We are all familiar with robots equipped with movable arms. They sit on the factory floor, perform mechanical work, and can be programmed. One robot can be used for multiple tasks.
        Tiny systems that transport negligible amounts of liquid through thin capillaries have been of little value to such robots until today. Developed by researchers as an adjunct to laboratory analysis, such systems are known as microfluidics or lab-on-a-chips and typically use external pumps to move fluids across the chip. Until now, such systems have been difficult to automate, and chips must be designed and manufactured to order for each specific application.
        Scientists led by ETH professor Daniel Ahmed are now merging conventional robotics and microfluidics. They have developed a device that uses ultrasound and can be attached to a robotic arm. It is suitable for a wide range of tasks in microrobotics and microfluidics applications and can also be used to automate such applications. The scientists report the progress in Nature Communications.
        The device consists of a thin, pointed glass needle and a piezoelectric transducer that causes the needle to vibrate. Similar transducers are used in loudspeakers, ultrasound imaging, and professional dental equipment. ETH researchers can change the vibration frequency of glass needles. By dipping a needle into a liquid, they created a three-dimensional pattern of many swirls. Since this mode depends on the oscillation frequency, it can be controlled accordingly.
        Researchers can use it to demonstrate various applications. First, they were able to mix tiny droplets of highly viscous liquids. “The more viscous the liquid, the more difficult it is to mix,” explains Professor Ahmed. “However, our method excels at this because it not only allows us to create a single vortex, but also effectively mixes fluids using complex 3D patterns made up of multiple strong vortices.”
       Second, the scientists were able to pump liquid through the microchannel system by creating specific vortex patterns and placing oscillating glass needles close to the channel walls.
        Thirdly, they were able to capture the fine particles present in the liquid using a robotic acoustic device. This works because the size of a particle determines how it responds to sound waves. Relatively large particles move towards the oscillating glass needle, where they accumulate. The researchers showed how this method can capture not only particles of inanimate nature, but also fish embryos. They believe it should also trap biological cells in liquids. “In the past, manipulating microscopic particles in three dimensions has always been a challenge. Our tiny robotic arm makes this easy,” said Ahmed.
        “Until now, advances in large-scale applications of conventional robotics and microfluidics have been done separately,” said Ahmed. “Our work helps bring these two approaches together.” One device, properly programmed, can handle many tasks. “Mixing and pumping liquids and capturing particles, we can do it all with one device,” said Ahmed. This means that the microfluidic chips of tomorrow will no longer need to be custom-designed for each specific application. The researchers then hope to combine multiple glass needles to create more complex vortex patterns in the liquid.
        In addition to laboratory analysis, Ahmed can imagine other uses for the micromanipulator, such as sorting tiny objects. Perhaps the hand could also be used in biotechnology as a way to introduce DNA into individual cells. They could eventually be used for additive manufacturing and 3D printing.
        Materials provided by ETH Zurich. The original book was written by Fabio Bergamin. NOTE. Content can be edited for style and length.
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