Development Of Multifunctional Flexible And Stretchable Sensors

In recent years,the flexible wearable devices are widely applied in medical health care,and human-computer interaction.However,the current flexible wearable sensors usually are of single function,which is often designed for specific application scenarios.In addition,for sensitive flexible sensors,there are a large number of distractions in the complex work environment,such as human sweat.Moreover,although we have made important progress in reducing power consumption of electronic devices,power supply is still the most critical constraint to the development of flexible electronics.The existing environmental energy harvesting devices usually have high environmental requirements,and poor stability,which limit their applications in wearable electronics.A flexible and renewable power source based on ambient environment energy harvesting technology for wearable sensing electronics with abundant reserves and little dependence on environmental conditions is still in urgent demand.Aiming at those challenges mentioned above,a multi-functional superhydrophobic smart sensing coating with good resistance to environmental interference and a fibrous strain sensor with ultrahigh stretchability and high sensitivity in whole working range were firstly prepared based on the intrinsic properties of the materials and structure design.We have also designed a variety of self-powered sensing systems based on environmental energy harvesting to address the energy constraints on wearable sensors.The main research results are summarized as follows:1.We constructed multifunctional smart sensing MWCNT/TPE coating with bottom-up gradient distributed elastomer(TPE),which shows extreme repellency to water,acid,and alkali.Besides,the multifunctional coating remained superhydrophobic property up to 50%tensile strain and 150°bending strain.Moreover,the smart coating has both strain sensing and superhydrophobic functions,which helps flexible wearable electronics get rid of environmental interference.The multifunctional smart coatings can be directly coated to clothing for real-time detection of human motions,which shows a promising prospect in fast fabricating stable wearable sensors.2.We developed an ultrathin and high stretchable MWCNT/TPE film and further constructed a buckled sheath-core fiber-based ultrastretchable sensor with large stain gauge enhancement by introducing wrinkle structure,based on the multifunctional smart coating.The ultrastretchable sensors eliminate the mechanical modulus mismatching between different material interfaces.Owing to its unique sheath-buckled microstructure,the fiber strain sensor has a large workable strain range(>1135%),fast response time(?16 ms),high sensitivity(GF of 21.3 at 0?150%,and 34.22 at 200?1135%),and repeatability and stability.These features endow the sensor with the ability to monitor both subtle muscle and large joints motions of the human body.Moreover,the sensor can be attached to a rat tendon as an implantable device,allowing quantitative evaluation of tendon injury rehabilitation.3.A fully solar-powered coaxial-fiber stretchable sensing system fabricated by integrating solar cells,a Zn-MnO2 battery,and a stretchable strain sensor can simultaneously realize energy harvest,storage,and utilization.Specifically,the harvested solar energy can be effectively converted into electricity by the solar cells and further stored as chemical energy in the stretchable Zn-MnO2 battery.More importantly,the solar-charged stretchable Zn-MnO2 battery can provide a steady and continuous power supply for the stretchable fibrous strain sensor.Thus,this work provides proof-of-concept design for next-generation multifunctional integrated devices.4.An ambient moisture-induced self-powered wearable sensing system was fabricated by integrating a porous polydopamine(PDA)layer with an asymmetric electrochemical oxidation and reduction constructed hydroxy group gradient(called g-PDA)based moisture-enabled power generator and a flexible pressure sensor.Rapid evaporation of the water solvent during the print process leads to widely distributed micropores on the PDA film,which facilitates the capture of water molecules.Due to the large amount of gradient-distributed free cations(H+)and locally confined anions produced in wide electrode spaces during hydration of the thin porous g-PDA film,the diffusion voltage can be generated.Finally,a self-powered wearable multifunctional sensing system has been demonstrated to be able to provide real-time monitoring of human physiological signals without external power supply,which enriches the energy harvesting methods of self-powered flexible wearable electronics.5.A sustainable flexible hydrovoltaic power generator(HPG)is obtained by assembling functional conductive carbon black(FCB)on a three-dimensional sponge(3DS)through PVA and then combining with the superabsorbent gel.Based on constructed functionalized nanochannels and the introduction of superabsorbent hydrogel water source,the HPG can take advantage of the spontaneous evaporation of water to continuously convert ambient heat into electricity.Moreover,the flexible hydrovoltaic nanogenerator can withstand a large range of bending deformation(up to 120°)without significant changes in power generation,which endows evaporation-induced HPGs with the ability to be applied as flexible portable power sources for wearable electronics and further reduced the dependence of wearable power harvesting devices on the environment.The fabricated sustainable flexible HPG further reduces the dependence of wearable energy harvesting devices on the environment.