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

We present a microneedle-integrated wearable biosensor array for minimally invasive detection of heroin, cocaine, and methamphetamine in interstitial fluid (ISF). The platform leverages aptamer-functionalized cholesteric liquid crystal-based interpenetrating polymer networks (CLCN-IPNs), which generate colorimetric responses through photonic bandgap (λ_PBG) shifts upon target binding. Each sensor chip exhibits a distinct initial color, allowing for multiplexed drug detection via visible spectral shifts. The biosensor array is embedded in a flexible polydimethylsiloxane (PDMS) patch interfaced with a microneedle substrate for minimally invasive ISF sampling. Upon drug exposure, the CLCN-IPN hydrogel contracts, inducing a blue shift in λ_PBG. The device demonstrated high selectivity and sensitivity, with detection limits below 1.3 ng/mL for all drugs. In vitro validation using a chicken tissue model confirmed accurate drug recovery (92.5-115%) and strong visual output. This battery-free, portable, and low-cost device offers a promising step toward next-generation wearable diagnostics for drug detection in clinical, forensic, and personal health applications.