On the topic of conferences and networking events, be sure to check out our reflection on the Lasers for Additive Manufacturing Workshop (LAM®). LAM® took place March 2-3, in Kissimmee, Florida, hosting over 170 attendees from 14 countries. The post gives an in-depth look at a handful of presentations from the event. LAM®brings industry leaders and researchers in the areas of 3D printing, cladding, and rapid manufacturing. The exhibitor reception gives attendees ample opportunities for networking. See photos and more from the event here: http://www.laserstoday.com/?p=5015
Missed the Lasers for Additive Manufacturing Workshop (LAM®)? Were you unable to attend the Lasers for Manufacturing Event (LME®)? Get the most out of your next laser technology event by brushing up on how to expand your laser technology network. The post is packed with plenty of tips to help you prepare for your next conference or other networking event. The tips can be found here: http://blog.lia.org/how-to-expand-your-laser-technology-network-at-conferences-and-trade-shows
Be sure to also check out our tips on Saving Time and Money and Manufacturing. From making sure you are up to date with current laser safety standards, to keeping up to date with the world of additive manufacturing, there are a number of ways to cut costs and save time in your manufacturing efforts. Read up on our tips here: http://blog.lia.org/how-to-save-time-and-money-on-manufacturing
Could lasers be the answer to ending cell phone use in theaters? In a few Chinese theaters, this using lasers to “shame” attendees with poor theater etiquette. Rather than having an usher advise guests to put their phone away, often causing a bigger disruption than the phone itself, the theater staff shine low-powered laser pointers at the device of the offender. While the practice has proven to be effective, there are a number of people expressing concerns about the use of lasers in a theater environment. Find out more here: http://www.laserstoday.com/?p=4860
As most internet providers brag about having the fastest download speeds, researchers at University of California, San Diego are working on creating a faster, more efficient internet using lasers. Expanding upon existing fiber optic technology, the team recognizes the limits of electricity and our current data storage limits. Read more about how lasers may usher in an era of faster, cleaner internet service here: http://www.laserstoday.com/?p=4868
Read about the “Photon Factory” at the University of Auckland, New Zealand. Here, Dr. Cather Simpson is trying to “bring the rich versatility of high tech ultrashort laser pulses to New Zealand academic and industry innovators.” The space is used currently for contracts, grant work, and as a testing space. Learn more about the development of the facility, and work performed on site here: http://www.laserstoday.com/?p=5010
Could lasers be an answer to reducing the required time for space travel? Using directed energy propulsion and a small, “wafer-thin” spacecraft, we may be able to reach Mars, and nearby star systems, in fractional amounts of time. While the tiny spacecraft is far from an option for manned missions, reducing travel time between destinations could be groundbreaking in terms of data collection, when exploring beyond our world. Curious? Find out more about the research behind the use of lasers in experimental space travel here: http://www.laserstoday.com/?p=4823
This Thursday, we took you back to the origin of the laser scalpel. Find out what types of lasers are used for specific medical procedures, as well as the laser scalpels rise from experimental equipment to an industry standard tool here: http://www.laserstoday.com/?p=4893
Last, but certainly not least, is an article by Wilhelm Pfleging, Melanie Mangang, Yijing Zheng, Peter Smyrek and Johannes Pröll. Learn about ultrafast laser processing in the development of Lithium-Ion Batteries, as well as the creation of new processes to generate 3D electrode designs. The post can be found here: http://www.laserstoday.com/?p=5012
By Wilhelm Pfleging, Melanie Mangang, Yijing Zheng, Peter Smyrek and Johannes Pröll
Introduction
Thick film anodes and cathodes with thicknesses ranging from 20-300 µm, in state-of-the-art and future lithium-ion cells are complex multi-material systems consisting of defined material components, grain sizes, porosities and pore size distributions in the micrometer and submicrometer ranges. State-of-the-art cells with pouch cell geometry for high power applications consist of thick film electrode stacks with capacities up to 40-50 Ah.
The development of three-dimensional (3D) cell architectures for electrodes in lithium-ion batteries is a promising approach to overcome problems like 1-dimensional lithium-ion diffusion, inhomogeneous current densities, power losses, high interelectrode ohmic resistances as well as mechanical stresses due to high volume changes resulting from lithium-ion insertion and deinsertion. By applying 3D battery architectures, one can achieve large areal energy capacities while maintaining high power densities at the same time. This feature is important, e.g., for thin film batteries where the lithium-ion diffusion is limited by the thickness of the compact film. A common approach for realization of 3D architectures in electrodes is the structuring of the substrate or current collector. An increased active surface achieved by 3D electrode architectures can induce large areal energy densities. Unfortunately, this approach is in a very early stage of development and in general it is not feasible for state-of-the-art electrodes.
