A novel, solid-state sensor for charge detection in biomolecular processes is proposed. The device, called charge-modulated field-effect transistor, is compatible with a standard CMOS process, thus allowing fully electronic readout and large scale of integration of biosensors on a single chip. The detection mechanism is based on the field-effect modulation induced by electric charge changes related to the bioprocess. A model of the device was developed, to provide a manageable relationship between its output and geometric, design and process parameters. Extensive two- and three-dimensional simulations of the proposed structure validated the model and the working principle.

Organic thin film transistors have been fabricated on plastic substrates using a combination of two ultrathin insulating films, namely a 6 nm Al2O3 film (grown by UV-Ozone treatment of a pre-deposited aluminium film) and a 25 nm parylene C film deposited by vapour phase, as gate dielectric. They show a very low leakage current density, around 2 × 10−9 A/cm2, and, most importantly, can be operated at voltages below 1 V. We demonstrate that this low-cost technique is highly reproducible and represents a step forward for the routine fabrication of ultra-low voltage plastic electronics.

An integrated field-effect device for fully electronic deoxyribonucleic acid (DNA) detection was realized in a standard CMOS process. The device is composed of a floating-gate MOS transistor, a control-capacitor acting as integrated counterelectrode, and an exposed active area for DNA immobilization. The drain-current of the transistor is modulated by the electric charge carried by the DNA molecules. After DNA hybridization, this charge increases and a change in the output current is measured. Experimental results are provided. Full compatibility with a standard CMOS process opens the way to the realization of low-cost large-scale integration of fast electronic DNA detectors.