Scientists arrange particles 100x thinner than human hair to perfection (2024)

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Modern-day electronics is all about maximizing features in a very small space. For instance, Toda, your smartphone, combines a music player, a memory stick, a gaming device, an alarm, a phone number, and much more into a sink device.

This has been made possible by microelectronics that enable many components and sensors to come together and operate in a small space while requiring material to make them.

Researchers have been looking to bring together components at an even smaller scale to make the next generation nanoscale devices but have yet to see much success so far.

However, a research collaboration between the Department of Chemical Engineering at the Vrije Universiteit Brussel (VUB), Riga Technical University, and the MESA+ Institute at the University of Twente has now succeeded in arranging very small particles in the range of 500 nanometers to 10 micrometers (up to 100 times thinner than the human hair) to perfection.

Challenges in designing nanoscale devices

According to Ignaas Jimidar, a postdoctoral researcher in the Department of Chemical Engineering at VUB, commonly used field methods depend on crystallizing solutions. These solutions have limited versatility and are a roadblock to making smaller devices.

The alternative approach involves using dry methods, which do not need a solution. However, this approach works well only with sticky surfaces. This is also limiting since not all surfaces can be easily made sticky.

The research collaboration sought an approach that allowed particles to be stuck to hard and nonsticky surfaces and found that the best way to do so was by rubbing them by hand.

By rubbing the particles on the surface for a mere 20 seconds, the team successfully got a single layer of densely packed particles arranged in a hexagonal pattern.

The rubbing was done using a stamp made of a silicon material called Polydimethylsiloxane (PDMS). However, what was happening on the material is something that even a fifth grader could explain.

How it works

"The static electricity generated by the rubbing process, especially on harder surfaces, and the forces between the particles and the surface are crucial for creating the desired patterns," said Kai Sotthewes, an associate professor at the University of Twente, who was involved in this research.

"We encounter this static electricity in everyday life, if we rub a balloon against our hair or feel a shock on a dry winter day when we touch a metal object."

Interestingly, the process worked well on conductive and non-conductive surfaces and achieved the best results with certain particle powders, such as polystyrene and polymethyl methacrylate or PMMA, also known as Plexiglass. Silica, the component used heavily in today's electronics, worked well only when the surface was covered with a fluorocarbon layer, a Teflon coating, the researchers said in the press release.

The research successfully created multiple microscopic patterns and logos on a large scale, which were confirmed using an atomic microscope.

"This represents a promising development for improving electronics, detecting all kinds of chemical and biological substances, and even detecting counterfeit goods," added Jimidar in the press release.

"The last is possible because particles in certain patterns refract light differently depending on the angle. So you could detect colors using these microparticles."

The research findings were published in the journalACS Applied Materials & Interfaces.