Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Swelling Stacks

31.03.2014

Optical components made of multiresponsive microgels

“Intelligent” materials that can respond to external stimuli are high on the wish lists of many scientists because of their possible usefulness in various applications from sensors to microrobotics. Canadian researchers are working with polymer-based microgels that can swell and shrink.

In the journal Angewandte Chemie, they introduce tiny, stacked structures of microgels whose optical properties change in response to light, changes in pH value, or temperature. They can also detect nerve gases.

Gels are cross-linked molecules that can hold a liquid within their “loops”, which makes them swell up; microgels are "small" colloidally stable gel particles. The microgels being investigated by Michael J. Serpe and his team at the University of Alberta are swollen at temperatures below 32 °C; at higher temperatures they collapse and shrink.

The researchers used these materials to make small stacked structures called etalons: they enclosed a whisper-thin layer of microgel between two thin layers of gold. When the gel swells up, the two sheets of gold move farther apart, when it shrinks they get closer to each other. The optical properties of the stack change significantly as the distance between the gold layers changes, meaning that they “respond” to a change in temperature.

However, the goal is to make the gels react to other stimuli besides temperature. The researchers thus also incorporated triphenylmethane leucohydroxide (TPL) into their microgels. This substance is a true jack-of-all-trades that makes the microgels receptive to a variety of stimuli.

Now irradiation with red laser light, which is absorbed by the TPL, leads to a local rise in temperature within the microgel, which causes the distance between the gold layers to decrease. In contrast, irradiation with UV light excites the TPL molecules so that they dissociate into leuco cations and hydroxy anions. The charges of these ions cause the microgel to absorb additional water—increasing the distance between the gold layers.

These effects make the microgel stacks interesting for the production of adjustable optical components. Another possible application is for drug delivery with remote triggering: when a diseased area of the body is irradiated with high-wavelength light through the skin, the drug contained in the transporter can be released selectively in only the desired location.

The microgel also reacts to a change in pH value: an acidic pH causes the formation of leuco cations, whose positive charge causes the gel to swell by taking up water. If the pH is raised back up, the microgel shrinks. This could be used for the selective release of antitumor drugs because tumors often have a somewhat different pH value than the surrounding tissue.

Interestingly, organophosphates react with TPL molecules, also forming leuco cations. The resulting swelling of the microgel and changes in the optical properties of the stacks could be used for the quantitative detection of nerve gases like tabun.

About the Author

Dr. Michael J. Serpe is an Assistant Professor in the Department of Chemistry at the University of Alberta. His research is focused on using polymer-based materials for multiple applications; with a particular focus on developing novel point of care diagnostics, water remediation systems, and polymer-based muscles and actuators. He was recently named a Grand Challenges Canada Rising Star in Global Health, received the 2013 Petro Canada Young Innovator Award, and has been named one of Edmonton's Top 40 Under 40 by Avenue Magazine for 2013-2014.

Author: Michael J. Serpe, University of Alberta, Edmonton (Canada), http://www.chem.ualberta.ca/~serpe/Serpe_Group/Serpe_Group_Home.html

Title: Optical Devices Constructed from Multiresponsive Microgels

Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201402641

Michael J. Serpe | Angewandte Chemie

Further reports about: gases materials microgels shrink skin stimuli structures temperature temperatures

More articles from Life Sciences:

nachricht How to become a T follicular helper cell
31.07.2015 | La Jolla Institute for Allergy and Immunology

nachricht Heating and cooling with light leads to ultrafast DNA diagnostics
31.07.2015 | University of California - Berkeley

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum Matter Stuck in Unrest

Using ultracold atoms trapped in light crystals, scientists from the MPQ, LMU, and the Weizmann Institute observe a novel state of matter that never thermalizes.

What happens if one mixes cold and hot water? After some initial dynamics, one is left with lukewarm water—the system has thermalized to a new thermal...

Im Focus: On the crest of the wave: Electronics on a time scale shorter than a cycle of light

Physicists from Regensburg and Marburg, Germany have succeeded in taking a slow-motion movie of speeding electrons in a solid driven by a strong light wave. In the process, they have unraveled a novel quantum phenomenon, which will be reported in the forthcoming edition of Nature.

The advent of ever faster electronics featuring clock rates up to the multiple-gigahertz range has revolutionized our day-to-day life. Researchers and...

Im Focus: Superfast fluorescence sets new speed record

Plasmonic device has speed and efficiency to serve optical computers

Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second and could form the basis of optical computing.

Im Focus: Unlocking the rice immune system

Joint BioEnergy Institute study identifies bacterial protein that is key to protecting rice against bacterial blight

A bacterial signal that when recognized by rice plants enables the plants to resist a devastating blight disease has been identified by a multi-national team...

Im Focus: Smarter window materials can control light and energy

Researchers in the Cockrell School of Engineering at The University of Texas at Austin are one step closer to delivering smart windows with a new level of energy efficiency, engineering materials that allow windows to reveal light without transferring heat and, conversely, to block light while allowing heat transmission, as described in two new research papers.

By allowing indoor occupants to more precisely control the energy and sunlight passing through a window, the new materials could significantly reduce costs for...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Euro Bio-inspired - International Conference and Exhibition on Bio-inspired Materials

23.07.2015 | Event News

Clash of Realities – International Conference on the Art, Technology and Theory of Digital Games

10.07.2015 | Event News

World Conference on Regenerative Medicine in Leipzig: Last chance to submit abstracts until 2 July

25.06.2015 | Event News

 
Latest News

Tool making and additive technology exhibition: Fraunhofer IPT at Formnext

31.07.2015 | Trade Fair News

First Siemens-built Thameslink train arrives in London

31.07.2015 | Transportation and Logistics

California 'rain debt' equal to average full year of precipitation

31.07.2015 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>