Human civilisation has always been shaped by breakthroughs in materials science. In the past, our greatest material triumphs defined entire eras of humanity, from the stone age to the bronze age to the iron age. Today, we have a far deeper understanding of materials, and now there is no single era-defining material of our time, but rather a host of promising material areas to explore.
From the climate crisis to quantum computers, materials research is poised to play a pivotal role in tackling some of the most pressing global challenges. Therefore, to accelerate progress in this important research field, NUS recently designated it a key area of focus. With this emphasis, NUS has reached the top-tier level in materials research globally, and has amassed some of the world’s most prolific and prominent talents.
This article aims to highlight a selection of these pioneering NUS scientists and their innovative research.
Professor Sir Konstantin Novoselov
One of the most important materials research advances of the 21st century was the isolation of graphene — the world’s first two-dimensional (2D) material. Since this breakthrough, research into 2D materials has flourished, and ground-breaking applications have emerged in areas such as photovoltaics, semiconductors, electrodes and water purification.
The discovery of 2D materials is co-credited to Professor Sir Konstantin Novoselov jointly with Professor Sir Andre Geim and the pair were awarded the 2010 Nobel Prize in Physics for this immense achievement. Prof Novoselov is now the Tan Chin Tuan Centennial Professor at NUS Materials Science and Engineering and continues to investigate this rich research area.
At just one atom thick, 2D materials are as thin as materials can possibly be, and today, approximately 700 stable 2D materials have been predicted, with many remaining to be synthesised. Of this vast range, “Different 2D materials hold different properties. They can be metals, semiconductors, superconductors, ferromagnets, and more,” Prof Novoselov explained.
This range of remarkable properties mean that 2D materials can be applied in numerous areas. “Our 2D materials are being used for a variety of applications, from energy solutions to composite materials, from printable electronics to optoelectronics,” he said. What’s more, Prof Novoselov’s latest research combines 2D materials and the principles which govern living matter, to develop new functional intelligent materials with bespoke properties. These bio-inspired materials could have applications in everything from artificial neural networks to smart membranes.
Professor Antonio Castro Neto
Another pioneer in the field of atomically thin materials is Distinguished Professor Antonio Castro Neto, Director of the NUS Centre for Advanced 2D Materials (CA2DM). The CA2DM was established in 2010 for the conception, characterisation, theoretical modelling and development of transformative technologies based on 2D crystals, such as graphene.
Prof Castro Neto is an expert in all aspects of graphene and he further described the unique advantages that 2D materials offer, “They have physical and chemical properties that normal three-dimensional materials do not have — such as extreme quantum behaviour. Meaning the electrons in these materials behave like waves, not particles.”
These extreme quantum behaviours could create the next generation of electronic components with revolutionary capabilities, and 2D materials like graphene are already being used in the development of quantum computers.
“New materials are the basis for the Industry 4.0,” said Prof Castro Neto, explaining the importance of materials research. “Advances in nanotechnology, biotechnology, quantum computing, artificial intelligence, 3D printing and the Internet of Things (IoT) all require new materials. These new materials then impact fundamental areas such as electronics, food, water, the environment, energy and more,” he stated.
Professor Barbaros Özyilmaz
Among his many research interests, the Head of NUS Materials Science and Engineering, Professor at NUS Physics, and Deputy Director of CA2DM, Professor Barbaros Özyilmaz, is focussed on accelerating the widespread adoption of graphene and other 2D materials into industry.
2D materials can generally be described as perfect crystals of atoms regularly spaced in an atomically thin sheet. While this fundamental structure gives 2D materials their incredible electrical and mechanical properties, it currently makes them costly and tricky to scale up for many industrial applications. Therefore Prof Özyilmaz investigates how to make 2D materials more robust.
