Issue 01 - April 2024 - Binder - Forging New Frontiers

CDE Forging New Fr ontiers

Dear Reader,

We a re e x cit ed t o i n tr o d u c e t he College of Design and Engineering (CDE) ne wsl e tt e r F o r g in g N e w F ro n ti e rs , our ne w p u bl i cation t h at co l lates an d showcases the progress we are making in academia and beyond.

Established in 2022, CDE is a fusion of two world-class schools with long, distinguished histories the Faculty of Engineering and the School of Design and Environment, at the National University of Singapore. It’s a place where we continue to exand our research focus into frontiers where design, technology and human factors meet.

The first issue of Forging New Frontiers dives into the theme of ‘Climate Resilience Technologies’, featuring a variety of domains spanning green transportation and efficient materials to greenhouse gas reduction, as well as sustainable architecture and urban planning.

Onespotlightshineson ProfessorYanNing’sworkonsustainablefoodproduction pathways — reimagining our approach to food security and sustainability.

We invite you to explore this pilot issue and join us in our journey to forge new frontiers in research and innovation!

Professor Teo Kie Leong Dean,CollegeofDesignandEngineering NationalUniversityofSingapore

Taking a bite out of carbon emissions

As climate change influences weather patterns and upsets food systems, researchers think it’s time to reimagine how food is farmed to ensure its security and sustainability.

Agriculture, for millennia, has been the backbone of societies, from Neolithic homo sapiens who favoured a reliable food supply over traditional hunter-gatherer lifestyles, to the Chinese Han Dynasty that birthed many agricultural inventions to improve farming efficiencies.

As societies all over the globe sowed the seeds of agriculture, cities and civilisations flourished, crops and livestock could be farmed to meet — and exceed — demand, and as a result, the global population skyrocketed, from some 5–6 million people 12,000 years ago to over eight billion today.

With such a boom in population comes unprecedented challenges, one of which is climate change Today’s food systems collectively emit around one-third of global greenhouse gas emissions and guzzle 15% of fossil fuels. From production to distribution to the consumer’s fork, each phase of the modern food system contributes to these emissions. Significant waste is also generated throughout the value chain, with an estimated 30% of food produced for human consumption being discarded — amounting to about USD1 trillion lost annually.

Climate change and our food system are tightly interwoven. More frequent and severe weather events can fuel the destruction of harvests and threaten food security across the globe, perpetuating a vicious cycle that not only exacerbates climate threats but also disrupts food production and distribution, particularly impacting vulnerable populations. Land scarcity and the excessive use of pesticides and fertilisers also add to the issue.

Professor Yan Ning from the College of Design and Engineering at the National University of Singapore has an important part to play in contributing a solution to these global challenges. At the Department of Chemical and Biomolecular Engineering, Prof Yan leads a team to research and develop a sustainable approach to food production, called “green chemical farming”.

Instead of relying on nature-based biological routes — with sunlight and chlorophyll playing lead roles — green chemical farming turns the spotlight to a chemical sleight of hand and some clever engineering. The research team published their idea in Nature Sustainability on 23 June 2022.

Artificial interventions

With chemistry and chemical engineering as the two main pillars, green chemical farming replaces plant-based biomass with chemically produced functional molecules, subsequently transforming these compounds into usable, nutritious food components.

This alternative route reduces the reliance on increasingly scarce natural resources like land and water. Highlighting this urgency, The Guardian reported that the

demand for fresh water is expected to exceed supply by 40% by the end of this decade.

Take some key compounds, such as water, carbon dioxide and ammonia, for example. In the team’s approach, these functional molecules can be transformed, ideally with the help of renewables, into hydrogen, a range of organics, and ammonia and amino acids, respectively.

“These chemical feedstocks can then be used as building blocks by a range of microbes, such as edible microalgae and yeast, for more complex food ingredients and flavouring,” explains Prof Yan. “The nutrient-laden microorganisms are subsequently harvested and processed as agricultural products and can be integrated with the rest of our food processing flow.”

The nutrients can also be upstream substrates for other emerging food technologies, including three-dimensional printing and non-animal-derived, laboratory-grown meat. The researchers looked into how green chemical farming might deliver new pathways to meat analogues that can complement traditional protein sources like beef.

Lab-grown cultured meat, which replicates animal muscle tissue, matching its protein profile and even taste, offers a sustainable alternative without emitting potent, planet-cooking greenhouse gases such as methane. This approach could create a significant dent in carbon emissions. To give a sense of the scale, cattle and dairy cows emit enough greenhouse gases to put them on par with the highest-emitting nations

Putting the green gears in motion

While not yet demonstrated at a systemic level, the science underpinning green chemical farming is now being rigorously researched — with some technologies reaching maturity and developers scaling up their applications.

One of the key components is the development of materials for carbon dioxide adsorption, which has made carbon capture in power plants economically viable. This advancement has made the compound available as a feedstock at a costeffective rate.

Complementing this are efforts to slash the costs of clean hydrogen, such as the US Department of Energy’s Hydrogen Shot initiative. This is vital for green chemical

farming, as affordable hydrogen is essential for converting carbon dioxide and nitrogen into green chemicals.

Moreover, the development of corrosionresistant multilayer anodes for seawater electrolysis is opening new routes for hydrogen fuel generation, further supporting the infrastructure needed for this innovative farming approach.

On the other hand, the production of amino acids from renewable carbon sources has recently been established, offering a sustainable pathway for singlecell protein production. These proteins are crucial for feeding microorganisms used in green chemical farming, such as model bacterial species and microalgae.

“Momentum is building, and a broad spectrum of research and incentives are making green chemical farming more palatable.”

“Momentum is building, and a broad spectrum of research and incentives are making green chemical farming more palatable,” adds Prof Yan. “McKinsey reported that an annual investment of around USD840 billion in food and agriculture is necessary to reach net zero by 2050. This could stimulate demand for the supplies and equipment that enable decarbonisation, spurring the commercialisation of new technologies for alternative protein sources.”

A way to go to palatability

As with any transformative technology, the path to realising green chemical farming is strewn with significant technical and economic hurdles. While the underlying science shows promise, scaling it up to a level that can meaningfully contribute to global food supplies presents thorny challenges. The costs associated with developing and maintaining the required infrastructure, along with manoeuvring the complex chemical processes at scale, put economic viability to the stand.

Moreover, the integration of these new methods with existing agricultural systems requires extensive planning as well as a huge appetite for investment, potentially making it a less accessible option for developing regions.

Understandably, many consumers have yet to develop the taste buds for chemically or laboratory-grown proteins. The concept of consuming food that isn’t derived from traditional farming but instead created in laboratories or through chemical processes is, after all, a substantial departure from conventional dietary habits. Meanwhile, promoting such foods requires a delicate balance between evidence-based education and gradual introduction, as overly aggressive advocacy might backfire, inadvertently giving rise to public resistance and widening the gap of mistrust.

Food for thought

Green chemical farming is particularly attractive in regions where resources are scarce, land is finite and traditional infrastructure is inadequate.

“Singapore is a prime example, with a population of nearly six million squeezed into a space of 730 km2,” says Prof Yan. “The city-state is heavily reliant on imports for 90% of its food, making it especially prone to supply-chain snags— made prominent during the COVID-19 pandemic.”

Advancing green chemical farming entails multi-disciplinary R&D efforts. To overcome the associated challenges, Prof Yan has a few suggestions.

First, the feasibility of the approach must be validated through systemslevel demonstrations. This involves chemists and chemical engineers working together to refine catalytic systems, enhancing the efficiency of key chemical reactions, while biochemists and bioengineers focus on identifying and addressing the rate-limiting steps in the production of biomass from nonconventional chemical substrates, such as ethanol.

In addition, cradle-to-grave and technoeconomic analyses are essential to paint a clearer picture of the system’s carbon footprint, its comparative advantages and weaknesses, as well as areas requiring further improvement.

“The city-state is heavily reliant on imports for 90% of its food, making it especially prone to supply-chain snags—made prominent during the COVID-19 pandemic.”

Equally crucial are rigorous studies ensuring food safety in the downstream processing of microbes into consumable products. In this context, consumer perception is key for the social acceptance of products derived from green chemical farming. The researchers underlined the importance of collaboration among governmental regulators, academic institutions, and the food industry to guarantee that these products can safely transition from farm to fork.

The traditional food-production industry should also be part of the equation. To grasp the broader impact of green chemical farming on the business landscape, environmentally extended input-outlet analyses are critical. These studies will reveal how this new approach affects various economic sectors, including standard food production, offering a window into its potential economic implications.

As the public and private sectors recalibrate the standard approach to food production in response to climate change, technologies like green chemical farming could become an integral element in a comprehensive strategy to mitigate its impacts on agriculture.

Driving that innovative spirit is the reality that even a slight increase in global temperatures can lead to profound, potentially irreversible disruptions in agricultural practices. This reality will, above all, inevitably impel a transformation of the sector in ways that are yet to be fully anticipated.

Transforming processes to slash carbon intensity

NUS CDE researchers design a novel and greener process to produce ethylene glycol, making use of carbon dioxide without emitting any wastes.

The transition to net-zero emissions is arguably one of the most pressing challenges of our time — not only prompting a rethink of how we produce, transport and consume but also driving transformations across virtually all major industries from the ground up.

Whether designing high-density batteries and advanced energy-storage solutions or promoting sustainable fuels in hard-to-abate sectors such as aviation, developing and deploying a diverse range of climate technologies is critical to reducing the amount of greenhouse gases we put into the atmosphere.

Researchers at the College of Design and Engineering, National University of Singapore, are delving into various climate mitigation strategies, with ongoing research efforts ranging from urban climate modelling to developing carboncapture technologies.

At the Department of Chemical and Biomolecular Engineering, Assistant Professor Wang Lei is focusing on using carbon dioxide as the feedstock for producing important chemicals such as ethylene glycol, an essential building block in common items like household containers, clothing and antifreeze for cars and air-conditioning systems.

