Category Archives: Laser Applications

Inventors Synthesize Graphene with Lasers

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As featured in the LIA TODAY

By Liliana Caldero

Graphene – it’s the two-dimensional (2D) allotrope of carbon atoms that ignited the imaginations of researchers across the globe. Heralded as a ‘miracle material’, its potential seemed limitless and it was predicted to usher in the next generation of technology. Flexible, stronger than steel, transparent, lightweight, and an amazing conductor of heat and electricity, it was going to revolutionize everything from household electronics to biomedical nanotechnology.

 

THE PROBLEM

Yet, nearly eight years after Dr. Andre Geim and Dr. Konstantin Novoselov earned the Nobel Prize in Physics for first isolating graphene and identifying its properties, graphene has encountered barriers to moving out of the lab and into the marketplace. According to Prof. Dr. Aravinda Kar of the University of Central Florida’s Center for Research and Education in Optics and Lasers (CREOL), one of the most prominent barriers has been finding scalable manufacturing processes that can produce graphene of a quality and quantity ready for consumers and businesses.

Graphene is notoriously difficult to synthesize in large quantities at a consistent quality. Early methods of isolating graphene involved a slow and tedious mechanical exfoliation technique; the researchers would extract a thin layer of graphite from a graphite crystal using regular adhesive tape, continually reducing the graphite sample by sticking the tape together and pulling it apart until only a small, 2D section of carbon atoms with a honeycomb lattice remained. Graphene’s unique characteristics are only present when it is one, two, or three layers of atoms thick – any thicker and it becomes graphite, losing all of the exceptional properties of graphene. The tape exfoliation method, although useful for the lab, was not going to translate very well to an industrialized process.

 

SOLVENT-AIDED EXFOLIATION AND CVD

Two of the more promising and potentially scalable methods of producing graphene are solvent-aided exfoliation and chemical vapor deposition (CVD). In solvent-aided exfoliation, sonication is used to exfoliate graphene crystals which are then further separated in a solvent and later gathered into graphene monolayers.  Scientists at the National University of Singapore have identified a flocculation method that reduces the amount of solvent needed for their exfoliation process, which could yield graphene using far less solvent than was previously needed. Another method experiencing innovation is CVD, which uses thermal chemical reactions to ‘grow’ graphene on substrates of specific materials, typically copper or silicon. Recently, engineers at MIT developed a CVD process for producing graphene filtration membrane sheets at 5 cm per minute. One of the biggest issues with traditional CVD and exfoliation methods is the need to transfer graphene from its fabrication platform to a substrate. Lasers are going to change that.

 

THE MISSING PIECE – LASERS

Lasers may provide yet another avenue to the elusive mass production of graphene, with an eye toward innovating the semiconductor industry. In 2003, Kar, along with Dr. Islam Salama and Dr. Nathaniel Quick, realized that laser direct writing could be used to fabricate carbon-rich nanoribbons on a silicon carbide (SiC) wafer in a nitrogen rich environment. Although these ribbons were too thick to be considered graphene, Kar believed that with a few changes, this process could be reworked to synthesize graphene in situ on a large scale, very quickly. In 2013, Kar and Quick were issued a patent for a Laser Chemical Vapor Deposition (LCVD) method that could be scaled for mass production.

Their method involved a few simple components: a frequency doubled Nd:YAG (green) laser of 532 nm wavelength, methane (CH4) gas, a silicon substrate, and a vacuum chamber.

The 532 nm wavelength corresponds to a photon of energy 2.33 eV, so the energy of two photons is 4.66 eV, just within the range of the C-H bond energy (4.3-4.85 eV) in CH4. Focusing the laser beam to a high intensity can induce two-photon absorption at the focal plane, causing the decomposition of CH4 to release the hydrogen atoms and deposit carbon atoms only on the substrate. The laser heating of the silicon substrate is just low enough to avoid melting the silicon, while providing sufficient thermal and electromagnetic energies to assist the carbon-carbon bonds rearrange into graphene’s trademark hexagonal pattern.

An experimental set-up for multiphoton photolytic laser chemical vapor deposition (LCVD) of graphene from methane precursor. Image courtesy of Dr. Kar and Dr. Quick.

LASER DIRECT WRITING OF GRAPHENE

Kar believes this process could be adapted to add graphene directly onto any substrate. Using laser direct writing, a company could easily draw graphene circuits onto a board. For companies using a hybrid approach, the graphene could be deposited at precise points as interconnects. “You would have all the CAD/CAM capability you could want,” says Quick. Currently, green lasers are available at high output powers, 100 W in continuous wave mode from most large laser manufacturers, so adding this additional step to the manufacturing pipeline for semiconductors would be easy and inexpensive compared to other methods.

