In this paper, a capacitive vibration-to-electrical energy harvester was designed. An integrated process flow for
fabricating the designed capacitive harvester is presented. For overcoming the disadvantage of depending on external
power source in capacitive energy harvester, two parallel electrodes with different work functions are used as the two
electrodes of the capacitor to generate a build-in voltage for initially charging the capacitor. The device is a sandwich
structure of silicon layer in two glass layers with area of about 1 cm2. The silicon structure is fabricated by using
silicon-on-insulator (SOI) wafer. The glass wafers are anodic bonded on to both sides of the SOI wafer to create a
vacuum sealed package.
A vibration-powered micro-power-generator has been presented in this paper, which has integrated two different energy
harvesting mechanisms, e.g., Capacitive and Piezoelectric Mechanisms. The periodic vibration of the mass on movable
electrode causes the variation of the capacitance, and the strain in the piezoelectric film. These two mechanisms can
harvest the vibration energy and generate current in the output circuit. By using two different metals with large difference
in working function as the two electrodes of the capacitor, our design, the combination of these two different scavenge
mechanisms, can overcome the dependence of the traditional capacitive converter on the separate voltage source and
improve the efficiency of power conversion. The volume of the designed device is less than 0.8 cm3. The simulated
results reveal that this energy converter can provide an average output power of 82.21μW at an external vibration with a
frequency of 111.4 Hz and amplitude of 0.2g.