Researchers are developing a nano-sized charger that could allow devices such as mobile phones to be recharged via sound waves generated by their users.
Researchers at Texas A&M University and the University of Houston have discovered that a type of material - when manufactured at a size of just 21 nanometres in thickness - can convert energy at a 100 percent increase, the university has announced.
The material is piezoelectric - a hard material, usually made of crystal or ceramics, that generates voltage when mechanical stress is applied.
The material is conductive enough to allow sound waves, as well as vibrations generated by walking, to build up an electric charge. Indeed, a gym and a nightclub are using the technology to power their buildings using the charge generated by their customers.
Piezoelectrics aren't new - they were discovered in the 1880s and are today used in microphones, car cigarette lighters and quartz watches.
But at 21 nanometres, piezoelectrics become much more efficient - and small enough to use in devices such as mobile phones and laptops.