Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Device for capturing signatures uses tiny LEDs created with piezo-phototronic effect: Your signature in lights

This schematic shows a device for imaging pressure distribution by the piezo-phototronic effect. The illustration shows a nanowire-LED based pressure sensor array before (a) and after (b) applying a compressive strain. A convex character pattern, such as "ABC," molded on a sapphire substrate, is used to apply the pressure pattern on the top of the indium-tin oxide (ITO) electrode.

Credit: Courtesy of Zhong Lin Wang
This schematic shows a device for imaging pressure distribution by the piezo-phototronic effect. The illustration shows a nanowire-LED based pressure sensor array before (a) and after (b) applying a compressive strain. A convex character pattern, such as "ABC," molded on a sapphire substrate, is used to apply the pressure pattern on the top of the indium-tin oxide (ITO) electrode.

Credit: Courtesy of Zhong Lin Wang

Abstract:
Researchers at the Georgia Institute of Technology want to put your signature up in lights - tiny lights, that is. Using thousands of nanometer-scale wires, the researchers have developed a sensor device that converts mechanical pressure - from a signature or a fingerprint - directly into light signals that can be captured and processed optically.

Device for capturing signatures uses tiny LEDs created with piezo-phototronic effect: Your signature in lights

Atlanta, GA | Posted on August 12th, 2013

The sensor device could provide an artificial sense of touch, offering sensitivity comparable to that of the human skin. Beyond collecting signatures and fingerprints, the technique could also be used in biological imaging and micro-electromechanical (MEMS) systems. Ultimately, it 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 Zhong Lin Wang, Regents' professor and Hightower Chair in the School of Materials Science and Engineering at Georgia Tech. "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 that are part of the device operate as tiny light emitting diodes (LEDS) when placed under strain from the mechanical pressure, allowing the device to provide detailed information about the amount of pressure being applied. Known as piezo-phototronics, the technology - first described by Wang in 2009 - provides a new way to capture information about pressure applied at very high resolution: up to 6,300 dots per inch.

The research was scheduled to be reported August 11 in the journal Nature Photonics. It was sponsored by the U.S. Department of Energy's Office of Basic Energy Sciences, the National Science Foundation, and the Knowledge Innovation Program of the Chinese Academy of Sciences.

Piezoelectric materials generate a charge polarization when they are placed under strain. The piezo-phototronic devices rely on that physical principle to tune and control the charge transport and recombination by the polarization charges present at the ends of individual nanowires. Grown atop a gallium nitride (GaN) film, the nanowires create pixeled light emitters whose output varies with the pressure, creating an electroluminescent signal that can be integrated with on-chip photonics for data transmission, processing and recording.

"When you have a zinc oxide nanowire under strain, you create a piezoelectric charge at both ends which forms a piezoelectric potential," Wang explained. "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 efficiency increase in the LED is proportional to the strain created. Differences in the amount of strain applied translate to differences in light emitted from the root where the nanowires contact the gallium nitride film.

To fabricate the devices, a low-temperature chemical growth technique is used to create a patterned array of zinc oxide nanowires on a gallium nitride thin film substrate with the c-axis pointing upward. The interfaces between the nanowires and the gallium nitride film form the bottom surfaces of the nanowires. After infiltrating the space between nanowires with a PMMA thermoplastic, oxygen plasma is used to etch away the PMMA enough to expose the tops of the zinc oxide nanowires.

A nickel-gold electrode is then used to form ohmic contact with the bottom gallium-nitride film, and a transparent indium-tin oxide (ITO) film is deposited on the top of the array to serve as a common electrode.

When pressure is applied to the device through handwriting, nanowires are compressed along their axial directions, creating a negative piezo-potential, while uncompressed nanowires have no potential.

The researchers have pressed letters into the top of the device, which produces a corresponding light output from the bottom of the device. This output - which can all be read at the same time - can be processed and transmitted.

The ability to see all of the emitters simultaneously allows the device to provide a quick response. "The response time is fast, and you can read a million pixels in a microsecond," said Wang. "When the light emission is created, it can be detected immediately with the optical fiber."

The nanowires stop emitting light when the pressure is relieved. Switching from one mode to the other takes 90 milliseconds or less, Wang said.

The researchers studied the stability and reproducibility of the sensor array by examining the light emitting intensity of the individual pixels under strain for 25 repetitive on-off cycles. They found that the output fluctuation was approximately five percent, much smaller than the overall level of the signal. The robustness of more than 20,000 pixels was studied.

A spatial resolution of 2.7 microns was recorded from the device samples tested so far. Wang believes the resolution could be improved by reducing the diameter of the nanowires - allowing more nanowires to be grown - and by using a high-temperature fabrication process.

In addition to Wang, the research team also included Caofeng Pan, Lin Dong, Guang Zhu, Simiao Niu, Ruomeng Yo, Qing Yang and Ying Liu, all associated with Georgia Tech. In addition, Pan is associated with the Beijing Institute of Nanoenergy and Nanosystems in the Chinese Academy of Sciences.

This research was supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-07ER46394; the National Science Foundation (NSF) under award CMMI-040367; and by the Knowledge Innovation program of the Chinese Academy of Sciences under KJCX2-YW-M13. The opinions and conclusions expressed are those of the authors and do not necessarily represent the official views of the DOE or NSF.

