A 4 × 4 Biosensor Array With a 42-<i>μ</i>W/Channel Multiplexed Current Sensitive Front-End Featuring 137-dB DR and Zeptomolar Sensitivity

Abstract

This paper presents a multiplexed current sensitive readout for label-free zeptomolar-sensitive detectors realized with large area Electrolyte Gated Organic Thin Film Transistors (EGOFETs). These highly capacitive biosensors are multiplexed using an OTFT line driver and OTFT switches, and interfaced to a 65-nm Si CMOS, low power, pA-sensitive front-end. The Si chip performs analogue-to-digital conversion and data transmission to a microcontroller too. A current domain interface is used to transmit the signals coming from multiple biosensors to the 1.2 V-supply CMOS Si-IC via the 30V-supply OTFT electronics. Exploiting an analogue module implemented in the Si-IC, the EGOFETs are precisely biased, even in presence of a large OTFT multiplexer resistance. The CMOS current sensitive front-end achieves a dynamic range (DR) of 137 dB and a power consumption of 42 lW per channel reaching a state-of-the-art DR-power-bandwidth FOM of 208 dB. The front-end has been designed with a first stage programmable-gain, active-feedback transimpedance amplifier topology that, contrary to common current-sensitive front-end solutions, is not affected by the sensor capacitance. The system has been validated with different concentrations of human IgG and IgM proteins using both a single sensor and a 4x4 array of EGOFETs. Thanks to the multiplexing strategy and the low-costs of its modules, the system here presented has the potential to enable widespread use of precision diagnostic with extreme sensitivity even in point-of-care and low-resource settings.