Low Battery?? Yell at your Phone to Charge it....

Imagine that one day you could charge your mobile phone, just by placing them in noisy areas or by yelling at them. Then you don’t have to struggle for the dead phone battery while travelling or during an outing when you are away from power sources. It’s no more an imagination…. Scientists have come up with a postage stamp-sized microphone out of paper that could boost your phone’s battery regulating sound. 

The scientists at the Georgia Institute of Technology developed a rollable, paper-based triboelectric nanogenerator (TENG) with 125 μm thickness for harvesting sound wave energy, which is capable of delivering a maximum power density of 121 mW/m² and 968 W/m³ under a sound pressure of 117 dBSPL. The amount of power the microphone provides depends on its size, but it's around 121 milliwatts per square meter. The TENG is designed in the contact-separation mode using membranes that have rationally designed holes at one side.

How this works? The researchers used a laser to zap a grid of microscopic holes in the paper, then coated one side in copper and laid it on top of a thin sheet of Teflon, joining the two sheets at one edge. Sound waves vibrate the two sheets in different ways, causing them to come in and out of contact. This generates an electric charge, similar to the one made when your rub a balloon on your hair, which can charge a phone slowly. The vibration creates an electric charge which can be used to charge a capacitor at the rate of 0.144 V/s.

Literally it does the recycling of sound energy from the environment, where one could get free electricity from the 'waste' sounds all around us. The charge can also be converted into a range of sound frequencies, allowing the initial sounds to be amplified.

What’s a nanogenerator? A nanogenerator is a device that utilizes piezoelectrics, triboelectrics, or paraelectrics, or all three of them, to convert mechanical action, thermal action, or other action into electricity for powering small electronic devices, mostly by converting mechanical energy. Triboelectric nanogenerator (TENG) uses the electrostatic charge created due to the triboelectrification process as a driving force for electron flow to an external load. Using this process today, we can achieve 55 percent energy conversion efficiency, the best so far. To know more about nanogenerators please follow the link to Wiki 

The scientists said the concept and design could be applied to a variety of circumstances for energy harvesting or sensing purposes.  The advantages of a broad working bandwidth, thin structure, and flexibility, a self-powered microphone for sound recording with rolled structure is demonstrated for all-sound recording without an angular dependence. The concept can be extensively applied to a variety of circumstances for either energy-harvesting or sensing purposes, would be toward wearable and flexible electronics, military surveillance, jet engine noise reduction, a low-cost implantable human ear and wireless technology.

The main benefit of such a microphone is that it could harvest acoustic energy to top up a phone charge on the go. The TENG can be implemented onto a commercial cell phone for acoustic energy harvesting from human talking. While the hope is that sound-powered devices could replace conventional chargers soon. It may not produce quite enough energy to do away with current charging methods entirely as it would only provide a small amount of power rather than fully charging the phone.

Transforming sound into battery power is not a novel idea. We first heard of a sound-charging phone that would power itself with the user's voice when a team of Korean researchers revealed their prototype in 2011.  However, it seems much more likely that a sound-powered charging may soon be a reality.