Atomistic investigation of ultrasound-triggered shape memory polymers

Shape memory polymers (SMPs) have gained significant interest for their applications in biomedical devices, soft robotics, and smart materials due to their ability to undergo programmed shape transformations. Among various external stimuli, focused ultrasound (FUS) has emerged as a promising non-contact activation method. While recent experimental studies have reported the potential of FUS-triggered SMPs, the atomistic mechanisms governing their thermal response and shape recovery behavior remain poorly understood. In this work, we investigate a tBA-co-DEGMA acrylate-based SMP using full-atomistic molecular dynamics simulations. We applied oscillations at amplitudes of 0.5–2 nm and frequencies of 25–75 GHz to SMPs with different crosslinking densities (0–63%) in atomistic simulations. Simulations reveal that increasing ultrasound frequency and amplitude leads to enhanced local heating, with the average temperature of the polymer simulation box reaching up to ~550 K after approximately 5 ns of excitation, and that greater crosslinking enhances thermal response and recovery. The SMP with 63% crosslinking achieved higher strain recovery than 43% crosslinked sample. The results offer critical understanding of how SMPs respond to FUS, guiding the design of advanced smart materials with customizable actuation for biomedical and engineering applications.