Engineers at Massachusetts Institute of Technology (MIT) have created soft, 3D-printed structures whose movements can be controlled with a wave of a magnet, much like marionettes without the strings.

This menagerie of magnetically manipulated structures includes 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. The spider can even be directed to wrap itself around a small pill and carry it across a table.

The researchers fabricated each structure from a new type of 3D-printable ink infused with tiny magnetic particles. Using an electromagnet fitted around the nozzle of a 3D printer, they were able to induce the magnetic particles to swing into a single orientation as the ink was fed through the nozzle. Controlling the magnetic orientation of individual sections in the structure allowed the researchers to produce structures and devices that can almost instantaneously shift into intricate formations, and even move about, as the various sections respond to an external magnetic field.
Xuanhe Zhao, a professor in MIT’s Department of Mechanical Engineering and Department of Civil and Environmental Engineering, says the group’s technique may be used to fabricate magnetically controlled biomedical devices.
For example, you could put a structure around a blood vessel to control the pumping of blood, or use a magnet to guide a device through the GI tract to take images, extract tissue samples, clear a blockage or deliver certain drugs to a specific location. You can design, simulate and then just print to achieve various functions.”
The team’s magnetically activated structures fall under the general category of soft actuated devices – squishy, moldable materials that are designed to shape-shift or move about through a variety of mechanical means. For instance, hydrogel devices can swell in response to changes in temperature or pH; shape-memory polymers and liquid crystal elastomers can deform in response to stimuli such as heat or light; pneumatic and hydraulic devices can be actuated by pumping air or water into them; and dielectric elastomers stretch under electric voltages.

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