CMOS multiplexer for portable biosensing system with integrated microfluidic interface

A portable biosensing system is presented in this work. The system consists of a measuring block featuring an integrated microfluidic interface on a secure digital (SD)-card form factor substrate. This SD substrate incorporates a biochip and a custom designed analog CMOS multiplexer. The integrated multiplexer is intended to connect to each sensor-FETs on the biochip individually, allowing a hot-plug connection to the measuring block. A low-cost PDMS glob top forms the package for protection of all wire-bonded integrated circuits and defines the microfluidic channel. Thus facilitating the delivery of the analyte to the biochip via a simple microfluidic interface without additional sealing. Employing the proposed CMOS multiplexer allows simpler, more rapid and more accurate measurements comparing with the previous lab-scale setup. Achievable performance and required calibration steps are discussed towards the CMOS multiplexers ON-resistance, leakage currents, and dynamic characteristics. Overall size, cost and reliability are compared to a discrete solution. The microfluidic part of the biosensing system incorporates a permanent magnet linear positioning drive and linear position sensor for effortless and dependable mechanical interfacing. The portable system is designed as a part of a PC-based setup and primed for stand-alone operation.