Microneedles with Recessed Microcavities for Electrochemical Sensing in Dermal Interstitial Fluid

Transdermal electrochemical sensors based on microneedle (MN) or MN array technology are the next frontier of personalized wearable devices in health monitoring and diagnostics. The performance of transdermal sensors is impacted mainly by damage or deformation of the sensing layer located on the MN surface, which usually occurs due to friction caused between the MN surface and skin tissue. In this work, we report the development of a 4 × 4 polymeric MN array (PMNA) with an individual MN height of ∼720 μm and integrated conductive recessed microcavities (MC) on the MNs surface to protect the sensing layer during insertion and removal from the skin. Characterization and proof-of-concept experiments on porcine skin reveal that PMNA/MC-based platforms retain their functionality and sensitivity of 2.36 ± 0.06 nA mM^-1 even after multiple skin applications. Three-dimensional nanostructuring of MNA hence provides alternative solutions to the critical issues of maintaining performance upon insertion into skin. This approach holds great potential in advancing transdermal sensing technology and affording reliable, cost-effective, and clinically adequate sensing devices.