Design and Implementation of an Integrated Fluidic MEMS Microsensor Testing Apparatus

With the increasing push towards smaller benchtop and point-of-care biomedical devices, lab-onchip systems utilizing microfluidics are at the frontier of biomedical device innovation. Currently, these systems lack access to readily available embeddable sensors common to larger in-line processes such as liquid pressure, density, and viscosity sensors. It is critical to the development of such embedded sensors that appropriate, inexpensive, and efficient microfluidic testing apparatuses exist that enable rapid prototyping of these devices. In this application, the device is a micro-resonator-based fluidic property sensor developed in the iSenSys Lab, which utilizes microelectromechanical systems (MEMS) based technology. An appropriate testing apparatus incorporates the design of an inexpensive flow cell controlled by syringe pumps and enclosed fluidic channels interfacing with the exposed MEMS sensor device and the associated readout circuitry. The thermally excited and piezoresistively sensed signal from the device interfaces with an open feedback loop that includes the re-evaluated excitation and readout circuitry along with the necessary signal conditioning. The testing apparatus incorporates the automation of the data acquisition (DAQ) systems for the probing of several sensor devices in parallel using LabVIEW to improve testing throughout and accelerate prototyping. This parallelization of device characterization required the design of an intensive multiplexing system capable of communicating among sixteen devices in multi-device and single-device operation and with the appropriate instruments (network analyzer, syringe pump, laboratory oven, etc.). Data processing and analysis of the frequency spectrum is conducted in MATLAB to extract and subsequently relate peak amplitude, peak frequency, and the peak Q factor to density and viscosity. The designed testing apparatus effectively decoupled the liquid-exposed microsensors from its electronic readout with minimal signal distortion, eventually enabling accurate characterization of liquid fluidic properties for both validation and potential redesign of the MEMS device.