Scientists have discovered that water moving over surfaces generates significantly more electrical charge than previously believed, particularly when it sticks and then slips past tiny obstacles.
This newfound knowledge could revolutionize surface design for safer fuel storage, better energy storage, and even faster-charging technologies.
Water Generates More Electricity Than Expected
Researchers from RMIT University and the University of Melbourne have discovered that water moving across a surface can generate an electrical charge up to 10 times stronger than previously thought.
The research team, led by Dr. Joe Berry, Dr. Peter Sherrell, and Professor Amanda Ellis, found that when a water droplet encounters a tiny bump or rough spot on a surface, it builds up force until it suddenly “jumps” or “slips” past the obstacle. This movement creates a lasting electrical charge, something scientists had not observed before.
This new understanding of water’s “stick-slip” motion opens the door to designing surfaces that control electrification. Potential applications include improving fuel storage safety, enhancing energy storage, and increasing charging efficiency.
Water’s Hidden Electrical Power
“Most people would observe that rainwater drips down a window or a car windscreen in a haphazard way, but would be unaware that it generates a tiny bit of electrical charge,” said Sherrell, whose research at RMIT’s School of Science specializes in capturing and using ambient energy from the environment.
“Previously, scientists have understood this phenomenon as occurring when the liquid leaves a surface, which goes from wet to dry.
“In this work we have shown that charge can be created when the liquid first contacts the surface, when it goes from dry to wet, and is 10 times stronger than wet-to-dry charging.
“Importantly, this charge does not disappear. Our research did not pinpoint exactly where this charge resides, but clearly shows that it is generated at the interface and is probably retained in the droplet as it moves over the surface.”
Berry said an electric shock inside a fuel container with flammable liquids could be dangerous, so charge build-up on a solid surface needs to be safely discharged after a liquid has moved on.
“Understanding how and why electric charge is generated during the flow of liquids over surfaces is important as we start to adopt the new renewable flammable fuels required for a transition to net zero,” said Berry, who is a fluid dynamics expert from the Department of Chemical Engineering at the University of Melbourne.
“At present, with existing fuels, charge build-up is reduced by restricting flow, using additives or other measures, which may not be effective in newer fuels. This knowledge may help us to engineer coatings that could mitigate charge in new fuels.”
Teflon and Water: A Surprising Combination
The team investigated this charging effect with water and the material used in Teflon, polytetrafluoroethylene (PTFE), in this study, published in Physical Review Letters.
Teflon is a type of plastic commonly used in pipes and other fluid handling materials, but it does not conduct electricity, meaning that the charge generated is not able to be safely or easily removed.
How the Team Measured Water’s Electrical Charge
The team measured the electrical charge and contact areas created by water droplets spreading and contracting on a flat plate of Teflon – effectively simulating the movement of droplets over the surface.
The team used a specialized camera to capture individual frames of droplets sticking and slipping, with the change in charge being measured simultaneously.
“We were lucky enough to have three fantastic Chemical Engineering Masters students help set up and run our experiments as part of their course here at the University of Melbourne,” Berry said.
Breakthrough Findings in Electrical Charge Measurement
Shuaijia Chen, first author and PhD student from the University of Melbourne, said the first time water touched the surface created the biggest change in charge, from 0 to 4.1 nanocoulombs (nC).
The charge oscillated between about 3.2 and 4.1 nC as the water-surface interaction alternated between wet and dry phases.
“To put things into perspective, the amount of electrical charge that water made by moving over the PTFE surface was more than a million times smaller than the static shock you might get from someone jumping next to you on a trampoline,” Chen said.
“That amount of charge may sound insignificant, but this discovery could lead to innovations that can enhance or inhibit the charge created in liquid-surface interactions in a range of real-world applications.”
The Future of Water-Based Electricity
The team says the impact of this research relies on the development of commercial technologies with prospective industry partners.
The researchers plan to investigate the stick-slip phenomenon with other types of liquids and surfaces.
“The amount and rate of charge in other liquid and surface material interactions may be relevant for a range of potential commercial applications,” Sherrell said.
“We plan to study where stick-slip motion can affect safety design of fluid handling systems, such as those used to store and transport ammonia and hydrogen, as well as methods to recover electricity and speed up charging from liquid motion in energy storage devices.”
Reference: “Irreversible Charging Caused by Energy Dissipation from Depinning of Droplets on Polymer Surfaces” by Shuaijia Chen, Ronald T. Leon, Rahmat Qambari, Yan Yan, Menghan Chen, Peter C. Sherrell, Amanda V. Ellis and Joseph D. Berry, 11 March 2025, Physical Review Letters.
DOI: 10.1103/PhysRevLett.134.104002
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1 Comment
Water based electricity. Butane smoke a tin jar lid. Add one drop of water. Observe the reaction.