Liquid Metal Electrode Based Stretchable Piezoelectric-enhanced Triboelectric Nanogenerator

With the wide popularity and continuous innovation of wearable intelligent devices,the demand for their miniature and portable properties are becoming more and more prominent.At present,the volume occupation and sustainable power supply of battery is a main factor hindering the miniaturization and convenience development of wearable electronic equipment.Designing a portable generation system for powering wearable intelligent devices is a feasible way to achieve its further development.Traditional power generation technology is not applicable to power supply for small electronic equipment because of its large equipment and complicated structure.In addition,a lot of mechanical energy in the process of human activity is difficult to be collected by the traditional electromagnetic power generation system because of its irregular and multiple freedom degrees characteristics.The successive emergence of piezoelectric nanogenerators(PENG)and triboelectric nanogenerators(TENG)for irregular energy collection makes collecting human mechanical energy possible.At present,the main development trend of nanogenerator(NG)is to further improve its generation performance to meet the demand of electronic equipment.TENG has higher electrical performance output than PENG,but its output is easy to be affected by temperature,humidity and other environmental factors;at the same time,PENG has the characteristic of collecting multiple freedom degrees deformation energy.Therefore,the TENG and PENG could be integrated by reasonable structural design,which can improve the output performance as well as obtain the output characteristic advantages of both.Moreover,achieving the flexible design of NG is necessary for effectively collecting the human energy,but the electrode is the main factor limiting NG flexible preparation.Because of the poor tensile property of the electrode prepared by traditional technology,its conductivity will attenuate or even lose in the stretching state,which affects the overall output of the NG.Based on the above problems,this article started with the selection of materials,adopted different layers preparation and integrated technology to prepare a piezoelectric-enhanced triboelectric nanogenerator(P-TENG)for human energy harvesting,which has both excellent electrical and mechanical properties.Specifically,highly stretchable rubber Ecoflex was used as triboelectric material,and triboelectric layer prepared by inverted mold process has outstanding electrical and mechanical properties;further,the flexible piezoelectric layer was prepared by incorporating barium titanate into flexible substrate,which was combined with triboelectric layer to enhance the electrical performance of nanogenerator,improve the output stability and increase the freedom degree of energy acquisition at the same time;more importantly,liquid metal was used as the electrode preparation material,deposited on the surface of the piezoelectric layer and encapsulated with triboelectric layer to achieve the preparation of electrode module and the integration of different functional layers,the electrode prepared by this process has excellent conductivity even under large deformation state,which significantly guarantees the output performance for highly stretchable nanogenerator.The prepared P-TENG was measured and analyzed from three aspects:mechanical properties,electrical properties and practical application.The elongation at break of the P-TENG sample can reach 743%.The peak to peak open circuit voltage and short circuit current of P-TENG with a size of 5×5cm~2 under contact-separation mode could reach 1.38k V and 36.13μA,respectively,the instantaneous power density can reach 1.1 m W/cm~2,and the transfer charge density in a single power generation cycle is about 11.8n C/cm~2.The prepared P-TENG showed excellent performance in powering small electronics and driving led as well as monitoring human posture.As shown above,the designed P-TENG possesses excellent mechanical and electrical properties,and has great application potential in wearable devices power supply or as self-powered sensors.