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
Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel
Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Materials Sciences
26.04.2017 | Agricultural and Forestry Science
26.04.2017 | Physics and Astronomy