Through his cutting-edge research, Prof Özyilmaz recently discovered that 2D materials could be synthesised in such a way that they are amorphous films rather than crystals. These amorphous 2D films still have some of the desirable properties of crystalline 2D materials, but are much more hardy, and cheaper to make. "Our amorphous films can be synthesised at much lower temperatures because they don’t need to be perfect in terms of the crystal structure," Prof Özyilmaz said.
This breakthrough is a leap forward in making 2D materials generally viable for industrial applications. "These amorphous films focus on a subset of 2D material properties, and sacrifice the rest, to ensure that they are more scalable, processible and manageable in terms of risk for industry," Prof Özyilmaz explained. This novel discovery is already of great interest to many companies by providing a shortcut to the commercialisation of graphene.
Professor Silvija Gradečak-Garaj
The goal of green energy production is a challenge that many areas of materials research strive to solve. Professor Silvija Gradečak-Garaj at NUS Materials Science and Engineering is a pioneer in this field, developing new materials for energy applications by understanding and controlling materials at the atomic scale. "My overall research strategy is to combine the synthesis of freestanding nanoscale objects and their assembly into functional devices for applications in nanoelectronics, nanophotonics and in energy harvesting and conversion," Prof Gradečak-Garaj said.
"In my laboratory, we design new methods that allow us to 'watch' materials as they grow and adjust parameters in-situ, during growth, to control composition, structure, size, and morphology of the resulting material," she explained. She then applies — and often designs from scratch — new methods to study how these materials behave under realistic conditions, under external stimuli like temperature or electricity. "We do this by utilising special microscopes that use electrons instead of light to study materials with atomic precision," she said.
As an example of her current work, Prof Gradečak-Garaj has recently developed flexible and semi-transparent solar cells that combine a range of nanoscale materials to improve the solar cell efficiency. These nanoscale materials include nanoparticles that absorb sunlight and produce electrons, nanowires that collect electrons efficiently, and graphene to conduct electricity. "These devices are flexible, so they can be used on large and curved surfaces, unlike conventional solar cells that are flat and rigid. Furthermore, as they are semi-transparent, they can be used even on windows," she said.
"Ultimately, the goal of our research is to design ways we can utilise energy more efficiently to preserve natural resources, address the challenges related to global warming, or heat island issues specific to urban environments like Singapore," she explained.
Professor Liu Bin
Professor Liu Bin, NUS Vice President (Research and Technology), and the Head of NUS Chemical and Biomolecular Engineering, is also interested in materials that interact with light for a variety of applications. “We aim to convert solar energy into clean and accessible energy fuels or value-added products by developing highly efficient organic semiconductor catalysts,” Prof Liu described.
Not only this, but her research is also focussed on the design and synthesis of organic functional materials, and their applications in biomedicine. She has successfully explored the vast potential of organic molecular and polymeric materials in biological applications by bringing them to aqueous media through nanofabrication.
“We endeavour to realise the visualisation of crucial biological processes and non-invasive treatment for some diseases using biocompatible organic materials, especially those with aggregation-induced emission (AIE) characteristics,” she explained
Based on the unique properties of AIE materials, she has invented AIE imaging tools which are highly sensitive, specific, photostable and biocompatible. “Targeting the unmet demand of the research community, we have commercialised our inventions through the NUS spin-off of LuminiCell, which would help solve the complex bioimaging problems for global researchers,” she said. LuminiCell provides real-time cell tracking with 3 times longer duration and 10 times brightness as compared to existing tools. With LuminiCell, researchers can image cell behaviour to enable new diagnostic and therapeutic capabilities for cancer, infectious disease, vascular diseases and more.
President's Assistant Professor Benjamin Tee
The area of biomedicine is one which relies on the regular development of new materials. A widely recognised innovator in this field is President’s Assistant Professor Benjamin Tee from NUS Materials Science and Engineering. His current research is advancing state-of-the-art smart electronic skin materials that can sense the environment.
