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水凝胶致动器，它可以在户外快速（0.5 s）和大幅度（80%）变形。由温敏PNIPA组成的水凝胶嵌入有用于产生内部静电的磁性排列的钛酸盐纳米片（TiNS），以及用于光热转换的金纳米颗粒。我们首先证实，当在其导带（<450 nm）处照射时，AuNP实现有效的光热转换，其中温度变得高于PNIPA的LCST。PNIPA的相变会导致TiNS之间的静电排斥增强，从而导致水凝胶的变形。事实上，这种级联机制在嵌入有TiNS和AuNP的PNIPA水凝胶中起作用。当用445-nm激光束照射时，水凝胶在垂直于TiNS平面的方向上非常迅速地且大部分地膨胀。响应时间小于1秒，而变形率大于80%。这些变形曲线处于所报道的水凝胶致动器的最高水平。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优异性能启发我们将其用作人造肌肉来模仿肌肉的运动。由于大的，快速的，可逆的，时空控制的变形，我们的水凝胶致动器封装在毛细管可以完美地模仿这种运动。

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.