Subcutaneous Photovoltaic Infrared Energy Harvesting for Bio-implantable Devices

Wireless biomedical implantable devices on the millimeter-scale enable a wide range of applications for human health, safety, and identification, though energy harvesting and power generation are still looming challenges that impede their widespread application. Energy scavenging approaches to power biomedical implants have included thermal, kinetic, radio frequency, and radiative sources. However, the achievement of efficient energy scavenging for biomedical implants at the millimeter-scale has been elusive. Here, we show that photovoltaic cells at the millimeter-scale can achieve a power conversion efficiency of more than 17% for silicon and 31% for GaAs under 1.06 mu W/mm(2) infrared irradiation at 850 nm. Finally, these photovoltaic cells demonstrate highly efficient energy harvesting through biological tissue from ambient sunlight, or irradiation from infrared sources such as used in present-day surveillance systems, by utilizing the near infrared transparency window between the 650- and 950-nm wavelength range.