| In recent years,with the development of science and technology,there are lots of wearable electronics appearing in people's life and the quantity is still in a state of steady increasing.These electronics have been applied widely to fields like health detection,internet of things,artificial intelligence and wireless sensor networks which extremely facilitate people's life.However,short endurance time and frequently charging or changing the battery,which is becoming a significant factor to hinder the development of wearable electronics and restrains its progress in miniaturization and handiness.To solve the problem,a practical way is that we could convert human motion energy to electric energy to drive electronics,so as to lengthen their endurance time and further realize self-powered wearable electronic devices.Besides,the mechanical energy from human body has advantages of continuous producing,not being influenced by the weather or the circumstance and non-pollution.The triboelectric nanogenerator(TENG)is a new-type energy conversion technology,which could convert mechanical energy to electric energy based on the effect of triboelectrification and electrostatic induction.The TENG has merits of wide material selection,low cost,high efficiency and harvesting low-frequency irregular mechanic energy efficiently compared with traditional electromagnetic generator.In this thesis,we developed a kind of soft,breathable and wearable TENG which could harvest mechanical energy from movements of human body and convert it to electric energy for charging wearable electronics.The performances of TENG are systematically tested.(1)We used the biaxial tension method to fabricate the hydrophobic nanofiber PTFE film.And we assembled a single electrode TENG based on the hydrophobic film.As a kind of wearable TENG,being washable or not is a crucial factor to judge its feasibility.The hydrophobic surface has the ability to realize washing function and rapid drying function at the same time.During the test of washability,the stained TENG could be cleaned and dried easily and quickly.Besides,it could also endure the stability test in a washer for many times.In the test of electric performance,a TENG sized 10 cm × 12 cm is stitched to a lab coat.When the person swing his arms,the clothes under his armpit contact and separate with the TENG to generate electricity.Its open circuit voltage can reach 1050 V while short circuit current is 22 ?A.The electric energy generated by the TENG could directly light up a night running light including 54 green LEDs or let an electronic watch work normally.(2)We used an electrospinning method to fabricate nanofiber PVDF film.The PVDF solution became fibrous jet under the force of electric field and was sprayed on the metal electrode with a conductive adhesive layer,so that the PVDF film could be combined with the electrode seamlessly.Then,we developed a type of highly stretchable electrodes with kirigami structure.Due to the advanced structure design,the electrodes could achieve stretching in 3D or tensile strain of 220% in two dimensions.The copper foil was attached to the clothes as another electrode.When the cotton fiber of the clothes came into contact with the PVDF film,it could convert mechanical energy of human motions into electricity.A 2 cm × 2 cm sized TENG could generate open circuit voltage of 840 V at 30 Hz,and the open circuit voltage increases as the contact force increases.Placing a wearable TENG onto the human body,it could convert corresponding mechanical energy into electrical energy and stored in an energy storage system based on lithium batteries.When the stored electric energy accumulates to a certain level,it could charge a smart watch and a mobile phone,respectively. |
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