Comments from Wei-Shou Hu

The talk will present a new method for 3D printing with soft silicone-based material by using inks made from multiphasic liquid/liquid/solid systems. These inks consist of water and two components, crosslinked polydimethylsiloxane (PDMS) microbeads and a liquid non-crosslinked PDMS phase. Owing to the capillary binding of the microbeads, their suspensions containing certain fractions of liquid PDMS precursor behave like thixotropic pastes, which are flowable at high shear stress, yet they possess high storage moduli and yield stresses needed for direct ink writing. Their rheology can be controlled by the volume fraction of the beads and liquid binder. These PDMS gels can be directly extruded and shaped on a 3D printer. The liquid bridges are thermally crosslinked after printing, resulting in remarkably elastic and flexible PDMS structures, due to the chemical similarity of the solid beads and the liquid phase that has been bridging them. Their porosity and mechanical properties, such as tensile modulus, could be controlled by the fraction of liquid precursor in the original multiphasic dispersion. The high softness, elasticity, and resilience of these 3D printed PDMS materials open new opportunities in the making of highly flexible 2D meshes and 3D macrostructures (patent appl. 2016, Adv. Mater. 2017). As this ink is made of porous biocompatible silicone and can be 3D printed under water, it may also find applications such as direct printing of bio-scaffolds on live tissue.