Engineering the electrochemical biosensors: Integrating experimental development and modeling for improved performance

The growing demand for accurate and rapid point-of-care diagnostics has driven increasing interest in biosensors, whose sensitivity and versatility allow the development of portable devices for on-field applications. Among them, electrochemical biosensors are particularly promising, yet their development remains challenging, as it requires not only a deep understanding of electrochemical, chemical, and physical phenomena but also careful consideration of the final application. This doctoral thesis addresses these challenges by optimizing the development of electrochemical biosensors to detect biological elements of increasing size and complexity, exploiting multiphysics simulations as support for experimental evidence to achieve improved sensing performance. During this thesis work, detection systems targeting nucleic acids, antibodies, bacteria, and phages were developed on screen-printed electrodes for applications in the agri-food and healthcare sectors. Electrochemical impedance spectroscopy and cyclic voltammetry demonstrated reliable detection performance, in good agreement with optical methods, and highlighted the critical role of surface chemistry and sample preparation in sensor functionalization. Progress toward device miniaturization was achieved with graphene-based field-effect transistors. To support experimental results, a novel multiphysics model was developed in COMSOL Multiphysics®, calibrated against experimental data. The simulations showed how electrode layout and surface morphology can influence electrochemical responses, providing valuable insights for design choices. In general, this thesis demonstrates that modeling and experimental development can be effectively combined to optimize biosensor performance. Reliable biosensors must be application-oriented and focused on the specific characteristics of the analyte of interest, while multiphysics simulations offer a powerful tool for device layout through the study of underlying electrochemical phenomena.