Soft, 3D-printed structures have been created whose movements can be controlled with a wave of a magnet, much like marionettes without the strings. The structures that can be magnetically manipulated include a smooth ring that wrinkles up, a long tube that squeezes shut, a sheet that folds itself, and a spider-like “grabber” that can crawl, roll, jump, and snap together fast enough to catch a passing ball. It can even be directed to wrap itself around a small pill and carry it across a table.
Each structure was fabricated from a new type of 3D-printable ink infused with tiny magnetic particles. An electromagnet was fitted around the nozzle of a 3D printer, causing the magnetic particles to swing into a single orientation as the ink was fed through the nozzle. By controlling the magnetic orientation of individual sections in the structure, structures and devices can be produced that can almost instantaneously shift into intricate formations, and even move about as the various sections respond to an external magnetic field.
The technique may be used to fabricate magnetically controlled biomedical devices; for example, a structure around a blood vessel that controls the pumping of blood. A magnet also can be used to guide a device through the intestinal tract to take images, extract tissue samples, clear a blockage, or deliver certain drugs to a specific location.
Individual sections of a structure each have a distinct orientation of magnetic particles. When exposed to an external magnetic field, each section should move in a distinct way, depending on the direction its particles move in response to the magnetic field. In this way, the structures should carry out more complex articulations and movements. The orientation of magnetic particles in a particular domain can be tuned by changing the direction of the electromagnet encircling the printer's nozzle as the domain is printed.
By programming complex information of structure, domain, and magnetic field, intelligent machines such as robots can be printed.