The research team of Xi 'an Jiaotong University and Northwestern Polytechnical University proposed a new technology of laser cutting water to provide a new idea for the application of "water"

Water is a natural resource that human beings depend on for survival and is used in many fields. In recent years, the patterning and flow control of trace water have attracted wide attention in materials science, chemistry, biomedicine and other fields.

"Draw the knife to cut off the water more flow"? No, it's "Laser cut water pattern"! On September 1, the reporter learned that Xi 'an Jiaotong University and the Northwestern Polytechnical University research team cooperated to propose a new technology of "laser cutting water" and realized this idea, providing a new idea for the application of "water".

Laser cut "water cake" to make various patterns.

Water is cut and processed by laser

How to "tame" water and make it useful to people has been a knowledge since ancient times. Cutting water, in people's eyes is an incredible thing, just as the Tang Dynasty poet Li Bai's famous lines: "Draw the knife to cut the water more flowing, raise a glass to dispel sorrow more sad." Water, as a disordered fluid, is difficult to plastic and cut by traditional methods.

At present, the main means of controlling the morphology and flow of trace amounts of water is to pre-process solid channels. However, due to the disorder and fluidity of water, there are still challenges in accurately processing water. Laser cutting, as a technology that uses photothermal effects to process solid materials, can it achieve water cutting and processing?

Based on the above ideas, the research group of Professor Li Fei from the School of Life Science and Technology of Xi 'an Jiaotong University and Associate Professor Li Xiaoguang from the School of Physics of Northwestern Polytechnical University have worked together to control the laser, which is known as the "fastest knife". The laser processing technology is used to realize the idea of "laser cutting water" by adjusting the fluidity and surface tension characteristics of water, and the "pumping knife cutting water" has become a reality.

The team first covered the surface of water with hydrophobic silica nanoparticles to build a "water cake" with a thickness of submillimeter, and then cut the "water cake" with a laser, successfully realized the concept of "laser cutting water", and created a variety of "patterns".

Trace the reason why the "water cake" can be cut

Why can lasers magically cut through water? According to the team's researchers, there are two main reasons why "water cake" can be cut by laser:

First, the silica nanoparticles on the surface of the "water cake" have a strong absorption of infrared laser with a wavelength of 10.6 microns. After laser irradiation, the silica nanoparticles absorb the laser energy and convert it into heat for the vaporization of water.

Second, when the local water is vaporized, the flow of water drives the surface silica nanoparticles to further cover the exposed water surface, thereby preventing the water from "healing" process.

Li Fei introduced that the team also explored the influence of the volume of water on the area of "water cake", the thickness of "water cake" on the cutting feasibility and the thickness of "water cake" and the laser scanning speed on the processing accuracy through experiments, and obtained the optimized experimental parameters of "laser water cutting". Subsequently, the application of laser cutting machine successfully processed microfluidic chips including cross channels, distributed channels and other common microfluidic chips, which confirmed the ability of "laser water cutting" to process complex microfluidic structures, and determined that the minimum microfluidic chip processed by "laser water cutting" can reach 350 microns.

The microfluidic chip prepared by "laser cutting water" can be applied in many fields

Fluid manipulation is one of the main applications of microfluidic chips and droplets. The team applied the microfluidic chip and droplet processed by "laser cutting water" to carry out relevant liquid manipulation, and confirmed the liquid manipulation function of the prepared self-supporting microfluidic chip and droplet.

In the research process, based on the openness of the microfluidic chip processed by "laser cutting water", the team applied the microfluidic chip processed by "laser cutting water" as a miniaturized reaction platform to achieve chemical synthesis.

For example, copper ammonia complexation reaction and synthesis of amino acids with ninhydrin hydrate reaction. Based on the light transmission of the microfluidic chip processed by "laser cutting water", the team developed it as a biochemical sensing microreactor and colorimetric detection platform for the detection of biomarkers such as metal ions, proteins, urea and nucleic acids. Finally, the processed microfluidic chip is used as a patterning mold to realize the electric control of liquid metal and the synthesis of patterning hydrogels, and as a drug gradient dilution and cell culture platform.

Through research, the team innovatively proposed a technology for processing water through laser cutting, which solved the problem of precise processing water by confining the flow of water. Microfluidic chips prepared by laser cutting water show potential in many fields such as chemistry, health, materials science and biomedicine.

Source: Xi 'an Daily