Thermoelectric generator for electrically active implants

This proposal investigates the potential of miniaturised thermoelectric generators (TEGs) for the unlimited operational life of medical implants. Such generators utilise the heat of the human body to supply electrical energy to electrically active implants via the Seebeck effect in thermoelectric material. Although simple TEGs exist for industrial and automotive applications involving temperature differences of several tens of degrees, no generator has been proposed specifically for use in medical implants. This work aims to meet the need for miniaturised TEGs that operate within the human body with typical temperature differences of just a few degrees.

To achieve optimal power output, two optimisation objectives must be met. Most importantly, the thermal load must be balanced to account for the thermal resistance of the implant and the thermal properties of the surrounding body tissue. This ensures optimal thermal boundary conditions for the implant. Secondly, the TEG design – in particular its electrical resistance – must take into account the input impedance of the connected circuits. Therefore, a finite element model (FE model) is developed that integrates the TEG, the housing and the surrounding body tissue in order to optimise the design whilst accounting for thermoelectric effects such as the Peltier effect. The tissue model should account for bio-thermal effects such as blood perfusion Q_b and metabolic heat generation Q_m. For efficient simulation, Model Order Reduction (MOR) is used to reduce the FE model on a large scale. Furthermore, a novel assembly and manufacturing approach for miniaturised TEGs is being developed. We envisage assembling hundreds of individual thermoelectric elements with sub-millimetre dimensions. Biocompatibility and suitability for use in magnetic resonance imaging are taken into account throughout the project.

Video to follow: TEG manufacturing