Sustainable Lasers
Laser technologies play a role in sustainable manufacturing processes.
As society’s already staggering demand for materials and goods continues to grow, the companies that produce these materials face increasing pressure to protect the global environment during manufacturing processes. Laser scientists and other photonics researchers certainly recognize the growing urgency to reduce costs and wastes while increasing efficiency and quality.
The quest for sustainable manufacturing processes has motivated many discussions on how laser-based technologies could help, especially in parts of Africa and other areas of the developing world that face unique infrastructure challenges and where sharing resources and knowledge is particularly important.
On the African continent, collaborations among international partners are opening new avenues for photonics research and industry to take hold, where they may help to reshape energy- and waste-intensive manufacturing practices in some of the continent’s strongest economies.
The UN, which is working toward 17 goals for sustainable development by 2030, has defined sustainable manufacturing as that which “meets the needs of the present without compromising the ability of future generations to meet their own needs.”
Science and technology have “a meaningful role to play in the development of sustainable manufacturing knowledge and technology,” said Sechaba Tsubella, a chemical engineer and deputy director of advanced manufacturing technologies at South Africa’s Department of Science and Technology.
But his country must first “come to terms with a definition of what it means to be sustainable,” he told attendees at a Sustainable Materials Processing and Manufacturing conference at the University of Johannesburg in January.
Representatives from academia, industry, and government there brought many examples of laser technologies that can help move South Africa and other developing countries toward defining and meeting international goals for sustainability. Scientists and engineers discussed projects such as manufacturing stronger steel, easily shaping titanium, and producing graphene in a single step.
Yet all face the reality that disparate knowledge, resources, and policies in different parts of the world slow progress toward realizing the potential of laser-assisted technologies to build locally sustainable processes.
Even so, improving the durability of widely used materials provides an attainable sustainability goal in many developing regions, which is why laser scientists from across the globe came together in January to share resources and knowledge.
Stainless steel is one of the most extensively used materials in structural projects from bridges to building frames, due to its excellent strength and corrosion resistance in dry environments. But it can suffer in gaseous and liquid environments.
To further enhance the utility of this widely available material, Jyotsna Dutta Majumdar, professor of metallurgical and materials engineering at the Indian Institute of Technology, investigates laser treatments that can increase the strength of stainless steel surfaces.
In laser composite surfacing, ceramic or metal particles are fed into a molten steel substrate. The resulting dispersed matrix on the surface improves strength and wear resistance and inhibits corrosion. The entire process not only reduces waste material and energy consumption while providing the requisite heating and cooling, but it eliminates radiation hazards, precisely processes complex shapes, and yields defect-free microstructures.
In a presentation at the conference in Johannesburg, Dutta Majumdar explained how different laser surfacing methods and additives improve the wear and corrosion resistance of steel. “The particle size and distribution can only be controlled by the proper combination of laser parameters,” she said. Scan speed, laser power, metal particle distribution, and flow rate for dopant distribution all affect the resulting alloy’s properties.
She melts the steel surface using a 1-2 kilowatt Nd:YAG laser, while simultaneously feeding a powder mixture of tungsten carbide, cobalt, and nickel chromide to the molten pool. The surface microhardness nearly doubles relative to the original material, but decreases as she increases the scan speed. In addition, the wear resistance improves due to increased surface hardness and reduced friction.
Illustrating the challenge of disparate resources in the developing world, Dutta Majumdar notes, “I don’t have a laser in my group, but hopefully we will establish it soon. I am grateful to have free access to lasers in different research organizations in India and also institutes in Germany, UK, and South Africa. I do my laser work in collaboration with laser laboratories and do characterization and performance tests in my institute.”
Her method is poised to help the many industries that rely on stainless steel. But making it available where needed still poses a challenge, as does understanding the precise combination of process parameters that lead to the desired product. “The manufacturing sectors need to join hands with materials scientists to understand the behavior of materials due to laser processing,” she concludes.
Due to its strength, corrosion resistance, limited chemical reactivity, and biocompatibility, titanium metal has gained favor as a material of choice in the chemical, aerospace, marine, and biomedical industries. New work in South Africa explores ways to reduce the metal’s high cost and simplify how it can be machined.
