| People have benefited a lot from the fast development and wide application of electronic devices.However,it may be troublesome or even difficult to power these electrical devices persistently or charge them periodically.Therefore,harvesting energy from environment to power these devices for constructing self-powered system has attracted more and more attention to solve this problem.Sound energy,as one of the most widely distributed mechanical energies,is always overlooked and wasted due to the lack of harvesting method.If the sound energy could be harvested and converted into electricity,it will serve as a power source for both infrastructure and environment monitoring to construct self-powered systems.The emerging energy harvesting device-triboelectric nanogenerator(TENG)can continuously convert tiny and irregular environmental mechanical energy into electricity,which provides a new way to harvest and utilize the sound energy.Based on the characteristic of the sound energy in our environment,we carry out some work around the design and optimization of sound driven triboelectric nanogenerator(STNG).Based on the triboelectrification and electrostatic induction,we design and fabricate a kind of TENG that could effectively harvest sound energy.Its maximum output current reaches 0.45 mA which is 28 times bigger than the previous record.The most important of all,the STNG could work normally without the resonance box,and work stably in a broad bandwidth ranging from 50 Hz to 450 Hz.The result means that the problems introduced by resonance box in previous work are effectively solved.Following the work above,we further demonstrate a multilayered sound driven triboelectric nanogenerator(MTNG)to improve the output of the STNG.This MTNG has a three-dimensional structure by stacking different working units.With different multifunctional units working harmonically,its maximum current and voltage can reach 2.1 mA and 232 V.These values are 4.6 times and 2.6 times bigger than that of the STNG,respectively.Except for the output performance of the STNG,we also need to consider other factors which may affect the working condition of TENG,such as dust,moisture and rain.These factors in environment could severely influence the output performance of TENG,which greatly limits the application of TENG.Here,we design and fabricate a packaged triboelectric nanogenerator(PTNG)that can work normally in dusty and humid environment to harvest the sound energy.Driven by a sound wave,the PTNG can generate a maximum output voltage of 72 V and a maximum output current of 0.66 mA.In the packaged structure,the friction layer is fully isolated from ambient environment,which provides an effective protect for the TENG to work steadily in dusty and humid conditions without any damping of its output performance.At last,the influence of friction layer on the output electric charges of TENG is studied both in experiment and theoretical calculation.The result shows that the output electric charges firstly increase with the increase of frition layer's thickness,and then reachs to a constant value.In addition,a smaller carrier mobility and concentration will result in the less combination of triboelectric charges.Guiding by these results,a composite structure constructed by PVDF and PS is used to improve the output electric charges of TENG.Utilizing the PVDF/PS composite friction layer,the maximum output electric charges and electric energy of STNG are 4.5 times and 20 times of the pure PVDF fiction layer's.This study not only promotes the application of sound energy harvester in our daily life,but also provides a new way for other triboelectric nanogenerators to improve its performance. |
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