Study Of Fabrication Of Flexible Triboelectric Nanogenerators For Wearable Self-charging Power System

With the rapid development of smart products,wearable electronic devices show great potential to replace traditional electronic products.At present,wearable electronic devices still use traditional batteries as power sources,but there are some problems of batteries such as large volumn,short life span,frequent replacement and environmental pollution.These restrict the further development and application of wearable electronic products.One of the conventional strategies to solve these problems is to integrate the energy collector and energy storage device into a self-charging system,and then use it to drive wearable electronic devices.The other is to realize self-powered wearable electronic devices,such as active sensors.The mechanical energy from human motion has the advantages of inexhaustibility,little affection by weather,non-pollution and so on.In addition,it can match with the working environment of the wearable devices.Therefore,it will be more convenient and efficient for self-charging system by using mechanical energy collector.Compared with other mechanical energy collectors,the triboelectric nanogenerator has the advantages of large output,high efficiency,low cost and good stability.The first aim of this thesis is to develop the flexible triboelectric nanogenerator.It can prevent the destruction of devices' structure from deformation during collecting mechanical energy generated by human movement such as stretching,twisting and bending.Besides,based on irregular human motion,the output and frequency of triboelectric nanogenerator are also unstable,and its peak output can not directly drive wearable electronic devices.And the capacitors can be used to store the electric energy produced by triboelectric nanogenerator.Thus,the second aim of this thesis is to intergrate the self charging system to drive the wearable electronic devices.In addition,the electrical output signal?voltage and frequency?of flexible triboelectric nanogenerator can reflect the information of mechanical contact?pressure,amplitude and frequency?.Therefore,the third aim of this thesis is to utilize the triboelectric nanogenerator directly as a self-powered sensor for pressure detection and motion sensing.The thesis has optimized srtucture of flexible triboelectric nanogenerator as in self-charging system and self-powered e-skin with active sensors from its tribo-materials and electrodes.The detailed contents are included as following:?1?We proposed a super-stretchable triboelectric nanogenerator?PL-TENG?with PEDOT:PSS solution as liquid electrode and silicon rubber as encapsulating material.Based on the high conductivity,fluidity,continuity and shape adaptability of liquid electrode,the PL-TENG can work effectively with stable outputs under different deformations,such as lateral tension,twisting,bending and longitudinal tensile,which can correspond to different movements of human body.Under motion frequency of 2.5Hz,the short-circuit current,open-circuit voltage and transferred charges of a PL-TENG are 24.9?A,247.1 V and⁸7.5 nC,respectively.As a mechanical energy collector,PL-TENG can directly drive LEDs.In addition,under the motion frequency of 2 Hz,a capacitor with 22?F can be charged to 2 V with 9 min,and then drive some electronic devices such as an electronic watch by DC current.?2?We proposed an ultralight and flexible self-charging power system via all electrospun paper based triboelectric nanogenerators?EP-TENGs?as energy harvester and all electrospun paper based supercapacitors?EP-SCs?as storage device,respectively.Under the motion frequency of 8 Hz,the short-circuit current,open-circuit voltage,transferred charges and average power density of an EP-TENG are 11.3?A,98.6 V,31.1 nC and 18.4 mW/m²,respectively.The EP-SC unit as an effective and flexible electronic energy storage device exhibits an excellent specific capacitance?150 F/g?.Based on each available unit,three-parallel EP-TENGs were further integrated with three-series EP-SCs to construct the all flexible electrospun papers based self-charging power system.In this flexible self-charging power system,the three-series EP-SCs can be charged to 2 V in 36 min,and then drive an electronic watch and a calculator.?3?We report a stretchable and transparent wrinkled PEDOT:PSS electrode based TENG?WP-TENG?that at enables an e-skin with function of biomechanical energy harvesting,tactile sensor and human motion monitor.The ptimum values of conductivity and transparency of wrinkled PEDOT:PSS electrode can reach 0.14 k?/?and 90%,respectively.Under motion frequency of 2.5 Hz,the short-circuit current,open-circuit voltage and transferred charges of a PL-TENG are 22.6?A,180.1 V and⁷5.3 nC,respectively.Based on large electric output,the WP-TENG can power LEDs directly or storage electricity in the capacitor to power the wearable electronics.Meanwhile,as the pressure increasing from 2 to 60 kPa,WP-TENG connected with a resistor of 100 M?can be used as tactile sensor with the pressure sensitivity of 0.08kPa^-1.The assembled self-powered tactile sensor array based on WP-TENG can be used for mapping the touch location or recording the shape of object contacted with the sensor.Furthermore,WP-TENG can be used as self-powered monitor to record the bended angles and frequencies of some parts of human such as bicep,joint and elbow.