Triboelectric Nanogenerators Based Multifunctional Devices For Human Health Management

Since the triboelectric nanogenerator(TENG)was firstly reported in 2012,due to its efficient mechanical energy conversion,and the good modulability of the generated electrical signals under the external mechanical force,it shows great potential application in both energy harvesting and force sensing.Therefore,the wearable health monitoring electronics based on TENGs develop rapidly.Nevertheless,wearable health monitoring electronics based on TENGs still face the following problems:(1)Low output power density.In order to apply TENGs to the wearable area more deeply and widely,it is necessary to obtain high output performance.Recent studies about TENGs applied in wearable health monitoring still need improvements.(2)Single fuction.The existing researches on TENGs mainly focus on improving output performance or the sensitivity of force detection.Other factors related to human health like body temperature and ambient environment were neglected.(3)Limited integration with clothes.In order to achieve good wearability of TENG based electronics,the flexibility of TENG is far from needs of customers.It is still a challenge to realize the stretchablity and air permeability of wearable devices without scarifing the multifunction and durability of the devices.To solve the above problems,this paper improved the output power density of TENG as well as wearing comfort with well selected materials,well designed structures,simple fabrication method and hybrid working machenism.The specific researches are as follows:(1)Tribo-and piezo-electric effects were integrated into one device to fabricate all-fiber hybrid nanogenerators.Silk fibroin(Diameter:280 nm)and poly(vinylidene fluoride)(PVDF)nanofibers(Diameter:160 nm)were electrospinning on conductive fabrics.Due to the large specific surface area of nanofibers and the extraordinary ability of silk fibroin to donate electrons in triboelectrification,the hybrid nanogenerator shows outstanding electrical performance.This novel all-fiber configuration provides all benefits of ordinary fabrics having flexible appearance and good air permeability,and it can be custom embedded in clothes in any desirable size and shape.Furthermore,the fabricated device allows identifying various types of body motion by a correlation between gesture and corresponding electrical signal.As potential application field,we foresee an autonomous wearable fall alert microsystem for elderly people and persons working in high risk areas.(2)A textile-based personal energy management device with multilayer-coating structure was fabricated by encapsulating commercial nylon cloth coated with silver nanowires into polydimethylsiloxane using continuous and facile dip-coating method.Fluoroalkylsilanes(FAS)was grafted onto the surface of the film through one single dip-coating process to improve its energy harvesting performance by 10 times.Furthermore,the film provided more thermal insulation than normal cloth and efficiently heated to 40°C rapidly when applied small voltage due to the silver nanowire network.The high flexibility and stability of the film ensure its wide and promise application in wearable field.(3)Active UV(ZnO)and IR(RGO)photosensitive materials were chosen to fabricate TENG with vertical structure.A self-powered,multifunctional e-eye for UV and IR light detection was developed.The e-eye harvests mechanical and thermal energy from the ambient environment by the triboelectric and thermoelectric effect to power itself.Providing electric power to UV detector asTENG,the maximum output power density of the e-eye reached 36.8?W/cm~2,which is able to power other microelectronic devices.The self-powered e-eye can distinguish UV and IR irradiation of different intensities individually or simultaneously through the generation of different electric signals,endowing the e-eye great with potential applications in portable/wearable UV and IR detection devices.(4)Polymer ionic conductor was introduced as electrode of the TENG based electronics to realize high stretchability,making it more attachable with human skin or clothes.At the same time,the fabricated device can detect stretching rate by outputting different electric signal with different stretching rate.What's more,oriented PVDF nanofibers were electrospinned onto the device to recognize the direction of the stretching,which can be applied in human-computer interaction,artificial intelligence and health monitoring.