A flat-screen panel your living room wall that resembles a TV could one day remotely charge smartphones and tablets within its line of sight, making dead batteries a thing of the past, according to new research.

Scientists, from the University of Washington and Duke University in the US, said that the technology already exists to build such a system.

"Whether its headphones, cell phones, watches, or even your mouse and keyboard, a major irritation for consumers is the hassle of being tethered to cords to recharge batteries," said David Smith, professor at Duke.

"Our proposed system would be able to automatically and continuously charge any device anywhere within a room, making dead batteries a thing of the past," said Smith.

"There is an enormous demand for alternatives to today's clunky charging pads and cumbersome cables, which restrict the mobility of a smartphone or a tablet," said Matt Reynolds, associate professor at University of Washington.

"Our proposed approach takes advantage of widely used LCD technology to seamlessly deliver wireless power to all kinds of smart devices," Reynolds said.

"The ability to safely direct focused beams of microwave energy to charge specific devices, while avoiding unwanted exposure to people, pets and other objects, is a game-changer for wireless power," he said.

"We're looking into alternatives to liquid crystals that could allow energy transfer at much higher power levels over greater distances," he added.

Some wireless charging systems already exist to help powerspeakers, cell phones and tablets.

These technologies rely on platforms that require their own wires, however, and the devices must be placed in the immediate vicinity of the charging station, researchers said.

The problem to date has been that the antennas in a wireless power transfer system would need to be able to focus on any device within a room.

This could be done with a movable antenna dish, but that would take up too much space, and nobody wants a big, moving satellite dish on their mantel, researchers said.

Another solution is a phased array – an antenna with a lot of tiny antennas grouped together, each of which can be independently adjusted and tuned.

That technology also exists, but would cost too much and consume too much energy for household use.

The solution proposed in the new study instead relies on metamaterials – a synthetic material composed of many individual, engineered cells that together produce properties not found in nature.