Research On MEMS Piezoelectric Energy Collecting Device Based On Flexible Substrate

With rapid development of the less sensor network and MEMS technologies, the power issue has become a bottle neck that confines the progress. As a result, energy harvesting from ambient has been widely focused and researched. Outline of this work is as following:This work has reviewed the physics of piezoelectric effects at first and studied the fundamental principles of existing piezoelectric energy harvesting methods and devices, pointing out their characteristics and working conditions.Next, researches utilizing finite element method (FEM) via Comsol Multiphysics software on ZnO integrated-nanowire-generator, PZT cantilevers and P(VDF-TrFE) membrane devices designed in this work are carried out. Piezoelectric energy conversion properties are studied under different conditions.Afterwards, a system to test piezoelectric energy conversion properties of devices with flexible substrate are designed and established. Mechanical platform and step-motor are utilized and controlling circuits are designed. The resulting system, including the micro-manipulator and semiconductor analyzer, is capable of testing energy conversion properties of flexible devices under different strains and frequencies.Furthermore, flexible piezoelectric energy conversion devices based on P(VDF-TrFE) with Kapton substrates are designed and manufactured. Physical tests are carried out to determine the existence of P-phase after poling. Piezoelectric energy conversion properties are tested with previously mentioned system, and resulting that:Under the condition of low frequencies: 1, Increasing output voltages and short circuit currents are observed with increasing applied strains in a constant frequency; 2, With the same scale of applied strain, output voltages and short circuit currents will also increase with the frequency; 3, With same scale of applied strains and frequencies, the output voltages will basically remain in a constant level, while short circuit currents will increase with the size of devices. Lastly, energy conversion co-efficiencies of P(VDF-TrFE) devices in all sizes are calculated, the average energy conversion co-efficiency is 12.2% when strains of 0.2% are applied with the frequency of 1 Hz.