Laser beam forming (LBF) offers a contact-free method for precisely shaping metals, by rapidly heating a localized area on the material’s surface with a defocused laser beam. It consumes less energy than traditional heat treatment since the heating is localized, reduces processing time, and offers control over the heat source power and geometry. Yet, questions remain about how the method affects the properties of common titanium alloys.
Stephen Akinlabi of the University of Johannesburg’s Department of Mechanical Engineering Science studies how the ‘workhorse’ alloy of the titanium industry, Ti6Al4V, responds to LBF. His goal is to control the processing parameters to achieve the desired properties for specific applications such as aircraft parts and medical implants.
Starting with a 4.4 kW Nd:YAG laser system, he simply varied the laser power to effectively monitor and control the alloy’s properties. At lower power, the interwoven ‘basket weave’ microstructure of two titanium phases increased the metal’s density. Higher power, however, increased the resulting microhardness.
This unique alternative system offers greater control than mechanical force-assisted forming. “Research into laser-related studies has grown tremendously in South Africa even though the actual equipment is not widely distributed across universities,” Akinlabi says. “Academics and scientists have utilized the limited equipment to the utmost, and results are available to buttress this claim.”
Lack of access to technologies and techniques limits the research that can happen ‘at home’ in many parts of the world. But countries with some of the strongest research infrastructure play an important role in spreading knowledge and products to the global market.
The traditional production method for graphene, for use in devices such as solar cells or touchscreen displays, involves growing each atoms-thin hexagonal lattice sheet separately at high temperatures and then transferring these to a metal or silicon base. This poses challenges, yet graphene-based technologies are increasingly valued because of their unique flexibility, strength, and conductive properties.
SPIE Fellow Xianfan Xu, professor of mechanical engineering and nanotechnology at Purdue University (USA), has developed an alternative method for growing graphene directly on the silicon substrate. Graphene films can form what’s known as a Schottky junction with silicon, which is a metal-semiconductor interface with a built-in electric field for use in photovoltaic or photodetectors.
“Laser manufacturing for nanomaterials reduces bulk processing. It’s like 3D printing for a specific piece, down to the p-n junctions [single crystal interfaces between semiconductor materials],” said Tien-Chen Jen of the University of Johannesburg, an organizer and chair of the conference.
In Xu’s method, a laser provides the heat source for graphene growth. The beam scans the surface, melting patterns in an acrylic film on the substrate. After just minutes of melting, graphene appears, derived from the evaporated film as gaseous molecules decompose on the molten surface. As it cools, precipitated carbon atoms coalesce and nucleate to form the graphene film.
“The focused beam locally melts the silicon, so graphene growth only happens in the melted area,” Xu explained in his conference presentation. The low-power laser (10 W), reduced substrate heating, and precise control over graphene position improves efficiency and reduces waste.
Xu applies a related technique to synthesize silicon nanowires, another promising material for next-generation electronic devices such as biosensors or solar cells. Here, reactive gases flow over the laser-heated silicon surface, where they decompose and write a chemical pattern in a single process. The method avoids metal catalysts and minimizes power to create a nanowire that is ready for use.
“The infrastructure in developing countries means that some of the nanomachining processes may not be possible there, nor is basic nanotech research. Our work is more relevant to producing products,” Xu says. Nonetheless, this work plays an important and necessary role in helping developing countries build their capacity.
Courtesy Stephen Akinlabi
Tsubella, the deputy director of the South African Department of Science and Technology, observes that as a materials engineer, he started his career with the “constant desire to ensure that we develop materials that are cheaper, more reusable, less energy intensive, and more amiable to environmental vulnerabilities.” But he’s struggled to find the support to do so.
Laser-assisted materials processing is plagued by the high costs associated with equipment installation and a lack of skilled experts. Dutta Majumdar advocates for central laser facilities in “different corners of any country” so people from different areas can have access.
In South Africa, most laser systems are housed at the Council for Scientific and Industrial Research, where laser technology research began with the National Laser Centre. But the desire to pursue photonics research everywhere prevails.
“If there was adequate funding to support equipment for laser related studies, then there would be more activity on this subject and double the current research outcomes in the areas of lasers,” Akinlabi predicts.
