therefore,this subject designs a thermoelectric generator（TEG）based on a refrigeration chip.This TEG is used to develop a wearable self-powered sweat lactic acid sensor with high selectivity and sensitivity as a power source.The specific contents of this research as follows:（1）The morphology and structure of the thermoelectric materials were characterized.The thermoelectric material is mainly composed of low-temperature thermoelectric material Bi-tellurium（Bi₂Te₃,Sb₂Te₃）,which is pressed into a sheet.The material has good thermoelectric properties.After ten thermoelectric devices being connected in series,the Seebeck coefficient of this TEG is about 5m V/K.The prepared TEG has small resistance and it has good output with stability and reliability.The best matching resistance of this TEG is about 50Ω,which can provide an external DC power supply for low-resistance and low-power devices.In this study,to improve the thermoelectric output of this TEG,a boost circuit was designed based on the CJMCU-3108 power management circuit and printed into a micro-circuit board（μ-PCB）.The working voltage of this kind ofμ-PCB can be as low as 20 m V.Theμ-PCB can convert the voltage to 2.5 V and stabilize the output for a long time,which provides effective technical support for the power management circuit of human wearable sensors.（2）Carbon cloth fiber is used as a conductive substrate to synthesize platinum nanoparticles in an electrochemical system.The size and density of nanoparticles can be stably controlled by changing the output power of the direct current.Then,the prepared carbon cloth fiber is used as an electrode,and it is combined with a thermoelectric generator based on a refrigeration chip to prepare a self-powered sweat lactic acid sensor with high selectivity and high sensitivity.The sensor will produce different current response signals in lactic acid solutions with different concentrations from 0.1 to 40m M.The current signal has a good linear relationship with the detection concentration.This lactic acid sensor aims at several specific concentrations of organic components in sweat and shows high selectivity in the control group detection.The control group consists of 100μM creatinine,10μM L-ascorbic acid,200μM glucose,and 60μM uric acid.At the same time,the lactic acid sensor combined with TEG as a power source,a wearable self-powered sweat lactic acid sensor was designed.When the temperature difference is 35K,it can effectively detect different concentrations of lactic acid solutions（0.1 to 80 m M）and show good sensitivity.This sensor can accurately collect and transport sweat for quantitative analysis of lactic acid,which demonstrates its application potential in the field of integrated microfluidic sensors.It is expected to help people better understand their physical condition,metabolism,and adaptability during exercise.At the same time,this sensor has more applications in diversified biomedical fields.