光で内部の静電反発力をオンオフする、高速・異方性ヒドロゲルアクチュエータの創成

在我的研究中，我成功地开发了一种光响应型水凝胶致动器，它可以在户外快速变形(0.5%S)和很大程度(80%)变形。这种水凝胶由热响应性PNIPA组成，嵌入了用于产生内部静电的磁性取向钛酸盐纳米片(TiNSS)和用于光热转化的金纳米颗粒。我们首先证实了AuNPs在其导带(&lt；450 nm)处实现了高效的光热转换，此时温度高于PNIPA的LCST。PNIPA的相变会导致TiNSs之间静电斥力的增强，从而导致水凝胶的变形。事实上，这种级联机制在嵌入TiNSs和AuNPs的PNIPA水凝胶中起作用。当用445 nm的激光照射时，水凝胶迅速膨胀，并且大部分在垂直于TINS平面的方向上膨胀。在变形率大于80%的情况下，响应时间小于1s。这些变形轮廓在已报道的水凝胶致动器中处于最高水平。变形是完全可逆和可重复的，没有任何明显的恶化。我们的水凝胶致动器的这些出色行为启发了我们将其用作人造肌肉来模仿蚯蚓的运动。由于大的、快速的、可逆的和时空可控的变形，我们的水凝胶致动器封装在毛细管中可以完美地模拟这种运动。

In my research, I successfully developed a photoresponsive hydrogel actuator which can deform quickly (0.5 s) and largely (80 %) in an open air. The hydrogel, composed of thermoresponsive PNIPA, is embedded with magnetically aligned titanate nanosheets (TiNSs) for generating internal electrostatics, together with gold nanoparticles for photothermal conversion. We at first confirmed that AuNPs realize efficient photothermal conversion when irradiated at their conduction band (<450 nm), where the temperature becomes higher than the LCST of PNIPA. The phase transition of PNIPA should cause the enhancement of the electrostatic repulsion between the TiNSs, thereby leading to the deformation of the hydrogel. Indeed, this cascade mechanism worked in the PNIPA hydrogel embedded with TiNSs and AuNPs. When irradiated with a 445-nm laser beam, the hydrogel expanded very quickly and largely in the direction perpendicular to the TiNS plane. The response time was less than 1 second, while the deformation ratio was more than 80 %. These deformation profiles are at the highest level of reported hydrogel actuators. The deformation was totally reversible and repeatable without any notable deterioration. These excellent behaviors of our hydrogel actuator inspired us to use it as artificial muscle to mimic the motion of the earthworm. Owing to the large, quick, reversible, and spatiotemporally controlled deformation, our hydrogel actuator encapsulated in a capillary can perfectly mimic this movement.