A bendy audio speaker literally made from liquid heavy metal could prove useful for the next generation of wearable technology.
Flexible speakers may be the key to better, wearable music listening devices, says Jeong Sook Ha of Korea University, but that will require alternatives to the rigid loudspeakers and microphones we use today.
Ha and her colleagues have developed a loudspeaker that plays a range of sounds, from piano notes to human voices, even when bent (watch the video below).
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The device is made from two strips of a liquid gallium alloy encased in a liquid electrolyte solution. Gallium is a heavy metal, meaning it has a high density. Running beneath the metal are two strips of copper that transmit an alternating current.
When current flows through the copper, it distorts the shape of the gallium alloy, expanding and contracting the liquid strips. These rapid vibrations generate sound.
The device produced around 45 decibels of sound when measured at a distance of 1 centimetre, which is the equivalent to the background sound in a library or conversation at home.
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It even worked when bent into an arc with a radius of 3 millimetres. Because the device is made primarily from liquid and viscous and elastic polymers, it isn鈥檛 damaged by being bent or deformed, says Ha.
The findings suggest that this liquid loudspeaker could be a prototype for future wearable audio devices, says Ha. It could also be worn on the skin to hear physiological signals like heartbeats.
Nevertheless, there are several obstacles to overcome before it is ready for widespread use.
鈥淎lthough the fabricated liquid metal devices produced audible sound pressure when placed close to the ear, the output was still much weaker than that of rigid commercial earphones,鈥� says Ha.
But the researchers hope their loudspeaker will be a building block for new soft acoustic devices and are tweaking the current model to improve the sound quality and volume.
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