Design of packaged thermoelectric generators for implantable medical devices: A comprehensive parameter study

Implantable thermoelectric generators (TEGs) have the potential to revolutionize healthcare by providing sustainable power for medical devices within the human body. However, a critical knowledge gap exists regarding their performance within the complex thermal environment of the body. This study addresses this gap by developing human torso and head models that incorporate bioheat effects, such as blood perfusion and metabolism. These models enable a comprehensive assessment of TEG performance in a realistic biological setting. A thorough numerical analysis was conducted to study the influence of various design parameters (thermopile configuration, packaging, implant locations, etc.) on TEG performance. Simulation results underscored the critical importance of achieving thermal matching between the TEG and its implantation site, alongside electrical load matching for maximizing power output. Additionally, we explored trade-offs among power output, miniaturization, hermeticity, and manufacturability. Simulations revealed that TEGs implanted in regions with thicker fat layers in the torso generated higher power. An optimized TEG with a 50 mm diameter and 15% fill factor, implanted in the chest with 14 mm of fat, produced 118μW. For cranial implantation in the head, a 30 mm diameter TEG generated 66 μW, increasing to 91μW with a 50 mm diameter heat spreader. The findings culminate in a proposed design guideline to aid the development of high-performance implantable TEGs.