MIT scientists have invented a way to develop nanoscale 3D objects of nearly any shape, which could be used in many fields -- from optics to medicine to robotics.
The objects can also be patterned with a variety of useful materials, including metals, quantum dots, and DNA, according to the research published in the journal Science.
"It's a way of putting nearly any kind of material into a 3D pattern with nanoscale precision," said Edward Boyden, an associate professor at Massachusetts Institute of Technology (MIT) in the US.
Using the new technique, the researchers can create any shape and structure they want by patterning a polymer scaffold with a laser.
After attaching other useful materials to the scaffold, they shrink it, generating structures one thousandth the volume of the original.
These tiny structures could have applications in many fields, from optics to medicine to robotics, the researchers said.
The technique uses equipment that many biology and materials science labs already have, making it widely accessible for researchers who want to try it.
Existing techniques for creating nanostructures are limited in what they can accomplish.
Etching patterns onto a surface with light can produce 2D nanostructures but doesn't work for 3D structures.
It is possible to make 3D nanostructures by gradually adding layers on top of each other, but this process is slow and challenging.
While methods exist that can directly 3D print nanoscale objects, they are restricted to specialised materials like polymers and plastics, which lack the functional properties necessary for many applications.
They can only generate self-supporting structures, researchers said.
They used a technique, known as expansion microscopy, which involves embedding tissue into a hydrogel and then expanding it, allowing for high resolution imaging with a regular microscope.
Hundreds of research groups in biology and medicine are now using expansion microscopy, since it enables 3D visualisation of cells and tissues with ordinary hardware.
By reversing this process, the researchers found that they could create large-scale objects embedded in expanded hydrogels and then shrink them to the nanoscale, an approach that they call "implosion fabrication."
The researchers used an absorbent material made of polyacrylate, commonly found in diapers, as the scaffold for their nanofabrication process.
The scaffold is bathed in a solution that contains molecules of fluorescein, which attach to the scaffold when they are activated by laser light.
Using two-photon microscopy, which allows for precise targeting of points deep within a structure, the researchers attach fluorescein molecules to specific locations within the gel.
The fluorescein molecules act as anchors that can bind to other types of molecules that the researchers add.
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