Recently discovered light-induced bilayered actuators comprising a light-responsive actuating layer supported by a passive layer are versatile in miniaturized robotics applications, owing to their simple, compact construction and wireless, self-contained mode of actuation. However, the chemo-mechanics and quantitative description of their actuation mechanisms are not sufficiently understood. Here, based on a chemo-mechanics model, a novel instability phenomenon leading to extraordinarily large magnitudes of the bending actuation of bilayered actuators is found and experimentally proven. At specific ratios of the elastic moduli and thicknesses of the active and passive layers, and activation volume of the actuation mechanism, the actuation of the active layer will be put into a positive feedback mode where the actuation-induced bending of the cantilever structure triggers a compressive stress in a surface region of the active layer which enhances further contractive actuation of the latter by means of light-induced water de-intercalation. The beneficial instability is observed and analyzed for two active material systems that exhibit such a light-induced water de-intercalation mechanism, namely, cobalt-oxides/hydroxides (C-O-H) and nickel hydroxide/oxyhydroxide (N-H-O). Experimental results agree well with predictions of the chemo-mechanics model, thus verifying its applicability to design high-performing actuation systems.

最近发现的包括由无源层支撑的光响应性致动层的光致双层致动器由于其简单，紧凑的结构以及无线，独立的致动模式而在小型化机器人应用中是通用的。但是，对它们的致动机理的化学力学和定量描述还不够充分。在此，基于化学力学模型，发现并实验证明了导致双层致动器的弯曲致动的幅度特别大的新型不稳定性现象。在主动和被动层的弹性模量和厚度的特定比例以及致动机构的激活体积下，有源层的致动将进入正反馈模式，其中，悬臂结构的致动引起的弯曲会触发有源层表面区域中的压缩应力，从而通过光诱导来增强后者的进一步收缩致动水去嵌入。对于表现出这种光诱导的水去插层机理的两种活性材料体系，即氧化钴/氢氧化物（COH）和氢氧化镍/羟基氧化物（NHO），观察和分析了有益的不稳定性。实验结果与化学力学模型的预测非常吻合，从而验证了其在设计高性能驱动系统方面的适用性。