A Harvard University research team proposes a novel recipe for almost-invisible stretchy speakers ideal laptops, mobile devices and noise-cancelling windows-- a mixture of saltware and polymer creating a "hydrogel."
As detailed in a paper called "Stretchable, Transparent, Ionic Conductors," hydrogel speakers take inspiration from the flow of electrical signals via ions (not electrons) in the human body.
Seawater is rich in free-flowing dissolved ions. Mixed with a polymer it creates the hydrogel, a flexible yet solid substance.
The actual speaker consists of a thin sheet of transparent, insulating rubber between 2 layers of gel connected to copper electrodes. Electrical signals from an audio source pass to the hydrogel via electrodes, causing the ions to flow. The movement of the ions causes the rubber in the middle to vibrate at specific frequencies, creating sound.