Being able to sense environmental changes in pressure, temperature and humidity is a natural ability all humans have, but it is much more difficult for machines to do that today. "Our skin is naturally ultra-robust, and adaptive to many different environmental conditions. In contrast, most materials do not have such flexibility, as many sensor materials are made from brittle elements such as silicon or metals," Asst Prof Tee explained. Therefore, he is exploring and developing new flexible, stretchable materials that can also provide more robust sensing capabilities.
In addition, these flexible 'electronic skins' can self-heal, just like real skin. This autonomous self-repair capability provides a new way for electronic devices to withstand damage. "If your mobile phone screen is made of self-repairable materials, you will not need to find a repair shop and risk exposing your data after dropping your phone on the rock hard pavement, because the cracked screen will magically heal itself," Asst Prof Tee said.
His research in electronic skins will also enable better prosthetic devices that are sensitive to the environment. This could reduce the phantom limb pain associated with limb loss, and the prosthetic devices would feel more natural and intelligent. "This can help patients regain normal lives and regain their mobility and confidence," Asst Prof Tee stated.
Professor Lim Chwee Teck
Another world-leader in the field of biomedicine is Professor Lim Chwee Teck, Director of the NUS Institute for Health Innovation & Technology (iHealthTech) and NUS Society Chair Professor at NUS Biomedical Engineering.
“It is known that cancer cells can change their biophysical properties, resulting in them being more deformable and less adhesive. These changes are significant and can lead to cancer metastasis, severe pathology and eventual death,” Prof Lim said.
Hence, using micro- and nanomechanical tools, he investigates why and how such biomechanical changes can occur in circulating cancer cells, so as to better understand their contributions towards metastasis — the main cause of death in patients. He hopes that such research will not only lead to the design of more effective technologies in the detection and diagnosis of cancer, but also better strategies in combatting this disease.
In fact, based on his research findings, Prof Lim has developed a microfluidic cancer biochip which can detect and isolate circulating tumour cells from peripheral blood of patients (known as liquid biopsy). This technology has since been commercialised by Biolidics Limited, which obtained an FDA listing in USA and China, and is being used in over 90 locations around the world.
Professor Gui Bazan
In addition to biomedical devices, another major area of exploration in materials that is of global interest are living composite materials. Composites consist of two or more different material types brought together to provide physical properties otherwise unattainable with individual components. Professor Gui Bazan, who will be taking up a position in NUS Chemistry and NUS Chemical and Biomolecular Engineering in January 2020, conducts innovative research in this area.
"Ever since straw or rice husks were added to mud bricks to make them more robust over 7000 years ago, humans have been aware of composite materials," Prof Bazan stated. But despite this history, there are very few examples of composites where living systems are considered an essential element. Prof Bazan explained this is why he is blazing a trail in this research area. “Our group is thus pioneering living ‘biocomposites’ containing microorganisms and a polymeric hydrogel matrix with metallic properties,” he said.
Prof Bazan's research coordinates principles from chemical synthesis, materials engineering, soft electronic matter and electromicrobiology. It lays the foundation for promoting and understanding electronic communication between synthetic elements and microbial communities. "Living microbial biocomposites provide us with a unique opportunity to harness the extraordinary diversity and adaptability of bacteria," he described.
With this approach Prof Bazan explained that, “It is possible with the right biotic/abiotic combination to use the bacteria for converting chemical energy (in other words its food) into electrical current at levels that are not attainable by any other way.” Given time, this may reveal the possibility to use wastewater as the food source and let the bacteria remove organic contaminants, while at the same time produce electrical power for a green source of energy.
Materials research is not only one of the most rapidly evolving and fastest growing scientific disciplines, but also one which stands at the forefront of modern technology, spanning every facet of 21st century life. The team of first-rate researchers collected at NUS is revealing brand new research insights and spearheading novel applications in all aspects of this field. Ultimately, the cutting-edge materials research conducted at NUS will have far-reaching societal benefits in Singapore and globally.