[1] [1] TWIEFEL J, WESTERMANN H. Survey on broadband techniques for vibration energy harvesting ［J］. J Intelligent Material Syst and Struc, 2013, 24(11): 1291-1302.

[2] [2] HO J S, YEH A J, NEOFYTOU E, et al. Wireless power transfer to deep-tissue microimplants ［J］. Proceed National Academy of Sci, 2014, 111(22): 7974-7979.

[3] [3] ZENG F G, REBSCHER S, HARRISON W V, et al. Cochlear implants: system design, integration and evaluation ［J］. IEEE Reviews in Biomedical Engineering, 2008, 1(1): 115-142.

[4] [4] HU H, HU Y, CHEN C, et al. A system of two piezoelectric transducers and a storage circuit for wireless energy transmission through a thin metal wall ［J］. IEEE Trans Ultrasonics, Ferroelectrics, and Frequency Control, 2008, 55(10): 2312-2319.

[5] [5] LARSON P J, TOWE B C. Miniature ultrasonically powered wireless nerve cuff stimulator ［C］// Proceed 5th Int IEEE/EMBS Conf Neural Engineering. Cancun, Mexico. 2011: 265-268.

[6] [6] MALEKI T, CAO N, SONG S H, et al. An ultrasonically powered implantable micro-oxygen generator ［J］. IEEE Trans Biomedical Engineering, 2011, 58(11): 3104-3111.

[7] [7] LIM H G, SEONG K W, JUNG E S, et al. Necessity of human middle ear characteristics at design of piezoelectric type round window vibrator ［C］// Proceed IEEE-EMBS Int Conf Biomedical and Health Informatics. Hong Kong, China. 2012: 548-550.

[8] [8] FADHIL N, SABER D, PATA P. Energy harvesting using nana scale dual layers PVDF film for blood artery ［C］// Proceed IEEE Long Island Syst, Applic and Technol Conf (LISAT). Farmingdale, NY, USA. 2013: 1-6.

[9] [9] DETERRE M, LEFEUVRE E, ZHU Y, et al. Micro blood pressure energy harvester for intracardiac pacemaker ［J］. J Microelectromechanical Syst, 2014, 23(3): 651-660.

[13] [13] GUO T, XU Z, JIN L, et al. Optimized structure design of a bridge-like piezoelectric energy harvester based on finite element analysis ［C］// Proceed 20th Int Conf Electrical Machines and Syst (ICEMS). Sydney, NSW, Australia. 2017: 1-5.

[14] [14] WANG G, XU J, ZHANG Y, et al. Characteristic analysis of novel double-fork piezoelectric energy harvester ［C］// Proceed First Int Conf Elec Instrum & Inform Syst (EIIS). Harbin, China. 2017: 1-4.

[15] [15] ASTHANA P, KHANNA G. Enhancing performance of a broadband seesaw piezoelectric energy harvester ［C］// Proceed 7th Int Conf Signal Proces Integr Networks (SPIN). Noida, India. 2020: 43-47.

[16] [16] DEBNATH B, KUMAR R. Design and simulation study of a new flared-U shaped springs based MEMS piezoelectric vibration energy harvester ［C］// Proceed IEEE Int Conf Comput, Power Commun Technol (GUCON). Greater Noida, India. 2020: 101-105.