Research On Electromechanical Transduction Structure And Application Based On Triboelectric Effect

Nowadays,with the rapid development of information intellectualization,Internet of Things(Io T)has been everywhere in our daily life.The Io T development level primarily depends on the advancement of sensing and power supply technologies,in which the common technology involved is energy transduction.Traditional energy transduction technologies include electromagnetic transduction,piezoelectric transduction,electret transduction and dielectric elastomer transduction etc.However,with the growing prosperity of the Io T,new demands for sensor performance and energy supply are put forward by some application scenarios,such as flexible sensing,flexible storage and miniaturization,light devices and systems.Therefore,to meet the new needs of social development,further research on energy transduction technology should be conducted.The new electromechanical transduction technology based on triboelectric effect owns many advantages,such as wide selection of materials,flexible structure and environmental protection,which is one effective way for transduction and energy collection.Therefore,this thesis is devoted to study various electromechanical transduction structures based on triboelectric effect,for flexible mechanical force sensing and mechanical energy harvesting,and show their potential application in the fields of human health monitoring,human–machine interaction and environmental monitoring.The main work of the thesis is summarized as follows:(1)The textile pressure sensor based on the triboelectric effect is studied.The core-sheath structure is adopted by this sensor,in which the inner core and outer sheath of the sensor are conductive yarn with good conductivity and silicone rubber tube,respectively.By utilizing the good elastic properties of the silicone rubber tube,the sensor can realize the fast response to the stress stimulation,and own good broadband response characteristics while meeting the requirements of the flexible sensing.In addition,the triboelectric charge generated within the silicone rubber tube cannot be affected by the external humidity through full package.Based on the theory of elastic mechanics and triboelectrification electromechanical transduction,the force-electric transduction relationship of the textile pressure sensor is derived.The experimental results show that the sensitivity of the sensor achieves up to 10.79 m V/Pa,the frequency response range is 0.1?40 Hz,the stable output in 20000 cycles of experimental tests is obtained,and meanwhile,the sensor exhibits both waterproof and washable properties.It's noteworthy that the textile pressure sensor can be directly sewed on traditional fabric in any form without complicated knitting process.In the experiment,the sensor is weaved into the bed sheet with 1.5 m × 2.0 m.Based on the as-fabricated sheet,an unconstrained sleep monitoring system has been developed to detect and analyze sleep posture,body movement and subtle physiological signals(including breath and heartbeat).It can monitor and timely intervene sudden diseases(such as long-term apnea,cardiac arrest,etc.)during sleep,providing a solution for sleep health monitoring.(2)The pressure sensor with spherical cap microstructure array is investigated.The sensor is composed of UV adhesives with spherical microstructure array and polydimethylsiloxane(PDMS)with graphene electrode.To meet the weak dynamic signal sensing under large static pressure,the spherical microstructure array can not only increase the effective contact area among the tribo-pair materials,but also enlarge the pressure response range of the sensor.Based on the theory of elastic mechanics and triboelectrification electromechanical transduction,the force-electric transduction relationship of the sensor is deduced.The experimental results show that the sensitivity of the sensor is 9.63 m V/Pa,the frequency response is 0.1?30 Hz,and it has good stability.We develop the cushion type subtle physiological pressure signal monitoring system based on the pressure sensor,which can accurately capture the response signals of breath and ballistocardiograph in sitting positions.Furthermore,we carry out the auxiliary diagnosis experiment of heart rate variability for different subjects.The experimental results are consistent with the hospital diagnosis results,providing a solution for non-skin contact health monitoring.(3)The stretchable sensor based on the triboelectric effect is researched.The sensor adopts a spiral core-sheath structure with the inner core consisting of conductive yarn spirally wound on the rubber wire,and the outer sheath consisting of PDMS.The spiral conductive yarn structure covered in the rubber wire can ensure that the electrode of the sensor will not be damaged even under the condition of large strain.At the meantime,good elastic recovery force can effectively shorten the response time of the sensor.The relationship between tensile strain and output voltage is analyzed based on the theory of elastic mechanics and triboelectrification electromechanical transduction.The sensing characteristics of the stretchable sensor are systematically studied through experiments.The sensor maintains good linearity between tensile strain and voltage output in the range of 0%?100%,also with sensitivity up to 2.47 V,response time <15ms,good frequency response and stability.A wearable sign language gesture recognition system based on the stretchable sensor is developed.By combining machine learning algorithm,a remarkable recognition rate of up to 98.63% and a short translation time(<1 s)are demonstrated by analyzing 660 acquired gesture recognition patterns.Sign language gesture recognition can be output in the form of text and voice at the same time,which improves the practicability of sign language gesture recognition system.(4)The study of arc-shaped fluid energy harvester using wasted milk carton as triboelectric material is conducted.The energy harvester is composed of an arc-shaped elastic beam vibration structure and L-shaped triboelectrification electromechanical devices using the wasted milk carton as triboelectric material.The milk carton is laminated(from inside out)with a layer of polyethylene(PE),a layer of aluminum foil and a pulp layer.Benefiting from such laminated materials,the fabrication process of back electrode of triboelectric material is omitted,only the surface processing of the PE layer is sufficient as the triboelectric material.Based on the principle of vortex induced vibration and the theory of triboelectrification electromechanical transduction,the transduction mechanism from fluid energy to electricity is analyzed.The influence of different structure parameters on the electrical output characteristics of arc-shaped fluid energy harvester is evaluated.By optimizing the structural parameters systematically,the arc-shaped fluid energy harvester achieves an instantaneous peak voltage of 600 V and a current of 40 ?A,respectively.The voltage output of the arc-shaped fluid energy harvester remains stable with continuous operation for 3 hours at 15 m/s wind speed,which proves the good stability.The fluid energy harvester array aforementioned to harvest the wind energy in the laboratory wind field environment and the fluid energy in the natural water flow environment,can be applied as the energy supply of the Io T nodes for environmental monitoring.