Microfluidic Bubble-Templating\nMultinozzle 3D Printing\nfor Preparations of Macroporous Hydrogels with Ordered Pores of Large\nSize Ranges

A strategy for fabrication of macroporous hydrogels through\n3D\nprinting assisted by molding and multiple microfluidic bubble-templating\nnozzles is proposed here. This approach aims to address the challenges\nfaced by methods for 3D printing macroporous hydrogels, such as difficulties\nin precisely controlling the spatial distribution of macropores, limited\nporosity, and low resolution of external boundaries due to the poor\nmechanical properties of hydrogel solutions as printing ink. In this\nmethod, fast-switching microfluidic bubble-templating nozzles of varying\nsizes allowed for precise control of target pore sizes over a wide\nrange. Cavities of polydimethylsiloxane (PDMS) molds were used to\ndefine the overall external shape of the hydrogels and enhance the\nresolution of the boundaries. During the printing process, the laminar\nshear force generated by a coaxial microfluidic system generated microbubbles\nwhich were then injected into the PDMS mold cavities. The spatial\ndistribution of the microbubble clusters within the cavities was controlled\nby a 3D motion module. Finally, macroporous hydrogels with a pore\nsize range of 238–930 μm were fabricated while avoiding\nmillimeter round corners on the boundaries. A control precision of\npore sizes was about 60 μm. Most importantly, this strategy\nbroke through the space occupancy limitations of pores in traditional\n3D printing methods for macroporous hydrogels. The space occupancy\nof pores could reach a maximum of about 87% within a single layer.