Using a method called “intense pulsed light sintering,” or IPL, the researchers used high-energy light over an area nearly 7000 times larger than a laser to fuse nanomaterials in seconds. The existing method of pulsed light fusion uses temperatures of around 250° C (482° F) to fuse silver nanospheres into structures that conduct electricity.
However, a new study, published in the Royal Society of Chemistry’s RSC Advances and led by Rutgers School of Engineering doctoral student Michael Dexter, showed that fusion at 150° C (302° F) works well while retaining the conductivity of the fused silver nanomaterials.
That RSC study, “Controlling processing temperatures and self-limiting behavior in intense pulsed sintering by tailoring nanomaterial shape distribution,” is available at http://pubs.rsc.org/en/content/articlehtml/2017/RA/C7RA11013H.
“Pulsed light sintering of nanomaterials enables really fast manufacturing of flexible devices for economies of scale,” said Rajiv Malhotra, the study’s senior author and assistant professor in the Department of Mechanical and Aerospace Engineering at Rutgers-New Brunswick. “Our innovation extends this capability by allowing cheaper temperature-sensitive substrates to be used.”
The research on IPL of nanomaterials began about 2009. Rutgers researchers, in collaboration with Oregon State Professor Chih-Hung Chang, have been working on IPL since 2015 via funding by the National Science Foundation and the Walmart Manufacturing Innovation Foundation, according to Malhotra. “We are currently working on expanding the capabilities of IPL by looking at rapid and scalable sintering of non-metallic materials on a variety of flexible substrate beyond polymers,” Malhotra added.
The engineers’ achievements started with silver nanomaterials of different shapes: long, thin rods called nanowires in addition to nanospheres. The sharp reduction in temperature needed for fusion makes it possible to use low-cost, temperature-sensitive plastic substrates like polyethylene terephthalate (PET) and polycarbonate in flexible devices without damaging them.
Fused silver nanomaterials are used to conduct electricity in devices such as radio-frequency identification (RFID) tags, display devices and solar cells. Flexible forms of these products rely on fusion of conductive nanomaterials on flexible substrates, or platforms, such as plastics and other polymers.
“The next step is to see whether other nanomaterial shapes, including flat flakes and triangles, will drive fusion temperatures even lower,” Malhotra said.
In another study, “Temperature, Crystalline Phase and Influence of Substrate Properties in Intense Pulsed Light Sintering of Copper Sulfide Nanoparticle Thin Films,” published in Scientific Reports, the Rutgers and Oregon State engineers demonstrated pulsed light sintering of copper sulfide nanoparticles, a semiconductor, to make films less than 100-nm thick.
“We were able to perform this fusion in two to seven seconds compared with the minutes to hours it normally takes now,” said Malhotra, the study’s senior author. “We also showed how to use the pulsed light fusion process to control the electrical and optical properties of the film.”
Their discovery could speed up the manufacturing of copper sulfide thin films used in window coatings that control solar infrared light, transistors, and switches, according to the study. This work was funded by NSF and The Walmart Manufacturing Innovation Foundation.
Malhotra, who graduated from Northwestern University in 2012 with a doctorate in Mechanical Engineering, worked at Oregon State as an assistant professor in 2014 and joined the department of Mechanical and Aerospace Engineering at Rutgers University in 2017. His research focuses on understanding the behavior of materials during manufacturing, often leading to innovation of processes that enable greater performance, lower costs, increased scalability and greater product customization. His work involves combining both computational models and experiments, and his research has recently focused heavily on scalable additive manufacturing with metallic and semiconductor nanomaterials using large-area applied electromagnetic fields.
“IPL has been used to fabricate components of solar cells, RFID devices, microscale touchpads, and personal heaters. We are currently trying to extend the capabilities of IPL towards non-metallic materials and trying to drive down the maximum temperatures during sintering to enable an even wider range of wearable, flexible and conformal devices to be manufactured in a scalable manner,” Malhotra said.
“The IPL method is a proven process for many metallic materials and some non-metallic materials, he added. “We are trying to develop an understanding of the process and the ways in which it affects material properties after IPL so that control of the process and full utilization of its potential capabilities can be achieved,” Malhotra explained. “At the same time, we are currently pursuing industrial collaborations for using IPL for both wearable and conformal devices.”
Tech Papers from SME Journals and Manufacturing LettersThese summaries, excerpts, and web links are from recent papers published in the SME Journal of Manufacturing Systems, Journal of Manufacturing Processes, and Manufacturing Letters, which are printed by Elsevier Ltd. and used here with permission.
Cyber-Human Systems Framework for Cyber-Physical SystemsIn their paper, “A complementary Cyber-Human Systems framework for Industry 4.0 Cyber-Physical Systems,” authors Matthew Krugh and Laine Mears of the Clemson University International Center for Automotive Research, Greenville, SC, describe the human aspect of new cyber-physical manufacturing in emerging automotive manufacturing models. Their paper, to be published in an upcoming issue of Manufacturing Letters, is available online at https://doi.org/10.1016/j.mfglet.2018.01.003.
Humans are a vital element to automotive manufacturing; however, skilled production personnel have largely been designated as data receivers in Cyber-Physical Systems (CPS) of Industry 4.0. A renewed focus on the human worker who completes significant portions of manual value-added content in automotive assembly through Cyber-Human Systems (CHS) is allowing humans to perform their jobs more safely, efficiently, and supporting enhanced control and quality monitoring of manual manufacturing tasks. There is a need for a unified complementary framework of CHS and CPS to guide the implementation of future smart manufacturing systems.
Humans are the backbone of automotive manufacturing; by playing a malleable role in production from master craftsman, to assembly associate, to engineer, the human worker has proven time and again to be manufacturing’s most flexible system. The automotive manufacturing industry is currently embracing Industry 4.0 in which the many disparate data systems are connecting together within an intelligent Cyber-Physical System environment to bridge the real and virtual worlds, to better enable a deeper understanding of the dynamics of manufacturing, but the human’s role in this evolution is not clearly defined.
Current trends in Industry 4.0 automation tend to displace the human worker in automotive manufacturing or places them into a supervisory role such as described by Ohno in 1988 as Autonomation to provide machines with access to higher intelligence. Due to the unique nature of automotive assembly comprising a significant portion of a vehicle’s total production time, and increasing manufacturing complexity requiring highly flexible processes, there has been a demonstrated pushback toward increasing the number of human assembly workers as automation cannot handle the increasing variety in vehicles from manufacturers such as BMW AG, Mercedes, and Toyota. This poses an opportunity to expand the view of human production personnel in Industry 4.0 from predominantly receivers of information to generators, collectors, and users; just as production tools and equipment have been transformed and connected under Industry 4.0, so, too, should the purview of the human capacity to supply, receive, and abstract information.