Gallium and gallium alloys are suitable. These “are attractive materials due to their unique electrical, thermal and fluidic properties,” according to the university. They “exhibit low melting point, non-toxicity and controllable shape”.
The metal blob in the shaped chamber (photo) extends out to along the passage towards the counter electrode (below it on the right) under the influence of voltage, then contracts when the bias is removed.
As the blob extends, a surface-tension gradient forms around it, causing the purple fluid between the blob and the walls to rush to the left – it is not driven to the right by any piston effect.
“Interestingly, the flow formed around the liquid metal core, called Marangoni flow when an external voltage is applied, eliminates the need for moving parts and relies instead on surface tension to do the pumping of the flow,” according to the university.
“It has no mechanical parts and can in principle be readily scaled up for commercialisation,” added UNSW chemical engineer Mohannad Mayyas.
The team is using it to drive chemical reaction in the surrounding fluid.
“The liquid metal can be easily integrated into a fluidic channel for constructing the continuous flow reactor,” according to fellow scientist Jialuo Han. “The liquid metal itself can spontaneously produce materials on the surface and the material is repelled away from its surface with the application of an external voltage.”
UNSW collaborated with Queensland University of Technology and University of California, Los Angles (UCLA).
This video shows the liquid metal pump in action
The work is covered in Matter as ‘Liquid metal enabled continuous flow reactor: A proof-of-concept‘