A 4 × 4 Biosensor Array With a 42-μW/Channel Multiplexed Current Sensitive Front-End Featuring 137-dB DR and Zeptomolar Sensitivity

This article 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 organic thin-film transistor (OTFT) line driver and OTFT switches and interfaced to a 65-nm Si CMOS, low-power, pA-sensitive front-end. The Si chip performs analog-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 30-V supply OTFT electronics. Exploiting an analog module implemented in the Si-IC, the EGOFETs are precisely biased, even in the 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-
$\mu \text{W}$
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 4
$\times $
4 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.