Researchers have demonstrated that they can use electric fields to steer tiny hydrogel robots created by three-dimensional printing (ACS Appl. Mater. Interfaces 2018, DOI: 10.1021/acsami.8b04250). In solution, these hydrogels swell and contract when the applied electric field changes the concentration of ions surrounding the materials. By precisely controlling the dimensions of the hydrogel structures, researchers could control how the robots move and change shape in response to the electrical stimulation. Robots printed by a team from Rutgers University and Korea University led by Howon Lee could walk and pick up objects. Someday, more sophisticated hydrogel structures could serve as artificial muscles, stimulated by electrical impulses in the human body, the researchers say.