- Researchers invent a new method to reduce the volume of objects of any shape and structure.
- It works for a wide range of materials, including metals, quantum dots, and DNA.
- The technique can be used in the field of robotics, medicine, and optics.
Existing nanofabrication technologies currently rely on 2D and 2.5D patterning techniques. Using light to print pattern on surfaces can create 2D nanostructures, but the strategy does not work for 3D structures. Although one can gradually add layers on top of each other to make a 3D object, the process is very slow and difficult.
And, while techniques exist for directly 3D printing nanostructures, they require special materials like plastics and polymers, which limits the functional properties for numerous applications. Also, these techniques are capable of producing only self-supporting structures. For instance, they can generate a solve pyramid, but not a hollow sphere or a linked chain.
To solve this issue, researchers at MIT developed a new method for fabricating nanoscale 3D objects of almost any shape and structure. It can produce objects with a range of materials, including, DNA and quantum dots. Overall, it provides a great control over feature size, geometry and chemical composition of the final material.
Shrinking The Volume Of Original Structure
A few years ago, MIT developed a technique called expansion microscopy to achieve high-resolution imaging using a conventional microscope. In this technique, the tissue is embedded into a hydrogel to expand it. Plenty of research labs are now using this method.
Researchers reversed this process to shrink the large-scale structure to the nanoscale. They are calling it ‘implosion fabrication’. They used an absorbent substance made of polyacrylate, as the scaffold, which is bathed in a fluorescein solution.
They then attached molecules of fluorescein to certain positions within the gel, using two-photon microscopy. These molecules serve as anchors that can hold molecules of other materials (like DNA or quantum dot).
Once the target molecules are added to the certain positions, the whole structure can be shrunk by adding a hydrochloric acid or divalent cations (for example, magnesium chloride). This blocks the negative charges within the gel, making it hard for molecules to repel each other and causing the entire structure to contract.
The method is capable of shrinking the structure up to 10-fold in each dimension, thus the volume can be reduced by 1000 times. Materials can be assembled in a low-density scaffold, and it also allows for increased resolution. After shrinking, the material becomes a dense solid.
Applying implosion fabrication to ‘Alice in Wonderland’ | Credit: Daniel Oran
All you need to do is embed a material in this gel, apply the technique, and it will reduce the volume of the material to the nanoscopic scale, without distorting its pattern.
The technology could have applications in several fields, from robotics to medicine to optics. For instance, it could be used for making specialized lenses to study properties of light, fabricating smaller, better lenses for devices like microscopes, endoscopes, and mobile cameras.
The technology uses instruments that are already available in many materials science and biology labs. Researchers who are interested in trying this technique can easily scan a pattern, deposit a target material, and shrink it down.