Researchers at Korea Advanced Institute of Science and Technology (KAIST) have developed a new graphene oxide-based speaker design said to be specifically targeted for the mobile audio market. The speaker does not require an acoustic box to produce sound.

The researchers used graphene in a relatively simple, two-step process that yielded a thermoacoustic speaker. Thermoacoustics is based on the idea that sound can be produced by the rapid heating and cooling of a material instead of through vibrations.

The team started by freeze-drying a solution of graphene oxide flakes. They then reduced and doped the oxidized graphene to improve its electrical properties. This resulted in an N-doped, three-dimensional, reduced graphene oxide aerogel (N-rGOA) that is freestanding. The final aerogel sound element has a porous macroscopic structure that can be easily modulated. The speaker consists of an array of 16 aerogels and operates on 40 watts of power. The speakers are flat and do not vibrate, which could make them suitable for embedding in walls and other surfaces.

Graphene-based speakers have been designed and tried quite successfully in the past, in examples like University of California's graphene-based earphone-sized speaker and Seoul's National University transparent and lightweight speaker made from Graphene. In this recent case, however, the simplicity and ease of the process make it potentially suitable for scaling up and hopefully reaching mass production.