Low-Voltage 3D-Printed Hydrogel Cilia Deliver Millisecond, Programmable Micromotions

Researchers fabricate 2–10 μm-diameter, 18–90 μm-tall acrylic-acid-co-acrylamide hydrogel microcilia with nanometre-scale porosity using two-photon printing and surround them with microelectrodes. Under a 1.5 V field, ion migration within the hydrogel (H+ in DI water; Na+ in saline) drives rapid, millisecond bending, enabling 3D reprogrammable motions (bending and rotation) and controllable fluid flows. Demonstrations include scalable arrays (up to 25×25 cilia), metachronal-like coordination, and integration on flexible substrates, with durability up to 330,000 actuation cycles. The work promises advanced microscale fluid manipulation, microrobotics and bioinspired devices in complex ionic environments.