Incorporating hydrogels that respond to physical, chemical or biological stimuli and actuate lens function, these liquid microlenses could advance lab-on-a-chip technologies, optical imaging, medical diagnostics and bio-optical microfluidic systems.
Jiang, a University of Wisconsin-Madison assistant professor of electrical and computer engineering; David Beebe, a professor of biomedical engineering, postdoctoral researcher Liang Dong, and doctoral student Abhiskek Agarwal describe the technology in the Aug. 3 issue of the journal Nature.
At this size-hundreds of microns up to about a millimeter-variable focal length lenses aren't new; however, existing microlenses require external control systems to function, says Beebe. "The ability to respond in autonomous fashion to the local environment is new and unique," he says.
In a lab-on-a-chip environment, for example, a researcher might want to detect a potentially hazardous chemical or biological agent in a tiny fluid sample. Using traditional sensors on microchips is an option for this kind of work-but liquid environments often aren't kind to the electronics, says Jiang.
That's where hydrogels - thick, jellylike polymers - are important. Researchers can tune a hydrogel to be responsive to just about any stimulus parameter, including temperature and pH, says Jiang. So as the hydrogel "senses" the substance of interest, it responds with the programmed reaction. "We use the hydrogel to provide actuation force," he says.
A water-oil interface forms his group's lens, which resides atop a water-filled tube with hydrogel walls. The tube's open top, or aperture, is thin polymer. The researchers applied one surface treatment to the aperture walls and underside, rendering them hydrophilic, or water-attracting. They applied another surface treatment to the top side of the aperture, making them hydrophobic, or water-repelling. Where the hydrophilic and hydrophobic edges meet, the water-oil lens is secured, or pinned, in place.
When the hydrogel swells in response to a substance, the water in the tube bulges up and the lens becomes divergent; when the hydrogel contracts, the water in the tube bows down and the lens becomes convergent. "The smaller the focal length, the closer you can look," says Jiang.
Because they enable researchers to receive optical signals, the lenses may lead to new sensing methods, he says. Researchers could measure light intensity, like fluorescence, or place the lenses at various points along a microfluidic channel to monitor environmental changes. "We've also thought about coupling them to electronics-that is, using electrodes to control the hydrogel," says Beebe. "Then you can think about lots of imaging applications, like locating the lenses at the ends of catheters."
Clustered in an array, the lenses also could enable researchers to take advantage of combinatorial patterns and provide them with more data, he says.
The array format improves upon the natural compound eye, found in most insects and some crustaceans. This eye essentially is a sphere comprised of thousands of smaller lenses, each of which has a fixed focal length. "Since the lenses are fixed, an object has to be a certain distance away for it to be clearly seen," says Jiang. "In some sense, our work is actually better than nature, because we can tune the focal length now so we can scan through a larger range of view field."
Fabricating lenses is a straightforward, inexpensive process that takes just a couple of hours. The real advantage, however, is their autonomous function, says Jiang. "That forms a universal platform," he says. "We have a single structure and we can put different kinds of hydrogels in and they can be responsive to different parameters. By looking at the outputs of these lenses, I know what's going on in that location."
Hongrui Jiang | EurekAlert!
New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology
Light rays from a supernova bent by the curvature of space-time around a galaxy
21.04.2017 | Stockholm University
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...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy