New Method To Make 3D Nanostructures Developed By MIT Scientists

Nanotechnology and nanoengineering have evolved a great deal in the last few years. Almost everything that’s electronic can be given a nano-avatar these days to make the device perform better and faster. Three dimensional nanostructures and metamaterials having certain unusual properties are used more in more in innovative applications from diverse fields such as photonics, optics, quantum mechanics, phononics, biomedicine, biotech, etc. These complex 3D nanostructures are microscopic and are less than a few billionths of a meter. This makes them extremely difficult to manufacture and fabricate. The conventional etching and manufacturing methods fail to provide the degree of complexity that will be demanded by the futuristic nano gadgets. So, a group of MIT scientists have stepped up to provide a solution for this problem and solve they did! Yes, these researchers have blended the two commonly used techniques of nanotechnology to come up with a new improved methodology.

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A 3D nanostructure with layers as seen by a Scanning Electron Microscope

The team of scholars and nanotech experts at the MIT has developed this novel nanofabrication procedure that can be used to create intricate, multifarious and multi-layered solid nano devices in one simple step! This awesome technique combines the features of the currently used ”top-down” and “bottom-up”  approaches. The research work related to this got published in the June edition of Nano Letters. The research paper was co-authored by Dr. Chih-Hao Chang; George Barbastathis, the Singapore Research Professor of Optics and Professor of Mechanical Engineering; and six MIT graduate students.

In the top-down method which is popularly known as phase shift lithography, a double layer mask is coated on a sheet of photoresist material. The mask is coated in different amount in different areas and some areas are left completely exposed. After that, the material is exposed to light and the uncovered patches get altered. Even though this method is very accurate, it requires great deal of time and money to manufacture the masks. In the bottom-up approach, the colloidal suspended nanoparticles are allowed to assemble by themselves into low entropy closely arranged packs. These packs are later used as masks in a number of physical deposition methods like vapor phase deposition, surface etching, etc. to produce 2-D surfaces. However, this method lacks the precision and is slow. Plus, while using it for 3-D structures, an error in one layer will simply creep down to all the rest. Some anomalies in the assembling of the nanoparticles can also cause defects in the structure.

The new method is nothing but a hybrid of the above two procedures and is like a golden means between the two. In this, the self assembly of the colloidal particles is done directly on the required substrate and this assembled array acts like a mask for the lithography. Each nanoparticles present on the surface acts like a minute lens that focuses the incident light beam into a pattern depending on its arrangement on the surface. The researchers believe that this approach can work for any three dimensional nanostructure or any device for nano scale research. The method can be used for varying degrees of complexity. Also, it has proved to be a relatively cheaper solution. The MIT researchers, who have optics as their area of expertise, are planning to manufacture photonic crystals using this technology first. Besides optical nanostructures, many other awesome 3D devices like filters with controlled porosity for biomedical uses, phononic devices that can alter and control the heat and sound waves, etc. can also be fabricated by this cool technique. The main thing that makes this nanofabrication procedure special is its simplicity and amazingly accurate results. Let’s hope that this discovery ushers in a host of new nanotechnology gadgets and applications.

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