A Solution-Gated Graphene FET Receiver for Molecular Communications with Low-Frequency PSD- and Derivative-Based Detection

Molecular communication (MC) is the exchange of information via signaling molecules, forming the backbone of biological networks and underpinning the development of the Internet of Bio-Nano Things (IoBNT). A critical challenge in engineering MC systems is the reliable detection of molecular signals in realistic environments, where slow diffusion, reaction noise, and memory effects in the channel not only cause intersymbol interference (ISI) but also lead to low signal-to-noise ratios, baseline drifts, and saturation of ligand–receptor interfaces. Conventional detection methods relying on equilibrium measurements are often too slow to capture dynamic concentration changes that encode the information and are vulnerable to ISI and receptor saturation. To evaluate dynamic detection strategies under these conditions on a practical electronic receiver, we require a device that operates directly in electrolyte, supports specific ligand–receptor binding, and can be integrated with controlled microfluidic flow. In this study, we experimentally implement and systematically compare two dynamic detection strategies, i.e., Derivative-Based Detection (DD) and Frequency-Domain Detection (FD), using an integrated microfluidic testbed featuring a GFET-based MC receiver. The GFET, functionalized with single-stranded DNA (ssDNA) probes for selectively capturing complementary, information-carrying target ssDNA molecules, transduces hybridization events into electrical signals in real time. We characterize the receiver's response and evaluate the performance of DD and FD against a conventional Difference-Based Detection (BD) benchmark across various communication scenarios with different flow rates and data rates. Our results demonstrate that DD and FD significantly outperform BD, particularly in high-ISI regimes. DD achieves superior detection performance when the signal-to-noise ratio (SNR) is high and temporal transitions are sharp, offering rapid pre-equilibrium detection. Conversely, FD, which analyzes the power spectral density (PSD) of binding‑induced current fluctuations, maintains superior robustness in low‑SNR and high‑ISI regimes where time‑domain signatures cannot be reliably resolved. This work provides the first experimental validation of DD and FD for GFET-based MC receivers, enabling a practical pathway toward reliable MC in complex, physiologically relevant environments.