| Since its invention,triboelectric nanogenerators(TENG)have become an emerging research hotspot due to their great potential in energy harvesting and self-powered sensing.The TENG can not only be used as an energy harvester to build a self-powered sensor system,but also can be used alone as a self-powered sensor.Energy harvesters based on TENG provide an efficient way to harvest ocean wave energy.It should be noted that the relative contact area of the TENG friction layer is an important factor for improve the output performance of the TENG.However,in the popular structures(like nested rollingspheres)of TENG,the energy harvesting efficiency is limited due to the small contact area of the point contact mode.At the same time,flexible sensors based on TENG has been widely used in wide-range biological strain detection(e.g.knee and finger bending,chest movement).However,they have not been widely developed for detecting weak strain at the cellular scale(e.g.cardiomyocytes’ contraction stress).This may be because the gap between the two triboelectric layers in conventional TENGs generally varies from a few millimeters to a few centimeters,which is not enough to detect the weak deformations that occur when cardiomyocytes’ contraction.Based on the above background,a regular tetrahedral TENG and bridge-structured TENG are designed and fabricated to harvest ocean wave energy and detect the contraction stress of cardiomyocytes in this topic,respectively.The details are as follows:A contact-separation mode TENG based on regular tetrahedral structure is designed,manufactured and tested in this topic.In this structure,a smaller tetrahedron is suspended inside a larger tetrahedron.When the TENG with regular tetrahedron structure is excited by external vibration,the two regular tetrahedrons contact and separate in a face-to-face mode and improve the efficiency of energy harvest.The first order oscillation frequency of the structure is designed to match the main frequency of ocean waves.In addition,the side-length ratio and structural attitude of the inner and outer regular tetrahedron are optimized,and the output power is further improved.The experimental data show that the peak output voltage and short-circuit current are as high as 200 V and 30 μA,respectively.At the same time,the peak power output reaches 14.7 m W under 10 MΩ load.The regular tetrahedral TENG can light up to 20 commonly used LED lamps(operating voltage is 3.0～ 3.4 V)and successfully drives a temperature and hygrometer to work normally.Therefore,the proposed TENG based on regular tetrahedron structure is expected to continuously harvest wave energy and establish a water self-power supply sensor system.In addition,the TENG with bridge structure is designed and manufactured in this topic,which can be used as self-powered flexible sensor.The sensor can reflect the efficacy of cardiovascular drugs by detecting the contraction stress of cardiomyocytes.In the design of the sensor,one of the friction layers is poly tetra fluoroethylene(PTFE)film with micron gap on the surface,and the other is silver.The two friction layers are separated by five rectangular polydimethylsiloxane(PDMS)films about 8 μm thick,ensuring that the gap between the two friction layers is micron to capture weak mechanical deformation contraction of cardiomyocytes seeded on PDMS film substrates containing micro-grooves results in changes in sensor output voltage.The sensor can continuously measure the contraction stress of cardiomyocytes.The contraction stress of neonatal mouse cardiomyocytes increased from 0.57 k Pa(7th day)to 1.58 k Pa(9th day),and then decreased to 0.98 k Pa(11th day).The average contraction stress was about 1.16 k Pa and the average beating frequency was about 1.23 Hz.The flexible sensors can also be applied to the screening of cardiovascular drugs.Experimental results show that the platform has great potential as a drug screening system with high biocompatibility,high stability and high sensitivity. |
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