In another breakthrough discovery, researchers were finally able to make liquid streams out of LASER beams.

Light Amplification by Stimulated Emission of Radiation beam or the LASER beam, undoubtedly, is one of the most important breakthroughs of the 20th century. Its application led to numerous innovations in different fields of sciences from medicine to astronomy.

Among its many applications, the laser is best known to be used in spectroscopy, heat treatment, photochemistry, laser cooling, and nuclear fusion. It is now also utilized by governments around the world in their military weapons.

Heck, scientists have even used them to find hidden compartments inside the Great Pyramid of Giza.

Another #Science #Discovery! Laser stream created out of laser beam & gold nanoparticles!Click To Tweet

With the passing of time, more and more discoveries are being made with the use of LASER.

Now, researchers from the University of Houston in Texas just made another astounding finding that will allow laser beams to create jet streams inside a liquid. The engineers called the process as ‘laser streaming.’

What is laser streaming and what is its potential applications?

Laser Streaming: Turning Laser Beam to Liquid Stream

It may sound like an advanced tech from a science fiction book or film. The sort that you find in many Netflix futuristic series or movies like Star Wars.

But, no.

Laser streaming is real, and it’s about to bring significant changes that will improve many research studies today!

Laser streaming was once just a dream for many scientists due to scientific and technological limitations. In a paper published in Arxiv entitled Laser Streaming: Turning a Laser Beam into a Flow of Liquid, the team of engineers cited:

Transforming a laser beam into a mass flow has been a challenge both scientifically and
technologically.

A laser can produce photons in tight beams of specific energy, hence why we often use the term ‘laser focus’ to describe high functioning mental acuity. A laser beam can transmit data, detect molecules, and burn through metal. As stated in the paper:

“The ray of a laser implies not only its high intensity and directionality, but also its mechanical impetus because photons carry linear momentum.”

The question now is:

Is it possible to transfer this unique characteristic of a laser beam to matter and generate rays of matter such as a stream or liquid flow?

YES. It is feasible to create a liquid stream, granted that all conditions are met.

“Through efficient momentum transfer, the answer is yes. In fact, the radiation pressure of a laser beam has been utilized to deform a liquid surface and even create a stream, but the conditions are difficult to achieve because that liquid would not only need to scatter light strongly, but also have near zero surface tension.”

Under normal circumstances, laser light does not interact with water, except if it interacts with another medium such as air. Photons can push against such interface and can produce transferable momentum. However, this transferable momentum is too weak to drive fluid flow.

Jiming Bao, co-researcher at the University of Houston, and his team found a solution that enabled them to generate a liquid stream in large volume.

Gold Nanoparticles and Liquid Stream

During their research, Bao and his team discovered that it is possible to create a large volume of the liquid stream using laser beam if the liquid contains gold nanoparticles. Apparently, these nanoparticles “exhibit a strong localized surface plasmon resonance around 525 nm, which allows them to effectively absorb the incident laser.”

To confirm their finding, the team shot a pulsed green laser through a liquid container’s glass wall. After a few minutes, they observed that it produces a liquid streaming along the direction of the laser beam. They wrote:

“Surprisingly, water near the laser spot on the cuvette seemed to be pushed away from the
cuvette wall by the laser after a few minutes of illumination, and after 10 more minutes an elongated stream emerged (Fig. 1c).

To generate a flow at an angle relative to the cuvette surface, we can simply tilt the cuvette as shown in Fig. 1b and focus the laser on a new spot on the cuvette. Figs. 1d-f show representative flows at incident angles of 10, 20 and 30 degrees.

In all these cases, the flows appear as liquid analogs of laser beams and move in the same directions of the refracted beams as if they are directly driven by photons of laser beams. We call this phenomenon laser streaming.”

The creation of laser stream by firing laser beam in water containing gold nanoparticles
Fig. 1. The creation of a laser stream by firing laser beam in water containing gold nanoparticles. | Bao et al. | arxiv.org

The nanoparticles played a significant role in Bao and his team’s discovery. If the water is pure, the laser beam only passes through. By adding gold nanoparticles, the water absorbed green light closer to the resonant frequency of the electrons they contain.

This enabled the particles to heat up and cool down with each pulse of light, making it contract and expand in the process. The process then generated acoustic waves in the water called acoustic streaming.

While acoustic streaming can make the water move, it is not guaranteed and therefore not enough to create a liquid stream. So, what created the phenomenon?

Upon further investigation, the researchers found that the heating and cooling of the gold nanoparticles near the container wall enables them to bond with the glass. As explained in Technology Review:

“So over a period of time, the gold nanoparticles actually encrusted around the point of light entry on the container wall. This crust created a sort of nanocavity. This in turn actually acts as a sort of loudspeaker for the light, allowing it to be focused to a point of always generated the stream.”

Further analysis of the phenomenon showed that the nanoparticles attached to the cavity surface have a similar size as the original ones, a clear indication that they are not fragments from original nanoparticles.

The discovery significantly highlighted the connection between nanophotonics, microfluidics, acoustics, and materials science.

Liquid Stream to Improve Lab-on-Chip Processes

Bao and his team’s discovery is a breakthrough that has many implications. Apparently, being able to move liquids on a microscopic scale using laser beam is crucial in many lab-on-chip experiments.

It can be used in nanofabrications and laser propulsions. Bao and his team wrote:

“Laser streaming will find applications in optically controlled or activated devices such as microfluidics, laser propulsion, laser surgery and cleaning, mass transport or mixing, to name just a few.”

For instance, laser streaming can significantly improve microfluidics, a study which focuses on the behavior, control, and manipulation of fluids that are geometrically constrained to small scale.

Microfluidic structures are used in handling off-chip fluids such as liquid pumps or gas valves, and on-chip handling of nanoliter and picoliter volumes. To date, the most successful application of microfluidic is the Inkjet Printhead. Imagine how laser streaming would revolutionize devices like this.

Not only that, laser streaming would enable biosensor chips containing multiple functions to be worn by humans in the form of wearable gadgets. This would potentially help in analyzing sweat or blood in order to detect multiple biomarkers linked to several diseases.

Right now, other applications of this discovery are still unknown. How it will revolutionize the many lab-on-chip experiments and devices are yet to be revealed in the future.

What can you say about this latest laser beam discovery? Let us know in the comment section below!

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