Micro energy harvesting for biomedical applications: A review

Energy Harvesting is the process of extracting small amount of energy from ambient environment. Reduction in size and shape of the electronic components make the power requirements down to the scale of mW. Due to this fact, Energy harvesting techniques and their applications gain much more attraction. Many techniques are being developed to gain energy from various available sources viz. wind, vibration, solar, biological, chemical etc. Out of these, human energies are being the point of interest for many years. For the functioning of many diagnostic and implantable biomedical devices, continuous power can be extracted from available human energies e.g. limb movements, body heat etc. This extracted energy can be utilized to reduce the battery replacement or battery charging problems. This paper gives a review of micro energy harvesting techniques and methods using piezoelectric sensors from biological sources. Main focus is on piezoelectric harvesting, because of relatively large electrical response available to human motion as compared to other means of harvesting techniques. But a problem with human energy harvesting is that extracted energies are of very low range (few μW). This issue is focused in this paper. Much attention is needed for increasing the power density and power management circuitry, so that it can be used as an onsite power generator for many applications.