Two-Photon Direct Laser Writing of Shape-Memory Polymer Networks

Shape-memory polymers have been widely popularized and studied since their debut decades ago and have recently been explored for their uses in soft robotics, adhesion, and medicine. Our lab is evaluating photoinitiator and resin systems for high-resolution, direct laser writing of shape-memory polymer networks. Traditional photoinitators generate free radicals which often catalyze undesirable side-reactions and can be quenched by oxygen, dampening reaction kinetics and reducing the resolution of the structure with unpredictable chemical network formation. Glass-forming thiol-acrylate and thiol-ene resins are examined that, when polymerized, exhibit thermally triggered shape-memory in the 40-50 °C range. Networks are formed using a light sensitive free-radical or photobase generator at either 390 nm or at 780 nm with a femtosecond pulsed laser, and the resulting chemical composition and thermomechanical properties are evaluated. Results offer pathways to significantly improve the resolution of shape-memory features beneath the micron scale, opening new avenues for topographical modulation of surfaces.