Fenestrated Microneedle Arrays with Hybrid Conductive Ink Coating for Transdermal Biosensing

Wearable electrochemical biosensors offer a promising alternative to conventional invasive blood-based methods for monitoring biomarkers in diagnostic or therapeutic applications. Microneedle (MN)-based technology provides direct access to the skin's interstitial fluid (ISF), enabling real-time monitoring of biomarkers. Nevertheless, current micro- and nanofabrication techniques do not adequately support the development of MN-based wearable technology that can utilize soft hybrid conductive inks, limiting its use in transdermal biosensing. Herein, an MN-based biosensing platform is developed by integrating 3D printing, soft lithography, and hybrid conductive ink technology, featuring a fenestrated MN shell (FMNS) that serves as a protective layer for the inner hybrid conductive ink coating and prevents delamination during skin application. This FMNS patch demonstrates a wide pH monitoring range, high selectivity and accurate detection of subtle ISF pH changes, safe integration of hybrid conductive inks, and reduced fabrication time and cost when compared to other microfabrication methods such as lithography and deep reactive ion etching. The biosensor excels in protecting the biosensing layer and demonstrates excellent analytical performance in monitoring changes in pH levels of the skin ISF. This micro- and nanofabrication approach has great potential in integrating hybrid conductive ink technology into transdermal wearable devices for health monitoring and diagnostics.