Kinetic and thermal energy harvesters for implantable medical devices and biomedical autonomous sensors

Abstract

Implantable medical devices usually require a battery to operate and this can represent a severe restriction. In most cases, the implantable medical devices must be surgically replaced because of the dead batteries; therefore, the longevity of the whole implantable medical device is determined by the battery lifespan. For this reason, researchers have been studying energy harvesting techniques from the human body in order to obtain batteryless implantable medical devices. The human body is a rich source of energy and this energy can be harvested from body heat, breathing, arm motion, leg motion or the motion of other body parts produced during walking or any other activity. In particular, the main human-body energy sources are kinetic energy and thermal energy. This paper reviews the state-of-art in kinetic and thermoelectric energy harvesters for powering implantable medical devices. Kinetic energy harvesters are based on electromagnetic, electrostatic and piezoelectric conversion. The different energy harvesters are analyzed highlighting their sizes, energy or power they produce and their relative applications. As they must be implanted, energy harvesting devices must be limited in size, typically about 1 cm3. The available energy depends on human-body positions; therefore, some positions are more advantageous than others. For example, favorable positions for piezoelectric harvesters are hip, knee and ankle where forces are significant. The energy harvesters here reported produce a power between 6 nW and 7.2 mW; these values are comparable with the supply requirements of the most common implantable medical devices; this demonstrates that energy harvesting techniques is a valid solution to design batteryless implantable medical devices.

Subthreshold Energy Harvesters Circuits for Biomedical Implants Applications

“…The human body itself is also a potential source of energy. These source can be harvested in particular from the kinetic and thermal energies of the humanbody [4].…”

“…An energy storage super capacitor and voltage regulators need to be designed to meet the specific voltage required by an implant sub-circuits. Table 1 reports average values of power required to supply some implantable medical devices [4]. As depicted in the table the power consumption is in the range of 8uW to 5mW.…”

Infrared Energy Harvesting in Millimeter-Scale GaAs Photovoltaics

“…Fully implanted systems [4]–[5] were developed recently with the aid of wireless energy harvesting methods [6]–[9] utilizing kinetic energy, ultrasonic mechanical vibrations for piezoelectric energy harvesting, thermal energy and radio frequency (RF) electromagnetic radiation for inductive coupling link. The main hurdles [7]–[8], [10] for these wireless energy harvesting are the robustness of ambient energy sources through the biological tissue or skull and miniaturization of implantable devices.…”

Mechanics of flexible and stretchable piezoelectrics for energy harvesting

“…Renewable, efficient, clean and no need for periodical replacement or recharging, flexible/stretchable piezoelectric energy harvesters have become more attractive and close to supply power for wearable and implantable devices or to act as supplement for batteries under certain circumstances [8][9][10]. Piezoelectric energy harvesters convert mechanical energy lying in the environmental vibration [11,12], human body movement and organ deformation [13,14] into electric energy through piezoelectric effect of piezoelectric materials like PVDF polymer, PZT ceramic, ZnO semiconductor in the form of thin film, polymer fiber composite (PFC), ribbons or nanowires. Devices made from different material in different forms end up with quite discrepancy in flexibility, efficiency, feasibility and other performance in scavenging certain mechanical energy.…”