Piezoelectricity essentially refers to current that accumulates in certain solids in response to applied mechanical stress.

BBC: Sensors

The outer two layers are made up of PZT-5H - a ceramic substance that produces an electrical charge when mechanical stress is applied.

BBC: Cyborg search-and-rescue insects' power source unveiled

This finding raises the question: can a small diameter lead be sufficiently robust to perform reliably over years of biologic exposure and mechanical stress in the human body?

FORBES: Robert Hauser, ICD Watchdog, Offers Viewpoint On Riata Controversy At HRS