Design and Fabrication of a Microfluidic System with Nozzle/Diffuser Micropump and Viscosity

TL;DR

This paper presents the design, fabrication, and analysis of a PDMS-based microfluidic micropump with a nozzle/diffuser, along with a real-time viscosity measurement method using pressure sensors and finite element analysis.

Contribution

It introduces a low-cost, simple piezoelectric micropump with validated simulation and experimental flow rates, and develops a mathematical and FEA model for real-time viscosity measurement using pressure sensors.

Findings

Flow rates of 9.49, 14.06, 20.87 uL/min at 12V, 14V, 16V

Finite element analysis confirms pump operation and pressure estimates

Viscosity can be dynamically measured via pressure difference changes

Abstract

Micropumps are one of the most important parts of a microfluidic system. In particular, for biomedical applications such as Lab-on-Chip systems, micropumps are used to transport and manipulate test fluids in a controlled manner. In this work, a low-cost, structurally simple, piezoelectrically actuated micropump was simulated and fabricated using poly-dimethylsiloxane (PDMS). The channels in PDMS were fabricated using patterned SU-8 structures. The pump flow rate was measured to be 9.49 uL/min, 14.06 uL/min, 20.87 uL/min for applied voltages of 12 V, 14 V, 16 V respectively. Further, we report finite element analysis (FEA) simulation to confirm the operation of the micropump and compare favorably the experimentally obtained flowrate with the one predicted by simulation. By taking these flow rates as a reference, the chamber pressure was found to be 1.1 to 1.5 kPa from FEA simulations. Viscosity measurement has wide-ranging applications from the oil industry to the pharmaceutical industry. This work provides an elaborate mathematical model and study of measurement of viscosity in real-time using pressure sensors. For a given flowrate, a change in liquid viscosity gives rise to a change in pressure difference across a particular section of the pipe. Hence, by recording the pressure change, viscosity can be calculated dynamically. Mathematical modeling as well as finite element analysis (FEA) modeling has been presented. A set of pressure sensors were placed at a fixed distance from each other to get the real-time pressure change. Knowing the flow rate in the channel, the viscosity has been calculated from the pressure difference. For the finite element analysis, the pressure sensors were placed 60 mm away from each other. A different ratio of the mixture of water and glycerol was used to provide variable viscosity, which led to the variation in pressure-difference values.