Modular and Self-Contained Microfluidic Analytical Platforms Enabled by Magnetorheological Elastomer Microactuators

Abstract

Portability and low-cost analytic ability are desirable for point-of-care (POC) diagnostics; however, current POC testing platforms often require time-consuming multiple microfabrication steps and rely on bulky and costly equipment. This hinders the capability of microfluidics to prove its power outside of laboratories and narrows the range of applications. This paper details a self-contained microfluidic device, which does not require any external connection or tubing to deliver insert-and-use image-based analysis. Without any microfabrication, magnetorheological elastomer (MRE) microactuators including pumps, mixers and valves are integrated into one modular microfluidic chip based on novel manipulation principles. By inserting the chip into the driving and controlling platform, the system demonstrates sample preparation and sequential pumping processes. Furthermore, due to the straightforward fabrication process, chips can be rapidly reconfigured at a low cost, which validates the robustness and versatility of an MRE-enabled microfluidic platform as an option for developing an integrated lab-on-a-chip system.

Keywords: actuators; lab-on-a-chip; magnetorheological elastomer; microfluidics; self-contained system.

Figure 1

Schematic illustration of the self-contained microfluidics platform enabled by magnetorheological elastomer (MRE). (a) Exploded schematic representation of the integrated platform. The lower inset shows the assembled model of the system. (b) Actual image of the assembled system integrated with a portable digital microscope.

Figure 2

Schematic illustration of the microfluidic chip design and the working principle of MRE actuators. Schematic of the working mechanism of a MRE (a) micropump, (b) microvalve and (c) micromixer. (d) Exploded schematic representation of one design of the MRE microfluidic chip. The upper insert illustrates the cross-sectional view for a MRE actuator. The lower inset shows actual image of an assembled chip (Scale bar = 10 mm). (e) Actual image of the assembled chip integrated with three MRE pumps, one mixer and one valve.

Figure 3

Experiments for examining on-chip MRE micromixer performance. (a) Actual image for the integrated MRE micromixer. The upper insert shows the microchannel design. (b) Top and bottom views of the micromixer channels. (c) Snapshots showing the mixing performance at inlet flow rates of 20 µL/min. Plot of the green colour intensity profiles along A-A′ shown in (a) across the microchannel at a flow rate of (d) 40 µL/min and (e) 100 µL/min with the magnet rotor rotating at speeds of 0, 60 and 150 RPM. Images of the channels at different RPMs are shown next to the legend.

Figure 4

Schematic of setup for integrated MRE valve. (a) Exploded schematic representation of the valve setup. The lower inset shows the actual image of the chip design for sequential pumping. (b) The disabled and enabled working states of the MRE valve. (c–e) Sequential snapchats showing achievement of sequential pumping. The lower insert plot shows the flow rate vs. rotation speed of the magnet rotor.