Illustration of a gold nanoparticle trapped near a locally heated gold surface by hydrodynamic and van der Waals forces. (Credit: Martin Fränzl/Leipzig University)

Researchers have succeeded in moving tiny amounts of liquid at will by remotely heating water over a metal film with a laser. The currents generated in this way can be used to manipulate and even capture tiny objects. This will unlock groundbreaking new solutions for nanotechnology, the manipulation of liquids in systems in tiny spaces, or in the field of diagnostics, by making it possible to detect the smallest concentrations of substances with new types of sensor systems.

They found that they can generate very strong fluid flows even in the tiniest of channels by heating a very thin metal film on one side of the channel with a focused laser beam. The flows originate in an ultra-thin liquid layer just a few nanometers above the surface of the metal and mix the liquid in the channel with a specific flow pattern. They measured this flow pattern using nanoparticles as tracers. Not only have the scientists succeeded in exploring the origin of these currents, but they have also shown that they can capture, separate or transport nano-objects by cleverly combining currents and controlling other forces remotely by laser.

The researchers are particularly interested in combining these laser-driven thermofluidics with machine learning techniques in order to create automated smart nanofactories — for nanoscale manufacturing, programmed material manipulation and sensor technologies — that optimize and adapt to new requirements based on the information they collect.

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