ZnO nanowires enable creation of pressure sensor with optical output

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Researchers at the Georgia Institute of Technology have developed a sensor device that converts mechanical pressure into light signals that can be captured and processed optically.

Beyond collecting signatures and fingerprints, the sensor could provide an artificial sense of touch and be used in biological imaging and MEMS systems. Ultimately, says the research team, the sensor could provide a new approach for human-machine interfaces. "You can write with your pen and the sensor will optically detect what you write at high resolution and with a very fast response rate," said Professor Zhong Lin Wang. "This is a new principle for imaging force that uses parallel detection and avoids many of the complications of existing pressure sensors." Based on an approach called piezo-photronics, the sensor comprises zinc oxide (ZnO) nanowires grown on a GaN film, with the nanowires operating as tiny LEDs when placed under strain. The sensor provides the ability to see all of the emitters simultaneously, bring a quick response. "The response time is fast and you can read 1million pixels in a microsecond," said Prof Wang. "When the light emission is created, it can be detected immediately with the optical fibre." The nanowires stop emitting light when the pressure is relieved, switching on or off in 90ms or less, Prof Wang added. A spatial resolution of 2.7µm has been achieved with samples tested so far, but Prof Wang believes the resolution could be improved, not only by reducing the diameter of the nanowires, but also by using a high temperature fabrication process.