Electrode Design And Performance Of Wearable Thermoelectric Devices

Thermoelectric device has shown the great advantages of providing electric power in support of wearable health testing equipment by using the metabolic heat of human body over the years.However,the output power density of the reported thermoelectric devices in the literature were still very low with insufficient flexibilities.In this work,we aim to improve the output power density and flexibility of wearable thermoelectric device by developing well-designed electrodes.Throughout the full text,two types of flexible wearable devices are designed for the human metabolic heat harvesting.The first mainly addresses the demand of flexibility so that the thermoelectric device can stretch and bend freely when subjected to external force by applying the well-designed in-plane “Island-bridge” electrode,while the second is aimed at achieving high power density by optimizing the internal thermal resistance network of the device.In order to increase the temperature difference between the hot and cold sides of the thermoelectric leg,a “mushroom-shaped” electrode with an out-of-plane topology was designed which exhibits a significant improvement in the output power of the thermoelectric device.Furthermore,configuration optimization of the electrodes is conducted by using COMSOL multiphysics software.The assembling of the two as-designed flexible thermoelectric devices are conducted by using the new electrode configurations and the commercially available Bi2Te3 based legs,together with essential welding mold.The flexible thermoelectric devices are also further embedded in the soft packing materials,such as PDMS,porous PDMS,textile fabrics,for further improving the wearing amenity.Additionally,to better simulate human-environment,a self-designed simulation test system is also applied in this work by using modified molds.This test system can well control the flow air with different temperatures and speeds and obtain the pressure between the skin and device simultaneously.For the “Island – bridge” flexible TEG,the effects of various PDMS packing technique and copper foam radiator on the output power are investigated.It shows that the PDMS packing increases the reliability but with the cost of heat leakage.The use of foamed copper heat sink increases the effective temperature difference of real wearable conditions from 0.19 °C to 0.31 °C.In indoor environment,an output power density of 1.2 ?W/cm2 can be achieved at condition of a wind speed of about 0.2 m/s(ambient temperature 21.5 °C,skin temperature 32 °C).For the “mushroom-shaped” flexible TEG,the effect of wind speed,ambient temperature and device height h1 on the output performance of the device is systematically studied.The "mushroom-shaped" electrodes significantly increases the temperature difference between the two sides of the thermoelectric leg reached 3 ?C due to the suppression of heat leakage between legs,which is the highest value of the wearable thermoelectric device in the human body test up to now.In indoor environment with wind speed of 2 m/s,the device achieves a peak output power of 2 m W(power density: 22.49 ?W/cm2)by using with 49 pairs of thermoelectric elements,which is sufficient to support the independent operation of many health detection sensors.