One-pot ternary sequential reactions for photopatterned gradient multimaterials
Sijia Huang, Steven M. Adelmund, Pradip Sairam Pichumani, Johanna J. Schwartz, Yiğit Mengüç, Maxim Shusteff, Thomas J. Wallin
Abstract
Seamless multimaterial construction is a common motif in animal physiology. Such continuous mechanical gradients remain challenging to reproduce in engineered systems, as current resin chemistries typically result in a single fixed set of properties. As an alternative to single-property materials, we introduce a thiol-ene-epoxy-based photothermal reaction scheme that produces multimaterials by altering the polymer microstructure within a single resin. In this system, the photodosage during the first stage of processing dictates the extent of conversion for each subsequent reaction. As a result, our photochemistry can exhibit a diverse range of soft (Young's modulus, E ∼ 400 kPa; elongation, d L / L 0 ∼ 300%) and stiff ( E ∼ 1.6 GPa; d L / L 0 ∼ 3%) mechanical properties. Furthermore, we pattern photostable and mechanically robust modulus gradients (d[ E r, stiff / E r, soft ]/d x > 1,000 mm −1 ) that exceed those found in squid beaks and human knee entheses. We demonstrate the ability to build intricate multimaterial architectures including a soft, wearable braille display.