Co-design of a Full Bio/CMOS Interface

While this book closes with the appendixes, this chapter closes the aim of the book by giving the opportunity to see how co-design a full Bio/Nano/Complementary Metal-Oxide Semiconductor (CMOS) interface. The chapter presents a series of examples that move to a full design of a Bio/CMOS interface. The proposed scenario is that of the sadly known case of the coronavirus pandemic (also known as COVID-19) that occurred worldwide during 2020–2022. The chapter aims to develop a proper Bio/CMOS interface to provide a single device for evaluating the stage of the disease in patients by the simultaneous detection of the virus and of both IgM and IgG anti-COVID immunoglobulins. IgM and IgG anti-COVID immunoglobulins correspond to the immune response of the patients. The learning approach proposed here is based on a series of examples with related solutions. As the design requires, examples and solutions are initially proposed for the preparation of the biolayer required to provide the right selectivity to that interface. Then, a possible electrode platform is designed, and its performance in terms of capacitive detection is provided. Methods to improve the interface performance are discussed, and the resulting sensitivity and limit of detection are computed to show the effective enhancement of the Bio/CMOS interface after integration with a proper nanolayer (made of gold nanoparticles). The chapter progresses by developing examples related to the best CMOS layer for the application scenario. In particular, detection with both frequency-to-capacitance and amperometric methods is presented and discussed. In both cases, block diagrams and CMOS circuits at the level of operational amplifiers are shown. For the case of amperometric detection, one example of CMOS design at the transistor level is also proposed by considering the simplest possible architecture for a differential amplifier. Along the chapter, a series of questions and related answers are proposed as well, with the aim of further discussing and comparing several options, which are possible in similar but different cases.