August 31, 2013

Transparent artificial muscle plays music

Gel-based audio speaker demonstrates capabilities of ionic conductors, long thought limited in application

In a materials science laboratory at Harvard, a transparent disk connected to a laptop fills the room with music — it’s the “Morning” prelude from “Peer Gynt” played on an ionic speaker.

No ordinary speaker, it consists of a thin sheet of rubber sandwiched between two layers of a saltwater gel, and it’s as clear as glass. A high-voltage signal that runs across the surfaces and through the layers forces the rubber to rapidly contract and vibrate, producing sounds that span the entire audible spectrum, 20 hertz to 20 kilohertz.