At 1.9 cm per second, or 45 inches per minute, this method of graphene production is fast and efficient. This LCVD method offers control over the number of graphene layers, whether one, two, or three are required.  This process also removes the need to manually place graphene onto its intended location, as it is synthesized precisely where it should be. It’s also worth mentioning that this process is conducive to minimal environmental impact, as the unreacted methane and hydrogen byproducts can be captured to be recycled and reused.

 

A LOOK AT THE FUTURE

Picture this: a template is placed over a substrate and a line-shaped laser beam sweeps over it briefly or a beam of large cross-sectional area illuminates the entire template in one shot; when the template is removed, an intricate graphene design has been printed onto a circuit board. That is the future that Kar says is possible, with the right equipment. He suggests that we need manufacturers to develop lasers producing line-shaped beams or large area beams with spatially uniform intensity profile to realize this vision cost-effectively. He emphasizes that a true line-shaped beam produced by a slab laser system or an array of optical fiber laser would be necessary, as shaping the beam synthetically by changing the shape of an aperture would result in too much lost energy. With this technology, graphene could easily be printed onto circuit boards immediately, only where it’s needed, saving in material costs and time.

Nearly 14 years after the excitement first began, researchers are still exploring the potential uses of graphene; from applications in microsupercapacitors to Organic LEDs in flexible displays to ultra-sensitive optical sensors, and even lightweight body armor, the possibilities are still as exciting as ever.

 

Acknowledgements

Prof. Dr. Aravinda Kar, University of Central Florida, CREOL

Dr. Nathaniel Quick, Executive Director of LIA

 

LEARN MORE

Laser Formation of Graphene: United States Patent 8617669. (N. Quick, A. Kar)
http://www.freepatentsonline.com/8617669.html

NUS-led research team develops cost effective technique for mass production of high-quality graphene – http://news.nus.edu.sg/press-releases/mass-production-graphene-slurry

MIT researchers develop scalable manufacturing process for graphene sheets – https://newatlas.com/mit-manufacturing-graphene-filtration-membranes/54274/

Air Flow Control for Remote Laser Beam Welding

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By Achim Mahrle1,2, Madlen Borkmann 2,1, Eckhard Beyer1,2, Michael Hustedt3, Christian Hennigs3, Alexander Brodeßer3, Jürgen Walter3, Stefan Kaierle3 

1 Fraunhofer IWS Dresden, Germany

2 TU Dresden, Germany

3 Laser Zentrum Hannover e.V. (LZH), Germany

Developers and users of industrial remote laser beam welding applications are often faced with different challenges under the conditions of series production. First, those applications are preferably conducted without any localized gas shielding, and therefore, specific interactions between the laser radiation and the welding fumes are very likely to occur, causing an impairment of the process stability, the reliability and the weld seam quality. Second, welding fume residuals are capable of contaminating workpieces, optical components and other parts of the processing chamber, and they are also able to cause a serious pollution of the cabin atmosphere, because a significant part of the welding fume species is harmful or even toxic and carcinogenic. Each of these points gives a good reason to develop appropriate cabin air flow concepts, but in practice, it is still a challenge to design and optimize the air or gas flow because (i) the conditions of an ideal gas flow regime are uncertain, (ii) different gas flows are able to interact in complex manners, and (iii) it is costly to describe and monitor the gas flow characteristics inside the processing chamber experimentally. Consequently, a complementary combination of experimental and theoretical work has been performed to improve the understanding of inherent issues and relationships.

The experimental work was focused on the characterization of process phenomena and the determination of reliable welding conditions. For that purpose, a particular processing chamber was designed as shown in Figure 01. The interior view of this chamber shows inlet nozzles from a flat-jet type at different positions (1-3) on the right-hand side, as well as a global and a local exhaust air funnel (4-5) on the left-hand side. An additional cross-jet was applied to protect the laser optics (6). In this processing chamber, welding trials with a multi-mode fiber laser at an applied laser power of 3 kW and a welding speed of 2 m/min were performed on mild steel sheets with a thickness of 10 mm. Welds generated without any air flow showed no clear indications of a deep penetration process, and the weld depth was rather low. In contrast, the penetration was more than doubled under the influence of a well-defined gas flow. These findings emphasize the importance of an adapted cabin air flow with respect to the process efficiency. In the case of the investigations performed, local gas flow velocities in the range of 1 – 2 m/s above the weld zone were found to be sufficient to achieve this effect, and it was proven that larger values do not increase the penetration depth further on. In addition, it was found that a particular height of the welding plume is acceptable for stable welding regimes with maximum weld penetration depth. These processing conditions have been considered as a basis for optimization efforts regarding the cabin air flow.