Advancing climate-positive chemical processes

Currently, producing the essential chemical is energy-intensive, leading to copious emissions of carbon dioxide and other wastes. With global production surpassing 40 megatons in 2020 — equivalent to almost 6 million elephants — the growing demand, expected to increase 5–10% annually, amplifies the need for more environmentally friendly production practices.

Addressing this challenge, Asst Prof Wang’s team developed a novel cascade catalytic system for the selective production of pure ethylene glycol. This process unfolds in two distinct steps — the first being an electrocatalytic reaction that generates a pure stream of hydrogen peroxide, followed by a thermal catalytic reaction where ethylene glycol is synthesised. The cascade system breaks away from traditional, highly polluting methods, combining the use of electricity and heat.

“The first electrochemical reactor constructed for this purpose showcased high Faradaic efficiency — exceeding 90% and allowed for adjustable current densities through a two-electron oxygen reduction reaction,” explains Asst Prof Wang. “This means the setup offers a low-energy alternative to conventional processes, all the while introducing modularity and the capacity to generate hydrogen peroxide on demand, obviating the need for storing and transporting the chemical.”

In the next thermal reactor, the generated hydrogen peroxide meets with ethylene, and with the help of a titanium-based catalyst and an acid, reacts to form ethylene

gly c ol a s t he s ole pro d u ct w it h ou t any w as t es. “Our d e s ign e f fec t ivel y decouples ethylene oxidation fro m electrod e p ot en ti a ls , t h us pr e v en t in g the overoxidation of ethylene an d streamlining both the reactor’s design and the downstream separation process,” adds Asst Prof Wang.

The team’s process achieved an efficiency of 70% a significant improvement over existing methods and demonstrated excellent stability, capable of continuous operation for up to 100 hours.

One step greener

“Our design effectively decouples ethylene oxidation from electrode potentials, thus preventing the overoxidation of ethylene and streamlining both the reactor’s design and the downstream separation process.”

“We also successfully adapted the process to produce ethylene glycol directly from carbon dioxide, bypassing the need for ethylene, which is derived from fossil fuels,” adds Asst Prof Wang. “This adaptation could complement nascent carbon-capture technologies, where the production of ethylene glycol could potentially turn into a climate-positive process.”

The applications of this cascade system are not confined to the production of ethylene glycol alone. Various other chemical reactions, such as methane and alcohol oxidation, and even epoxidation, which is a crucial step in formulating pharmaceuticals, can also benefit from the system.

“Our next steps involve optimising the system for enhanced efficiency and assessing its commercial potential. We’re also exploring how this technology can be applied to produce a wider range of chemicals,” adds Asst Prof Wang.

The team's findings were published in the journal Nature Catalysis on 26 June 2023.

Chemical and Biomolecular Engineering

Getting the most out of the sun

NUS CDE researchers combine perovskite and organic semiconductors to create next-generation thin-film photovoltaic cells.

Photovoltaic cells, fundamental components of solar panels, continue to be a cornerstone in the renewable energy sector and are poised to surpass coal as the world’s largest source of power capacity in the next few years

At the College of Design and Engineering (CDE), National University of Singapore (NUS), researchers such as Assistant Professor Hou Yi from the Department of Chemical and Biomolecular Engineering continue to innovate at the forefront of solar technology, designing photovoltaics that are more efficient at converting sunlight into electricity.

Some of Asst Prof Hou’s inventions include solar cells composed of perovskite and organic semiconductors, which complement each other to offer both flexibility and efficiency that leapfrog conventional counterparts. These advancements are a crucial cog in the engine steering the world toward a greener and more sustainable future, unlocking more of the sun’s potential to provide a clean and abundant source of power.

Mix and match

While conventional, silicon-based solar panels have become a common means of harvesting the sun’s energy, they are also quickly nearing their theoretical maximum efficiency, known as the Shockley-Queisser limit.

An approach to work around this barrier involves employing a different material, such as perovskite, which excels at absorbing light compared to silicon. It also exploits untapped regions of the solar spectrum. By integrating thin perovskite layers with other solar cell technologies, in a configuration known as tandem solar cells (TSCs), researchers have exceeded the efficiency limits of single-material solar cells.

At NUS CDE, researchers are exploring the use of organic semiconductors in place of silicon, and in tandem, which could lead to more adaptable and flexible ultrathin solar cells for applications like vehicle- and building-integrated photovoltaics.

“Perovskite/organic TSCs offer a blend of flexibility and efficiency that surpasses traditional solar technology with their tuneable chemical composition and bandgap,” says Asst Prof Hou. “However, their performance still lags behind other thin-film technologies.”

These TSCs face issues like open-circuit voltage losses, impacting the cell’s efficiency in converting solar energy into electricity. Additionally, their performance is further impeded by inefficiencies in the layers that connect different parts of the cell.

