Date Published: April 3, 2017
Publisher: Public Library of Science
Author(s): John R. Lake, Keith C. Heyde, Warren C. Ruder, Meni Wanunu.
Microfluidics are widely used in research ranging from bioengineering and biomedical disciplines to chemistry and nanotechnology. As such, there are a large number of options for the devices used to drive and control flow through microfluidic channels. Commercially available syringe pumps are probably the most commonly used instruments for this purpose, but are relatively high-cost and have inherent limitations due to their flow profiles when they are run open-loop. Here, we present a low-cost ($110) syringe pressure pump that uses feedback control to regulate the pressure into microfluidic chips. Using an open-source microcontroller board (Arduino), we demonstrate an easily operated and programmable syringe pump that can be run using either a PID or bang-bang control method. Through feedback control of the pressure at the inlets of two microfluidic geometries, we have shown stability of our device to within ±1% of the set point using a PID control method and within ±5% of the set point using a bang-bang control method with response times of less than 1 second. This device offers a low-cost option to drive and control well-regulated pressure-driven flow through microfluidic chips.
Microfluidic systems have become one of the more prolific tools for researchers in the chemical and biological sciences. The small volumes of reagents and samples required for use in microfluidic systems, combined with a widespread ability to fabricate high performance microfluidic chips using poly(dimethylsiloxane) (PDMS), makes microfluidics especially attractive for bioengineering and biomedical research [1–3]. As a platform, PDMS-based microfluidic devices are used for a wide range of applications including immunoassays, separation of proteins and DNA, and the sorting and manipulation of living cells allowing for researchers to gain insights into cell biology . However, microfluidic systems are not limited to biological research, as they have been used by nanotechnology researchers as a high-throughput way of producing nanodevices  and as a platform for many analytical chemistry techniques such as electrophoresis and chromatography .
The syringe pressure pump demonstrated here provides a flexible tool for researchers that can be used in a variety of applications requiring well-regulated pressure-driven flow for microfluidics. These pumps can offer an easy-to-use device which can be fabricated in less than one day at a very low cost. It also can be used across many different research areas, as pressure-driven microfluidics spans a broad range of disciplines. This syringe pressure pump demonstrates that relatively high performance flow control can be achieved by combining low-cost hardware and electronics with fundamental control algorithms. Additionally, with the continuing advancement of 3D printing technologies, academic labs are increasingly relying on rapid prototyping techniques to accelerate the development of tools used in their research. For this reason, these pumps can provide a broad audience of researchers access to a useful tool for microfluidics studies.