A miraculous device that can generate electricity seemingly out of thin air has been developed by engineers. Called a thermal resonator, it relies on fluctuations in temperature between day and night to produce electricity. It can be used without the need for sunlight, batteries or wind, making it ideal for situations where these resources can't be relied upon. The technology has the potential to power sensors and communications devices for years without the need for batteries. Experts at the Massachusetts Institute of Technology's (MIT) department of chemical engineering are behind the find. Their gadget is a twist on a thermoelectric generator, which creates power when one side of the device is a different temperature from the other. Researchers say that the power levels generated by the new system so far are modest. However, it outperformed a commercially available pyroelectric material - an existing method for converting temperature fluctuations to electricity - by 300 per cent. Professor Michael Strano, who led the study, said: 'We basically invented this concept out of whole cloth. 'It's something that can sit on a desk and generate energy out of what seems like nothing. 'We are surrounded by temperature fluctuations of all different frequencies all of the time. These are an untapped source of energy.' Such systems could provide low-power but long-lasting energy sources for landers or rovers exploring remote locations, including other moons and planets, says Volodymyr Koman, an MIT postdoc and co-author of the new study.