3D Printing of Interconnection-Tunable Porous Ink

An interconnection-tunable porous ink (ITPI) platform is introduced for fabricating three-dimensional (3D) porous structures with programmable pore connectivity. The ITPI is a multiphasic suspension consisting of a polymer precursor solution as the continuous medium, sacrificial solid particles, and a surface-wetting liquid that forms capillary bridges. The formulation is tailored to possess rheological properties suitable for 3D printing via direct ink writing, facilitating the patterning of elastic porous architectures. This ITPI design allows fine control of the interconnection width between pores by adjusting the wetting liquid content while maintaining the overall porosity and pore size. As a representative case, <i>p</i>-ITPI, composed of polydimethylsiloxane, sugar particles of approximately 30 μm, and glycerol, is used to fabricate highly elastic 3D sponges with tunable interconnection widths ranging from a few to several tens of micrometers. The resulting structures exhibit excellent shape fidelity, adjustable permeability, and long-term superelasticity over 1000 compression cycles. Demonstrated applications include selective oil absorption, programmable-delay passive fluid release in microfluidics, and piezoresistive sensing via liquid metal (LM) infusion. Notably, LM-infused sponges enable real-time tactile feedback in robotic coil embolization simulations. This strategy offers a generalizable route for engineering porous materials with tunable interconnectivities for filtration systems, microfluidics, soft robotics, and biomedical systems.