(777e) Three-Dimensional Printing By Multiphase Silicone/Water Capillary Inks

Three-dimensional (3D) printing of polymers is accomplished easily with thermoplastics as the extruded hot melt solidifies rapidly during the printing process. Printing with liquid polymer precursors is more challenging due to their longer curing times. One curable liquid polymer of specific interest is polydimethylsiloxane (PDMS). We demonstrate a new efficient technique for 3D-printing with PDMS by using a capillary suspension ink containing PDMS in the form of both pre-cured microbeads and uncured liquid precursor, dispersed in water as continuous medium. Owing to the capillary binding of the microbeads, their suspensions bound by small fractions of liquid precursor behaved like pastes, which are flowable at high shear stress and possess high storage moduli and yield stresses that are needed for direct ink writing. The resulting three-phase capillary ink could be 3D printed and cured both in air and under water. The liquid PDMS bridges were thermally crosslinked after printing, resulting in structures that were remarkably elastic and flexible. Their porosity and mechanical properties, such as tensile modulus, could be controlled by the fraction of liquid precursor in the original multiphasic dispersion. Self-standing elastic structures could also be made by directly printing and curing the ink under aqueous solutions. As this ink is made of porous biocompatible silicone, it can be used in 3D printed biomedical products, or in applications such as direct printing of bio-scaffolds on live tissue. The patent-pending method (prov. filed 2016) may also open new opportunities in soft robotics and stimuli-responsive materials.