Tiny Robots Move with Nothing But a Magnet Swipe
Ben Sullivan
Iron ions drift into a freshly printed gel, soaking through its polymer mesh the way water moves into a sponge. Then the gel is dipped into a second bath, this one laced with hydroxide ions, and something clicks: the iron bonds, crystallizes, becomes magnetite, iron oxide nanoparticles forming in place, locked inside the structure, too small to see without an electron microscope. The gel, moments earlier just a passive polymer scaffold, is now magnetic. Not uniformly, not randomly, but in...