However, with respect to the whole cabin flow, simple rules for an appropriate design are hardly available and optimal parameter configurations are difficult to find by means of empirical approaches because of the high number of control factors and factor combinations. To give an example, the individual air flow out of the applied flat-jet nozzle type is determined by 4 factors, namely the flow rate, the nozzle inclination, the distance to the processing zone and the outflow aperture. For the whole cabin air flow, 19 factors of influence have to be taken into account in total, which means that 219, i.e. more than a half million, factor-level combinations are possible if each factor is tested at only two value levels. Obviously, there is no alternative to Design-of-Experiments (DoE) methods which provide so-called screening designs to identify the most vital factors from a group of 19 factors with a minimal number of 192 runs. Such an analysis was performed by means of a Computational-Fluid-Dynamics (CFD) model to derive detailed information on cause-effect relationships regarding the cabin air flow. Exemplarily, Figure 02 (left) shows a computed air flow field for a particular parameter constellation. Process emissions were modeled as metal vapor inflow rate, and the height of a particular vapor concentration isoline was used as model response for the cabin flow evaluation. As a result of the screening analysis, 6 factors out of 19 were found as the most vital ones. With such a reduced number of factors, it became possible to apply a so-called multi-level Response-Surface-Method (RSM) as a basis for an air flow optimization. With a numerical effort of 157 additional computation runs, the functional dependencies between control factors and outcomes were quantified and described by a cubic regression model. Such a regression model is numerically easy to use and can be applied efficiently to determine optimal parameter configurations by computing the desirability function, plotted in Figure 02 (right) as a measure of the degree of fulfillment of defined optimization criteria, i.e. the limitation of the welding plume height to an acceptable level with minimal overall air or gas consumption.

The study has demonstrated a methodology to optimize the complex cabin air flow under the conditions of remote laser beam welding. However, the specific results cannot be generalized in a simple way as adaptable rules for the design of industrial processing cabins, because the characteristics of particular chambers, the spatial and temporal processing conditions, the type of applied air-flow components and the peculiarities of the specific welding applications always have to be taken into account for a profound analysis.

 

Acknowledgements

The work was performed in close collaboration by the Laser Zentrum Hannover e.V. (LZH) and the Fraunhofer IWS Dresden as part of the publicly funded research project “Steigerung von Prozessstabilität und Schweißnahtqualität beim Remote-Laserschweißen durch gezielte Strömungsführung mittels Anlagenadaption” (RemoStAad) with the reference number IGF 18149 BG. The authors acknowledge the financial and administrative support by the Bundesministerium für Wirtschaft und Energie (BMWi), the Arbeitsgemeinschaft industrieller Forschungsvereinigungen “Otto von Guericke e.V.” (AiF), the Forschungskuratorium Maschinenbau e.V. (FKM), and the Forschungsvereinigung Schweißen und verwandte Verfahren e.V. (DVS).

Figure 01: Interior view of the processing chamber with installed components (left) and weld seam cross-sections without (right a) and with air flow control (right b).

 

 

Figure 02: Computed air flow field (left) and desirability plot revealing parameter constellations for an optimized cabin flow (right).

 

Highlights from LIA’s Lasers for Manufacturing Event (LME): Prima Power Holds Open House

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By Ron Schaeffer

Prima Power was an exhibitor at Laser Institute of America’s LME 2018, held March 28-29 at the Renaissance Schaumburg Convention Center, Schaumburg, IL. After show hours on March 28, Prima Power hosted an Open House at its showroom in nearby Arlington Heights, IL. A large group of visitors, composed of laser industry experts, suppliers, and prospective customers were able to get a close-up view of the Prima Power Laser Next 3D Laser.

Thanks to a deep and unique experience of over 35 years in this field and to a continuous dialogue with customers and partners operating in the car industry, Prima Power has designed the new 3D laser machine for automotive production: Laser Next.  In developing Laser Next, Prima Power has focused on the achievement of the following main benefits for the user:

Maximizing throughput with a dramatic reduction of cycle times. During the last 10 years, the performance of Prima Power 3D laser machines for automotive applications has been growing steadily. With Laser Next, a fundamental step forward was made: productivity on a typical benchmark component (B-pillar) was raised by 25%. In other words, four Laser Next systems produce as much as five machines of the previous model.

