The advantages and potential of electret-based vibration-driven micro energy harvesters

In this paper, we clarify the use and potential of the electret, in the context of vibration-driven micro-energy harvesting that seeks to obtain energy from a vibrating environment to power small electronic devices. An electret is an insulator containing a permanent electric charge or dipole. We make broad comparisons against other methods such as electromagnetic methods and methods using piezoelectric materials, in order to identify the advantages and disadvantages of the electrets. In particular, we introduce a new general model that covers both the electrets and piezoelectric materials to enable comparisons on a common basis. This is followed by a review of a recent method, developed by our group to make full use of the implanted charge inside an electret. Furthermore, we investigate other ways to realize the full potential of the electret as a key material for electromechanical energy conversion in applications where only small forces are involved. Copyright (C) 2009 John Wiley & Sons, Ltd.