Rolling out efficient ultra-thin solar cells

Asst Prof Hou’s research team implemented two key strategies to address these challenges. Firstly, they used benzylphosphonic acid to passivate the nickel oxide hole-transport layers (HTLs) — the ‘highway’ for moving positive charges towards the metal electrode. This modification reduced surface recombination losses,

enhancing the open-circuit voltage in the perovskite layer, and thus the power conversion efficiency of the cell.

The second strategy involved engineering a four-nanometre-thick interconnecting layer of iridium zinc oxide (IZO), sandwiched between organic bathocuproine and molybdenum oxide. With its excellent electrical and optical properties, the layer improved electrical conductivity and boosted near-infrared light absorption.

Together, the passivated nickel oxide and IZO layers enabled the perovskite/organic TSC to achieve an impressive power conversion efficiency of 23.60%, with high stability maintained over 20 days of continuous use.

Additionally, Asst Prof Hou’s research revealed crucial insights into the design of interconnecting layers in perovskite-based TSCs. Discussing the complex interplay between the surface coverage of the layers, the directional movement of charge carriers and the lifespan of electron-hole recombination processes, the team’s findings provide a blueprint for optimising interconnecting layers to enhance the overall efficiency of TSCs.

“We are excited by the outcomes of our research, which shows the great potential of perovskite/organic TSCs to rival or even surpass the performance of other existing thin-film TSCs in module sizes,” says Asst Prof Hou. “Further innovation in narrow-bandgap organic materials, improving the stability of HTLs and suppressing phase segregation in wide-bandgap perovskites are vital next steps for advancing these solar cells.”

The team’s findings were published in Nature Energy on 20 January 2022.

Darkness is no enemy to this solar tech

NUS CDE researchers demonstrate the possibility of harnessing solar power even under after the sun has set.

Harnessing the sun’s energy continuously — even without direct sunlight — has long been an alluring goal. The growing demand for reliable power sources in off-grid applications, particularly for the increasingly prevalent Internet-of-Things sensors, has fuelled extensive research in this area. Innovations in off-grid renewable energy systems are crucial for delivering secure, affordable electricity to rural communities all over the globe.

Professor Wang Qing from the Department of Materials Science and Engineering at the College of Design and Engineering, National University of Singapore, has a solution — harvesting solar heat using devices that convert thermal energy to the electrical kind. This makes possible the utilisation of solar energy, even under the cover of darkness.

Befriending the dark

Solar panels, without an energy storage system, function only when the sun is shining. While thermoelectric generators — devices that scavenge heat to produce electricity — offer an alternative, their effectiveness is hindered by limited spatial temperature differences and low efficiencies.

A team led by Prof Wang developed an electricity generator based on a charging-free, thermally regenerative electrochemical cycle (TREC) system, in which temperature differences at different times drive electricity generation.

This system is unique in that it incorporates a graphene-based, bifunctional component that acts both as a solar absorber and a radiative cooler — enabling round-the-clock electricity generation without requiring an external power source. Here, the role of graphene is key. The ‘wonder material’, known for its exceptional thermal properties, is capable of amplifying the temperature difference in the TREC system between day and night to over 40 °C, which in turn enhances the thermoelectric conversion process.

Through the integration of lithium-based redox couples and some clever engineering, the team’s TREC system outperformed existing solutions, achieving a thermoelectric efficiency of 19.91% — almost quintupling the maximum efficiency of previously reported charging-free TRECs. Moreover, the system’s power density exceeded that of earlier TRECs by more than tenfold. Power density, which measures the amount of power generated per unit area, is a key indicator of efficiency; the higher it is, the more efficient and effective the system.

Practicality first and foremost

A rooftop trial at NUS showcased the system’s capability to continuously generate electricity for two days, effectively harvesting low-grade heat from the environment. This demonstration underlines the system’s practicality for all-day power generation, suitable for powering IoT devices and other electronics that require distributed power.

“There’s plenty of room to improve the system’s performance,” says Prof Wang. “For instance, to boost its efficiency and power output, we can look into the materials’ temperature coefficients and charge densities, alongside reducing their heat capacities. It’s also crucial to consider scaling up the system to meet diverse energy needs, as this will broaden its applicability in utilising low-grade heat from a variety of sources.”

The team’s findings were published in Joule on 19 July 2023.

Electrical and Computer Engineering

Injecting fresh energy into membrane technology

NUS CDE researchers challenge the status quo of membrane technology with a novel design that promises enhanced energy efficiency and versatility.

Whether it’s ensuring the safety of drinking water or filtering pathogens in air purification systems, membranes have long been inseparable from many modern industrial processes fundamental to our daily lives.

Inorganic membranes are a lot like kitchen sieves. Like how sieves separate liquids from fine solids in cooking, inorganic membranes, typically made of ceramics or metals, selectively isolate molecules based on various factors such as size and charge.

As the global push towards climate protection prompts stricter emissions standards, the race is on to develop membrane technologies that enable more efficient and environmentally sustainable practices.

