Scale is not a limitation of 3D printing. There are factory-sized 3D printers and 3D printers that can produce nanoscale 3D geometries. And then there’s Shrinky Dinks. Everyone remembers those kits designed to shrink in the oven after being colored by hand. Take 3D printing, merge it with Shrinky Dinks, and the result is MIT’s latest breakthrough where gel scaffolds holding conductive materials and biomolecules are shrunk via acidic dehydration. See, it’s exactly like Shrinky Dinks.
One of the biggest problems to going smaller is maintaining precision and accuracy; the smaller the features, the harder it becomes to physically manipulate objects into their intended location and orientation. Compare, for instance, the difference in difficulty between working with Legos and watchmaking.
The material sciences have revealed various materials that have very defined and predictable shrinkage when carefully dehydrated, such as the hydrogel the MIT researchers worked with. Their hydrogel shrunk ten-fold in each dimension when dehydrated, resulting in volumetric shrinkage of 1,000 times and taking the resolution of the object down to the nanoscale at 50 nanometers.
“It’s a way of putting nearly any kind of material into a 3D pattern with nanoscale precision,” said Edward Boyden, the Y. Eva Tan Professor in Neurotechnology at MIT. They call their process Implosion Fabrication (ImpFab). It involves using lasers to optically position 3D silver nanostructures or other materials in a gel scaffold. “You attach the anchors where you want with light, and later you can attach whatever you want to the anchors,” Boyden says. “It could be a quantum dot, it could be a piece of DNA, it could be a gold nanoparticle.” The scaffold is then exposed to an acid that dehydrates the gel into 1 cubic millimeter solid. The positioning and orientation of the inserted objects are accurately preserved, maintaining functionality at a scale that’s smaller than what could be fabricated at that scale.
The method evolved from expansion microscopy, a technique used in brain tissue imaging where tissue is embedded into a hydrogel and then expanded, providing high-resolution imaging on a regular microscope. Boyden took that process, flipped it and reversed it, and invented ImpFab. Daniel Oran is one of the lead authors of the paper, explaining, “It’s a bit like film photography — a latent image is formed by exposing a sensitive material in a gel to light. Then, you can develop that latent image into a real image by attaching another material, silver, afterwards. In this way implosion fabrication can create all sorts of structures, including gradients, unconnected structures, and multimaterial patterns.”
Generally, the smaller (or larger) a technology can go, the greater the amount of applications it can be applied to. The researchers expect interest from the optics and medical industries, but they anticipate inquiries from unexpected avenues. “There are all kinds of things you can do with this,” Boyden says. “Democratizing nanofabrication could open up frontiers we can’t yet imagine.”