A new sensor device uses "thousands of nanometer-scale wires" to covert pressure into visible light signals.
The system works on fingerprints, signatures, and other similar imprints. It could also be used for "biological imaging and micro-electromechanical (MEMS) systems," a Georgia Tech press release reported.
"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," Zhong Lin Wang , Regents' professor and Hightower Chair in the School of Materials Science and Engineering at Georgia Tech, said. "This is a new principle for imaging force that uses parallel detection and avoids many of the complications of existing pressure sensors."
"Individual zinc oxide (ZnO) nanowires" act as light-up diodes to relay information about the applied pressure.
The technology, known as piezo-phototronics, "provides a new way to capture information about pressure applied at very high resolution: up to 6,300 dots per inch," the press release stated.
"When you have a zinc oxide nanowire under strain, you create a piezoelectric charge at both ends which forms a piezoelectric potential," Wang said. "The presence of the potential distorts the band structure in the wire, causing electrons to remain in the p-n junction longer and enhancing the efficiency of the LED."
The nanowires create "pixeled light emitters," that act accordingly with the amount of pressure applied.
The team grew the nanowires on a gallium nitride thin film substrate, IEEE Spectrum reported.
The researchers added a polymer to close the gap between the nanowires.
"A nickel-gold electrode is then attached to the gallium-nitride film to form an ohmic contact, and a transparent indium-tin oxide (ITO) film is deposited on top of the array to serve as a common electrode," IEEE Spectrum reported.
Applying pressure to the nanowires, such as writing a signature, compresses them in their axial directions "creating a negative piezo-potential, while uncompressed nanowires have no potential," the press release reported.
The researchers found that when they pressed a letter into the top of the device, corresponding light came out the bottom. Switching between modes takes only about 90 milliseconds.
"The response time is fast, and you can read a million pixels in a microsecond," Wang said. "When the light emission is created, it can be detected immediately with the optical fiber."