The hottest scientists realize that laser drives w

Scientists realize the use of lasers to drive water flow

Chinese and foreign scientists have worked together to solve a problem that has plagued the scientific community for many years - using lasers to drive the movement of macro matter. Under real conditions, scientists have realized the continuous high-speed movement of water flow driven by pulsed laser in pure water for the first time

this research achievement was recently published in scienceadvances, a subsidiary of science magazine

since the invention of laser in 1960, it has been widely used in optical fiber communication. However, how to convert the energy or momentum of photons into macroscopic forces to drive the motion of objects has been puzzling scientists. Because the direct energy or momentum transmission force of photons is very weak, it is difficult to provide macro driving force. The indirect driving force produced by photothermal effect or photochemical reaction has high requirements for fluid properties, especially for transparent liquids such as water, which have little absorption of excitation light

a joint scientific research team composed of University of Electronic Science and technology, Henan Institute of engineering, University of Houston and other Chinese and foreign universities accidentally found a unique photoacoustic fluid effect in the ordinary nonlinear optical properties experiment of gold nanoparticles. In a glass container, after a period of nanosecond laser irradiation, the aqueous dispersion of gold nanoparticles will form a high-speed flow field. The flow field direction is consistent with the laser propagation direction, and the length can run through the entire 10mm glassware. Under the irradiation of 120 MW laser, the flow rate can reach 4 cm/s, and the flow field can last for nearly hours

the main author of this paper, Wang Zhiming, executive dean of the Institute of basic and frontier research at the University of Electronic Science and technology, explained that the phenomenon of photoacoustic fluid effect is actually a combination of photoacoustic effect and acoustic driving effect, and its "mystery" lies in "gold nanoparticles". Further research found that a micro cavity shaped like a crater and attached with a large number of gold nanoparticles was produced at the laser focus on the inner wall of the glassware. Under the irradiation of pulsed laser, gold nanoparticles will undergo rapid and periodic volume expansion and contraction, resulting in ultrasonic waves. Under the joint action of gold nanoparticles and cavity, the directional high-frequency ultrasonic wave drives the dispersion to produce high-speed flow through the sound wave driving effect

"the microcavity attached to gold nanoparticles is the key to connecting photoacoustic effect and acoustic driving effect. Once the standard background and content of GB 8624 ⑵ 012 are introduced, briefly describe the cavity formation, replace the dispersion of gold nanoparticles with pure water or other solutions, and laser can also drive other liquids to flow." Wang Zhiming said

this research makes it possible to realize microfluidic chip and laser remote drive. Different from the traditional way of using mechanical devices to generate ultrasonic waves to promote the flow of liquid, laser driven fluid technology can realize the fluid control of how much micron plastic is burned and buried to the centimeter level, which is widely used in microfluidic systems and even wearable portable medical devices. It is reported that the research team plans to conduct in-depth research on the formation process of microcavity, which we do not hold great hope