A team of researchers from the College of Design and Engineering at the National University of Singapore, led by Professor Ho Ghim Wei from the Department of Electrical and Computer Engineering, has developed energy-efficient and highly customisable inorganic membranes.

The newly designed membranes have the potential to benefit applications beyond filtration and separation. From energy conversion to catalysis and sensing, versatility is also a key feature of the membranes, which could help drive efficiency and sustainability in various industrial processes.

Reimagining membranes from the ground up

Conventional organic membrane technologies, typically used in purification and separation processes, tend to be energy-intensive, which results in considerable operational costs. Over time, these organic membranes also require regeneration, while the filtered components require further treatment — all of which equate to more expenses.

“Such limitations have driven us to reconsider membranes in terms of what they’re made of, how they’re structured and what they can do,” says Prof Ho. “Membranes play an integral, and often enabling role in many industrial processes. Enhancing their energy efficiency is what we can do to reduce the overall power consumption and, consequently, the carbon emissions associated with these processes.”

“Membranes play an integral, and often enabling role in many industrial processes.”

With this goal in mind, Prof Ho’s research team developed a technique for creating ultrathin, free-standing inorganic membranes. Crucially, these membranes can operate without the need for a supporting substrate — a big plus for their flexibility and functionality.

“Our method involves taming chaotic, free-floating, inorganic building blocks in a liquid environment, coaxing them to self-assemble into the desired membrane structure,” explains Dr Zhang Chen, a postdoctoral fellow in the team and first author of the study. “From a structural perspective, the membranes have more geometric diversity than their conventional counterparts — this means we can design them for specific, customised applications. Furthermore, unique membrane structures with diverse topologies have been fabricated, including those formed by mixing two particle types, continuous patchwork of non-mixing particle domains, and vertically stacked membranes.”

Functionality leads to versatility

Functionality was also a key focus for the team. They engineered the membranes to act as highly selective two-dimensional barriers, across which energy transfer can be precisely controlled. This unique feature enables the membranes to filter ions by charge, selectively concentrate certain molecules and harness different forms of energy, such as thermal, electrical or light, in the separation process.

The ability to create flexible, functional, freestanding inorganic membranes is a boon for many industries that rely heavily on membranes for their operations, particularly those related to the energy or environmental sectors. The researchers reckon that their novel design could be deployed in applications such as advanced spatial dynamic separation, catalysis, sensor technology, memory storage and ionic conductors.

Published in Nature on 29 March 2023, the team’s paper also includes a synthesis template on which other researchers can base their work. This could spur the development of a broader array of novel membranes with more diverse compositions.

New sieves on the block

“This advancement in inorganic membrane design opens new possibilities, essentially rejuvenating what is considered a mature field of membrane technology,” adds Prof Ho.

Motivated by the potential of this breakthrough, Prof Ho is now leading a multidisciplinary team to further explore the vast spectrum of membrane compositions and couple them with various forms of energy. They are also concurrently focusing on developing automated manufacturing tools to facilitate the large-scale production of this technology.

Biomedical Engineering

MORPHing metamaterials into biomarker-detection powerhouses

Molecular diagnostics get a shot in the arm with hydrogelbased metamaterials, enhancing precision and speed in identifying critical biomarkers for disease monitoring.

Smart materials, from sunlight-responsive windows to shape-shifting alloys in medical devices to self-powered light sensors, play an increasingly integral role in our everyday lives due to their ability to react to various external stimuli such as light, temperature or moisture.

Among smart materials, metamaterials stand out for their engineered structures with unique properties not commonly found in nature. With rationally designed patterns, these materials work in unison to offer precise control and unprecedented functionalities. This characteristic renders them versatile across many applications, ranging from advanced optics to medical technologies, through the manipulation of energy and signals in novel ways.

At the College of Design and Engineering, National University of Singapore, researchers have achieved a breakthrough in biomolecule profiling by designing a hydrogel-based metamaterial specially engineered to visually detect the presence of extracellular vesicles in patient samples, with potential applications in disease diagnosis and monitoring.

Led by Associate Professor Shao Huilin, the team’s research was published in Nature Biomedical Engineering on 27 October 2022.

Unlocking the biomedical potential of metamaterials

Mechanical metamaterials have recently garnered interest in biomedicine for applications in diagnostics and treatments as they can dramatically alter an object’s mechanical response through their structured composition.

Take, for instance, metamaterials with a lattice structure. Such materials have a negative Poisson’s ratio — meaning they expand laterally when stretched, in contrast to most that tend to contract. This makes them highly valuable in crafting impact-resistant materials and in the design of medical implants.

Yet, the full potential of these materials in medical applications remains largely untapped. A key challenge in harnessing mechanical metamaterials for biomedical purposes lies in their limited response range, especially when considering hydrogels.

While hydrogels are responsive to environmental changes, their structural flexibility during preparation can compromise the precision required for biomedical applications. They also react rather slowly. Molecules within a hydrogel network interact with one another via gradual diffusion, which limits its ability to detect changes swiftly and accurately in different areas.