Figure1. Laser-generated self-organized microstructure in composited electrode cathode material
At the Karlsruhe Institute of Technology (KIT), a new process for the generation of 3D electrode designs has been created by developing two processes; 1.) Laser-assisted self-organized structuring (Fig. 1) and 2.) direct structuring of tape cast electrodes [1-3].
In each case, the laser structured electrodes exhibit a significant improvement in liquid electrolyte wetting as well as in electrochemical performance after laser treatment. During the manufacturing process of lithium-ion cells, liquid electrolyte filling is a cost- and time-consuming process. Insufficient electrolyte wetting in turn can lead to unexpected cell failure under challenging cycling conditions. At KIT, a cost efficient laser-based technology for the realization of 3D architectures in thick-film tape-cast electrodes was developed to accelerate the wetting process and to also shorten the time-span for cell manufacturing (Fig. 2).
Figure2. State-of-the-art processing route for liquid electrolyte filling of lithium-ion cells with time-consuming warm aging (top) and KIT process without warm aging due to laser structured battery materials (bottom)
In addition, an improved cell operation with extended life-time and increased capacity retention at high charging and discharging currents could be achieved. For the development of advanced laser processes in battery manufacturing, a complete lithium-ion cell manufacturing process cycle has been built-up which includes electrochemical characterization of lithium-ion cells (Fig. 3).
Figure 3. Process chain for cell fabrication and testing including laser processing of battery materials
Experimental Setup
Different types of electrode materials were already investigated such as LiCoO2 (LCO), LiMn2O4 (LMO), SnO2 (SnO), fluorine doped SnO2 (FTO), Li(NiMnCo)O2 (NMC), silicon (Si), graphite (C) and LiFePO4 (LFP). Thin films as well as thick films were applied. Thick film electrodes are composite materials which consist of active material, carbon black, graphite and binder. All lithium-ion cells were assembled either in an argon-filled glove box or in a dry room. An ultrafast fiber laser system (Tangerine, Amplitude Systèmes, France), a ns fiber laser system (YLPM, IPG Photonics, Germany), or an excimer laser system (ATLEX-1000-I, ATL Lasertechnik GmbH, Germany) were used to manufacture 3D architectures into the thin or thick film electrode layers.
Figure 4. Rapid wetting of laser structured electrodes
The Results
In general, electrolyte filling of lithium-ion cells is realized by time and cost consuming vacuum and storage processes at elevated temperatures. Nevertheless, by applying state-of-the-art electrolyte filling processes, insufficient wetting of electrode and separators is one drawback resulting in a certain production failure rate accompanied with a lowered cell capacity or a reduced cell life-time. Laser structuring has been developed for the formation of capillary micro-structures in thick film tape-cast electrodes which resulted in the acceleration of electrolyte wetting in comparison to unstructured electrodes (Fig. 4). The removal of the complete electrode material from the ablation zone delivers the most efficient capillary transport [4].
For the formation of capillary structures, ns-laser ablation as well as ultrafast laser processing was investigated.
For ns-laser radiation (l=1064 nm, pulse length 200 ns) the laser beam energy is absorbed at the material surface and, due to heat conduction, the temperature of the surrounding composite material increases. The binder material for tape-cast electrodes (~5 wt%) is PVDF which has a low decomposition temperature in the range of 250–350° C [5]. Therefore, the PVDF binder matrix spontaneously evaporates and active particles are removed from the laser beam interaction zone.
Figure 5. Capillary structures in NMC electrodes. Cross section and SEM top view of ns- (a & b) and fs- (c & d) laser structured NMC (pitch of capillary structures: 200 µm, pulse lengths: 200 ns, 350 fs)
With ns-laser radiation, structure widths of about 40-55 µm can be achieved (Fig. 5a & 5b). The current collector for cathodes are made of aluminium with a thickness of 20 µm and for anodes they consist of copper with a thickness of 10 µm. Laser structuring with a ns-laser can be realized without damage of the current collector (Fig. 5a). Laser structuring can be realized even for double-side coated aluminium substrates, which is a required processing step for process up-scale for manufacturing of lithium-ion cells with high capacities [4].
