Preliminary Rapid Assessment of Light Penetration in Human Tissue

As biophotonics advances, the demand for various light sources in medical engineering applications is rising. The development of medical devices often relies on in-vitro data sourced from human and other tissue samples. However, certain human tissues, such as those from the hand, may present irregular contact surfaces and compositional variability. Moreover, even when utilizing light sources with identical wavelengths, beam angles or light distribution variations can result in degrees through human tissue, which may not be fully predictable based on literature-derived parameters. To overcome these challenges, we developed a simple and reproducible testing methodology designed to effectively evaluate the penetration efficiency of various small light sources on human tissue, specifically focusing on the earlobes. By testing conditions where the light source is gently applied to the earlobe, we uncovered several significant findings from commonly available light therapy devices. These findings are often challenging to deduce from existing literature on wavelengths, emphasizing the urgent need for medical device designers to implement a quicker testing process to ensure that their chosen light sources adequately fulfill the penetration requirements in real-world conditions.