Research On Design And Application Of Stretchable Piezoelectric Energy Harvester

Active wearable and implantable electronic devices rely on power supply for operation. Traditional piezoelectric cantilever beams based on mechanical vibration work in an effective way, while they are hard to be integrated with existing flexible electronics, and hence to fabricate a flexible and stretchable piezoelectric energy harvester has been a key component in flexible electronics. To overcome the disadvantages of inorganic piezoelectric material's being hard and brittle, this paper designs a method of fabricating stretchable interdigital electrode with wavy structure and deposits PZT membrane onto MgO substrate via photolithographic method, and then transfers them to PDMS,and thus a stretchable piezoelectric energy harvester is fabricated and integrated with human's skin. Outline of this work is presented as following:Firstly, piezoelectric effects and PZT as well as its operational modes are discussed, and d33 mode is selected owing to its better performance; a stretchable interdigital electrode based on U-patterned wavy structure is proposed and the electrode is integrated with PZT nanoribbons to form a flexible system to harvest energy. The system's stretchability is calculated by finite element method and an optimized structure meeting the stretchability demand with the best piezoelectric response is designed.Next, a set of fabrication process suit for fabricating stretchable piezoelectric energy harvester is designed. PZT nanoribbons sputtered on MgO substrate are post-processed via annealing and poling. They are characterized by using XDR and ferroelectric measurement, and the results show the fabricated nanoribbons have good perovskite structure(100). The device is transferred from hard MgO substrate to soft PDMS substrate via transfer printing and its piezoelectric response as well as its performance is conducted.Finally, the device's mechanics is analyzed by FEA and experiments, and the results shows when it is bent, the maximum strain in PZT is 0.024% and when it is stretched to 20%, the maximum strain is 0.69%, which are all within the fracture strain 1%. The fabricated piezoelectric energy harvester and an energy storage circuit are integrated to human's skin, energy can be harvested and stored with body movement, which indicates the device has fine ability of deformation and energy harvesting.