Space-efficient layout both for stand-alone and multi-machine configuration. Space is money, and a well-conceived layout helps save square meters and optimizes plant logistics. The compactness of the installation further improves installing more machines, since you can have up to three units one next to the other connected to the same magnetic scrap conveyor, with no need of excavation works. Given the same area, in fact, it is possible to install more machines (e.g. four Laser Next instead of three units of the previous model). Considering the performance of Laser Next, the productivity per square meter ratio is simply astonishing.

Improved Overall Equipment Efficiency (OEE). For Laser Next, Prima Power capitalized on its experience of hundreds of installations for the 24/7 manufacturing of high-strength steel components, widely used in car production.

Every detail was studied and developed to maximize machine uptime. Maintenance was also lowered and simplified to reduce non-productive times and the need of specialized resources dedicated to these activities.

Laser Next has a working range of 3,050 x 1,530 x 612 mm and is equipped with 3 kW or 4 kW high brilliance fiber laser. Its compact focusing head, fully sealed for best protection, features direct drive motors, double protection SIPS, fully-metallic sensor, and Focal Position Control.

 

Dr. Kay Ball Releases Revision of Lasers – The Perioperative Challenge Through Laser Institute of America

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ORLANDO, FL, March 21, 2018 — Published through the Laser Institute of America (LIA), renowned author Dr. Kay Ball has revised her book, Lasers – The Perioperative Challenge, to provide updated laser technology information to healthcare professionals. This is the fourth edition; the first was published in 1990, and Dr. Ball notes that much has evolved in the laser world since then.

“Dr. Ball’s book is an excellent read for medical personnel who are new to the use of lasers in medicine and wish to get a comprehensive understanding of lasers used in surgery and other areas outside of the OR. The book is written with the reader in mind and the information is easily understood,” said Gus Anibarro, LIA’s Education Director.

While writing this edition of her book, Dr. Ball focused on evidence from research and published articles on laser procedure applications and outcomes. Since she also travels the world to present laser technology, she included personal clinical experience and addressed common questions she receives from practitioners worldwide.

“Lasers: The Perioperative Challenge takes a complex technology and simplifies it for ready access by nurses, physicians, risk managers, and other healthcare providers. It offers valuable information on how to apply current standards and guidelines for a laser-safe environment,” said Dr. Ball. “I updated the book because there’s such a lack of comprehensive books on the market that address all aspects of laser technology in healthcare.”

The book highlights laser research and applications while incorporating current laser standards and guidelines. Sample laser safety policies provide templates for writing policies and procedures for the clinical environment.

“Everyone needs a really good reference or resource—especially if you’re just beginning your laser services,” said Vangie Dennis, who helped review the book and is the Executive Director of Perioperative Services for WellStar Atlanta Medical Center and Atlanta Medical Center South located in the metropolitan area of Atlanta. “It’s a really great product. It’s the ‘Alexander’ of the operating room—except for lasers.”

Within its 410 pages, the book contains more than 300 illustrations and graphics that are intended to deepen the reader’s understanding of foundational physics, safety, and administrative aspects. There is also an extensive glossary that offers an easy reference for laser terminology.

“As new procedures are introduced and accepted, laser safety is the strong foundation upon which practices are based. When safety is the primary cog in the wheel of laser applications, successful outcomes can be evidenced to validate practice changes.  Laser technology continues to advance and mature as safe practices are demonstrated while patients benefit,” said Dr. Ball in the preface of her book.

The 18 chapters are broken up into three sections: “Laser Biophysics, Systems, and Safety,” “Clinical Laser Applications,” and “Administrative Aspects of a Laser Program.”

The cost of the book is $80 for LIA members and $90 for non-members.

“This book is a ‘must’ for all professionals participating in laser surgery and therapy,” said Dr. Ball.

It can be purchased at www.lia.org/store/product/241.

About Laser Institute of America

Laser Institute of America (LIA) is the professional society for laser applications and safety serving the industrial, educational, medical, research and government communities throughout the world since 1968. http://www.lia.org, 13501 Ingenuity Drive, Ste 128, Orlando, FL 32826, +1.407.380.1553.

Metal 3D Printing: A Machine Shop’s 73 Year-old Journey in the Industry

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By Wesley Hart

Imperial Machine & Tool Co. took delivery of their first metal additive manufacturing (AM) machine in 2013 — a Selective Laser Melting system from SLM Solutions. The decision to invest was made after seeing one of these “metal 3D printers” in action, growing a component layer-by-layer from titanium. That demonstration made it clear to Imperial that this was powerful technology, and would play an integral role in the future of advanced manufacturing.

An SLM 280 HL and an SLM 280 HL “Twin-Laser” in Imperial’s additive manufacturing laboratory.