Leveraging this research to develop sustainable manufacturing, and pushing techniques to widespread use, requires a commitment to sharing resources and knowledge across and within international boundaries.
Wilson R. Nyemba, engineer and researcher with the Department of Mechanical Engineering Science at the University of Johannesburg, documented the challenges in procuring basic engineering equipment at higher education institutions in Sub-Saharan Africa.
Many laboratories have obsolete or poorly functioning equipment, obtained during the colonial era (1960-80) when institutions such as the University of Zimbabwe were managed as colleges of European universities. When these colleges became independent universities, their founders gradually returned home but did not leave sufficient plans for equipment replacement or repair. This resulted in obsolescence, underutilization, or disrepair, with no capacity to withstand setbacks.
Through his research, Nyemba has developed a strategic model that employs a holistic approach to drive “Smart Procurement Partnership” collaborations between universities and private sector industry. The aim is to build capacity in equipment maintenance and management during engineer training programs, while ultimately reducing foreign aid dependence.
He highlights the need to establish links with the private sector to improve institutions’ access to modern equipment. Similarly, exposure to modern engineering practice and new technology is best achieved through industry-relevant research, he says.
Taking this approach, the University of Zimbabwe has benefitted from newly-acquired modern engineering equipment including computer numerically controlled (CNC) machining equipment, a live global system for mobile (GSM) telecommunications base station, and a mobile renewable energy lab called the solar trailer. “All this was courtesy of local Zimbabwean companies that have embraced the strategic model as a ‘win-win’ situation for all stakeholders,” Nyemba says.
His exemplary efforts have fostered nurturing partnerships with industry, while developing long-term frameworks for training, capacity building, and sustainability within universities.
– Rachel Berkowitz is a US-based freelance science writer.
Institutions in South Africa that are nurturing the next generation of optics and photonics innovators include the Council for Scientific and Industrial Research (CSIR), the University of the Witwatersrand, Johannesburg (South Africa), Stellenbosch University, and University of Johannesburg.
SPIE Student Chapters are active at CSIR, Wits, and Stellenbosch as well as in Tunisia, Egypt, and Cameroon.
A paper describing the activities of optics students in Africa was presented in 2014 at an SPIE conference on education and training in optics and photonics. See: dx.doi.org/10.1117/12.2070775.
A “training the trainer” program called Active Learning in Optics and Photonics (ALOP) has also helped raise awareness about the importance of optics education. ALOP workshops have reached more than 1000 teachers from about 50 developing countries in Africa, Asia, and Latin America since the program was created in 2004 under the auspices of the United Nations Educational, Scientific, and Cultural Organization (UNESCO).
Members of the ALOP team received the 2011 SPIE Educator of the Year Award.
SPIE is a major supporter of an optics program at the Abdus Salam International Centre for Theoretical Physics (ICTP) in Italy that supports optics researchers from developing countries.
The SPIE-ICTP Anchor Research in Optics Program has evolved into a wellequipped lab where optics associates at ICTP, postdocs, attendees of the annual Winter College on Optics, and scientists visiting from developing countries can conduct laser and microscopy research. Work has included projects in quantum cascade lasers, optical tweezers, and microscopy for applications in the physical and life sciences.
One of the goals is to make the research sustainable by showing visiting researchers how to set up similar labs in their home institutions with a modest investment.
SPIE Fellow Andrew Forbes of University of the Witwatersrand (South Africa) is hoping to gain support to relaunch the Photonics Initiative in South Africa (PISA) later this year.
The initiative, supported by the SA Department of Science and Technology, was established in 2008 to stimulate multidisciplinary research and human capital development, as well as to stimulate South Africa’s economy via photonics.
PISA quickly led to the creation of industrial clusters in the country, but it never got off the ground.
Forbes, who helped organize a June workshop in South Africa on sustainable photonics for telecommunications, said he hopes he and others in the photonics field can raise awareness among the public and government officials about the importance of the field and come up with a new strategy to relaunch the initiative.
Optical and photonics technologies can ensure the safety of food, bring inexpensive and efficient health care to rural and developing areas, enable instant communications, and otherwise bring tangible social, environmental, health, and economic gains to humanity.
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