Triboelectric Nanogenerator/Primary Battery Dual-mode Power Source For Wearable Devices And Implantable Transient Electronics

With the rapid development and progress of material applied science,analysis and detection technology,device design and assembly methods,new invivo and invitro diagnosis and treatment methods emerge endlessly.As a typical representative among them,wearable and implantable electronics have been widely used in people’s daily life.At present,such devices are developing rapidly towards miniaturization,multi-function,automation and integration.Among them,the power supply system plays an important role in the stable operation of such devices.The power supply system that can be used in wearable and implantable electronics are mainly divided into two categories,energy harvesting power system and energy storage power system.As an energy-harvesting power source,the triboelectric nanogenerator can collect external mechanical energy and convert it into electricity.Its main feature is that the output voltage is high but the output current density and power are low;the primary battery is a classic energy-storage power source,which consume its own chemical energy and convert it into electricity,its main feature is low output voltage but with high output current density and power.Due to the large differences in the power generation principle and output performance of the two,there has been no report of coupling the two to prepare a dual-mode power source.In this work,we have prepared a triboelectric nanogenerator（TENG）/primary battery（PB）dual-mode power source（TENG-PB）,systematically studied its electrical output performance and demonstrated its application in wearable and implantable electronics.The main work content and conclusions are as follows:（1）Preparation of the TENG-PB:Screen the materials of triboelectric layer and choose gelatin and L-polylactic acid（PLLA）to use,the methods of freeze drying and electrospinning are used to increase the specific surface area and porosity of the triboelectric layer,on the one hand,the surface charge density of the triboelectric layer is increased,and the electrical output performance in the TENG mode is improved,on the other hand,the resistance in the PB mode is effectively reduced.We compare a variety of metal electrodes,iron foil and magnesium foil are selected as the current collecting electrodes under the TENG mode and as the positive and negative electrodes under the PB mode.Single or mixed solutions such as Fe SO₄solution,phosphate buffer solution and simulated body fluid are also used as electrolytes for TENG-PB under the PB mode,we find that using the Fe SO₄electrolyte can significantly improve the output performance of TENG-PB at large current density.Finally,polydimethylsiloxane（PDMS）film and PLLA film are used to encapsulate TENG-PB according to different usage scenarios（wearable and implantable electronics）.（2）Electrical output characteristics of TENG-PB in TENG mode and PB mode:In the dry state,TENG-PB works in the TENG mode as an energy harvesting power source.The influence of the frequency,magnitude of external pressure and external load on the output voltage,short-circuit current and output power of TENG are systematically investigated.In the wet state,TENG-PB works in PB mode as an energy storage power source.The electrode reaction on the surface of the positive and negative electrodes in different electrolytes is clarified,the influence of electrolyte concentration,discharge current and external load on the output voltage,output current and output power of the primary battery is explored.On this basis,series and parallel LED are further used to visually compare the electrical output performance of TENG and PB mode.The results show that the output voltage in the TENG mode is higher but the output current density and power are lower,which is suitable for series circuit.TENG-PB has a lower output voltage but higher output current density and power in the PB mode,which is suitable for parallel circuits.（3）TENG-PB as the power of wearable and implantable electronics:TENG-PB is attached to the arm of the human body in the dry state and the wet state,which can power small electronic calculators and electronic watches.Besides,TENG-PB can be attached to the heel as a motion sensor in a dry state,the motion signal can be transmitted to the mobile phone terminal through a wireless bluetooth module to realize real-time exercise health monitoring.In addition,attach the TENG-PB to the rabbit heart inside/outside and implant the TENG-PB subcutaneously for animal experiment.The results show that TENG-PB can collect the mechanical energy generated by the heartbeat and external forces in the dry state and convert it into electricity.Meanwhile,a variety of electrolyte solutions are used for discharge test,which prove that TENG-PB can be activated by a variety of electrolyte solutions and work normally in the wet state.Finally,L929 are used to explore the biocompatibility of TENG-PB,the degradability is also evaluated in phosphate buffer solution.The results show that TENG-PB has excellent biocompatibility and fully biodegradation,which has huge development potential in the field of transient implantable electronics.In summary,this work has cleverly combined the TENG with the PB（energy harvesting power source and energy storage power source）,preparing a composite power source TENG-PB with two working modes（TENG and PB）and two working scenarios（in vivo and in vitro）.At the same time,TENG-PB has excellent biocompatibility and degradability,which has huge development potential in the field of wearable and implantable electronics.