Achilles tendons and other soft bodily tissues can produce an electric voltage when squeezed, a finding that could aid the diagnosis of some medical problems.

Crystals, some semiconductors, dry biological tissues such as bone and other materials exhibit the piezoelectric effect, which is the ability to generate electricity when placed under mechanical stress. However, it was not clear whether soft tissues have the same property.

Kenji Ikushima and his colleagues at Tokyo University of Agriculture and Technology tested for the effect in samples of aortic walls and heart valves from pigs, and Achilles tendons from cows. The researchers induced mechanical stress in the tissues by blasting them with focused pulses of ultrasound waves. Using a tiny antenna, the team detected the resulting electromagnetic waves produced by the piezoelectric effect. The stronger the ultrasound waves and stresses, the stronger was the signal the antenna picked up.

Piezoelectric forces could one day be used to help detect fibrosis: scarred tissue that damages an organ’s ability to function.