Structural Design Of Triboelectric Nanogenerator And Applications In Self-powered System

Since the 21 st century,due to the rapid development of mobile internet technology,Internet of Things（IoT）has becoming a component and stage of the next generation of information technology.Internet of thing is a technological developer that link moving things or any things around the world on the internet,such as shipping objects,cargo carriers and people.IoT needs widely distributed sensors for health monitoring,medical care,environmental protection,infrastructure monitoring and security.The power for driving each sensor is small,but the number of such units can be huge in the order of billions to trillions.The most conventional technology is using batteries,which may not be the solution for IoT with considering the limited lifetime,wide distribution,high maintenance cost and environmental issues.In 2006 and 2012,Prof.Wang developed nanogenerators based on piezoelectric and triboelectric for harvesting mechanical energy from their working environment,so that the devices can operate sustainably.That is so called self-powered system.In this paper,based on triboelectric nanogenerator（TENG）,from the energy harvesting unit,energy storage unit,power management,self-powered sensor and application of self-powered system,we dedicate to push triboelectric nanogenerator as a technique to realize self-powered system.The details of this research are listed as follows:（1）As the energy source of the self-powered system,the most important research direction is the structural design and material modification of triboelectric nanogenerator.In this paper,from the aspect of structural design,we dedicate to extend the application scenarios of triboelectric nanogenerator.Firstly,utilizing PTFE film with the thickness of micrometers,a sandwiched TENG was designed and fabricated for harvesting airflow energy.This kind of airflow induced triboelectric device process a relatively high output frequency,which makes it to be a stable power source.After combining with a dye-sensitized solar cell,the hybridized device can simultaneously harvesting wind and light energy.Secondly,with the novel checker-like interdigital electrodes design,a nanogenerator that can be used for harvesting translational motion energy in all directions was fabricated.Utilizing PET film as the interlayer,the device durability was largely enhanced.As an application,the device was fabricated in the mouse and mouse pad system,and successfully harvested mouse operation energy.Lastly,employing PET and PTFE as the tribo-material,we designed a spiral-interdigital electrode based dual functional TENG that can used for harvesting translational energy and rotational energy.Moreover,this device can be act as a dual functional sensor for detecting momentum and rotation speed.（2）Tribo-material abrasion and environmental factors（such as humidity）are two most important issues that prevent TENG from practical applications.In this paper,from the aspect of structural design,we dedicate the strategy for solving these issues.Firstly,by creatively utilizing the rolling friction as the charge replenishment for free-standing mode TENG,we present an ultrarobust,high-performance route for rotational kinetic energy harvesting.Secondly,the particle or moisture in ambient environment would have bad effect on TENG,through the noncontact force between the paired magnets,we proposed a strategy to fully package TENG of all kinds with hybridizing electromagnetic generator.The fully insulated structure makes TENG water-proof,and can work in harsh environments.（3）The triboelectrification not only happens between two solid materials,but also occurs between liquid and solid interface.In this paper,utilizing tribo-effect between hydrophobic PTFE and water interface,we designed and fabricated a triboelectric micro fluidic sensor for detecting both liquid and gas flow.We systematically studied the sensing mechanism and measured the performance.This kind of self-powered micro fluidic sensor has big potential application in medical science and industrial production.（4）In self-powered system,self-charging power unit is a device that can converting and storing ambient energy into the form of electricity by integrating energy harvesting unit and energy storing unit.In this paper,firstly,using silicone rubber as tribo-material and Ag nanowire as electrode,we fabricated a shape-adaptive and stretchable single electrode TENG.Utilizing kirigami sand paper as the substrate and graphite as active material,we fabricated a flexible and stretchable supercapacitor.By integrating and assembling them with silicone rubber,a water-proof stretchable self-charging power unit was achieved.Secondly,using paper as the substrate and assembled kirigami architecture,we designed and fabricated a rhombic-shaped TENG,which can enhanced the charge output by integrating plenty of TENG unit in a certain volume space.Taking advantage of the paper substrate,this kind of device holds nearly 15 times enhancement in specific mass/volume charge output than that of traditional acrylic based TENG.With combination of paper based supercapacitor,an ultralight and all-paper based self-charging power unit was obtained.（5）Triboelectric nanogenerator（TENG）has the output characteristics of high voltage but low current/charge transfer,making its low efficiency in powering most of electronics.To address this problem,power management circuits consisting of coupled inductors or transformers are usually employed.Here we reported an inductor-free,auto-power-management design based on automatic switches between serial-connected and parallel-connected capacitors in a rationally designed manner,so that the output voltage can be lowered and the output charge is enhanced in proportion.Compared to previous work,this power-management design shows advantages of capability for harvesting low power/frequency scale energy,high scalability,and lightweight,which paves a new approach for achieving high-efficient portable TENG-based self-powered system.（6）Heavy metals contained in wastewater are one of the most serious pollutions in natural resources.A self-powered electrochemical recovery system for collecting Cu ions in wastewater by incorporating a rolling friction enhanced freestanding triboelectric nanogenerator（RF-TENG）was developed here.By using the kinetic energy of flowing water,a collection efficiency of up to 80% for Cu²⁺ ions in wastewater has been achieved.Self-powered electrochemical systems are one of the most promising applications of TENGs for independent and sustainable driving of electrochemical reactions without the need for any additional power supply.This research is a substantial advancement towards the practical applications of triboelectric nanogenerators and self-powered electrochemical systems.