Marbles have been around for a long time. Crude versions were found in the ashes of Pompeii and the tombs of ancient Egyptians.
Researchers have developed liquid metal marbles that can bounce and retain their shape.
But these little balls of fun have come a long way in the past few thousand years via schoolyards all over the world.
Their latest incarnation is in a liquid metal form, a world-first breakthrough that advances research in "soft electronics".
Imagine a bendable tablet computer with a screen you can fold up like paper, or a mobile phone you can roll up and shove in a pocket.
Flexible electronics, while still in its infancy, has the potential to revolutionise technology such as smartphones, solar cells, sensors and medical implants.
Similar technology has also been developed to create a liquid metal pump, which may provide new opportunities for lab-on-a-chip technologies such as bio-sensing and blood analysis.
The "liquid metal marbles" are droplets of liquid metal with a solid powder coating which can be micro or nano scale.
The team of RMIT researchers behind the breakthrough are the first to combine the two concepts of liquid marbles with liquid metal droplets.
Lead researcher Dr Vijay Sivan, who is with the University's Platform Technologies Research Institute, says the marbles were developed as part of investigations into flexible conductive systems for electronic and electromagnetic units.
"They are like flexible ball bearings with extraordinary properties," Sivan says.
"We were surprised to see that the marbles bounced off a surface. We were expecting them to splash but we were able to keep them the same form even at high impact."
The innovation offers great potential in industrial sensing technologies.
"When they are used in a sensor for detecting heavy metals in solutions, they improved sensitivity by 80 times, especially to lead," Sivan says.
This means they provide a safer alternative to mercury-based heavy metal ion sensors.
Meanwhile, the team behind the liquid metal pump is hoping it will revolutionise the way chemicals are processed and bio-particles are manipulated on a micro-scale.
The pump pushes liquid through a system using tiny droplets of galinstan - a non-toxic liquid metal alloy.
Lead researcher Dr Khashayer Khoshmanesh, from RMIT's Centre for Advanced Electronics and Sensors, says the pump could be used in industrial experiments, medical experiments and to cool applications such as mobile phones.
"The advantages are that it is very small, it's maintenance-free because it doesn't have any breakable parts, and it can produce a high flow rate under very low power consumption," Khoshmanesh says.
"It only uses five volts of electricity, so from a safety perspective it is very good compared to a pump that might use 100 or even 1,000 volts.
"The alloy is also safe compared to other materials such as mercury, which is toxic."
So far, the team has created a pump that is between two and three millimetres in diameter. Their next challenge is to shrink the pump.
"If you really want to integrate it for micro-applications you have to make it 20 times smaller," Khoshmanesh says.
The RMIT multi-disciplinary team joined forces with the Queensland University of Technology and the University of Adelaide on the research.
Story: Rachel Kleinman
Video: Phred Petersen
This story was first published in RMIT's Making Connections magazine.