Researchers have created 3D-printed flexible mesh structures that can be controlled with applied magnetic fields while floating on water. The structures can grab small objects and carry water droplets, giving them the potential to be useful as soft robots that mimic creatures living on water surfaces or that can serve as tissue scaffolds for cell cultures.
To create these structures, an ink was made from silicone microbeads, bound by liquid silicone and contained in water. The resulting “homocomposite thixotropic paste” resembles common toothpaste that can easily be squeezed out of a tube, but then maintains its shape on the toothbrush without dripping. A 3D printer was used to shape the paste into mesh-like patterns. The patterns are then cured in an oven to create flexible silicone structures that can be controlled — stretched and collapsed — by the application of magnetic fields. This self-reinforced paste allows structures to be created that are ultra-soft and flexible.
Embedding iron carbonyl particles — which are widely available and have a high magnetization — allows a strong response to magnetic field gradients to be imparted. The structures are also auxetic, which means that they can expand and contract in all directions. With 3D printing, the shape can be controlled before and after the application of the magnetic field.
The structures’ properties also allow them to be used while floating on water, similar to water striders — insects that skim or hop across water surfaces.
Mimicking live tissues in the body is another possible application for the structures. The researchers designed reconfigurable meshes, a structure that could “grab” a tiny ball of aluminum foil, and a structure that can “carry” a single water droplet and then release it on demand through the mesh.