Researchers at Northwestern University report a clear physical explanation for everyday static shocks. When two objects slide against each other, nanoscale bumps on their surfaces deform in different ways at the front and the back of the sliding motion. These uneven deformations create different electrical charges across the object, which adds up to a measurable current and the familiar zap.
The mechanism relies on elastic shear, a simple idea in which a material resists a sliding force. Push a plate across a table and it fights the push, then stops as soon as you let go. That resistance concentrates forces at tiny surface features, moving charges and separating them so that the leading and trailing edges carry different signs.
The team also shows that a new model can calculate the resulting current in line with experiments. This work builds on their earlier research that tied static charging to the bending of microscopic protrusions on contacting surfaces, a proposal they set out in a 2019 study. Together, these results turn a long standing puzzle into a concrete, testable picture.
Understanding this simple origin matters for daily life and industry. Static charge affects how powders flow and dose, can spark dangerous fires in factories, and even plays a role when grains clump in space during the early steps of planet formation. A clearer mechanism should help engineers reduce risk and design better processes.
Nano Letters – What Puts the ‘Tribo’ in Triboelectricity? – 2024
Formal paper that explains why sliding produces static electricity. The authors show that different deformations at the front and back of a sliding contact create charge separation and a current, and they provide a model that matches experiments.
Northwestern University – Why petting your cat leads to static electricity – 2024
University news release that describes the new model in plain language, defines elastic shear, and notes implications for safety, manufacturing, and planetary science. Confirms the study was published on September 17, 2024 in Nano Letters.
Popular Science – After 2,600 years, we finally know how static electricity really works – 2024
Media coverage highlighting the key finding that nanoscale surface imperfections and elastic shear during sliding create different charges at the front and back, producing current.
Background study – Physical Review Letters – Does Flexoelectricity Drive Triboelectricity? – 2019
Earlier theoretical work from the same group proposing that flexoelectric effects from inhomogeneous strain at nanoscale asperities drive charge separation during contact and sliding, paving the way for the 2024 model.
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