Armored Regenerable Cilia.

Flexible cilia of natural species are well-known for their capabilities to transport objects by their collective motions. Therefore, well-ordered, flexible, and stimuli-responsive artificial cilia have been developed to render similar functionalities. However, flexibility and stimuli-responsiveness of a microcilium are inherently incompatible with durability/robustness against mechanical damage, limiting the artificial cilia to applications with only gentle operating conditions. The critical (but long neglected in surface engineering) property of natural hairs is that they are rooted under the skin, allowing the regeneration of the damaged hairs from their undamaged roots (hair follicles). To integrate the functionalities of cilia and hair, we developed a fabrication strategy called stencil-assisted self-alignment of iron-laden aerosols to produce a surface termed armored regenerable cilia. This surface contains well-ordered, appropriately packed, flexible, and magneto-responsive artificial wires rooted within pores. The wall of the pore serves as the armor to protect the bottom part of the wires from mechanical damage, allowing the remaining wires to regrow when the self-alignment of iron-laden aerosols repeats. The armored regenerable cilia with functionalities such as water repellency, object manipulation, and impurity removal are expected to guide the design and fabrication of smart surfaces serving real-life applications.