SBIR/STTR Award attributes
Significant advances have been made for additive manufacturing (AM) of both thermoplastics and optically cured thermosets. AM of thermally cured thermosets has lagged behind. Materials that belong to this thermally cured class of thermosets, such as silicone rubbers and polyurethanes, are not well represented in the AM space, despite their widespread use in medical, military, and other arenas. There is a clear need to develop a practical and commercially viable means for AM of thermally cured thermosets. Ideally, this solution would enable AM of current commercially viable thermally cured thermosets with a speed that is comparable to those already realized for thermoplastics and optically cured thermosets. Realizing this goal will provide several benefits, including: Parts built from thermally cured thermosets with designs that cannot be achieved via casting/molding. Iteration of part designs without having to invest the time and funds in new molds. Medical and military devices and personal protection equipment (PPE), custom-fit to the end-user. Ability to print multifunctional composite materials, with a soft inner layer and a harder outer layer. Rapid production capability for DoD personnel when deployed overseas at forward locations. Simplification of supply chains, as stocks of different parts is replaced by a single raw material. This project will develop a printer capable of printing composites of commercially available thermally cured PDMS, directly yielding a cured final part. This work will be accomplished by a team of three organizations, Actuated Medical, Actinic, and the Lear Research Group at the Pennsylvania State University. Actuated Medical has significant engineering, 3D printing, and commercialization experience, while Actinic and the Lear Research Group have already constructed a primitive working PDMS printer, upon which this work builds. Using the photothermal effect of gold nanoparticles, the Lear Laboratory attained extremely rapid temperature cycling rates, moving from room temperature to 1000 K in 8 ns. Both the rate and the final temperature are many orders of magnitude greater than what is required to meet the technical challenge outlined above. The Lear Research Group has also demonstrated the chemical relevance of this heat, which provides up to a one billion (109) fold enhancement to the rate of polyurethane, epoxy, and silicone curing, suggesting that photothermal curing can be used to bring rapid (less than 1 ms), on-demand curing to a wide range of thermally cured thermoset polymers using a range of photothermal composite materials (carbon fiber, ceramics, graphene, metals, and metal oxides). Importantly, the physical and mechanical properties of materials that were photothermal cured were controllable and similar to those attained using bulk-scale heat (ovens) to cure. The photothermal approach to curing will enable AM of commercial PDMS.
