Chapter 7 - Electronic devices for biomarker monitoring

Abstract

This chapter details the various transistor architectures that are applied to biosensors, and particularly for the detection and quantification of biomarkers. After a general introduction on the application of transistors for the detection of biomarkers, a list of potentially pertinent biomarkers is drawn up, then details are given on the operation principles of transistors, in particular field-effect ones. It is first explained why these devices rely on charged interfaces, which define the sensitive surfaces. Then, several architectures are detailed such as single-gate and dual-gate ion sensitive field-effect transistors (ISFETs) that allow to place transistors around their best functioning point, leading to better gain and sensitivity. ISFETs and their derivatives, the electric double-layer field-effect transistors (FETs), may present some drawbacks such as high operating potentials. Electrolyte-gated FETs, by suppressing the intermediate dielectric layer, allow to lower this potential down to a few tens or hundreds of millivolt, for low power consumption and better functioning without any risk of water splitting. Organic semiconductors give excellent results in this configuration, but graphene and its derivatives, even of being not semiconductors, also give very promising results because they allow for high currents so high sensitivities, along with excellent stability. Most of these transistors are still at the research stage, however. Conversely, extended-gate FETs are very promising devices which take advantage of the existing CMOS technology, just adding an extension to the gate contact of a commercial FET, which serves as sensing electrode. Extreme miniaturization can be achieved with these transistors and commercial applications are expected shortly.