Tag Archives: Greg Herman

Creating new manufacturing technologies with photonic sintering

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There’s a nice of explanation of nanoparticle sintering, a process which is central to producing new materials, according to a Dec. 1, 2015 Oregon State University (OSU) news release (also on EurekAlert),

Engineers at Oregon State University have made a fundamental breakthrough in understanding the physics of photonic “sintering,” which could lead to many new advances in solar cells, flexible electronics, various types of sensors and other high-tech products printed onto something as simple as a sheet of paper or plastic.

Sintering is the fusing of nanoparticles to form a solid, functional thin-film that can be used for many purposes, and the process could have considerable value for new technologies.

Photonic sintering has the possible advantage of higher speed and lower cost, compared to other technologies for nanoparticle sintering.

The news release goes on to provide some technical details and information about commercialization efforts,

In the new research, OSU experts discovered that previous approaches to understand and control photonic sintering had been based on a flawed view of the basic physics involved, which had led to a gross overestimation of product quality and process efficiency.

Based on the new perspective of this process, which has been outlined in Nature Scientific Reports, researchers now believe they can create high quality products at much lower temperatures, at least twice as fast and with 10 times more energy efficiency.

Removing constraints on production temperatures, speed and cost, the researchers say, should allow the creation of many new high-tech products printed onto substrates as cheap as paper or plastic wrap.

“Photonic sintering is one way to deposit nanoparticles in a controlled way and then join them together, and it’s been of significant interest,” said Rajiv Malhotra, an assistant professor of mechanical engineering in the OSU College of Engineering. “Until now, however, we didn’t really understand the underlying physics of what was going on. It was thought, for instance, that temperature change and the degree of fusion weren’t related – but in fact that matters a lot.”

With the concepts outlined in the new study, the door is open to precise control of temperature with smaller nanoparticle sizes. This allows increased speed of the process and high quality production at temperatures at least two times lower than before. An inherent “self-damping” effect was identified that has a major impact on obtaining the desired quality of the finished film.

“Lower temperature is a real key,” Malhotra said. “To lower costs, we want to print these nanotech products on things like paper and plastic, which would burn or melt at higher temperatures. We now know that is possible, and how to do it. We should be able to create production processes that are both fast and cheap, without a loss of quality.”

Products that could evolve from the research, Malhotra said, include solar cells, gas sensors, radiofrequency identification tags, and a wide range of flexible electronics. Wearable biomedical sensors could emerge, along with new sensing devices for environmental applications.

In this technology, light from a xenon lamp can be broadcast over comparatively large areas to fuse nanoparticles into functional thin films, much faster than with conventional thermal methods. It should be possible to scale up the process to large manufacturing levels for industrial use.

This advance was made possible by a four-year, $1.5 million National Science Foundation Scalable Nanomanufacturing Grant, which focuses on transcending the scientific barriers to industry-level production of nanomaterials. Collaborators at OSU include Chih-hung Chang, Alan Wang and Greg Herman.

OSU researchers will work with two manufacturers in private industry to create a proof-of-concept facility in the laboratory, as the next step in bringing this technology toward commercial production.

Here’s a link to and a citation for the paper,

On the self-damping nature of densification in photonic sintering of nanoparticles by William MacNeill, Chang-Ho Choi, Chih-Hung Chang, & Rajiv Malhotra.  Scientific Reports 5, Article number: 14845 (2015)  doi:10.1038/srep14845 Published online: 07 October 2015

This is an open access paper.

Using your microwave for DIY (do it yourself) solar panels?

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The researchers at Oregon State University seem to think that their discovery will scale up to commercial levels for manufacturing solar panels that are cheaper and easier. Still, if all you need is a microwave, then I imagine some enterprising do-it-yourselfer will give this technique a try.

Microwave oven

This microwave oven technology is being used to produce solar cells with less energy, expense and environmental concerns. (Photo courtesy of Oregon State University Copied from: http://www.flickr.com/photos/oregonstateuniversity/7841150094/in/photostream)

From the Aug. 24, 2012 news item on Nanowerk,

The same type of microwave oven technology that most people use to heat up leftover food has found an important application in the solar energy industry, providing a new way to make thin-film photovoltaic products with less energy, expense and environmental concerns.

Engineers at Oregon State University have for the first time developed a way to use microwave heating in the synthesis of copper zinc tin sulfide, a promising solar cell compound that is less costly and toxic than some solar energy alternatives.

The Oregon State University Aug. 24, 2012 news release which originated the news item provides additional detail about the technology and future plans for commercializing it,

“All of the elements used in this new compound are benign and inexpensive, and should have good solar cell performance,” said Greg Herman, an associate professor in the School of Chemical, Biological and Environmental Engineering at OSU.

“Several companies are already moving in this direction as prices continue to rise for some alternative compounds that contain more expensive elements like indium,” he said. “With some improvements in its solar efficiency this new compound should become very commercially attractive.”

These thin-film photovoltaic technologies offer a low cost, high volume approach to manufacturing solar cells. A new approach is to create them as an ink composed of nanoparticles, which could be rolled or sprayed – by approaches such as old-fashioned inkjet printing – to create solar cells. [emphasis mine]

To further streamline that process, researchers have now succeeded in using microwave heating, instead of conventional heating, to reduce reaction times to minutes or seconds, and allow for great control over the production process. This “one-pot” synthesis is fast, cheap and uses less energy, researchers say, and has been utilized to successfully create nanoparticle inks that were used to fabricate a photovoltaic device.

From a do-it-yourself point of view, this technology sounds even more promising with the mention of an inkjet printer.