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 Invasive Plants Influence an Ecosystem
28.07.2016 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Perseus translates proteomics data
27.07.2016 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Self-assembling nano inks form conductive and transparent grids during imprint

Transparent electronics devices are present in today’s thin film displays, solar cells, and touchscreens. The future will bring flexible versions of such devices. Their production requires printable materials that are transparent and remain highly conductive even when deformed. Researchers at INM – Leibniz Institute for New Materials have combined a new self-assembling nano ink with an imprint process to create flexible conductive grids with a resolution below one micrometer.

To print the grids, an ink of gold nanowires is applied to a substrate. A structured stamp is pressed on the substrate and forces the ink into a pattern. “The...

Im Focus: The Glowing Brain

A new Fraunhofer MEVIS method conveys medical interrelationships quickly and intuitively with innovative visualization technology

On the monitor, a brain spins slowly and can be examined from every angle. Suddenly, some sections start glowing, first on the side and then the entire back of...

Im Focus: Newly discovered material property may lead to high temp superconductivity

Researchers at the U.S. Department of Energy's (DOE) Ames Laboratory have discovered an unusual property of purple bronze that may point to new ways to achieve high temperature superconductivity.

While studying purple bronze, a molybdenum oxide, researchers discovered an unconventional charge density wave on its surface.

Im Focus: Mapping electromagnetic waveforms

Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.

Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...

Im Focus: Continental tug-of-war - until the rope snaps

Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases

Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

GROWING IN CITIES - Interdisciplinary Perspectives on Urban Gardening

15.07.2016 | Event News

SIGGRAPH2016 Computer Graphics Interactive Techniques, 24-28 July, Anaheim, California

15.07.2016 | Event News

Partner countries of FAIR accelerator meet in Darmstadt and approve developments

11.07.2016 | Event News

 
Latest News

World first demo of labyrinth magnetic-domain-optical Q-switched laser

28.07.2016 | Information Technology

New material could advance superconductivity

28.07.2016 | Materials Sciences

CO2 can be stored underground for 10 times the length needed to avoid climatic impact

28.07.2016 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>