Biological Component Detection Using Needle-Shaped Microdevices

Monitoring the concentration of biological components is essential for assessing physiological conditions. Although blood sampling remains the most reliable method, its high invasiveness limits its suitability for continuous monitoring. To enable minimally invasive and continuous measurement of biological components, we have developed thin, needle-shaped devices capable of detecting concentration changes within the skin. Acupuncture needles were selected as the base material due to their excellent skin penetrability and mechanical rigidity. Using a custom-developed non-planar microfabrication technique, functional microstructures were fabricated directly onto the needle surfaces. We developed two types of needle-based sensors, each based on a distinct measurement principle. The first employs a microperfusion-based approach, wherein a microfluidic channel with a perforated membrane is integrated onto the needle. A perfusate is circulated through the channel to extract biological components from the interstitial fluid, enabling continuous sensing by analyzing the collected fluid outside the body. The second device utilizes an integrated micro-optical waveguide to deliver near-infrared light into the skin, where absorbance is measured to estimate the concentration of specific biological components. These devices have demonstrated the capability to estimate concentrations of target analytes such as lactate and glucose without the need for conventional blood sampling, offering a promising platform for minimally invasive and continuous health monitoring.