Frequency-domain modeling and optimization of graphene FET-based molecular communication receivers

Molecular Communication (MC) is a bio-inspired communication paradigm utilizing molecules for information transfer. Research on this unconventional communication technique has recently started to transition from theoretical investigations to practical testbed implementations, primarily harnessing microfluidics and sensor technologies. Developing accurate models for input-output relationships on these platforms, which mirror real-world scenarios, is crucial for assessing modulation and detection techniques, devising optimized MC methods, and understanding the impact of physical parameters on performance. In this thesis, we consider a practical microfluidic MC system equipped with a graphene field effect transistor biosensor (bioFET)-based MC receiver as the model system, and develop an analytical end-to-end frequency-domain model. The model provides practical insights into the dispersion and distortion of received signals, informing the design of new frequency-domain MC techniques, such as modulation and detection methods. The accuracy of the developed model is verified through particle-based spatial stochastic simulations of pulse transmission in microfluidic channels and ligand-receptor binding reactions on the receiver surface. In the second part, I detail the fabrication and characterization of a graphene bioFET-based MC receiver. This micro/nanoscale receiver is integrated into a microfluidic channel and functionalized with a biorecognition layer composed of single-stranded DNA molecules-based receptors, designed to detect the target information molecules flowing through the fluidic channel. A pre-equilibrium detection method was explored to improve the data rate. The sensor's initial performance tests involved detection experiments with information encoded into ionic concentration. The fabricated MC receiver was electrically characterized in terms of transfer characteristics and hysteresis at each step of functionalization. The parasitic current and mobility of the device is obtained. After functionalization with probe DNA, the receiver's time-varying response to concentration pulses of complementary target DNA was acquired with both fixed and varying pulse widths. Additionally, an intersymbol interference (ISI) analysis was conducted to evaluate the sensor's ISI performance. Finally, binary data transmission was performed using the MC setup, exploring various data rates and system parameters. The effects of key factors such as pulse width, symbol duration, flow velocity, and target DNA concentration were investigated. As such, this experimental work refined and optimized methodologies and designs from previous research, aiming at advancing practical MC techniques.