Body Self-powered Sensor Network Based On Triboelectric Nanogenerator

Since the 21 st century,the aging of the population is escalating in China,and with the decline of physiological functions of the elderly,various diseases pose a great threat to their lives.Besides,people are paying more and more attention to their health care,and there is an urgent need for real-time health monitoring.The body sensor network provides an effective method for human health monitoring,which can realize real-time acquisition and monitoring of human health information and contributing to solve the medical information and network of human health.However,the power supply for each sensor node distributed in the human body has become an important issue that hinders the continuous monitoring,easy to wear and stable operation of the body sensor network.The power supplies of conventional sensors and systems mostly employ batteries or power with the physical connection.These method greatly limit long-distance and real-time health monitoring,and battery replacement/maintenance is also very difficult,which significantly limit the applications of body sensor networks.Meanwhile,the battery contains heavy metals,existing potential environmental pollution.With the rapid development of electronic technology,electronic products become integrated and low power consumption.Thus,it is possible to harvest energy from human motions for powering the body sensor network and develop self-powered sensors,realizing a self-powered body sensor network.As a new energy harvesting and sensing technology,triboelectric nanogenerator(TENG)has been proved as the best way for mechanical energy harvesting and dynamic sensing with the characteristics of diverse material selectivity,light weight,high conversion efficiency,and high output.In this paper,a body self-powered sensor network was built based on the triboelectric nanogenerator,and the triboelectric nanogenerator based human energy harvesting and sensing,as well as the power management and system integration,were developed and studied.The details of this research are listed as follows:(1)Harvesting energy from human motions is the core component of the body self-powered sensor network.So an airtight-cavity-airbag structural insole based on the TENG was designed to collect mechanical energy from human walking.Reliance on the coupling effect of contact electrifcation and electrostatic induction,the designed energy harvesting insole is able to generate an alternating current with a maximum power of 5.47 mW,utilizing an elastic airbag to drive the contact and separation of triboelectric layers.The effects of gas volume,presisure,and frequency on energy harvesting performance were investigated.The open-circuit voltage and short-circuit current produced by the energy harvesting insole are about 528 V and 81.2 ?A at the excitation of 5 Hz and 500 N,respectively.The stability and water resistance of the energy harvesting insole as a wearable device were explored,which could be used as a stable power supply to drive wearable electronics.This design not only provides a waterproof and flexible method but also offers a new opportunity in the development of wearable human energy harvester.(2)Since the fluctuation of the body's center of gravity when the human is walking,there is a large amount of inertial energy.Thus,it is an effective way to harvest the inertia energy to power wearable electronic devices.A triboelectric nanogenerator based on spring-vibrator model is designed to harvest human inertial energy.The effects of the number of triboelectric layers and the vibration frequency on the output performance of the TENG were investigated systemically.The theoretical analysis and experimental investigation of the energy conversion efficiency are carried out.The maximum energy conversion efficiency can come up to 57.9% at the vibration frequency of 10 Hz.The theoretical model is used to analyze the influence of human walking speed on the output performance of the TENG.Experiments verify that the energy harvester can convert the inertial energy into electrical energy efficiently and power the body sensing system.The spring-vibrator based TENG provides an example of scavenging the human inertial energy and can be extended to other forms of energy harvesting technology.(3)Due to the low frequency motion of the human body,converting the low-frequency energy output of the human body into a high-frequency electric output will contribute to the improvement of energy harvesting efficiency.Thus,a single pendulum inspired TENG operating at the free-standing mode is proposed.A single trigger from the human motion,the pendulum inspired TENG shows a continuous electrical output for 120 s at a frequency of 2 Hz.The experimental results show that the output energy of the TENG is 14.2 times compared with the conventional free-standing TENG,and the energy harvesting efficiency at the low frequency is greatly improved.The durability and stability of the TENG were explored and analyzed.This work presents a method for TENGs to achieve high efficiency and stability for human energy harvesting but also push the frequency-multiplied energy harvesting technology.(4)Sleep monitoring is playing an increasingly important role in the diagnosis and treatment of various sleep disorders related to diseases.A pressure-sensitive,large-scale,and washable smart textile is reported based on TENG array as bedsheet for self-powered sleep behavior monitoring and sleep warning.The output characteristics of pressure sensitive,response time and stability of the textile as a sensor were investigated.The experimental results show that the the textile as a sensor features an excellent pressure sensitivity of 0.77 V/Pa,fast response time of less than 80 ms,and high durability.A highly integrated data acquisition,processing,and wireless transmission system is established and equipped with the sensor array to realize real-time sleep behavior monitoring and sleep quality evaluation.The smart textile provides a new approach for sleep behavior monitoring in clinical medicine and can be extended to other fields such as tactile sensing,remote wireless medicine and clinical nursing(5)Gait monitoring has attracted increasing attention,especially for health monitoring and early diagnosis such as the dementia risk.An ease-of-use and wearable smart insole based on triboelectric nanogenerator was developed for real-time multifunctional gait monitoring.The cavity structural triboelectric nanogenerator based sensors are embedded in the front and rear position of the insole to sense the pressure from feet.The influences of pressure and frequency on the sensor were explored.Theoretical analysis and experimental verification of the shield electrode can effectively eliminate the interference signals from the environment.And based on the time difference of the forefoot and heel of the foot contact with the ground,various gait patterns can be monitored accurately.The smart insole could also be used to monitor the abnormality of gait for rehabilitation assessment.The demonstrations of the smart insole applied to sports training,disease monitoring and fall warning were also investigated.This work broadens the applications of the TENG as self-powered sensors.(6)The respiratory signal of the human body is an important indicator for evaluating the human health,and the wearable respiratory sensor will be beneficial to the practical applications.A wearable and triboelectric nanogenerator based textile was reported for real-time human respiratory monitoring.The output characteristics of the wearable electronic textile for the pressure,tension and bending were investigated.According to the correlation between output amplitude and respiration rate/depth,the respiration rate and depth can be record and calculated.The proposed wearable textile provides a possible method for human body wearable breathing sensing,and can be extended to other human physiological sensing.(7)Owing to the high voltage,low current and high impedance of the triboelectric nanogenerator,the transformer is integrated into the power supply circuit for power management,which effectively solves the problem of low energy conversion efficiency.The energy conversion efficiency of the power management circuit is studied by the tests of charging a capacitor.By integrating the signal processing unit,signal analysis unit,a self-powered body sensor network based on triboelectric nanogenerator is built,providing an example for the new generation of human sensing system.