Nanosecond laser ablation is not appropriate for each type of electrode material. For example, ns laser structuring of LFP electrodes always leads to melt formation and therefore to an undesired modification of the active material. Furthermore, the ablation efficiency of LFP increases by a factor of 3 by using femto- or pico-second laser ablation in comparison to ns-laser ablation [6]. Another aspect is the loss of active material due to the ablation process. For the application of structured foils in batteries, it is important to reduce the amount of ablated material which in turn means that small capillary widths and high aspect ratios are preferred. By using ultrafast laser ablation it could be shown that the aspect ratio could be significantly increased (Fig. 5c & 5d) and that the loss of active material can be reduced from 20 percent down to values below 5 percent [7].
Capacity retention and cell life-time can be illustrated by plotting the cell voltage as function of discharge capacity for different cycle numbers. For the lithium-ion cell with the structured NMC electrode, the 80 percent capacity limit of the initial discharge capacity is reached after 2290 cycles (Fig. 6). While the cell life-time for the lithium-ion cell with unstructured electrodes is reached after 141 cycles. Furthermore, the discharge capacity of the cell with the laser-structured NMC electrode reaches a value of 108 mAh/g after 2290 cycles indicating that efficient liquid electrolyte transport due to micro capillary structures improves the electrochemical performance for cell without cost- and time-consuming storage procedures.
Figure 6. Cell voltage versus discharge capacity for pouch cells with laser-structured (right) and unstructured (left) NMC electrodes and without storage [4]
Summary & Conclusion
A new technical approach of using laser-generated capillary structures in electrode materials was presented. This technology can be applied in order to increase cell reliability during the production process, to shorten production times of lithium-ion cells as well as to increase the cell life-time during cycling. Due to an improved cycle life-time and increased capacity retention, the use of high power batteries in 2nd life applications becomes interesting. Cost-efficient ns fiber lasers can be applied for carrying out the structuring process for several types of electrode materials. Nevertheless, regarding the structuring of LFP, a further reduction of active mass loss, and an up-scaling of the structuring process, the use of ultrafast laser processing becomes necessary.
References
J. Pröll, H. Kim, A. Piqué, H.J. Seifert, W. Pfleging, J. Power Sources, 255(0) (2014), 116-124.
J.H. Park, R. Kohler, W. Pfleging, W. Choi, H.J. Seifert, J.K. Lee, RSC Adv., 4(9) (2014), 4247-4252.
R. Kohler, J. Pröll, M. Bruns, S. Ulrich, H.J. Seifert, W. Pfleging, Appl. Phys. A, 112(1) (2013), 77-85.
W. Pfleging, J. Pröll, J. Mater Chem A, 2(36) (2014), 14918-14926.
J. Choi, E. Morikawa, S. Ducharme, P.A. Dowben, Mater Lett, 59(28) (2005), 3599-3603.
M. Mangang, H.J. Seifert, W. Pfleging, J. Power Sources, 304 (2016), 24-32.
P. Smyrek, J. Pröll, H.J. Seifert, W. Pfleging, J. Electrochem Soc, 163(2) (2016), A19-A26.
Wilhelm Pfleging, Yijing Zheng, Peter Smyrek and Johannes Pröll are all with the Karlsruhe Nano Micro Facility in , Germany. They are joined by Melanie Mangang in their work at Karlsruhe Institute of Technology (KIT).
Invented just over 50 years ago, the laser scalpel is used in an array of surgical procedures, across medical fields. A laser scalpel is typically either a CO2 laser or a excimer laser, depending on the surgery. For soft tissue procedures, such as removing a birthmark or teeth whitening, a CO2 laser is used. A C02 laser’s wavelength is absorbed by water, which allows the laser to vaporize the surrounding tissue with minimal damage inflicted. Bleeding, swelling, and chances for infection are greatly decreased in procedures performed by CO2 lasers, which led to their adoption in the fields of dermatology, dentistry, oncology and beyond.
The CO2 laser was initially developed in 1964 at Bell Laboratories. Through the decade, and into the 1970s, researchers took interest in the gas-based, manipulable laser and its potential medical applications. Until the early 1980s, the laser scalpel was used almost exclusively in academic medical settings due to its size and availability. Once smaller, more powerful lasers were made accessible, the CO2 laser scalpel found its way into most hospitals and specialist’s offices.
In the case of laser eye surgery, an excimer laser is the preferred tool for LASIK procedures. The excimer laser has a high ultraviolet output, making it a strong candidate for use in surgical procedures. Researchers at IBM’s T.J. Watson Research Center began looking at the excimer laser’s potential for use on biological materials in the early 1980s. The precise, neat incisions created by the excimer qualified it for use in the medical field, ultimately resulting in a patent. The larger size of the excimer laser scalpel hinders its utilization in a number of medical fields. However, as the necessary technology is developed, the equipment is scaling down to fit a multitude of purposes.
