Featured Research

from universities, journals, and other organizations

Metal nanoparticles shine with customizable color

Date:
February 23, 2012
Source:
Harvard University
Summary:
Engineers have demonstrated a new kind of tunable color filter that uses optical nanoantennas to obtain precise control of color output.

The color output of a new type of optical filter created at Harvard depends on the polarization of the incoming light.
Credit: Image courtesy of Tal Ellenbogen.

Engineers at Harvard have demonstrated a new kind of tunable color filter that uses optical nanoantennas to obtain precise control of color output.

Related Articles


Whereas a conventional color filter can only produce one fixed color, a single active filter under exposure to different types of light can produce a range of colors.

The advance has the potential for application in televisions and biological imaging, and could even be used to create invisible security tags to mark currency. The findings appear in the February issue of Nano Letters.

Kenneth Crozier, Associate Professor of Electrical Engineering at the Harvard School of Engineering and Applied Sciences (SEAS), and colleagues have engineered the size and shape of metal nanoparticles so that the color they appear strongly depends on the polarization of the light illuminating them. The nanoparticles can be regarded as antennas -- similar to antennas used for wireless communications -- but much smaller in scale and operating at visible frequencies.

"With the advances in nanotechnology, we can precisely control the shape of the optical nanoantennas, so we can tune them to react differently with light of different colors and different polarizations," said co-author Tal Ellenbogen, a postdoctoral fellow at SEAS. "By doing so, we designed a new sort of controllable color filter."

Conventional RGB filters used to create color in today's televisions and monitors have one fixed output color (red, green, or blue) and create a broader palette of hues through blending. By contrast, each pixel of the nanoantenna-based filters is dynamic and able to produce different colors when the polarization is changed.

The researchers dubbed these filters "chromatic plasmonic polarizers" as they can create a pixel with a uniform color or complex patterns with colors varying as a function of position.

To demonstrate the technology's capabilities, the acronym LSP (short for localized surface plasmon) was created. With unpolarized light or with light which is polarized at 45 degrees, the letters are invisible (gray on gray). In polarized light at 90 degrees, the letters appear vibrant yellow with a blue background, and at 0 degrees the color scheme is reversed. By rotating the polarization of the incident light, the letters then change color, moving from yellow to blue.

"What is somewhat unusual about this work is that we have a color filter with a response that depends on polarization," says Crozier.

The researchers envision several kinds of applications: using the color functionality to present different colors in a display or camera, showing polarization effects in tissue for biomedical imaging, and integrating the technology into labels or paper to generate security tags that could mark money and other objects.

Seeing the color effects from current fabricated samples requires magnification, but large-scale nanoprinting techniques could be used to generate samples big enough to be seen with the naked eye. To build a television, for example, using the nanoantennas would require a great deal of advanced engineering, but Crozier and Ellenbogen say it is absolutely feasible.

Crozier credits the latest advance, in part, to taking a biological approach to the problem of color generation. Ellenbogen, who is, ironically, colorblind, had previously studied computational models of the visual cortex and brought such knowledge to the lab.

"The chromatic plasmonic polarizers combine two structures, each with a different spectral response, and the human eye can see the mixing of these two spectral responses as color," said Crozier.

"We would normally ask what is the response in terms of the spectrum, rather than what is the response in terms of the eye," added Ellenbogen.


Story Source:

The above story is based on materials provided by Harvard University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Tal Ellenbogen, Kwanyong Seo, Kenneth B. Crozier. Chromatic Plasmonic Polarizers for Active Visible Color Filtering and Polarimetry. Nano Letters, 2012; 12 (2): 1026 DOI: 10.1021/nl204257g

Cite This Page:

Harvard University. "Metal nanoparticles shine with customizable color." ScienceDaily. ScienceDaily, 23 February 2012. <www.sciencedaily.com/releases/2012/02/120223221957.htm>.
Harvard University. (2012, February 23). Metal nanoparticles shine with customizable color. ScienceDaily. Retrieved October 30, 2014 from www.sciencedaily.com/releases/2012/02/120223221957.htm
Harvard University. "Metal nanoparticles shine with customizable color." ScienceDaily. www.sciencedaily.com/releases/2012/02/120223221957.htm (accessed October 30, 2014).

Share This



More Matter & Energy News

Thursday, October 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Mind-Controlled Prosthetic Arm Restores Amputee Dexterity

Mind-Controlled Prosthetic Arm Restores Amputee Dexterity

Reuters - Innovations Video Online (Oct. 29, 2014) A Swedish amputee who became the first person to ever receive a brain controlled prosthetic arm is able to manipulate and handle delicate objects with an unprecedented level of dexterity. The device is connected directly to his bone, nerves and muscles, giving him the ability to control it with his thoughts. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Robots Get Funky on the Dance Floor

Robots Get Funky on the Dance Floor

AP (Oct. 29, 2014) Dancing, spinning and fighting robots are showing off their agility at "Robocomp" in Krakow. (Oct. 29) Video provided by AP
Powered by NewsLook.com
Saharan Solar Project to Power Europe

Saharan Solar Project to Power Europe

Reuters - Business Video Online (Oct. 29, 2014) A solar energy project in the Tunisian Sahara aims to generate enough clean energy by 2018 to power two million European homes. Matt Stock reports. Video provided by Reuters
Powered by NewsLook.com
Lowe's Testing Robot Sales Assistants in California Store

Lowe's Testing Robot Sales Assistants in California Store

Buzz60 (Oct. 29, 2014) Lowe’s is testing out what it’s describing as a robotic shopping assistant in one of its Orchard Supply Hardware Stores in California. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins