Liman Gorkem, Mutluturk Esma, Demirel Gokhan
Bio-inspired Materials Research Laboratory (BIMREL), Department of Chemistry, Gazi University, 06500 Ankara, Türkiye.
Department of Chemistry, Polatlı Faculty of Arts and Sciences, Ankara Hacı Bayram Veli University, 06900 Ankara, Türkiye.
ACS Mater Au. 2024 Mar 22;4(4):385-392. doi: 10.1021/acsmaterialsau.4c00005. eCollection 2024 Jul 10.
Light-responsive hydrogel systems have gained significant attention due to their unique ability to undergo controlled and reversible swelling behavior in response to light stimuli. Combining light-responsive hydrogels with nonresponsive polymers offers a unique self-folding feature that can be used in soft robotic actuator designs. However, simple formulation of such systems with rapid response time is still a challenging task. Herein, we demonstrate a simple but versatile bilayer polymeric design combining light-responsive spiropyran-polyacrylamide (SP-PAAm) with polyacrylamide (PAAm) hydrogels. The photochromic spiropyran in our polymer design is a closed-ring, hydrophobic compound and turns into an open-ring, hydrophilic merocyanine isomer under light irradiation. The swelling degree of SP-PAAm and PAAm hydrogels was evaluated using LED lights with different wavelengths and solvent media (e.g., water, ethanol, DMF, and DMSO). We observed that SP-PAAm hydrogels reached a swelling ratio of ∼370% with the illumination of the blue LED in the DMF medium. By combining light-responsive SP-PAAm hydrogels with nonresponsive PAAm, a proof-of-concept demonstration was performed to demonstrate the applicability of our fabricated platforms. Although fabricated one-armed bilayer hydrogels possessed self-folding ability with a folding angle of ∼40° in 30 min, the four-armed bilayer platforms demonstrated more efficient and rapid folding behavior and reached a folding angle of ∼75° in ∼15 min. Given their simplicity and efficiency, we believe that such polymeric designs may offer new avenues for the fields of polymeric actuators and soft robotic systems.
光响应水凝胶系统因其在光刺激下具有独特的可控且可逆的溶胀行为而备受关注。将光响应水凝胶与非响应性聚合物相结合，可提供一种独特的自折叠特性，可用于软机器人致动器设计。然而，简单地配制具有快速响应时间的此类系统仍然是一项具有挑战性的任务。在此，我们展示了一种简单但通用的双层聚合物设计，将光响应性螺吡喃 - 聚丙烯酰胺（SP - PAAm）与聚丙烯酰胺（PAAm）水凝胶相结合。我们聚合物设计中的光致变色螺吡喃是一种闭环疏水化合物，在光照下会转变为开环亲水部花青异构体。使用不同波长的LED灯和溶剂介质（如水、乙醇、DMF和DMSO）评估了SP - PAAm和PAAm水凝胶的溶胀程度。我们观察到，在DMF介质中用蓝色LED照射时，SP - PAAm水凝胶的溶胀率达到约370%。通过将光响应性SP - PAAm水凝胶与非响应性PAAm相结合，进行了概念验证演示，以证明我们制造的平台的适用性。尽管制造的单臂双层水凝胶具有自折叠能力，在30分钟内折叠角度约为40°，但四臂双层平台展示了更高效、快速的折叠行为，在约15分钟内达到约75°的折叠角度。鉴于其简单性和效率，我们相信这种聚合物设计可能为聚合物致动器和软机器人系统领域提供新的途径。
