This approach creates a high-impedance source and, unlike chemical batteries, the devices will work at a very wide range of temperatures.
The beta particles essentially transfer electronic charge from the thin film to the cantilever.
As long as the isotope is decaying - a process that can last for decades - the tiny cantilever will continue its up-and-down motion.
Radioactive isotopes can continue to release energy over periods ranging from weeks to decades.
Researchers have demonstrated devices with about 7% efficiency with high frequencies of 120 Hz to low-frequency (every three hours) self-reciprocating actuators.