Abstract: This invention concerns miniature implantable power sources that harvest or scavenge energy from the expansion and contraction of biological tissues, for example, an artery or a bundle of muscle fiber. Such power sources employ an energy harvesting element that converts mechanical or thermal energy existing or generated in or from a pulsatile tissue into a form of electrical energy that can be used or stored by an implanted medical device, such as a blood pressure sensor, a flow meter, or the like. Preferred energy harvesting element embodiments utilize a piezoelectric thin film embedded within a flexible, self-curling medical-grade polymer or coating. Such power sources can be used to produce self-powered implanted microsystems with continuous or near-continuous operation, increased lifetimes, reduced need for surgical replacement, and minimized or eliminated external interface requirements.