Biological cilia that generate fluid flow or propulsion are often found to exhibit a collective wavelike metachronal motion, i.e. neighboring cilia beat slightly out-of-phase rather than synchronously. Inspired by this...

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.

Cilia are microscopic hair-like external cell organelles that are ubiquitously present in nature, also within the human body. They fulfill crucial biological functions: motile cilia provide transportation of fluids and...

Magnetic artificial cilia (MAC) are small actuators inspired by biological cilia found in nature. In microfluidic chips, MAC can generate flow and remove microparticles, with applications in anti‐fouling. However, the MAC used for anti‐fouling in the current literature has dimensions of several hundred micrometers in length, which limits the application to relatively large length scales. Here, biologically‐sized magnetic artificial cilia (b‐MAC) which are only 45 micrometers long and that are randomly distributed on the surface, are used to remove microparticles. It is shown that microparticles with sizes ranging from 5 to 40 µm can be removed efficiently and the final cleanness ranges from 69% to 100%, with the highest cleanness for the highest actuation frequency applied (40 Hz). The lowest cleanness is obtained for microparticles with a size equal to the average pitch between the b‐MAC. The randomness in cilia distribution appears to have a positive effect on cleanliness, compared with the authors’ earlier work using a regular cilia array. The demonstrated self‐cleaning by the b‐MAC constitutes an essential step toward efficient self‐cleaning surfaces for real‐life application in miniaturized microfluidic devices, such as lab‐on‐a‐chip or organ‐on‐a‐chip devices, as well as for preventing fouling of submerged surfaces such as marine sensors.

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