MORPHing molecular diagnostics

In response to these challenges, Assoc Prof Shao’s team introduced the MORPH system — a hydrogel-based mechanical metamaterial operating at a critical point for hyper-responsive analysis.

“The hydrogel is specially designed for detailed molecular profiling at the nanoscale, making it highly sensitive to specific biological markers,” said Assoc Prof Shao. “When it encounters targeted biomarkers, such as extracellular vesicles specific to cancer patient samples, an antibody-antigen binding reaction occurs. Here, antibodies that integrated into the hydrogels bind with these biomarkers.”

This interaction triggers a physical transformation in the hydrogel’s structure, which is further intensified by plasmonic heating. This ensures that the hydrogel remains in a sensitive transition state — primed to react to the slightest biomolecular shifts. As a result, these shifts are easily detectable using simple optical methods, including tools as simple as a smartphone camera — enhancing the system’s practicality in clinical settings.

Expanding diagnostic horizons

With enhanced sensitivity and specificity, the MORPH system can be precisely fine-tuned to various biomolecular stimuli, especially in analysing exosomes. This shows promise for early detection in a spectrum of diseases, including cancers and neurodegenerative disorders.

“There’s room for incorporating a wider range of bio-responsive hydrogels to boost the system’s responsiveness. This could open new avenues for detecting and analysing transient molecular interactions,” adds Assoc Prof Shao, highlighting the system’s versatility.

The researchers also explored adapting the system to develop complex 3D architectures, including designs inspired by Japanese origami and kirigami. Crafting such intricate metamaterials could bring about sophisticated methods in signal transduction and amplification, all of which refine the system’s analytical capabilities. Translating these techniques to biomedicine could lead to faster biomarker discovery, a better understanding of disease progression and more effective personalised medicine and diagnostics.

Architecture

Architecting resilient, future-proof cities

NUS CDE researchers design a multi-scale, climate-sensitive framework to support urban design decision-making.

While urban centres have become the engine of national and global economic growth, generating over 80% of global GDP and lifting millions out of poverty, this shift is no bed of roses. The speed and scale of urbanisation tugs with it unprecedented challenges, from increased prevalence of infectious diseases to substantial changes in land use to escalating urban heat risk.

Perhaps one of the most recognisable hallmarks of densely populated cities is the urban heat island (UHI) effect. Travel from Bishan Park to downtown Singapore, for instance, and you may quite literally notice a tangible change in the atmosphere. On top of the warming already caused by climate change, the UHI effect intensifies urban temperatures, posing significant risks to human comfort, health and even economics.

Associate Professor Yuan Chao from the Department of Architecture (DOA) and NUS Cities at the College of Design and Engineering, along with Zhang Liqing, a PhD student from the same department, have developed a framework for climatesensitive urban planning, taking Singapore as a focal case study.

Through a three-pronged approach — assessing UHI, wind and design implications — the researchers, who are affiliated with the Urban Climate Design Lab, aimed to weave climate considerations into urban planning to mitigate the UHI effect. This could help urban planners and governments alike make more informed decisions that balance both the local climate and urban development needs.

The study was published in Urban Climate on 28 February 2023.

Popular hotspots

The way cities are structure — with their concrete skyscrapers, extensive asphalt roads and sprawling vehicles — inherently amplifies and retains heat that is supposed to be dispersed at night. This leads to the UHI effect, where pockets of land in urbanised areas are several degrees warmer than the surrounding, suburban areas.

The implications of even a slight temperature rise are far from trivial, as it can pose substantial risks to human health, contributing to chronic illness and even death. Various conditions such as heat exhaustion, kidney damage and even cardiovascular diseases are exacerbated. For instance, one study in the Catalonia region of Spain reported a 19% increase in daily mortality following three consecutive days of intense heat.

“Optimising urban configurations is critical in the design and planning of cities,” says Assoc Prof Yuan. “Though the benefits may not be immediate, careful planning helps governments to reap benefits in the long run, creating sustainable and resilient living environments fit for the future.”

Future-proofing urban landscapes

The study’s first step involved assessing UHI intensity to locate urban hotspots. Utilising a Geographic Information System (GIS)-based digital climate platform, they mapped areas in the city-state experiencing higher temperatures compared to the rural area, Pulau Ubin. This enabled them to pinpoint specific areas that are most affected — notably Chinatown and some eastern areas, where the air temperature is three to five degrees higher.

“Employing accessible tools such as GIS-based digital platforms enable urban planners to conduct environmental assessments and identify the unique challenges specific to their cities,” explains Assoc Prof Yuan.

Natural wind was explored in the next step. By analysing the impact of buildings, terrain and trees on urban wind, potential air paths could be discerned to more efficiently harness natural ventilation to improve outdoor thermal comfort and air quality in urban areas. This highlighted how natural processes could be part of the solution too.

With these insights, the researchers formulated strategies that incorporate climate considerations into urban planning. These strategies encompass various elements, from the specific design of buildings to the integration of green-blue spaces, as well as how these components are spatially laid out within the urban fabric.

