A Wearable Microneedle-Integrated Multiplexed Photonic Aptasensor for the Detection of Illicit Drugs in Interstitial Fluid

We present a microneedle-integrated wearable biosensorarray for minimally invasive detection of heroin, cocaine, andmethamphetamine in interstitial fluid (ISF). The platform leveragesaptamer-functionalized cholesteric liquid crystal-based interpenetratingpolymer networks (CLCN-IPNs), which generate colorimetricresponses through photonic bandgap (λPBG) shifts upon targetbinding. Each sensor chip exhibits a distinct initial color, allowing formultiplexed drug detection via visible spectral shifts. The biosensorarray is embedded in a flexible polydimethylsiloxane (PDMS) patchinterfaced with a microneedle substrate for minimally invasive ISFsampling. Upon drug exposure, the CLCN-IPN hydrogel contracts,inducing a blue shift in λPBG. The device demonstrated highselectivity and sensitivity, with detection limits below 1.3 ng/mLfor all drugs. In vitro validation using a chicken tissue model confirmed accurate drug recovery (92.5−115%) and strong visualoutput. This battery-free, portable, and low-cost device offers a promising step toward next-generation wearable diagnostics for drugdetection in clinical, forensic, and personal health applications.