An Organic Field-Effect Transistor–Based NANOFLEX-BIOCHIP for Ultrasensitive and Rapid Detection of HBV and HIV Biomarkers Using Atangana–Baleanu–Caputo Fractional- Order Modeling

Early and accurate detection of viral infections remains a major challenge in global healthcare, particularly for Hepatitis B virus (HBV) and Human Immunodeficiency Virus (HIV), where biomarker concentrations during early infection are often below the detection limits of conventional diagnostic assays. This study reports the design, fabrication, and experimental validation of an organic field-effect transistor (OFET)–based NanoFlex-BioChip for the ultrasensitive and rapid detection of HBV and HIV biomarkers. The platform employs a bottom-gate, top-contact OFET architecture fabricated using solution-processed organic semiconductors and a selectively biofunctionalized sensing interface targeting hepatitis B surface antigen (HBsAg) and HIV-1 p24 antigen. Electrical characterization demonstrates reproducible modulation of transfer and output characteristics upon biomarker binding, manifested as systematic threshold voltage shifts and drain current suppression. The NanoFlex-BioChip achieves femtomolar-level limits of detection for both HBsAg and HIV p24, enabling reliable sensing at clinically relevant concentrations associated with early-stage infection. Rapid signal transduction is observed, with response times below one minute using microliter-scale sample volumes, supporting suitability for point-of-care applications. To interpret the complex sensing dynamics inherent to organic bioelectronic systems, a fractional-order modeling framework based on the Atangana–Baleanu–Caputo (ABC) fractional derivative is introduced. This approach captures nonlocal memory effects, charge trapping, and anomalous transport phenomena characteristic of organic semiconductors, providing substantially improved agreement between experimental data and theoretical predictions compared to classical integer-order models. The device further exhibits stable performance under physiologically relevant variations in pH, temperature, and ionic strength, while maintaining mechanical compatibility with flexible substrates and scalable fabrication processes. The NanoFlex-BioChip integrates ultrasensitive, label-free biosensing with advanced fractional-order signal interpretation, offering a robust, low-cost platform for decentralized viral diagnostics. The findings demonstrate the potential of combining organic bioelectronics and fractional calculus to advance early disease detection, outbreak surveillance, and accessible healthcare delivery.