A key principle in the framework is the integration of multi-spatial scale analysis, bridging insights from large-scale urban studies to guide smaller, localised design decisions. This approach ensures that neighbourhood-level planning is cognisant of broader urban trends. “It’s about ensuring that every local project fits well within the broader urban climate system — one that is more efficient and unified,” says Assoc Prof Yuan.

Looking ahead, researchers will explore the balance between social science and technology for climate sustainability and resilience, considering socioeconomic impacts and acceptability across various demographic groups at the individual, household and community levels. Assoc Prof Yuan adds, “This is crucial in developing environments that are sustainable and resilient to climate change while enhancing the liveability of cities in the long term.”

Future-proofing Singapore’s climate resilience

The Coastal Protection and Flood Resilience Institute

Singapore aims to bolster local capabilities and expertise in coastal protection and flood management.

As the world’s oceans run a fever due to anthropogenic climate change, the expansion of ocean waters, coupled with the melting of land-based ice sheets, is causing sea levels to swell. Even a small rise can precipitate devastating effects on coastal communities, increasing flood risks and endangering homes and critical infrastructure. The urgency of this threat is underscored by projections suggesting a potential rise in sea levels of over 30 centimetres by 2050, which could displace millions of people, creating a crisis of climate refugees.

The city-state of Singapore is particularly vulnerable due to its geographical location and low-lying land area—about 30% of its land surface is less than five metres above mean sea level. These weather events could greatly affect Singapore’s resources, biodiversity and public health, making it all the more pressing to develop defensive strategies through focused research.

To help Singapore adapt to the evolving climate, the Coastal Protection and Flood Resilience Institute (CFI) Singapore was launched at NUS by the Minister for Sustainability and the Environment Ms Grace Fu on 7 September 2023. It is the first Centre of Excellence in the city-state dedicated to strengthening local capabilities and expertise in coastal protection and flood management research and solution development.

Hosted at NUS, the institute is a key pillar under PUB’s S$125 million Coastal Protection Research Programme (CPRP) , bringing together local universities, research institutes and industry partners in a collaborative effort. Together, they will carry out research projects aimed at advancing core domain knowledge and developing innovative solutions to safeguard Singapore’s coastlines against rising sea levels and manage flood risks during intense rainfall events.

Collaborative research for coastal resilience

Overseeing CFI Singapore’s research activities and leading the institute’s management team as the Executive Director is Professor Richard Liew, Head of the Department of Civil and Environmental Engineering under the NUS College of Design and Engineering. NUS is partnering with four other institutes in Singapore: Nanyang Technological University, (NTU) Singapore University of Technology and Design (SUTD), Singapore Institute of Technology (SIT) and the Agency for Science, Technology and Research (A*STAR).

CFI Singapore has commenced the first tranche of research projects, encompassing nine projects across four key areas: coastal science research; monitoring, prediction and digitalisation of coastal environment; integrated nature-based solutions; and innovative engineering solutions.

“As the host institution, we will contribute resources and expertise in Ocean Infrastructure and Renewables, Resilient Infrastructure and Climate Change Mitigation across the university to support CFI Singapore,” says Prof Liew. “Research institutes on campus, such as the NUS Centre for Nature-based Climate Solutions (CNCS) and the Tropical Marine Science Institute (TMSI) will also play a crucial role in the success of this nationwide initiative.”

One notable project at CFI Singapore involves the development of nature-based solutions, employing an integrated meta-hydro-ecological approach to protect Singapore’s coastlines. This project, which includes a multi-disciplinary team from three NUS research units — CNCS, TMSI and the Technology Centre for Offshore and Marine, Singapore — will evaluate the effectiveness of hybrid coastal protection solutions, such as perched beaches with seagrass and mangroves integrated with rock revetments. The researchers will explore the feasibility of these hybrid solutions around Singapore, evaluating their ecological and societal benefits.

Another project involves a collaboration between NUS, SIT and industry partners such as engineering consultancy Surbana Jurong. This project is dedicated to developing modular, climate-response solutions to adapt to the challenges posed by high uncertainties in rising sea levels.

A cradle of future talent

Besides conducting world-class research and developing innovative solutions for Singapore’s unique coastal challenges, CFI Singapore will also serve as a training ground for a new generation of researchers and engineers — critical to addressing the nation’s long-term needs in coastal protection and flood management.

The institute’s strategy includes a suite of educational programmes, workforce training initiatives and scientific seminars, all aimed at building a vibrant research ecosystem and expanding the pool of expertise in climate research. For instance, NUS will offer a Master of Science Programme specialising in Sustainable Climate Resilience, a Graduate Certificate Programme in Coastal Protection and Flood Management and another Graduate Certificate Programme in Digital Water

“Education and training will be critical outputs of the institute. We will identify programmes across the partner institutes that can be tapped into to develop the diverse, interdisciplinary talent required,” says Prof Liew.

College of Design and Engineering

Taking a byte out of data centre emissions

A new testbed facility is launched at NUS to fast-track the testing and adoption of sustainable cooling technologies for data centres in tropical climates.

