Hydrogel-Gated Organic Electrochemical Transistors for Wearable and Portable Direct Detection of Aerosol-Borne Viral Antigens

Direct detection of viral antigens in respiratory aerosols is challenging because affinity-based organic electrochemical transistors (OECTs) typically rely on liquid samples. Here, a non-flowing agarose hydrogel replaced the liquid electrolyte to capture aerosols, conduct ions, and support target transport. Before OECT readout, a separate 1-min ring-electrode field-assistance step was applied to facilitate target delivery to the aptamer-functionalized gate. Under the optimized conditions, the device achieved a solution-phase concentration-based limit of detection (LoD) of 1.27 fM and a sample-to-result time of 17 min. The approach was implemented in face-mask and handheld formats with a portable wireless readout system. In nebulization-based tests using SARS-CoV-2 spike protein, the LoDs expressed in terms of the concentrations of the nebulizer source solutions were 6.89 pM and 1.19 pM for the face-mask and handheld configurations, respectively. These results demonstrate that hydrogel-mediated aerosol capture and ionic coupling, ring-electrode field assistance, and OECT transduction can be integrated to enable direct electrical detection of aerosol-borne viral antigens, supporting further development of wearable and portable respiratory screening systems.