The scientists at ETH Zurich work with wires etched into a silicon chip, which have a diameter of only 300 to 500 nanometers. That’s less than a hundredth of the diameter of a human hair. They construct nano-valves in these lines by slightly narrowing the line by nanolithography and attaching an electrode on either side of the narrow point.

As part of a proof of concept , the researchers used a silicon chip to create a separation and sorting lock with one branch and three valves. At the branching point, a single nanoparticle can be captured and examined. The valves can then be controlled in such a way that the particle leaves the system through one of two output lines. Nanoparticles in liquid can be sorted into two classes using this method. Together with colleagues from the University of Zurich, ETH Zurich researchers were able to use this system to handle even tiny semiconductor nanoparticles (quantum dots) as well as antibodies, both with a diameter of just 10 nanometers. As the scientists emphasize, it is basically possible to arrange an arbitrarily complex nano-line system with any number of controllable valves on a silicon chip.

The technology is now to be further developed jointly with partners in order to use it for applications. For example, particles could be sorted on a small chip, which would be of interest to materials science or biomedicine.