Suitability of a thermoelectric power generator for implantable medical electronic devices

Abstract

Embedding a thermoelectric generator (TEG) in a biological body is a promising way to supply electronic power in the long term for an implantable medical device (IMD). The unique merit of this method lies in its direct utilization of the temperature difference intrinsically existing throughout the whole biological body. However, little is known about the practicability of such a power generation strategy up to now. This paper attempts to evaluate the energy generation capacity of an implanted TEG subject to various physiological or environmental thermal conditions. Through theoretical analysis, it was found that the highest temperature gradient occurs near the skin surface of the human body, which suggested a candidate site for implanting and positioning the TEG. In addition, numerical simulations were performed on three-dimensional bioheat transfer problems in human bodies embedded with TEGs at different implantation depths and configurations. To further enhance energy generation of an implanted TEG, several external technical approaches by intentionally cooling or heating the skin surface were proposed and evaluated. Conceptual experiments either in vitro or in vivo were implemented to preliminarily test the theoretical predictions. Given the fact that an IMD generally require very little working energy, the TEG could serve well as a potential long-term energy supplier for such medical practices.

An efficient boost converter control for thermoelectric energy harvesting

“…In this particular case τ P , given by (2), is controlled between 20ns and 200ns to meet all different combinations of variable input and output voltages. The value of parasitic capacitance C X can be easily estimated, and in this case it is approximately 2pF.…”

“…The highest temperature gradient is available just under the surface of the skin in the fat layer, where temperature difference can reach up to 5K. However, the actual difference between the plates of the harvester is expected to be much lower, from 0.5K to 2K [2]. Therefore, the resulting output voltage may be as low as 40mV and the output power only 4μW even when a state-of-the-art thermoelectric device is used [3].…”

An Efficient Inductorless Dynamically Configured Interface Circuit for Piezoelectric Vibration Energy Harvesting

“…By minimizing the power consumption, researchers and engineers have attempted to extend battery lifetime and to avoid replacing or recharging batteries too frequently. While batteries have remained the primary energy sources due to their energy density, in certain sensing contexts requiring the operation of sensors and sensor systems over a significant period of time [6], including implantable biomedical electronic devices [7] and tire pressure sensors [8], battery usage may be both impractical and add extra cost due to the requirements for periodic re-charging and/or replacement [9]. In order to address this challenge and extend the operational lifetime of wireless sensors, there has been an emerging research interest to harvest energy from environmental kinetic vibration [10], [11].…”

Equivalent Electrical Circuits of Thermoelectric Generators under Different Operating Conditions

“…For instance, the wireless sensors used in medical applications require autonomous power sources capable of powering nodes with expected lifetimes exceeding 10 years [1,2]. The low power consumption of these systems is desirable but not sufficient to ensure the continuity of their operation during time.…”