Microfluidic devices are gaining extensive interest due to their potential applications in wide-ranging areas, including lab-on-a-chip devices, fluid delivery, and artificial vascular networks. Most current microfluidic devices are in a planar design with fixed configurations once formed, which limits their applications such as in engineered vascular networks in biology and programmable drug delivery systems. Here, shape-programmable three-dimensional (3D) microfluidic structures, which are assembled from a bilayer of channel-embedded polydimethylsiloxane (PDMS) and shape-memory polymers (SMPs) via compressive buckling, are reported. 3D microfluidics in diverse geometries including those in open-mesh configurations are presented. In addition, they can be programmed into temporary shapes and recover their original shape under thermal stimuli due to the shape memory effect of the SMP component, with fluid flow in the microfluidic channels well maintained in both deformed and recovered shapes. Furthermore, the shape-fixing effect of SMPs enables freestanding open-mesh 3D microfluidic structures without the need for a substrate to maintain the 3D shape as used in previous studies. By adding magnetic particles into the PDMS layer, magnetically responsive 3D microfluidic structures are enabled to achieve fast, remote programming of the structures via a portable magnet. A 3D design phase diagram is constructed to show the effects of the magnetic PDMS/SMP thickness ratio and the volume fraction of magnetic particles on the shape programmability of the 3D microfluidic structures. The developed shape-programmable, open-mesh 3D microfluidic structures offer many opportunities for applications including tissue engineering, drug delivery, and many others.
Keywords: compressive buckling; magnetic actuation; shape-memory polymers; shape-programmable microfluidics; three-dimensional microfluidics.