Implications of Wound Healing on Subcutaneous Photovoltaic Energy Harvesting

Abstract

Objective: Implanted cardiac pacemakers must be regularly replaced due to depleted batteries. A possible alternative is proposed by subcutaneous photovoltaic energy harvesting. The body's reaction to an implant can cause device encapsulation. Potential changes in spectral light transmission of skin can influence the performance of subcutaneous photovoltaic cells and has not yet been studied in large animal studies. Methods: Subcutaneous implants measuring changes in the light reaching the implant were developed. Three pigs received those implants and were analyzed for seven weeks. Spectral measurements with known irradiation were performed to identify possible changes in the transparency of the tissues above the implant during the wound healing process. A histological analysis at the end of the trial investigated the skin tissue above the subcutaneous photovoltaic implants. Results: The implants measured decreasing light intensity and shifts in the light's spectrum during the initial wound healing phase. In a later stage of tissue recovery, the implants measured a generally reduced light intensity compared to the healthy tissue after implantation. The spectral distribution of the measured light at the end of the trial was similar to the first measurements. The histological analysis showed subcutaneous granulation tissue formation for all devices. Conclusion: The varying reduction of light intensity reaching the implants means that safety margins must be sufficiently high to ensure the power. At the end of the wound healing process, the spectral distribution of the light reaching the implant is similar to healthy tissue. Significance: Optimizations of spectral sensitivity of photovoltaic cells are possible.

Optical Wireless Power Transmission Through Biological Tissue Using Commercial Photovoltaic Cells Under 810 nm LEDs: Feasibility Study

“…The V OC of a single PV cell is a reliable indicator for assessing the depth of light penetration into the human body and the amount of external light collected by the PV cell implanted within the body; this is because the PV cell exhibits high sensitivity to variations in low-light environments [31]. Figures 6(a), (b), (c) show the results of PV#1, PV#2, and PV#3, respectively.…”

“…This study did not include repeat measurements; thus, future studies should consider conducting repeated measurements and analyzing them statistically. This is crucial due to the potential deviations between initial and final measurements, as highlighted by [31].…”