For the millions of people every year who have or need medical devices implanted, an advancement in 3D printing technology could enable significantly quicker implantation of devices that are stronger, less expensive, more flexible, and more comfortable than anything currently available. Such devices are molded, which could take days or weeks to create customized parts designed to fit an individual patient. The 3D printing method cuts that time to hours; additionally, small and complex devices such as pressure-sensitive valves, simply cannot be molded in one step.
There are countless ways to use soft, solid materials that fluidize and become solid again with small variations in applied stress. The traditional routes of microgel synthesis produce materials that swell in aqueous solvents or, less often, in aggressive organic solvents, constraining ways that these useful materials can be used. Aqueous microgels, for example, have been used as the foundation of 3D bioprinting, but the incompatibility of available microgels with nonpolar liquids, such as oils, limits their use in 3D printing with oil-based materials such as silicone.
The new method makes micro-organogels swollen in mineral oil, using block copolymer self-assembly. The rheological properties of this micro-organogel material can be tuned, leveraging the jamming transition to facilitate its use in 3D printing of silicone structures. The new material provides support for the liquid silicone as it is 3D printing, allowing the creation of very complex structures and even encapsulated parts out of silicone elastomer. It also could pave the way for new therapeutic devices that encapsulate and control the release of drugs, or small molecules for guiding tissue regeneration or assisting diseased organs such as the pancreas or prostate.
The new method was born out of work done to create printable organs and tissues. The team made a significant discovery when it created a revolutionary way to manufacture soft materials using 3D printing and microscopic hydrogel particles as a medium. The previous granular gel materials were water-based, so they were incompatible with oily “inks” like silicone. The solution was to develop an oily version of the microgels. The oily silicone inks printed into the oily microgel materials enabled the printed parts to hold their shapes.