Beyond sci-fi: Manipulating liquid metals without contact
Look Ma. No hands!

Date:
February 7, 2022
Source:
ARC Centre of Excellence in Future Low-Energy Electronics
Technologies
Summary:
Research inspired by Terminator 2's shape-shifting, liquid metal
robot sees liquid-metal electrical conductors manipulated in
mid-air without contact. The liquid wires can be controlled to move
in any direction, and manipulated into unique, levitated shapes
such as loops and squares using a small 'triggering' voltage and
a magnet. The new technology has potential application in advanced
manufacturing and dynamic electronic structures, augmenting other
non-contact manipulation technologies such as acoustics or optical
tweezers.



FULL STORY ==========================================================================
In a landmark discovery, FLEET University of Wollongong (UOW) researchers
have realised the non-contact manipulation of liquid metal.


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The metals can be controlled to move in any direction, and manipulated
into unique, levitated shapes such as loops and squares by using a small voltage and a magnet.

The liquid metal used is galinstan, an alloy of gallium, indium and tin,
which favours the formation of droplets due to its high surface tension.

Under the application of a small 'triggering' voltage, this liquid-metal becomes a wire as the voltage causes electrochemical oxidation which
lowers the surface tension of the metal.

"Because these reactions require an electrical current passing through the wire, it becomes possible to apply a force to the wire via application
of a magnetic field (ie, electromagnetic induction; the same mechanism
as drives motion in an electric motor).

Thus, the wires can be manipulated to move in a controllable path, and
can even be suspended (against gravity) around the circumference of the
applied magnetic field, assuming controlled, designed shapes." said Prof Xiaolin Wang the leader of this project.



==========================================================================
"The non-contact manipulation of liquid metal allows us to exploit and visualise electromagnetism in new ways." "The ability to control streams
of liquid metals in a non-contact manner also enables new strategies
for shaping electronically conductive fluids for advanced manufacturing
and dynamic electronic structures" said Wollongong PhD student Yahua He,
the lead author of the study.

Non-contact methods of manufacturing and manipulation can minimise
unwanted disturbance of objects being studied or manipulated. Previously developed non- contact technologies include object manipulation by
acoustic manipulation or optical tweezers.

However, to date, free-flowing liquid streams have been particularly
difficult to manipulate in a non-contact manner. Realising
highly-controlled changes in directionality or complex shaping of liquids, especially without disrupting the cross-sectional shape of the stream,
was the challenge for the team at UOW.

"There was an enjoyable element of discovery in this scientific
process. Once the team started working on this topic, we realised that
there is much more behind it," said team leader Prof Xiaolin Wang.



==========================================================================
"The liquid metal wires form by applying a small voltage (approximately
1 volt). However, our team found that a considerable electrical current
(up to 70 mA) could be measured in the resulting wires.

"There was a creative leap at this point, as the team realised that electromagnetic induction could be used to control the liquid metal wires
in a non-contact manner. This was the key to finally successfully solving
the challenge, thereby developing a new strategy for shaping fluids in
a non- contact manner." The UOW team's findings are published in the
January issue of Proceedings of the National Academy of Sciences (PNAS).

Prof Xiaolin Wang is a node leader and theme leader at the ARC Centre of Excellence for Future Low-Energy Electronics Technologies (FLEET), and led
the research team from UOW's Institute for Superconducting and Electronic Materials within the Australian Institute for Innovative Materials.

"By combining electromagnetic induction and fluid dynamics, we were able
to manipulate the liquid metal in a controllable way, and move like soft robotics," Professor Wang said.

"The research in liquid metals was inspired by biological systems as
well as science fiction, including the shape-shifting, liquid metal
"T-1000" robot in the James Cameron-directed film Terminator 2." "This research is more than science fiction, we have conceived and realised
this non-contact method for liquids, offering a new way to manipulate
and shape fluids." This non-contact manipulation is made possible by
the material's unique fluid dynamic and metallic properties. As soft, current-carrying conductors, the wires present minimal resistance
to manipulation via Lorentz force under a controlling the magnetic
field. Thus, the wires could be easily manipulated in designed ways.

This very low resistance to movement allows unusually fine control of
resulting shapes.

"Usually, liquid streams break up into droplets. For example, streams of
water coming from a faucet or hose start out as a cylinder, but quickly
break up into droplets. However, the liquid metal wire has a string-like property, similar to waving ribbons in the air. That property allowed
us to manipulate the liquid metal stream into continuous loops and other shapes," said co-corresponding author Prof Michael Dickey (North Carolina
State University).

This is a UOW-led collaboration with FLEET researchers at UNSW and North Carolina State University. The Australian Research Council supported the research through an ARC Future Fellowship Project and ARC COE in FLEET.

========================================================================== Story Source: Materials provided by ARC_Centre_of_Excellence_in_Future_Low-Energy_Electronics
Technologies. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Yahua He, Jianbo Tang, Kourosh Kalantar-Zadeh, Michael D. Dickey,
Xiaolin
Wang. Noncontact rotation, levitation, and acceleration of flowing
liquid metal wires. Proceedings of the National Academy of Sciences,
2022; 119 (6): e2117535119 DOI: 10.1073/pnas.2117535119 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220207172949.htm

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