A new method that creates large-area patterns of three-dimensional nanoshapes from metal sheets represents a potential manufacturing system to inexpensively mass produce innovations such as "plasmonic metamaterials" for advanced technologies.
The metamaterials have engineered surfaces that contain features, patterns or elements on the scale of nanometers that enable unprecedented control of light and could bring innovations such as high-speed electronics, advanced sensors and solar cells.
The new method, called laser shock imprinting, creates shapes out of the crystalline forms of metals, potentially giving them ideal mechanical and optical properties using a bench-top system capable of mass producing the shapes inexpensively
Findings are detailed in a research paper appearing Friday (Dec. 12) in the journal Science. The paper is authored by researchers from Purdue University, Harvard University, Madrid Institute for Advanced Studies, and the University of California, San Diego. The research is led by Gary Cheng, an associate professor of industrial engineering at Purdue.
The shapes, which include nanopyramids, gears, bars, grooves and a fishnet pattern, are too small to be seen without specialized imaging instruments and are thousands of times thinner than the width of a human hair. The researchers used their technique to stamp nanoshapes out of titanium, aluminum, copper, gold and silver.
A key benefit of the shock-induced forming is sharply defined corners and vertical features, or high-fidelity structures.
"These nanoshapes also have extremely smooth surfaces, which is potentially very advantageous for commercial applications," Cheng said. "Traditionally it has been really difficult to deform a crystalline material into a nanomold much smaller than the grain size of starting materials, and due to the size effects the materials are super-strong when grain size has to be reduced to very small sizes. Therefore, it is very challenging to generate metal flow into nanomolds with high-fidelity 3-D shaping."
The researchers also created hybrid structures that combine metal with graphene, an ultrathin sheet of carbon promising for various technologies. Such a hybrid material could enhance the plasmonic effect and bring "metamaterial perfect absorbers," or MPAs, which have potential applications in optoelectronics and wireless communications.
"We can generate nanopatterns on metal-graphene hybrid materials, which opens new ways to pattern 2-D crystals," Cheng said.
The technique works by using a pulsed laser to generate "high strain rate" imprinting of metals into the nanomold.
"We start with a metal thin film, and we can deform it into 3-D nanoshapes patterned over large areas," Cheng said. "What is more interesting is that the resulting 3-D nanostructures are still crystalline after the imprinting process, which provides good electromagnetic and optical properties."
Whereas other researchers have created nanoshapes out of relatively soft or amorphous materials, the new research shows how to create nanoshapes out of hard and crystalline metals.
The silicon nanomolds were fabricated at the Birck Nanotechnology Center in Purdue's Discovery Park by a research group led by Minghao Qi, an associate professor of electrical and computer engineering.
"It is counter-intuitive to use silicon for molds because it is a pretty brittle material compared to metals," Qi said. "However, after we deposit an ultrathin layer of aluminum oxide on the nanomolds, it performs extremely well for this purpose. The nanomolds could be reused many times without obvious damage. Part of the reason is that although the strain rate is very high, the shock pressure applied is only about 1-2 gigapascals."
The shapes were shown to have an "aspect ratio" as high as 5, meaning the height is five times greater than the width, an important feature for the performance of plasmonic metamaterials.
"It is a very challenging task from a fabrication point of view to create ultra-smooth, high-fidelity nanostructures," Qi says. "Normally when metals recrystallize they form grains and that makes them more or less rough. Previous trials to form metal nanostructures have had to resort to very high pressure imprinting of crystalline metals or imprinting amorphous metal, which either yields high roughness in crystalline metals or smooth surfaces in amorphous metals but very high electrical resistance. For potential applications in nanoelectronics, optoelectronics and plasmonics you want properties such as high precision, low electromagnetic loss, high electrical and thermal conductivity. You also want it to be very high fidelity in terms of the pattern, sharp corners, vertical sidewalls, and those are very difficult to obtain. Before Gary's breakthrough, I thought it unlikely to achieve all of the good qualities together."
The paper was authored by Purdue doctoral students Huang Gao, Yaowu Hu, Ji Li, and Yingling Yang; researcher Ramses V. Martinez from Harvard and Madrid Institute for Advanced Studies; Purdue research assistant professor Yi Xuan, Purdue research associate Chunyu Li; Jian Luo, a professor at the University of California, San Diego; Qi and Cheng.
Future research may focus on using the technique to create a roll-to-roll manufacturing system, which is used in many industries including paper and sheet-metal production and may be important for new applications such as flexible electronics and solar cells.
The work was supported by the National Science Foundation, National Institutes of Health, Defense Threat Reduction Agency, Office of Naval Research and the National Research Council.
Writer: Emil Venere, 765-494-4709, email@example.com
Sources: Gary J. Cheng, 765-494-5436, firstname.lastname@example.org
Minghao Qi, 765-494-3646, email@example.com
Note to Journalists: A copy of the article is available by contacting the Science Press Package team at 202-326-6440, firstname.lastname@example.org
Large Scale Nanoshaping of Ultrasmooth 3D Crystalline Metallic Structures
Huang Gao1,3,*, Yaowu Hu1,3,*, Yi Xuan2,3,*, Ji Li1,3, Yingling Yang1,3, Ramses V. Martinez4,5, Chunyu Li3,6, Jian Luo7, Minghao Qi2,3, Gary J. Cheng1,3,8†
1 School of Industrial Engineering, Purdue University
2 School of Electrical and Computer Engineering, Purdue University
3 Birck Nanotechnology Center, Purdue University
4 Department of Chemistry and Chemical Biology, Harvard University
5 Madrid Institute for Advanced Studies, IMDEA Nanoscience, Ciudad Universitaria de Cantoblanco
6 School of Materials Engineering, Purdue University
7 Department of NanoEngineering, University of California San Diego
8 School of Mechanical Engineering, Purdue University
* These authors contributed equally to this work
† Corresponding author. E-mail: email@example.com
This paper reports a low-cost, high-throughput, benchtop method that enables thin layers of metal to be shaped with nanoscale precision by generating ultrahigh-strain-rate deformations. Laser shock imprinting can create 3D crystalline metallic structures as small as 10 nm with ultrasmooth surfaces at ambient conditions. This technique enables the successful fabrications of large-area, uniform nanopatterns with aspect ratios as high as 5 for plasmonic and sensing applications, as well as mechanically strengthened nanostructures and metal-graphene hybrid
Emil Venere | EurekAlert!
Innovative process for environmentally friendly manure treatment comes onto the market
03.05.2018 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
No compromises: Combining the benefits of 3D printing and casting
23.03.2018 | Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences