3D printing of functionally graded porous materials using on-demand reconfigurable microfluidics

Tailoring the morphology of macroporous structures remains one of the biggest challengesin material synthesis. Here, we present an innovative approach to fabricatecustommacroporous materials with pore size varying throughout the structure by up to an order of magnitudeusingon-demand reconfigurable microfluidics. We employavalve-based flow-focusing junction(vFF)in which the size of the orifice can be adjusted in real-time (within tens of milliseconds)to generate foams withon-linecontrolled bubble size. We use the junction tofabricatelayered and smoothly graded porous structureswith pore size varying in the range 80-800 μm.Additionally, to further exploit thecapacityof the technique, we mount vFF on top of an extrusion printer and 3D-print constructscharacterized by a predefined 3D geometryand controlled spatiallyvaryinginternal porous architecture, such asa model of a bone. The presented technology opensup new possibilities in macroporous material synthesis with potential applications ranging from tissue engineering to aerospace industry and construction.