Pressure sensors are used in electronic devices across all industries and making them as accurate as possible means making them as thin as possible. Researchers from Khalifa University have developed a method to use a novel 2D material for highly-sensitive and tunable flexible pressure sensors.Ìę

Compared with conventional rigid silicon-based electronics, thin, flexible electronics can withstand various deformations such as tension, compression, bending and twisting. Pressure sensors that can transform external pressure into electrical signals are an indispensable application of flexible electronics, particularly for biomedical applications.

A team of researchers from Khalifa University has investigated how to develop a pressure sensor using a novel 2-Dimensional (2D) material, which is a single sheet of material that is just one atom thick, and 3D printing. They published their results in The research team includes Jing Fu, Research Associate, Somayya Taher, PhD candidate, Prof. Rashid Abu Al-Rub, Director of the Advanced Digital and Additive Manufacturing Group and Professor of Mechanical Engineering, Prof. TJ Zhang, Professor of Mechanical Engineering, Prof. Vincent Chan, Professor of Biomedical Engineering, and Prof. Kin Liao, Professor of Aerospace Engineering.

“Pressure sensors can be divided into various categories, including piezoelectric pressure sensors and piezoresistive pressure sensors,” Dr. Kin explained. “The working principle of a piezoresistive pressure sensor capitalizes on the change in the electrical resistance of the sensor against applied pressure. Such sensors have a simple structure, high sensitivity, fast-frequency response and low-energy consumption, making them popular candidates for various applications.”

An effective pressure sensor needs to be sufficiently thin. A sensor that is too thick may give erroneous readings as the sensor would press into a soft material, decreasing the load between the objects and increasing the measured pressure. To be as accurate as possible, researchers have turned to 2D materials to achieve sensors that are thin as possible.

“The engineering performance and robustness of a piezoresistive sensor mainly hinge on the sensor’s embedded active material,” Dr. Kin explained. “So far, different kinds of conductive materials have been used, such as metal nanoparticles, conductive polymers, graphene, and transition metal compounds. More recently, 2D materials have captured researchers’ attention worldwide, particularly transition metal carbides and nitrides or MXenes.”

MXenes are a family of 2D materials comprised of a pretransition metal, such as titanium (Ti), zirconium (Zr) or hafnium (Hf), with carbon and/or nitrogen, and hydroxyl, oxygen or fluorine surface functional group. These combinations give MXenes excellent electrical conductivity and hydrophilicity, making them promising candidates for applications such as piezoresistive sensors.Ìę

As a 2D material, MXenes can be used as sheets and stacked on top of each other via van der Waals forces or hydrogen bonding between the functional groups. This way, MXenes can be formed into flexible and stable films, although the resulting material shows a very weak piezoresistive effect because when compressed, the structure of the sheet doesn’t allow for much deformation. Using MXenes in a 3D structure with similar length scales in all three dimensions would overcome this issue and make best use of the novel MXene material.

The Khalifa University team used additive manufacturing to develop the 3D structures. Traditional methods use templates upon which MXene layers are deposited before the templates are removed. While this does work, it does not allow for precise control of the internal structure of the resulting 3D scaffold. 3D printing overcomes this, with the technology able to fabricate flexible pressure-sensitive sensors with a high dynamic range through an easy to manipulate and large-scale manufacturing method.

“There are enormous possibilities in the design of internal structures that could be produced by 3D printing, but the triply periodic minimal surface (TPMS) structure is one of the more interesting,” Dr. Kin said. “The TPMS structure is known for possessing characteristics of surface area, mechanical robustness and thermal conductivity with an edge-free structure. Fabrication of 2D MXenes into the periodic, porous TPMS structure will lead to the development of novel 3D scaffolds with excellent electrical conductivity and mechanical properties.”

The team developed a simple and efficient method to combine MXene with a uniquely designed TPMS gyroid structure to create a 3D MXene-based gyroidal structure for use as a piezoresistive sensor with extremely high sensitivity, good response time and improvable durability. This method can be used to fabricate 3D MXene structures with any size, shape and internal structure.

More recently, Prof. Liao’s group has been working on constructing 3D structures of heterogenous 2D materials – different types of 2D materials organized in layered manner – for applications such as sensors, electromagnetic interference shielding, as well as energy-related applications.

