MEMS vibration electret energy harvester with combined electrodes

A novel in-plane MEMS electret energy harvester with combined electrodes of overlapping-area-change and gap-closing converters is proposed for large output power both at low and high vibration accelerations. An early prototype has been successfully micro-fabricated with the single layer silicon-on-insulator process. Soft X-ray charging is employed to establish uniform surface potential around 60 V on vertical electrets on the sidewall of the comb fingers. Up to 1.6 μW output power has been obtained, which corresponds to the effectiveness as high as 57%.