| Title | Valves for Tiny Particles | |
| Date | Sunday May 27 2018, @02:40AM | |
| Author | Fnord666 | |
| Topic | ||
| from the tiny-traffic-lights dept. | ||
Researchers from ETH Zurich have developed tiny valves that enable individual nanoparticles in liquids to be separated and sorted. The valves can be used for a very broad range of tiny particles, including individual metal and semiconductor nanoparticles, virus particles, liposomes and larger biomolecules such as antibodies.
The nanovalves work differently than classic valves, which are used to mechanically close and open flow in pipelines, as in a tap. "These mechanical valves can be miniaturised, but not as far as we would need for nanoscale applications," explains ETH professor Poulikakos. "If channels are thinner than a few dozen micrometres, they cannot be mechanically closed and opened with any regularity."
In order to open and close the nanoparticle flow in ultrathin channels, the ETH scientists made use of electric forces. They worked with channels etched into a silicon chip. These had a diameter of just 300 to 500 nanometres -- less than a hundredth of the diameter of a human hair. They then constructed nanovalves in these channels by narrowing the channels at desired valve locations using nanolithography and placing an electrode on both sides of these bottlenecks.
Nanoparticles in pure water cannot simply pass through the bottleneck; for them, the valve in its basic state is closed. By activating the electrode in particular ways, the electrical field in the bottleneck can be changed. This leads to a force acting on any nanoparticles present, which pushes the particles through the bottleneck -- this is how the valve is "opened."
Nanoparticles in a saline solution, however, behave differently: they can pass through the bottleneck in its basic state -- for them, the valve is "open." Yet as the scientists were able to show these particles can be stopped at the electrodes through a skilful application of alternating electrical fields. In this way, for example, biological particles such as viruses, liposomes and antibodies that are usually present in saline fluids both in nature and in the laboratory can be easily manipulated.
"It is fundamentally difficult to examine individual nanoparticles in a liquid, because Brownian motion acts on the nanoscale," explains Hadi Eghlidi, Senior Scientist in Poulikakos' group. The tiny particles do not remain still but instead vibrate constantly, with a movement radius that is many times their diameter. "However, we can capture the molecules in a small space between two or more valves and then examine them under a microscope, for example."
Patric Eberle, Christian Höller, Philipp Müller, Maarit Suomalainen, Urs F. Greber, Hadi Eghlidi, Dimos Poulikakos. Single entity resolution valving of nanoscopic species in liquids. Nature Nanotechnology, 2018; DOI: 10.1038/s41565-018-0150-y
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printed from SoylentNews, Valves for Tiny Particles on 2024-04-18 15:54:55