Metachronal μ-Cilia for On-Chip Integrated Pumps and Climbing Robots.

Biological cilia often perform metachronal motion, that is, neighboring cilia move out of phase creating a travelling wave, which enables highly efficient fluid pumping and body locomotion. Current methods for creating metachronal artificial cilia suffer from the complex design and sophisticated actuation schemes. This paper demonstrates a simple method to realize metachronal microscopic magnetic artificial cilia (μMAC) through control over the paramagnetic particle distribution within the μMAC based on their tendency to align with an applied magnetic field. Actuated by a 2D rotating uniform magnetic field, the metachronal μMAC enable strong microfluidic pumping and soft robot locomotion. The metachronal μMAC induce twice the pumping efficiency and 3 times the locomotion speed of synchronously moving μMAC. The ciliated soft robots show an unprecedented slope climbing ability (0 to 180°), and they display strong cargo-carrying capacity (>10 times their own weight) in both dry and wet conditions. These findings advance the design of on-chip integrated pumps and versatile soft robots, among others.