The total came to around $20. Williams is tall and balding, with wire-rim glasses that make him look like an engineer, which he is. He directs a center on technology in education at Kennesaw State University and is the kind of guy who spends his free time chatting up people on his ham radio or trying to glimpse a passing comet with his telescope. But this project was different.

When he got home, he took his supplies into his office. He heated up his soldering iron, hoping his wife wouldn’t see what he was up to. He fished a few wires out of his desk and built a simple circuit. Using alligator clips, he connected the circuit to two kitchen sponges soaked in saline and strapped them to his head with a sweatband.