Search for: All records

Abstract Focused ultrasound (FUS) presents unique advantages for noninvasive localized heating, crucial for controlled shape recovery in shape memory polymers (SMPs), especially in biomedical applications. To enhance FUS-driven actuation efficiency, we propose boron nitride (BN)-infused SMP composites (SMPCs) tailored for targeted biomedical interventions. Using tert-butyl acrylate (tBA) and di(ethylene glycol) dimethacrylate as base materials, we integrated BN fillers at varying concentrations (1, 5, and 10 wt.%). A thorough characterization was carried out, including dynamic mechanical analysis, scanning electron microscopy, uniaxial tensile testing, and swelling study. These results show that increasing the BN content improves shape recovery efficiency significantly. Specifically, the 10 wt.% BN composites outperformed plain SMP in terms of shape recovery ratio when activated with FUS, and the highest shape recovery ratio can achieve 75%. However, higher BN content decreases crosslinking density and stiffness, as shown by a lower Young’s modulus and glass transition temperature. This study demonstrates the promise of BN-infused SMPCs for advanced applications in biomedical application, where noninvasive spatiotemporal actuation of SMPs is required. 

High-intensity focused ultrasound (HIFU) has been investigated as a remote and controlled activation method to noninvasively actuate shape memory polymers (SMPs), specifically in biomedical applications. However, the effects of aqueous environment on shape recoverability of in vivo HIFU-actuated SMPs have yet to be explored. HIFU directs sound waves into a millimeter-sized tightly focused region. In this study, the response of hydrophilic and hydrophobic photopolymerized thermoset SMP networks under HIFU activation in an aqueous environment was investigated. Acrylate-based SMP networks were copolymerized in specific ratios to produce networks with independently adjusted glass transition temperatures ranging from 40 to 80 °C and two distinct water uptake behaviors. The results link the polymer swelling behavior to shape recoverability in various acoustic fields. The presence of absorbed water molecules enhances the performance of SMPs in terms of their shape memory capabilities when activated by HIFU. Overall, understanding the interplay between water uptake and HIFU-actuated shape recovery is essential for optimizing the performance of SMPs in aqueous environments and advancing their use in various medical applications.