Measurement of lactate concentration using a minimally invasive needle with non-planer optical waveguides

Traditional methods for sampling biological substance concentrations in blood are invasive and unsuitable for continuous monitoring. This paper presents a minimally invasive device equipped with optical waveguides on the surface of an acupuncture needle for measuring lactate concentration in subepidermal tissue, potentially in a continuous fashion. The device utilizes absorbance measurements, based on the correlation between absorbance and lactate concentration in tissue. The needle, with a diameter of 200 microm, exhibits good penetrability, particularly when coated with a biocompatible epoxy, which reduces insertion resistance. The experimental results demonstrate that the device can successfully measure the concentration of lactate solutions, with light intensity decreasing as the lactate concentration increases. However, challenges remain in optimizing the device to reduce optical losses and enhance measurement accuracy. Future work will focus on reducing optical loss, conducting animal experiments, and developing a miniaturized system for simultaneous measurement of multiple biological substances, aiming for practical applications in daily health monitoring.