In just over half a century, the laser scalpel has evolved from a potential medical tool to an industry standard. A push for more powerful, free electron lasers coupled with the push for smaller equipment will likely increase the utilization of the laser scalpel. In the very near future, laser technology will be used for as many internal procedures as it is currently used for external. With lasers already in use for clearing clogged arteries and oral surgery, the future of the laser in surgical procedures is closer than most of us realize.
When it comes to space travel, getting from point A to point B, at a faster rate is among the biggest challenges facing researchers, eager to explore new worlds. One researcher, however, thinks that he has found a solution that could reduce travel time to Mars to less than one hour, using laser-based technology.
The process, known as directed energy propulsion, involves focusing a laser on small spacecraft, speeding it up to a fraction of the speed of light. In doing so, trips to nearby systems can be potentially fractionalized, taking hours rather than months to reach a destination. This could all be possible thanks to the research of Phillip Lubin, a scientist working with NASA’s Innovative Advanced Concepts Program.
According to Lubin’s research, space travel via directed energy propulsion would require a small, “wafer-thin” spacecraft. The spacecraft would be equipped with a laser sail, just over three feet long called DE-STAR (Directed Energy System for Targeting of Asteroids and ExploRation.) A strong laser in Earth’s orbit would be fired at the sail, accelerating it into space.
The small size of the spacecraft (around 200 lbs) would not make directed energy propulsion an option for manned travel or heavy cargo. However, equipping the craft with simple instruments as a way to collect data in “fly-by” missions is something it is more than capable of. Another concern for the concept is the fact that without an equal laser at the opposite end of where the craft is headed, it would not stop. While this does limit the capabilities of the craft, using it almost exclusively as a research tool opens up the door for future, similar developments. Rather than relying on rocket fuel, accelerating through chemical propulsion, using light to obtain lightspeeds uses electromagnetic acceleration, in a fraction of the time. Lubin expands on this in the paper A Roadmap To Interstellar Flight, which details the research that earned Lubin and his team a proof-of-concept grant from NASA.
Should NASA greenlight direct energy propulsion for space travel, the proposed spacecraft could potentially expand past our neighboring planets and into nearby star systems, like Alpha Centauri. The speed made possible by directed energy propulsion could cut down the travel time to the star system, located approximately four light years away, to less than 20 years. “There is no known reason why we cannot do this,” Lubin says in “Going Interstellar,” a NASA 360 video, detailing the concept.
While shooting lasers at a spacecraft, headed toward Mars sounds like a science fiction concept, it is very much rooted in what is possible today. As the application of laser-based technologies becomes more commonplace in utilization, LIA continues to foster lasers and laser safety worldwide. For information on laser safety training and more, please visit www.lia.org
If you have ever been to Auckland, New Zealand, you know the natural beauty of its surroundings and the vibrancy of the city. What you may not know is that the campus of the University of Auckland is home to a unique facility, one that uses the power of intense pulses of light to manipulate, measure and machine matter — it uses photons as its ‘machinery.’
The Photon Factory
This unexpected find is the result of the efforts of Dr. Cather Simpson, who joined the faculty of the University of Auckland in 2007. Soon after arriving, Dr. Simpson challenged herself to “bring the rich versatility of high-tech ultrashort laser pulses to New Zealand academic and industry innovators.” This challenge resulted in the creation of a facility dubbed the ‘Photon Factory.’ The Photon Factory fulfills multiple functions: it is a laboratory for education, research, innovation and even economic development.
The ‘Photon Factory’ at the University of Auckland (left) and Dr. Cather Simpson (right) along with members of her team of students, researchers & entrepreneurs
Dr. Simpson became familiar with ultrafast lasers and their extremely short pulses (on the order of 100 fs = 100 x 1015 seconds) while pursuing research in ultrafast energy conversion in molecules. She used them as a tool in her lab when she started her career as a professor at Case Western Reserve University (CWRU). Light can be converted by molecules into other forms of energy; by studying the dynamics of molecular complexes excited by light on femtosecond to microsecond timescales through both experiments and modeling, it is possible to learn how molecules direct the energy acquired in light absorption. The ultimate goal of these investigations is to understand how the structure and environment influence molecular functions so that photochemical and photophysical behavior can be both predicted and tailored.
Having achieved tenure at CWRU, she found the opportunity to move to New Zealand compelling, and there, her research has flourished to span from fundamental spectroscopy to applied device development. The Photon Factory is the facility and resource she has developed to accomplish her research goals and to bring the power of laser light to New Zealand, and beyond.
