Science Advances: Researchers have developed a technology to precisely arrange n

It is reported that researchers have developed a technology to precisely arrange nano particles on the surface, such as silicon chips, without damaging the materials.

MIT researchers have developed a technology that can precisely control the arrangement and placement of nanoparticles on materials, such as silicon for computer chips, without damaging or polluting the surface of materials.

Nanoparticle contact printing enables accurate, scalable and original particle patterns.

This technology combines chemical and directional assembly processes with traditional manufacturing technologies, which can effectively form high-resolution, nanometer level features, and integrate them with nano particles of sensors, lasers, LED and other devices, so as to improve their performance.

Transistors and other nanoscale devices are usually manufactured from top to bottom - materials are etched to achieve the desired nanostructure alignment. However, creating the smallest nanostructures capable of achieving the highest performance and new functions requires expensive equipment, and is still difficult to do at the scale and required resolution.

Improve the transfer yield through interface engineering.

A more accurate way to assemble nano devices is from the bottom up. In the experiment, engineers use chemical methods to "grow" nanoparticles in the solution, drop the solution onto the template, arrange the nanoparticles, and then transfer them to the surface. However, this technology also faces severe challenges. First, thousands of nanoparticles must be effectively aligned on the template. However, transferring them to the surface usually requires chemical glue, high pressure or high temperature, which may damage the surface and the final equipment.

MIT researchers have developed a new way to overcome these limitations. They use the powerful force existing on the nanometer scale to effectively arrange particles in the required mode, and then transfer them to the surface at a lower temperature without any chemical substances or high pressure. Because the surface materials remain original, these nanoscale structures can be incorporated into the components of electronic and optical devices, and even small defects will affect the performance.

A wide variety of surfaces and designs.

This research was published in the journal Science Advances. Niroui's co authors are Weikun "Spencer" Zhu (a graduate student of the Department of Chemical Engineering), the main author, and Peter F. Satterthwaite, Patricia Jastrzebska Perfect and Roberto Brenes, the graduate students of EECS.

Use forces

In order to start their manufacturing method, the so-called nano particle contact printing, researchers used chemical methods to create nanoparticles with specific size and shape in solution. To the naked eye, this looks like a small bottle of colored liquid, but when magnified with an electron microscope, millions of cubes, each only 50 nanometers in size, will be found. (Human hair is about 80000 nanometers wide.)
Then, the researchers made a flexible surface template, which was covered with nanoparticle sized guides or traps, arranged according to the shape of the nanoparticles they wanted. After adding a drop of nanoparticle solution to the template, they used two nanoscale forces to move the particles to the correct position. The nanoparticles are then transferred to any surface.

Uniform spectral response of printed particles on a mirror nano cavity array.

On the nano scale, different forces become the dominant force (just as gravity is the dominant force on the macro scale). When the nanoparticles are in the liquid, the capillary force dominates, while the van der Waals force dominates at the interface between the nanoparticles and the solid surface they contact. When the researcher adds a drop of liquid and drags it across the template, capillary force moves the nanoparticles into the desired trap and places them precisely in the correct position. Once the liquid dries, van der Waals will keep these nanoparticles in place.

They designed the template deflectors to the correct size and shape, and arranged them in a precise and correct way, so that the forces work together to arrange the particles. The nanoparticles are then printed onto the surface without any solvent, surface treatment or high temperature. In this way, the original nature and characteristics of the surface can be maintained, while allowing more than 95% yield. To facilitate this transfer, the surface force needs to be designed so that the van der Waals force is strong enough to uniformly promote the release of particles from the template and attach to the receiving surface when in contact.

Unique shape, diverse materials, scalable processing

The team used this technology to arrange nanoparticles into arbitrary shapes, such as letters in an alphabet, and then transfer them to silicon with extremely high positional accuracy. The method is also applicable to nanoparticles with other shapes, such as spheres, and different material types. It can effectively transfer nanoparticles to different surfaces, such as gold, and even flexible substrates for next-generation electronic and optical structures and devices.

Their approach is also scalable, so it can be extended to real world devices.

An array of plasma nanocavities is integrated using a nanoparticle contact printed emitter.

Niroui and her colleagues are now working on using this method to create more complex structures and integrate them with other nanomaterials to develop new electronic and optical devices.

This work is partially supported by the National Science Foundation (NSF) and NSF Graduate Scholarship Program.

Source:Nanoparticle Contact Printing with Interfacial Engineering for Deterministic Integration into Functional Structures, 10.1126/sciadv.abq4869