Fig. 11. Particle and droplet manipulation by artificial cilia. (a) Particle removal, self-cleaning and anti-biofouling by artificial cilia exhibiting tilted conical motion (upper left panel). Reproduced from ref. 27 with permission from John Wiley and Sons. (a1) Use of magnetic artificial cilia to remove PLA particles in water. (i) SEM image of the MAC used in the article. (ii) shows the state of the surface before cleaning, (iii) is the state of the surface after actuating MAC for 60 s. (a2) Removal of natural sand grains by magnetic artificial cilia. (i)–(iii) show the cleaning process after 0 s 16 s and 30 s, respectively. a1 and a2 reproduced from ref. 27 with permission from John Wiley and Sons. (a3) Anti-biofouling by magnetic artificial cilia. (i) Broader bright-field microscopy image of the ciliated part after 28 days actuation, showing that the central unciliated area is almost perfectly clean. (ii) Broader bright-field microscopy image of a control experiment after 28 days, showing that the complete channel is fouled indiscriminately. Reproduced from ref. 28 with permission under open license CC BY-NC-ND. (b) Particle transport by artificial cilia exhibiting tilted conical motion (upperleft panel). (b1) Transport of ice particles by magnetically responsive film-like cilia. Because of the superhydrophobic wetting properties, ice particles form with nearly perfect spherical shapes. Reproduced from ref. 159 with permission under open license CC BY. (b2) (i) Transporting droplets back and forth on a superhydrophobic magnetically responsive microplate array. (ii) Process of directional propulsion, merging, and mixing of water droplets on the surface. (iii) A simple chemical reaction based on the rapid droplet horizontal propulsion and microscopic positioning and merging. (iv) A water droplet (volume around 3 μL) climbing up an inclined superhydrophobic magnetically responsive microplate array surface at an inclination angle of around 5.4°. Reproduced from ref. 158 with permission from the American Chemical Society. (b3) (i and ii) Morphology and corresponding water droplet contact angles of the magnetic microcilia before and after superhydrophobic modification, respectively. (iii) A water droplet can be switched between states of rolling down and pinning on an inclined surface by changing the magnetic field. (iv) Oil droplet manipulation in water on an inclined surface. Reproduced from ref. 146 with permission under open license CC BY. (c) Particle control by artificial cilia exhibiting metachronal motion (lower middle panel). Reproduced from ref. 155 and 158 with permission from the American Chemical Society. (c1) (i) Magnetic artificial cilia with size of 50 μm in diameter, 350 μm in height. (ii) Top view of tilted conical motion shown by actuated cilia. (iii and iv) Top-view time-lapse trajectory of a particle transported along controlled directions. Reproduced from ref. 25 with permission under open license CC-BY-NC-ND. (c2) Water droplet capture and on-demand release by a superhydrophobic magnetically responsive microplate array surface. Reproduced from ref. 158 with permission from the American Chemical Society. (c3) (i) Water droplet moves reciprocally on a magnetic responsive cilia surface. (ii) Two droplets moving in parallel on a surface. (iii) Merging of droplets. (iv) Directional stable transportation of a droplet along a circular orbit. Reproduced from ref. 155 with permission from the American Chemical Society.