A Factory of Ideas & People, Powered by Light
How did the Photon Factory come into being? When Dr. Simpson moved to New Zealand, the country was undergoing a transformation in how academic research was being funded. A newly-formed government was in the process of making structural changes, closing the Ministry of Research, Science and Technology and moving some of its functions to a newly created agency, the Ministry of Business Innovation and Employment. This signaled the new government’s stance that science and technology were to be viewed as drivers of economic development. Because she arrived at this time and had no history with the previous methods of funding, Simpson was able to embrace and navigate the new system. She realized that the government wanted to use the academic community to fill a large gap in R&D spending that New Zealand companies were not filling — the level of spending on internal R&D was well below that of international companies, and nearly non-existent. She also realized that, unlike what she had encountered in America, funding sources would scrutinize how she engaged with industry and what type of business case there was for the proposed work as a key factor in whether her work would be funded or not. She began to pay attention to what companies were identifying as the problems they wanted to solve. But at the same time, she was eager to continue her ultrafast chemistry research.
Dr. Simpson recognized that the laser tools that she was using in chemistry were being used for other applications, some that might have more immediate use to industry. Her experience and interest in laser-matter interactions was a natural bridge into material processing applications. She also understood that there were challenges, such as slow machining speeds, that kept ultrashort pulsed machining from widespread use. With these ideas in mind, the multi-purpose, multi-user Photon Factory, was born.
Since its opening in 2010, the facility has grown to over 30 students and employees from physics, chemistry and engineering backgrounds who work on dozens of academic and commercial projects. These activities range from basic research stemming from Simpson’s chemistry background, such as evaluating the photobehavior of improved solar energy harvesting molecules, to more industry-friendly applied research, such as fabricating photomasks for microfluidic chip production.
The Photon Factory generates commercial contracts and grants, and also serves as a test bed for science innovation and a training ground for future scientists and engineers. Interactions with New Zealand-based companies including Next Window, Rakon, Fisher & Paykel, Izon and others have produced such wide-ranging results as improved touch-sensitive displays, better locking nuts, more efficient designs for solar thermal energy harvesting, and new designs for GPS chips. Global companies like Intuitive Surgical (based in Sunnyvale, CA) have brought projects to the Photon Factory to develop laser-based surgery in difficult tissue. Such projects have yielded patent filings, and an increased ability to understand commercial opportunities. They have also created conditions for both students and Dr. Simpson herself to get involved in industry-sponsored and spin-off technologies.
Entrepreneurship has become a buzzword in academic circles, but in New Zealand, the Photon Factory takes the concept to heart. Two spin-off companies have already been generated by the work of the Photon Factory. The first, Engender Technologies, Ltd., was established in 2011 as a result of taking a serious look at the challenges faced by New Zealand’s dairy industry. When approached by a venture capital firm with the five top problems in that sector, Dr. Simpson found one that seemed possible to address by photonics and then chose a team of students and engineers to find a solution. The problem she chose was that of improving sperm sorting by sex, to address the needs of dairy farmers who are turning to artificial insemination to control the numbers of bulls versus cows. The resulting microfluidic and photonic device is a huge departure from the state-of-the-art flow cytometry based solution, and one that could only be identified by people with a new set of tools at their disposal. A second spin-off is currently being formed to commercialize a new centrifugal microfluidic technology developed in the Photon Factory to analyze milk at “point of cow” in the milking shed. The new company already has backing from VC and other investors. It is probably no coincidence that both start-ups are addressing New Zealand’s important agricultural sector.
Cell-sorting prototype developed within the Photon Factory
Transforming Matter & Lives
So, what has the Photon Factory achieved thus far? Besides new chemical insights, material processing to solve diverse problems, and generating novel concepts and devices, it has turned Dr. Simpson into an entrepreneur and led her to tackle questions that she previously would not have envisioned. Her passion for research has been applied to significant problems in diverse application areas, from touch sensor displays to challenges in dairy farming. And perhaps most importantly, this passion has been applied to developing future engineers and scientists with deep curiosity and an entrepreneurial spirit. All of these things have resulted from the fortuitous confluence of a researcher, with a specialized high-tech tool, finding interesting challenges and opportunities based on New Zealand’s desire to develop more innovation to drive economic growth. Who knew that photons could be so powerful?
For more information, or to reach Dr. Cather Simpson, visit www.photonfactory.auckland.ac.nz/en.html
![Figure 6. Cell voltage versus discharge capacity for pouch cells with laser-structured (right) and unstructured (left) NMC electrodes and without storage [4]](https://www.laserstoday.com/wp-content/uploads/2016/04/Fig-6-1024x400.jpg)
