TechXplore reports that five bubbles arranged in an L directed the flow into a curve.
TechXplore reports that ultrasound-powered microbubbles steered fluid flow in real time on a chip. Five bubbles arranged in an L directed the flow into a curve.
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Cornell researchers built a chip-scale platform that creates hydrogen microbubbles exactly where they are needed, then uses ultrasound to make those bubbles move the surrounding liquid. The team describes the system in a peer-reviewed Science Advances paper, presenting it as a way to replace fixed, passively trapped bubbles with elements that can be generated, resized and removed while the device is operating.
Each bubble starts at a small platinum electrode immersed in an ionic water-based solution. A low direct-current voltage drives electrolysis, producing hydrogen gas at the electrode. Keeping the voltage on for longer grows a larger bubble; turning it off stops the growth and leaves the bubble pinned to the electrode.
Ultrasound then makes the bubble oscillate. That motion produces acoustic microstreaming, a steady flow in the liquid around it. Bubble size matters because it determines which acoustic frequency produces a strong response. As the researchers put differently sized bubbles on individually controlled electrodes, they could choose which bubbles responded and how their flows combined.
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In Cornell’s account of the work, one experimental setup packed nine electrodes into a 3-millimeter area. Each electrode was 6 micrometers wide and produced bubbles ranging from 10 to 100 micrometers. The paper also reports tests on a 3-by-3 array in which the team varied bubble placement and diameter to redirect the net flow.
The useful trick is not simply making one microscopic pump. A single oscillating bubble creates local circulation, while two neighboring bubbles can produce either symmetric or directional flow depending on their relative sizes. Larger patterns extend that control: Cornell reported that three bubbles in a row pushed liquid from left to right, three arranged diagonally sent it up and left, and five in an L-shaped pattern bent the stream around a curve.
The array can be reconfigured without rebuilding the chip. Raising the electrolysis voltage generates gas quickly enough to detach an unwanted bubble, after which a replacement can be grown on the same electrode. Under ultrasound, that rapid gas generation also produced a “bubble shooting” mode; the paper reports that changing the incident ultrasound frequency selected the direction of the resulting flow.
The experiments show programmable flow control on a laboratory chip, not a finished medical device or microrobot. The researchers suggest that the approach could eventually support reconfigurable microfluidics, tiny robotic systems and highly targeted drug delivery. Cornell says a next step is to design circuits that can generate and control the bubbles directly on robots.
@physorg_comRT @TechXplore_com: Ultrasound-powered microbubbles steer fluid flow in real time on a chip, with just five bubbles arranged in an L direct…@physorg_comRT @TechXplore_com: Ultrasound-powered microbubbles steer fluid flow in real time on a chip, with just five bubbles arranged in an L direct…@physorg_comRT @TechXplore_com: Ultrasound-powered microbubbles steer fluid flow in real time on a chip, with just five bubbles arranged in an L direct…@physorg_comRT @TechXplore_com: Ultrasound-powered microbubbles steer fluid flow in real time on a chip, with just five bubbles arranged in an L direct…
