Bioinspired reconfiguration of 3D printed microfluidic hydrogels via automated manipulation of magnetic inks

Abstract

One of the key components in controlling fluid streams in microfluidic devices is the valve and gating modules. In most situations, these components are fixed at specific locations, and a new reconfiguration of microchannels requires costly and laborious fabrication of new devices. In this study, inspired by the human vasculature microcapillary reconfiguration in response to blood transport requirements, the idea of reconfigurable gel microfluidic systems is presented for the first time. A simple approach is described to print microchannels in methacrylated gelatin (GelMA) hydrogels by using agarose fibers that are loaded with iron microparticles. The agarose fibers can then be used as valves, which are then manipulated using a permanent magnet, providing the reconfigurability of the system. The feasibility of agarose gels is tested with different iron microparticle loadings as well as their resistance to fluid flows. Further, it is shown that using this technique, multiple configurations, as well as reconfigurability, are possible from a single device. This work opens the framework to design more intricate and reconfigurable microfluidic devices, which will decrease the cost and size of the final product.

Figure 1

Procedures for fabricating a reconfigurable microfluidic junction: a) a 3D printer was used to print two perpendicular magnetic agarose gel fibers on a glass slide, b) the GelMA solution was cast on the fibers and exposed to UV light for curing, c) spherical magnets were placed at the end of the fibers, d) the printer nozzle was used to move the magnetic fibers inside the gel. By moving the magnetic fibers (d, e), a custom configuration (L-connector) could be achieved. f) Finally, the metallic piston is moved upward, and the magnet is released.

Figure 2

a) Reconfigurability of the GelMA microfluidic device using magnetic agarose gels with 10–40% (w/v) iron microparticles concentration and magnetic forces ranging from 0.6 to 5.5 N. b) The resistance of magnetic agarose valves with 10–40% (w/v) iron microparticles concentration against 10–1000 μL/min flow rates.

Figure 3

Twelve different configurations for the fluid flow path in a 4-way junction could be achieved using the proposed reconfigurable method, as explained in the following. a-d) The vertical and horizontal fibers are moved upward/downward and rightward/leftward to create the L connectors. e, f) Horizontal fiber is moved rightward/leftward, while the vertical fiber is moved out of the channel. g, h) Vertical fiber is moved upward/downward, while the horizontal fiber is moved out of the channel. i, j) Horizontal or vertical fiber is taken out of the channel, while the other fiber is not moved. k) Both fibers are taken out of the channels. l) Both fibers are left in their initial locations. The scale bar is 1 mm.

Figure 4

The fluid flow behaviors in a) flow focusing and b) T-junction configurations are shown. The scale bar is 1 mm. This image exemplifies the reconfigurability potential of hydrogel microfluidic devices for different applications.