New tool for nanotechnology: Thermal clamps

Random forces (due to Brown motion) can be used to trap and manipulate nanoparticles on the one with the presence of laser radiation calculated by Australian optics. This is an astounding result because the common force of Brown force is often detrimental to optical trapping of particles under 100 nm. " Thermal clamps " can be used for manufacturing techniques with nanometer scale resolution such as recording images or memory elements with recorded surfaces (According to results published in Applied Physics Letter 90 054108, 2007. ).

Optical clamps used to manipulate particles use a strong focused laser beam to create an inductive electric dipole in the particle as one of the fascinating research topics of modern optics. This research direction has created a multimillion-dollar attractive market due to the huge applications in health, life sciences, micro-motors, sensors and measurement techniques.

However, optical manipulation on particles less than 100 nm is often difficult due to the dominance of Brown's random forces rather than the force generated by gradient traps by heterogeneous optical fields. Recently, the team of Dmitri Gramotnev and colleagues at Queensland University of Technology (Australia) calculated that Brown force could in fact use an effective way to trap and manipulate small particles and atoms on the surface when there is a strong temperature variation.

Scientists have long known that temperature gradients in solid environments can cause anisotropic diffusion (anisotropy) of atoms or particles from the hot region to the cold - the effect is related to Brown motion and is called the " thermophoresis " effect. However, Gramotnev and his colleagues showed that the themophoresis effect on the surface proved to be more effective for redistributing particles, atoms from the hot zone to a few steps cooler than in the internal environment. Solids. This means that the surface thermophoresis effect can be used for new techniques (which scientists call "thermal tweezer" for trapping and manipulating nanoparticles.

Figure of Gramotnev's thermal trap principle. (Photo: Vatlyvietnam)

According to calculations, the researchers created a temperature gradient using two (or more than two) short laser pulses that operate in the visible region. They found that this trap's thermal efficiency increased as the size of the particles decreased. This is exactly the opposite of the classic optical clamps, whose efficiency decreases when particle size decreases. This type of laser technique can be used for fabricating nanostructures with a resolution of only a few tens of nanometers and forming surface substrates.

"This is likely to be the first step to access completely optical processing technologies such as atoms and nanoparticles deposition technology with pulsed laser deposition technology (Pulse Laser "Deposition - PLD" - Gramotnev explains - "And this thermal clamp can also be used to control particles deposited and arrange them at predetermined positions in nanometer ladder resolution."

(Photo: Vatlyvietnam)

Another application of this technique may include imaging and memory elements by recording the surface, Gramotnev adds."All types of images can be generated by Holography techniques on the principle of being able to record smoothly by redistributing nanoparticles or atoms and particles on the surface" - As explained. Gramotnev's.

The Queensland team is working on the study of these thermal clamp applications in the presence of interactions between particles, in the hope of significantly increasing the trap performance. And Gramotnev said that they are also looking to invest in conducting a comprehensive empirical research to develop this technique.

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