Fabrication and characterization of solution-gated graphene field-effect transistors and graphene hall sensors for developing microfluidic molecular communication receivers

Molecular Communication (MC) is a bio-inspired communication paradigm that uses chemical signals to transmit information between spatially separated entities. While significant research has been conducted on the theoretical aspects of MC, there remains a notable gap in developing practical systems that can transition these concepts into real-world applications. The absence of established testbeds at the micro- and nanoscale often leads researchers to rely on simplified assumptions regarding channel conditions and transceiver designs. Furthermore, MC presents unique challenges due to its highly complex, nonlinear, and time-varying channel properties, which conventional ICT tools cannot adequately address. As a result, many existing MC methods, largely adapted from traditional electromagnetic communication models, remain unvalidated without practical testbeds. To bridge this gap, it is essential to develop practical MC systems with nanoscale MC receivers that can serve as testbeds for advancing realistic MC methods and Internet of Bio-Nano Things (IoBNT) applications. In this context, micro/nanoscale field-effect transistor (FET)-based biosensors and Hall effect sensors emerge as promising architectures for practical MC receivers due to their ability to selectively detect a wide range of molecules that can be used to encode information. FET-based sensors detect charged information molecules, such as nucleotides, through ligand-receptor interactions that modulate the FET channel conductivity. In contrast, Hall effect sensors are designed to detect magnetic nanoparticles (MNPs), which alter the local magnetic field, inducing measurable voltage modulation based on the Hall effect. Both sensor architectures enable continuous, label-free, and selective molecular detection, making them well-suited for integration into MC systems as receivers. Graphene, with its exceptional electrical properties, stands out among nanomaterials used for FET-based biosensors and Hall effect sensors. In light of this, in this thesis, I report the design and fabrication processes of MC receivers based on graphene FET-based DNA sensors and graphene Hall effect sensors. Key challenges addressed include precise graphene transfer, formation of high-quality metal electrodes, deposition of effective dielectric layers, and integration with microfluidic channels, along with specific challenges related to MC receiver applications beyond conventional sensing. Through optical and electrical characterization methods, I evaluate the performance and quality of both sensors, confirming their potential as sensitive and reliable MC receivers. As such, this thesis lays the foundation for the development of practical MC systems and contributes to advancing realistic MC methods and IoBNT applications.