Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
Nature. 2022 May;605(7908):76-83. doi: 10.1038/s41586-022-04561-z. Epub 2022 May 4.
Living cilia stir, sweep and steer via swirling strokes of complex bending and twisting, paired with distinct reverse arcs. Efforts to mimic such dynamics synthetically rely on multimaterial designs but face limits to programming arbitrary motions or diverse behaviours in one structure. Here we show how diverse, complex, non-reciprocal, stroke-like trajectories emerge in a single-material system through self-regulation. When a micropost composed of photoresponsive liquid crystal elastomer with mesogens aligned oblique to the structure axis is exposed to a static light source, dynamic dances evolve as light initiates a travelling order-to-disorder transition front, transiently turning the structure into a complex evolving bimorph that twists and bends via multilevel opto-chemo-mechanical feedback. As captured by our theoretical model, the travelling front continuously reorients the molecular, geometric and illumination axes relative to each other, yielding pathways composed from series of twisting, bending, photophobic and phototropic motions. Guided by the model, here we choreograph a wide range of trajectories by tailoring parameters, including illumination angle, light intensity, molecular anisotropy, microstructure geometry, temperature and irradiation intervals and duration. We further show how this opto-chemo-mechanical self-regulation serves as a foundation for creating self-organizing deformation patterns in closely spaced microstructure arrays via light-mediated interpost communication, as well as complex motions of jointed microstructures, with broad implications for autonomous multimodal actuators in areas such as soft robotics, biomedical devices and energy transduction materials, and for fundamental understanding of self-regulated systems.
活体纤毛通过复杂的弯曲和扭转的漩涡状运动来搅动、清扫和转向，并伴有明显的反向弧。合成模拟这种动力学的努力依赖于多材料设计，但在一个结构中编程任意运动或多种行为存在限制。在这里，我们展示了通过自我调节，单一材料系统中如何出现多种复杂的、非互易的、类似冲程的轨迹。当一个由光响应液晶弹性体组成的微柱体，其中介晶沿结构轴倾斜排列，暴露在静态光源下时，动态舞蹈会随着光引发的旅行有序-无序转变前沿而演变，瞬时光结构会变成一个复杂的、不断变化的双折射体，通过多级光化学-机械反馈进行扭曲和弯曲。正如我们的理论模型所捕捉到的，旅行前沿不断地重新定向分子、几何和照明轴相对于彼此的方向，从而产生由一系列扭曲、弯曲、避光和趋光运动组成的路径。在模型的指导下，我们通过调整参数，包括照明角度、光强、分子各向异性、微结构几何形状、温度和辐照间隔和持续时间，精心编排了广泛的轨迹。我们进一步展示了这种光化学-机械自我调节如何通过光介导的中柱间通信在紧密间隔的微结构阵列中创建自组织变形模式，并展示了连接微结构的复杂运动，这对软机器人、生物医学设备和能量转换材料等领域的自主多模态执行器以及对自我调节系统的基本理解具有广泛的意义。