Over the last four years, the folks at Imperial have spent thousands of hours working with their additive machines. According to Christian G. Joest, Vice President of Sales and Business Development at Imperial, that’s what it takes to be successful. “Metal AM has come a long way since its inception, but it’s not a turn-key operation; you’ve got to put in the time to master your machines and lock down your process. Early adopters must be willing to problem solve and learn along the way. We understood that, and decided to make the investment — even though the path forward was not entirely clear.”

The “dive-in” approach employed by Imperial has provided them with unique and useful insight — especially for those wondering how additive manufacturing will affect their own business. LIA invited Imperial to share some of their insight during a 30 minute presentation at the Industrial Laser Conference held at IMTS 2016. This article focuses on some of the key takeaways from that presentation.

Why Invest in Metal Additive Manufacturing?

Christian began the presentation by sharing some background on Imperial, and the primary reasons they decided to get into metal additive manufacturing.

“Imperial is a 73 year-old advanced manufacturing company. Since the 1940s, we’ve been known for tackling the most challenging machining and fabricating efforts in the industry. Our earliest work was for the military and we still do a large amount of work for the DoD, but over the years we’ve expanded to serve many other high-end sectors including the semiconductor, energy and optical equipment industries.

To be successful at challenging manufacturing projects, we rely on the most cutting edge manufacturing technology available; it’s one of the reasons we’ve remained competitive and relevant over the last seven decades and a big part of why we got into metal additive manufacturing. In the 40s that meant advanced Jig-boring machines, in the 70s it was CNC machining centers, and today it’s metal additive manufacturing. We wanted to get out in front of the technology.”

The second reason was more personal.

“The other reason we became involved in additive is because we’re a fourth-generation, family-run business. We consider investments in terms of decades and generations, and we believe metal AM will be required for success for the next generation of Imperial. We understood we wouldn’t see a financial return on our investment right away, but that wasn’t what was driving this decision; we wanted to begin developing expertise as early as possible.”

Christian went on to explain how the impact of additive will be felt across all industries in a variety of ways. For example, current Imperial customers working in laser and energy beam related industries are particularly interested in metal AM for the conformal cooling possibilities.

The Importance of Hybrid Manufacturing

As the presentation continued, Christian built to an important point, “It’s not just press print.”

Christian explained that customers are looking for high-quality end-use components. Additive manufacturing can help realize innovative new designs, but they are not pulled straight from the printer.

“Misconception comes with the territory; the technology is young. Most of the public doesn’t even know that printed parts are actually welded by laser to the build plate, and must be cut off!”

Precision machining a metal 3D printed component, part of the “Hybrid Manufacturing” approach.

To successfully yield end-use components Imperial had to develop a “hybrid manufacturing” approach — using their additive capabilities in conjunction with their traditional machining capabilities. For example, they might use their metal printer to manufacture a topology optimized hydraulic manifold with complex internal channels, but they still rely on high-precision CNC machining centers to mill special SAE threads and flatten critical mating surfaces. That’s in addition to the thermal conditioning operations Imperial performs to yield the best material properties. All of these steps must be planned and accounted for before manufacturing begins! This is a far cry from pulling an end-use component straight from the printer.

The Real-World Applications of 3D Printing

Christian went on to explain the education process that must occur when interacting with new customers; getting the most out of additive manufacturing requires an understanding of what it’s best used for.

“It doesn’t make sense to use a power drill when you need a hammer. A power drill may be a more advanced tool, but that doesn’t mean it’s better than a hammer. You’ve got to choose the right tool for the right job.”

The value of AM is not in making the same part designed for CNC machining on a metal printer, it’s in realizing designs never before possible. Christian spoke of how Imperial works closely with their customers to ensure they understand the reality of when additive manufacturing makes sense, and when it does not.

“Over the years we developed a list that breaks down the best applications for additive manufacturing, based on our experience with customers and our background in manufacturing. Our goal is to provide a strong foundation for our customers to continue exploring from. Once customers understand these applications, they begin to think on their own about how additive manufacturing can positively affect their business and industry.”

A Look Toward the Future

As the presentation wound down, the focus turned to what it will take for metal AM to become mainstream. “You’re all here today because you’re interested in additive manufacturing on some level. That’s the first step. Don’t be afraid to explore further. You’re in the right place, at the right time in history to be a part of this emerging technology. Embrace the opportunity.”

Metal additive manufacturing is already making a big impact for Imperial Machine & Tool Co. and their customers. How will metal AM affect you, and what you do?

Wesley Hart is the Marketing Director of Imperial Machine & Tool Co.