Images: Energy-saving sensors

The green field is an electron microscope image of an array of zinc oxide nanowires. In the middle is a drawing of how the probe, from an atomic force microscope, bends the nanowires. The third field shows the voltages produced by the array as it is scanned.

At Intel, researchers are looking at ways to let radio-frequency identification tags exploit energy from RFID readers to perform additional tasks. The sensor detects motion around it. The microprocessor inside the sensor does not run on batteries or electricity from a wall socket, but on energy stored from a blast from an RFID reader.

Joshua Smith of Intel Research Seattle and a WISP light sensor. In an experiment, Smith hung the sensor on his window and it detected light levels for 12 hours. These sensors take an ordinary RFID tag and increase its functionality.

A WISP sensor running a second hand on a watch. If companies can develop microprocessors that require almost no power, sensors can be placed everywhere and their owners won't have to worry about changing the batteries.