Terminator-style liquid metal 'EATS' its way through obstacles courses
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The terrifying dystopia of shapeshifting metal assassins seen in Terminator 2 may not have been as far-fetched as once thought.
Researchers from China have created droplets of liquid metal that move through obstacle courses and Petri dishes by 'eating' flakes of aluminium.
These so-called 'self-fuelling liquid motors' can also change shape and squeeze through tight spaces.
Researchers from Tsinghua University in China have created droplets of liquid metal that move through obstacle courses by 'eating' flakes of aluminium. These so-called 'self-fuelling liquid motors' can also change shape and squeeze through tight spaces (pictured)
The liquid motors were designed by Dr Jing Liu, Lei Sheng and Jie Zhang from Tsinghua University, China and their findings are published in the Wiley Online journal Advanced Materials.
The motors are made from an alloy of gallium, indium and tin dropped into a solution of sodium hydroxide. The process also works in salt water.
Gallium is liquid at 29°C (84°F), while indium has a higher melting point of 156°C (312°F).
But when combined, the alloy remains liquid at room temperature with a high surface tension of around 500 millinewtons per meter (mN/m).
This means that when this alloy is placed on a flat table it forms into an almost perfect sphere and can hold its shape.
When aluminium flakes are placed in this solution, along the edge of a maze for example, it causes a reaction that creates hydrogen bubbles.
The motors are made from an alloy of gallium, indium and tin dropped into a solution of sodium hydroxide. The process also works in salt water. These bubbles help propel the droplets forward, with the aluminium flakes acting as a type of fuel, and the propulsion is enough to push them around a Petri dish (pictured)
In addition to creating bubbles, the researchers said the reaction creates a 'charge imbalance' between the front and rear of the drop, which causes the pressure and force on each side to differ. This pressure also forces the droplets to shift their shape in order to squeeze through spaces and round corners (pictured)
These bubbles help propel the droplets forward, with the aluminium flakes acting as a type of fuel, and the propulsion is even enough to push them 'uphill' on zig-zag obstacle courses.
It also forces the droplets to shift their shape in order to squeeze through spaces, and can be used to change their direction.
Dr Liu told New Scientist that the reaction creates a 'charge imbalance' between the front and rear of the drop, which causes the pressure and force on each side to differ.
This changing pressure is what generates movement.
The research builds on previous studies from Dr Liu' s team, as well as breakthroughs made by a team of scientists from North Carolina State University.
They previously spotted that drops can act like a 'pump' when an electric fieldare applied to them.
The scientists used a similar alloy of gallium and indium to create the liquid metal and found the surface tension of droplets was reduced when a voltage of less than one volt was applied to it.
This caused the metal to spread out flat on the surface.
The effect is also reversible; if the charge is flipped from negative to positive, the liquid metal returns to a spherical shape.
Changing the voltage also changes the amount of surface tension and the viscosity of the metal blob, allowing it to shape-shift into different structures.
'The resulting changes in surface tension are among the largest ever reported, which is remarkable considering it can be manipulated by less than one volt,' said Dr Michael Dickey, an associate professor at North Carolina State University.
These findings could pave the way for drops that are used to move materials through pipes or even deliver medicine in blood vessels, for example. It is also part of a project to create intelligent 'soft' robots that change their shapes, reminiscent of Robert Patrick's T-1000 in Terminator 2: Judgement Day (pictured)
'We can use this technique to control the movement of liquid metals, allowing us to change the shape of antennas and complete or break circuits.
'Many materials form surface oxides, so the work could extend beyond the liquid metals studied here.'
Both findings could pave the way for drops that are used to move materials through pipes or even deliver medicine in blood vessels, for example.
The research is also part of a project to create intelligent 'soft' robots that change their shapes.
The 'self-fuelling' research builds on previous studies from Dr Liu's team, as well as breakthroughs made by a team of scientists from North Carolina State University. They previously spotted that drops of the alloy can act like a 'pump', and change shape, when an electric field are applied to them (pictured)
Scientists used an alloy of gallium and indium to create the liquid metal. Gallium is liquid at 29° C (84° F), while indium has a higher melting point of 156°C (312°F). This means that when this alloy is placed on a flat table, it will form into an almost perfect sphere and hold its shape (pictured)
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