Data centres are the engines powering the digital age. Every time a photographer stores pictures in the cloud, an astrophysicist simulates the number of atoms in the observable universe, or a climate modeller forecasts the week’s weather, a data centre somewhere in the world springs into action, processing, analysing or tucking away vast amounts of data.

Such data centres are also notoriously power-hungry, consuming more electricity than entire countries. In 2020, global data centres consumed between 200–250 TWh, surpassing the power consumption of nations such as South Africa, Egypt and Argentina.

Much of that electricity — up to 40% of it — is dedicated to cooling the hardware that keeps data centres operational. As digital transformation permeates virtually every sector, coupled with the proliferation of energy-intensive applications such as generative artificial intelligence, the power consumption of data centres will only go in one direction. Projections suggest it could quadruple by 2030.

To address this challenge, the Sustainable Tropical Data Centre Testbed (STDCT) was launched at NUS on 29 November 2023 by Singapore’s Minister of State for Trade and Industry, Mr Alvin Tan.

Supported by the National Research Foundation (NRF) and various industry players, the programme is designed to fast-track the testing and adoption of sustainable cooling technologies for data centres in tropical climates, which aligns with the Research, Innovation and Enterprise (RIE) 2025 plan to position Singapore as a leading centre for green services and solutions to transform sustainable industries.

Minister of State for Trade and Industry Mr Alvin Tan (third from right) launched the Sustainable Tropical Data Centre Testbed (STDCT) at NUS. The STDCT is the first of its kind for the tropical environment. From left to right: Associate Professor Lee Poh Seng, STDCT Programme Director, Professor Teo Kie Leong, NUS College of Design and Engineering then Acting Dean, Professor Liu Bin, NUS Deputy President (Research and Technology), Mr Alvin Tan, Minister of State for Trade and Industry, Professor Lam Khin Yong, NTU Vice President (Industry), Professor Wen Yonggang, STDCT Programme Co-Director.

Tailored for hot and humid climates

Designed as a flexible, full-scale living laboratory, the STDCT is at the centre of a national-level research programme jointly led by NUS and Nanyang Technological University (NTU), Singapore, together with key stakeholders in Singapore’s data centre industry.

Spanning 770 m2, the testbed is the world’s first facility dedicated to developing innovative and high-efficiency cooling solutions and establishing new sustainability benchmarks for data centres in tropical climates.

This initiative is especially pertinent for hot and humid countries such as Singapore, where data centres currently account for 7% of the nation’s total electricity consumption, which is expected to nearly double by the end of the decade if it is business as usual.

“Conventional data centres rely on energy-intensive cooling systems, which are costly to run and have a significant environmental footprint,” says Associate Professor Lee Poh Seng from the NUS College of Design and Engineering, who serves as the Programme Director of STDCT. “Our goal at STDCT is to achieve a 40% reduction in energy consumption and reduce water usage by 30 to 40% compared to typical data centres.”

“Our goal at STDCT is to achieve a 40% reduction in energy consumption and reduce water usage by 30 to 40% compared to typical data centres.”

These reductions will lower carbon dioxide emissions of data centres by approximately 40%, while achieving a Power Usage Effectiveness (PUE), a common metric used to describe the energy efficiency of a data centre, of less than 1.20 for a combination of air and liquid cooling. To put this in perspective, the global average PUE for data centres in 2022 was 1.50. Meanwhile, in the same year, the Singapore government set a PUE requirement of 1.30 for new data centres.

Collaboration at the heart

The STDCT programme has attracted more than S$30 million in investments for the facility and five research work packages led by researchers from NUS and NTU in collaboration with 20 industry partners, who have contributed state-of-the-art technologies and are actively engaged in technology co-development. Additionally, the programme also receives support from the Infocomm Media Development Authority.

Among the five research work packages, three are spearheaded by NUS researchers, focusing on the development of cutting-edge cooling technologies. One team is designing an immersion-cooled unibody heat sink for enhanced cooling performance. Another is working to raise the air supply temperature to the data hall, a method demonstrated in NUS’ testbed using air cooling and hot aisle containment, aligning with the latest industry standards for optimising data centre energy consumption in tropical climates. The data hall’s flexible layout further allows researchers to perform side-by-side performance comparisons between two cooling strategies.

Another team is pioneering the world’s first direct-chip hybrid cooling system. This system features a high-performance hybrid sink design that utilises both air and liquid cooling. Liquid, being a more effective heat transfer medium than air, can better manage heat from computer hardware such as CPUs and GPUs.

On the other hand, the potential of a novel dehumidification solution using a high-performance hygroscopic material is also being validated. It could significantly improve the indirect evaporative cooling efficiency of data centres, especially those living in hot and humid tropical climates.

“We look forward to validating alternative, sustainable cooling technologies under real-world conditions, with the aim of developing optimal guidelines for industry adoption,” says Assoc Prof Lee. “Our work will set new standards for greener data centre operation in the tropics, helping to ensure a more sustainable digital future in Singapore and beyond.”