####

For more information, please click here

Contacts:
John Toon

404-894-6986

Copyright © Georgia Institute of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Affordable STM32 Cloud-Connectable Kit from STMicroelectronics Puts More Features On-Board for Fast and Flexible IoT-Device Development April 26th, 2017

Geoffrey Beach: Drawn to explore magnetism: Materials researcher is working on the magnetic memory of the future April 25th, 2017

Using light to propel water : With new method, MIT engineers can control and separate fluids on a surface using only visible light April 25th, 2017

Nanoparticle vaccine shows potential as immunotherapy to fight multiple cancer types April 24th, 2017

Imaging

Nanoparticles open new window for biological imaging: “Quantum dots” that emit infrared light enable highly detailed images of internal body structures April 10th, 2017

The Catholic University of Rome uses the JPK NanoWizard® AFM & CellHesion® systems to understand how cells sense and respond to mechanical stimuli April 5th, 2017

Tiny sensor lays groundwork for precision X-rays detection via endoscopy:Nanoscale fiber-integrated X-ray sensor opens new doors for medical imaging and radiotherapy March 29th, 2017

“Cysteine Rose” Wins 2016 Thermo Fisher Scientific Electron Microscopy Image Contest: Thermo Fisher honors Andrea Jacassi of the Italian Institute of Technology for image of cysteine crystals using focused ion beam techniques March 27th, 2017

Cryo-electron microscopy achieves unprecedented resolution using new computational methods March 25th, 2017

Display technology/LEDs/SS Lighting/OLEDs

New ultrafast flexible and transparent memory devices could herald new era of electronics April 1st, 2017

Research opens door to smaller, cheaper, more agile communications tech February 16th, 2017

Dual-function nanorod LEDs could make multifunctional displays February 11th, 2017

Law enforcement/Anti-Counterfeiting/Security/Loss prevention

Leti Announces Backside Shield that Protects Microchips from Physical Attacks March 8th, 2017

NUS engineers develop low-cost, flexible terahertz radiation source for fast, non-invasive screening: Novel invention presents promising applications in spectroscopy, safety surveillance, cancer diagnosis, imaging and communication February 1st, 2017

Govt.-Legislation/Regulation/Funding/Policy

Graphene holds up under high pressure: Used in filtration membranes, ultrathin material could help make desalination more productive April 24th, 2017

Nanoparticle vaccine shows potential as immunotherapy to fight multiple cancer types April 24th, 2017

NanoMONITOR shares its latest developments concerning the NanoMONITOR Software and the Monitoring stations April 21st, 2017

Better living through pressure: Functional nanomaterials made easy April 19th, 2017

MEMS

Smart multi-layered magnetic material acts as an electric switch: New study reveals characteristic of islands of magnetic metals between vacuum gaps, displaying tunnelling electric current March 1st, 2017

Engineers shrink microscope to dime-sized device February 17th, 2017

Leti Coordinating Project to Adapt Obstacle-Detection Technology Used in Autonomous Cars for Portable and Wearable Systems: INSPEX to Combine Knowhow of Nine European Organizations to Create Portable and Wearable Spatial-Exploration Systems February 2nd, 2017

Manufacturing platform makes intricate biocompatible micromachines January 7th, 2017

Sensors

Better living through pressure: Functional nanomaterials made easy April 19th, 2017

A Sensitive And Dynamic Tactile Sensor Read more from Asian Scientist Magazine at: https://www.asianscientist.com/2017/04/tech/tactile-3d-active-matrix-sensor/ April 18th, 2017

AIM Photonics Presents Cutting-Edge Integrated Photonics Technology Developments to Packed House at OFC 2017, the Optical Networking and Communication Conference & Exhibition April 11th, 2017

New technology could offer cheaper, faster food testing: Specialized droplets interact with bacteria and can be analyzed using a smartphone April 7th, 2017

Discoveries

Geoffrey Beach: Drawn to explore magnetism: Materials researcher is working on the magnetic memory of the future April 25th, 2017

Using light to propel water : With new method, MIT engineers can control and separate fluids on a surface using only visible light April 25th, 2017

Graphene holds up under high pressure: Used in filtration membranes, ultrathin material could help make desalination more productive April 24th, 2017

Nanoparticle vaccine shows potential as immunotherapy to fight multiple cancer types April 24th, 2017

Announcements

Affordable STM32 Cloud-Connectable Kit from STMicroelectronics Puts More Features On-Board for Fast and Flexible IoT-Device Development April 26th, 2017

Geoffrey Beach: Drawn to explore magnetism: Materials researcher is working on the magnetic memory of the future April 25th, 2017

Using light to propel water : With new method, MIT engineers can control and separate fluids on a surface using only visible light April 25th, 2017

Graphene holds up under high pressure: Used in filtration membranes, ultrathin material could help make desalination more productive April 24th, 2017

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

Using light to propel water : With new method, MIT engineers can control and separate fluids on a surface using only visible light April 25th, 2017

Graphene holds up under high pressure: Used in filtration membranes, ultrathin material could help make desalination more productive April 24th, 2017

Nanoparticle vaccine shows potential as immunotherapy to fight multiple cancer types April 24th, 2017

Russian scientists create new system of concrete building structures: Sientists of Peter the Great Saint-Petersburg Polytechnic University developed a new construction technology April 24th, 2017

Research partnerships

Better living through pressure: Functional nanomaterials made easy April 19th, 2017

Shedding light on the absorption of light by titanium dioxide April 14th, 2017

AIM Photonics Presents Cutting-Edge Integrated Photonics Technology Developments to Packed House at OFC 2017, the Optical Networking and Communication Conference & Exhibition April 11th, 2017

Nanoparticles open new window for biological imaging: “Quantum dots” that emit infrared light enable highly detailed images of internal body structures April 10th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project