This tiny sensor could sleep for years between detection events

It’s easy enough to put an always-on camera somewhere it can live off solar power or the grid, but deep in nature, underground, or in other unusual circumstances every drop of power is precious. Luckily, a new type of sensor developed for DARPA uses none at all until the thing it’s built to detect happens to show up. That means it can sit for years without so much as a battery top-up. The idea