Featured Research

from universities, journals, and other organizations

Shifting Liquid Crystals May Serve As Personal, Portable Chemical Sensors, Researchers Report In Science

Date:
August 20, 2001
Source:
American Association For The Advancement Of Science
Summary:
Liquid crystals formed from molecules weakly tethered to a nanotextured surface could form the basis of highly sensitive, wearable sensors to detect personal exposure to certain synthetic organic chemicals, researchers report in the 17 August 2001 issue of the journal Science.

Liquid crystals formed from molecules weakly tethered to a nanotextured surface could form the basis of highly sensitive, wearable sensors to detect personal exposure to certain synthetic organic chemicals, researchers report in the 17 August 2001 issue of the journal Science. Such sensors could be used to detect environmental exposure to residential pesticides, monitor chemical markers of food spoilage, and could possibly serve some day as sensors for certain toxic nerve gases such as sarin, according to Science co-author Nicholas L. Abbott of the University of Wisconsin, Madison.

Related Articles


Techniques to detect such compounds already exist, but these methods (like mass spectrometry) are mostly confined to the laboratory--too bulky and complex to provide real-time, portable detection.

"These lab methods are extremely sensitive, but they're never going to be the basis for measuring personal exposure. We wanted to create something that could be worn like a badge, like those worn to detect radiation," says Abbott.

The sensor devised by Abbott and co-author Rahul R. Shah of the 3M Corporation (formerly of University of Wisconsin) consists of an ultrathin gold film with nanoscale corrugation. The surface of the gold film is then dotted with protruding chemical receptors that weakly anchor liquid crystal in a well-defined orientation along the film's surface.

When these receptors are exposed to the specific chemical that is the object of detection, however, they bond more strongly with that target chemical than they do with the liquid crystal. In effect, the target chemical muscles in on the liquid crystal's territory, shoving it away from the receptors. This displaces the liquid crystal into a new orientation that is controlled by the underlying surface texture, and the new orientation is visible to the naked eye as a change in the sensor's color or brightness.

On a surface with carboxylic acid receptors, for instance, exposure to a vapor of the chemical hexylamine caused the liquid crystal to shift from an orientation perpendicular to the gold film's corrugations to an orientation that was parallel with the corrugations. The two orientations are visually distinct, report Shah and Abbott.

The sensors are extremely sensitive--triggered by exposure to parts-per-billion vapor concentrations--and quick, taking only seconds to complete detection and to reset after being removed from exposure, say the Science researchers.

By pairing particular liquid crystals and receptors with specific chemical properties, the sensors can be tailored to detect specific compounds. Multiple receptor/liquid crystal combinations can be patterned over the sensor's surface, allowing simultaneous detection of several different chemicals.

The "competitive binding" mechanism also allows the sensor to tolerate non-targeted compounds, such as water, which can interfere with detection in other types of sensors, says Abbott. In this case, the non-target forms an even weaker bond with the receptor than the liquid crystal, and is unable to dislodge it.

Shah and Abbott's sensors can be used to measure cumulative exposure over time, by measuring the spread of the targeted chemical across the liquid crystal, and the sensor surfaces can also be designed to trigger an instantaneous response upon exposure.

The researchers hope that their sensors will prove useful in food safety applications, such as monitoring levels of putrescine and cadaverine, the smelly compounds produced by rotting fish and meat, as well as sensors to detect exposure to pesticides such as diazinon and parathion.

This research was supported in part by the National Science Foundation and the Office of Naval Research.


Story Source:

The above story is based on materials provided by American Association For The Advancement Of Science. Note: Materials may be edited for content and length.


Cite This Page:

American Association For The Advancement Of Science. "Shifting Liquid Crystals May Serve As Personal, Portable Chemical Sensors, Researchers Report In Science." ScienceDaily. ScienceDaily, 20 August 2001. <www.sciencedaily.com/releases/2001/08/010820072256.htm>.
American Association For The Advancement Of Science. (2001, August 20). Shifting Liquid Crystals May Serve As Personal, Portable Chemical Sensors, Researchers Report In Science. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2001/08/010820072256.htm
American Association For The Advancement Of Science. "Shifting Liquid Crystals May Serve As Personal, Portable Chemical Sensors, Researchers Report In Science." ScienceDaily. www.sciencedaily.com/releases/2001/08/010820072256.htm (accessed October 25, 2014).

Share This



More Matter & Energy News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

IKEA Desk Converts From Standing to Sitting With One Button

IKEA Desk Converts From Standing to Sitting With One Button

Buzz60 (Oct. 24, 2014) IKEA is out with a new convertible desk that can convert from a sitting desk to a standing one with just the push of a button. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com
Ebola Protective Suits Being Made in China

Ebola Protective Suits Being Made in China

AFP (Oct. 24, 2014) A factory in China is busy making Ebola protective suits for healthcare workers and others fighting the spread of the virus. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com
Real-Life Transformer Robot Walks, Then Folds Into a Car

Real-Life Transformer Robot Walks, Then Folds Into a Car

Buzz60 (Oct. 24, 2014) Brave Robotics and Asratec teamed with original Transformers toy company Tomy to create a functional 5-foot-tall humanoid robot that can march and fold itself into a 3-foot-long sports car. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Police Testing New Gunfire Tracking Technology

Police Testing New Gunfire Tracking Technology

AP (Oct. 24, 2014) A California-based startup has designed new law enforcement technology that aims to automatically alert dispatch when an officer's gun is unholstered and fired. Two law enforcement agencies are currently testing the technology. (Oct. 24) Video provided by AP
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