ENGINEERING TECHNOLOGY

Researchers have developed a new type of lubricating surface


As the saying goes, “Man goes to the high place, and the water flows to the low place.” So, have you ever seen a picture of water going up?

Du Xuemin’s team from the Institute of Biomedicine and Health Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and wang drilling and opening team from the City University of Hong Kong, have developed a lubricated surface based on intelligent polymer materials (LICS) that can generate electricity through light and further accurately control liquids.

This new lubricated surface demonstrates a wide range of application potential in biomedical fields such as coagulation detection, in situ cell stimulation and cell response monitoring. The results were published in Science Advances on July 9.

Du Xuemin and Wang Zhankai are the co-corresponding authors of the paper, and Wang Fang and Liu Meijin, postdoctoral fellows of shenzhen advanced institute, are the co-first authors of the paper. A number of teachers from the University of Science and Technology of China and Nanjing University helped with the work.

Light generates electricity to achieve precise liquid control

In nature , ” Nepenthes ” has a smooth leaf surface , the inner wall of which secretes a layer of lubricant , and due to the long-term tilt and vertical state of the pitcher , it will slip into the pitcher when the prey approaches , becoming a plate of N. nepenthes.

On the lubricated leaf surface of Nepenthes, water droplets are subjected to gravity and flow downwards. So, is it possible to make water droplets go up on the lubricated surface?

“The lubrication layer covering the solid surface often shields the structural and functional characteristics of the surface, such as the surface structure gradient or charge gradient, which makes it difficult to manipulate the liquid through the surface gradient or the field, which greatly affects the droplet control effect of the lubricated surface and its practical application.” Du Xuemin said.

In response to this challenge, the research team has constructed a new type of intelligent polymer material lubrication surface (LICS), which consists of three core elements, namely liquid metal particles with excellent photothermal effect, and polyvinylidene fluoride-trifluoroethylene polymer with unique ferroelectric effect, which can synergistically convert photothermal into surface charge, and micro-cone array structure for locking the lubrication layer.

Through the light-thermal induction of surface charge generation of intelligent polymer materials, LICS can realize the precise control of droplets at high speed, long distance, antigravity, simple liquid to complex liquid, single to multiple droplets, microscopic to macroscopic scale droplets, plane to surface substrate, open to closed system.

In simple terms, it is to use light to precisely control the movement of droplets on the LICS. So, to achieve precise control of droplets, are there any requirements for the intensity of light and the weight of droplets?

“LICS has requirements for the weight of the droplets, because the resistance of different weight droplets is not the same, but we can adjust the intensity of the light to pull the droplets of different weights. We precisely manipulate water droplets as small as 1 nanoliter and as large as 1.5 milliliters. Du Xuemin said.

Precise control of liquids thanks to THE excellent surface charge regeneration ability of LICS, LICS in 0.5 seconds of near-infrared radiation, can produce a surface charge density of up to 1280 pch (pC / mm2), effectively eliminating the lubrication layer to the surface characteristics of the shielding, for the droplet rapid response, movement to provide a large force; Moreover, the charge regeneration performance is not significantly attenuated for up to 6 months after 10,000 nir-infrared light on/off cycles or immersion in silicone oil, and this stable charge regeneration performance ensures the long-term effectiveness of LICS for droplet manipulation.

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Light manipulation of 1 nanoliter droplet (top) and 1.5 ml droplet (bottom) movement comparison chart Source: Courtesy of the scientific research team

The application potential in the biomedical field is great

Microfluidics technology is widely used in biological, chemical and medical research due to its precise and high-throughput sample processing and accelerated biochemical reaction capabilities. Compared with traditional detection technology, microfluidic technology integrates the basic operations of biochemical experiments such as sample reaction, preparation, separation, and detection into a very small chip. However, traditional microfluidic systems require both complex pipe connections and large equipment to power the liquid.

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LICS packaged into a microfluidic chip

In this study, based on the flexible and conformal characteristics of LICS, the researchers packaged LICS into a closed microfluidic chip, and the droplets in the LICS chip can be quickly and accurately crossed the chip channel using a handheld laser pointer. In addition, the non-contact, remote light-driven droplet function in the LICS chip can prevent droplet volatilization without adding substances that assist droplet movement in the droplet, avoid cross-contamination, and show excellent reliability in biological applications such as coagulation detection.

In addition, the researchers used real-time light and heat to induce functional characteristics of surface charge generation in LICS, and successfully realized real-time stimulation of cells in the LICS chip and in situ monitoring of cell response.

“LICS not only realizes the efficient control of droplets under the development system, but also realizes the pumpless, remote, anti-volatile, anti-pollution control and biological application of droplets in the closed microfluidic chip, bringing new ideas to the development of new interface materials and microfluidics, and demonstrating the potential application value of chemical and biomedical applications.” Du Xuemin said.

In the future, the research team will further optimize the accuracy and universality of droplet light manipulation on the surface of such intelligent polymer materials, and expand the application of such intelligent polymer materials and LICS microfluidic chips in the biomedical field. (Source: China Science Daily Diao Wenhui)

Related paper information:https://doi.org/10.1126/sciadv.abp9369



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