Tag Archives: Chih-Hung Chang

Creating new manufacturing technologies with photonic sintering

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.

Silver nanoparticle production at room temperature

I hadn’t thought silver nanoparticles were important to electronics but it seems I was wrongish. A July 2, 2015 news item on Nanowerk describes a breakthrough in silver nanoparticle production, which could increase its possible impact on electronics,

Engineers at Oregon State University [OSU] have invented a way to fabricate silver, a highly conductive metal, for printed electronics that are produced at room temperature.

There may be broad applications in microelectronics, sensors, energy devices, low emissivity coatings and even transparent displays.

A patent has been applied for on the technology, which is now available for further commercial development. The findings were reported in Journal of Materials Chemistry C. …

A July 1, 2015 OSU news release (also on EurekAlert), which originated the news item, expands on the theme of silver nanoparticles and electronics,

Silver has long been considered for the advantages it offers in electronic devices. Because of its conductive properties, it is efficient and also stays cool. But manufacturers have often needed high temperatures in the processes they use to make the devices, adding to their cost and complexity, and making them unsuitable for use on some substrates, such as plastics that might melt or papers that might burn.

This advance may open the door to much wider use of silver and other conductors in electronics applications, researchers said.

“There’s a great deal of interest in printed electronics, because they’re fast, cheap, can be done in small volumes and changed easily,” said Chih-hung Chang, a professor in the OSU College of Engineering. “But the heat needed for most applications of silver nanoparticles has limited their use.”

OSU scientists have solved that problem by using a microreactor to create silver nanoparticles at room temperatures without any protective coating, and then immediately printing them onto almost any substrate with a continuous flow process.

“Because we could now use different substrates such as plastics, glass or even paper, these electronics could be flexible, very inexpensive and stable,” Chang said. “This could be quite important and allow us to use silver in many more types of electronic applications.”

Among those, he said, could be solar cells, printed circuit boards, low-emissivity coatings, or transparent electronics. A microchannel applicator used in the system will allow the creation of smaller, more complex electronics features.

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

Room temperature fabrication and patterning of highly conductive silver features using in situ reactive inks by microreactor-assisted printing by Chang-Ho Choi, Elizabeth Allan-Cole, and Chih-hung Chang. J. Mater. Chem. C, 2015, Advance Article DOI: 10.1039/C5TC00947B First published online 26 May 2015

I believe this paper is behind a paywall.

Combining optical technology with nanocomposite films at Oregon State University (OSU)

There is a lot of pressure in the US to commercialize nanotechnology-enabled products—a perfectly understandable stance after investing over $22B since 2000. Engineers at Oregon State University (OSU) are hoping to attract industry partners to improve and commercialize their gas sensors (from an April 2, 2015 OSU news release also on EurekAlert),

Engineers have combined innovative optical technology with nanocomposite thin-films to create a new type of sensor that is inexpensive, fast, highly sensitive and able to detect and analyze a wide range of gases.

The technology might find applications in everything from environmental monitoring to airport security or testing blood alcohol levels. The sensor is particularly suited to detecting carbon dioxide, and may be useful in industrial applications or systems designed to store carbon dioxide underground, as one approach to greenhouse gas reduction.

Oregon State University has filed for a patent on the invention, developed in collaboration with scientists at the National Energy Technology Lab or the U.S. Department of Energy, and with support from that agency. The findings were just reported in the Journal of Materials Chemistry C.

University researchers are now seeking industrial collaborators to further perfect and help commercialize the system.

“Optical sensing is very effective in sensing and identifying trace-level gases, but often uses large laboratory devices that are terribly expensive and can’t be transported into the field,” said Alan Wang, a photonics expert and an assistant professor in the OSU School of Electrical Engineering and Computer Science.

“By contrast, we use optical approaches that can be small, portable and inexpensive,” Wang said. “This system used plasmonic nanocrystals that act somewhat like a tiny lens, to concentrate a light wave and increase sensitivity.”

This approach is combined with a metal-organic framework of thin films, which can rapidly adsorb gases within material pores, and be recycled by simple vacuum processes. After the thin film captures the gas molecules near the surface, the plasmonic materials act at a near-infrared range, help magnify the signal and precisely analyze the presence and amounts of different gases.

“By working at the near-infrared range and using these plasmonic nanocrystals, there’s an order of magnitude increase in sensitivity,” said Chih-hung Chang, an OSU professor of chemical engineering. “This type of sensor should be able to quickly tell exactly what gases are present and in what amount.”

That speed, precision, portability and low cost, the researchers said, should allow instruments that can be used in the field for many purposes. The food industry, for industry, uses carbon dioxide in storage of fruits and vegetables, and the gas has to be kept at certain levels.

Gas detection can be valuable in finding explosives, and new technologies such as this might find application in airport or border security. Various gases need to be monitored in environmental research, and there may be other uses in health care, optimal function of automobile engines, and prevention of natural gas leakage.

The paper can be found here,

Plasmonics-enhanced metal–organic framework nanoporous films for highly sensitive near-infrared absorption by Ki-Joong Kim, Xinyuan Chong, Peter B. Kreider, Guoheng Ma,  Paul R. Ohodnicki, John P. Baltrus, Alan X. Wang, and Chih-Hung Chang. J. Mater. Chem. C, 2015,3, 2763-2767 DOI: 10.1039/C4TC02846E First published online 09 Feb 2015

It is behind a paywall.