Integrating microelectronics with microfluidics, especially those implemented in silicon-based CMOS technology, has driven the next generation of in vitro diagnostics. This CMOS/microfluidics platform offers close interfaces between electronics and biological samples and tight integration of readout circuits with multi-channel microfluidics, both of which are crucial factors in achieving enhanced sensitivity and detection throughput. Importantly, conventionally bulky benchtop instruments are now being transformed into millimeter-sized form factors at low cost, making the deployment for Point-of-Care (PoC) applications feasible. Conventional CMOS/microfluidics integration has typically followed a “modular” approach, where the CMOS electronics package and the microfluidics are prepared separately and then attached through in-house assembly. However, such an approach suffers from significant misalignment between the microfluidics and the sensing transducers on the chip, especially when the transducer sizes are reduced or the microfluidic channel width shrinks. The full potential of CMOS parallel readout has not been fully realized.
In this project, we introduce a microfluidics platform embedded within a silicon chip implemented in CMOS technology. The platform utilizes a one-step wet etching method to create fluidic channels by selectively removing CMOS back-end-of-line (BEOL) routing metals. We term our technique “subtractive” microfluidics, to complement those fabricated with additive manufacturing. Three types of structures are presented in a TSMC I80-nm CMOS chip: (1) passive microfluidics in the form of a micro-mixer and a 1: 64 splitter, (2) fluidic channels with embedded ion-sensitive field-effect transistors (ISFETs) and Hall sensors, and (3) integrated on-chip impedance-sensing readout circuits including voltage drivers and a fully differential transimpedance amplifier (TIA). Sensors and transistors are functional pre-and post-etching with minimal changes in performance. Our CMOS subtractive microfluidics technique enables tight integration of fluidics and electronics, paving the way for future small-size, high-throughput lab-on-chip (LOC) devices. We are now expanding this technique toward assays toward single-molecule sensitivity.
Project is currently funded by: Federal