Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, 92093, USA.
Department of Mechanical and Aerospace Engineering, Jacobs School of Engineering, Department of Surgery, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA.
Small. 2022 Nov;18(47):e2204288. doi: 10.1002/smll.202204288. Epub 2022 Oct 10.
Stimuli-responsive hydrogels with programmable shapes produced by defined patterns of particles are of great interest for the fabrication of small-scale soft actuators and robots. Patterning the particles in the hydrogels during fabrication generally requires external magnetic or electric fields, thus limiting the material choice for the particles. Acoustically driven particle manipulation, however, solely depends on the acoustic impedance difference between the particles and the surrounding fluid, making it a more versatile method to spatially control particles. Here, an approach is reported by combining direct acoustic force to align photothermal particles and photolithography to spatially immobilize these alignments within a temperature-responsive poly(N-isopropylacrylamide) hydrogel to trigger shape deformation under temperature change and light exposure. The spatial distribution of particles can be tuned by the power and frequency of the acoustic waves. Specifically, changing the spacing between the particle patterns and position alters the bending curvature and direction of this composite hydrogel sheet, respectively. Moreover, the orientation (i.e., relative angle) of the particle alignments with respect to the long axis of laser-cut hydrogel strips governs the bending behaviors and the subsequent shape deformation by external stimuli. This acousto-photolithography provides a means of spatiotemporal programming of the internal heterogeneity of composite polymeric systems.
具有可编程形状的刺激响应水凝胶是制造小型软执行器和机器人的研究热点。在制造过程中对水凝胶中的颗粒进行图案化通常需要外部磁场或电场，因此限制了颗粒的材料选择。然而，声驱动的颗粒操纵仅取决于颗粒和周围流体之间的声阻抗差异，使其成为一种更通用的空间控制颗粒的方法。在这里，通过将光热颗粒的直接声力与光光刻相结合，报道了一种方法，以在温度响应性聚（N-异丙基丙烯酰胺）水凝胶内空间固定这些排列，以在温度变化和光暴露下触发形状变形。通过声波的功率和频率可以调整颗粒的空间分布。具体而言，改变颗粒图案之间的间距和位置分别改变了复合水凝胶片的弯曲曲率和方向。此外，颗粒排列相对于激光切割水凝胶条的长轴的方向（即相对角度）控制了外部刺激下的弯曲行为和随后的形状变形。这种声光光刻为复合聚合物系统的内部不均匀性的时空编程提供了一种手段。