Jade Sterling
Science Writer
25 May 2022

The post Advances in Flexible Pressure Sensors Using 3D Printing and 2D Materials appeared first on Khalifa University.

Khalifa University competed in the Planet X Youth Challenge, a nationwide event aimed to promote students’ interest in STEM. The competition was launched by the Emirates Mars Mission, in partnership with Dubai Airshow 2021, and was designed specifically to inspire the youth to pursue careers in space and aviation.Ìę

A prequalification round was held in September where more than 200 teams from various universities in the country applied to be part of the challenge. This was followed by a two-day training in October. And finally, the main challenge that took place during the Dubai Airshow 2021.ÌęÌę

AeroX, KU’s representative team to the competition, was among the top 6 groups that qualified to compete in the final stage of the challenge after scoring a high score in the Python Hackathon. The team was composed of undergraduate students:

• Soghah Mohamed Ali Jedeid Alshehhi (Electrical Engineering);
• Ahmed Husain Hamad Abdulla Alawani (Aerospace Engineering);
• Somayyah Mohamed Rashed Abdulla Althabahi (Aerospace Engineering); and
• Fatema Saleh Hasan Ali Almarzooqi (Aerospace Engineering).Ìę

During the finals, the teams worked on two main challenges:

• UAV Challenge – The teams were tasked to design, print, and present an unmanned aerial vehicle (UAV) that will be able to conduct exploration missions and collect samples on a fictional planet, Planet X. In creating the model UAV, the teams had to consider the physics behind the design, as well as the environment of the planet.Ìę
• UGV Challenge – This challenge required teams to program an unmanned ground vehicle robot to accomplish several tasks while successfully overcoming obstacles within the 5-minute time limit.Ìę

The AeroX team designed an UAV specific to the environment of Planet X, taking into consideration its gravity, surface temperature, atmospheric pressure, etc. The team observed the differences between Earth’s environment and Planet X, and from their observations they were able to develop their UAV “HEXAPLORE”. Hexaplore is a unique UAV that has five main parts: hexagonal body (base), hexa rotor, higher antenna, drills, and a multi-mission radioisotope thermoelectric generator (MMRTG). It is designed to automatically perform the missions required to explore Planet X, including discovering new areas, taking pictures, and collecting samples.

“From this experience, we are able to sharpen our way of thinking and we have gained a lot of knowledge about space missions, especially the Emirates missions. Furthermore, the challenges introduced us to a new programming language and designing software that helped us complete the challenges,” Fatema and Soghah said.Ìę

“We are very honored that we got the chance to meet people from the Mohammed bin Rashid Space Centre (MBRSC) who are currently working on different space missions and Eng. Omran Sharaf, the project manager of the UAE’s first mission to Mars. Winning the prize wasn’t our only consideration in participating but meeting these passionate people who push us, the youth, to take part in these amazing opportunities and motivate us to work hard to have a bright future working on STEM jobs,” they added.

Ara Maj Cruz
Creative Writer
26 December 2021

The post Khalifa University Participates in Emirates Mars Mission’s Planet X Youth Challenge appeared first on Khalifa University.

‘CovidSense’ App Will Collect Metadata and Self-Reported Health Status data, Along with Breathing Sounds, Cough, Heart Rate, and GPS Location from Smartphones Ìę

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A team of researchers at Khalifa University of Science and Technology launched an app to collect data from smartphone users to identify, through machine intelligence, whether they are in the CoVid-19 ‘high risk’ category.Ìę

The app named ‘CovidSense’ will target all mobile phone users. It will also help those users under quarantine to monitor their symptoms and location, while assisting them with their health control measures. The app will record metadata and self-reported health status data, along with breathing sounds, cough, heart rate, the GPS location from a smartphone, as well as details of those who the user has interacted with.

The data collected from the smartphones can be used to monitor the evolution of the health status over a period of time, informing the status of the Covid-19 patients to the connected physicians. At the same time, it will allow researchers to form ‘Deep Learning’ models in order to come up with a ‘reliable predictive high-risk index’ in an updated version at a future date. This update will also help minimize spreading by alerting or helping healthcare workers to act at the correct time and place.

The development of ‘CovidSense’ app is being led by Dr. Leontios Hadjileontiadis, Professor, Electrical Engineering and Computer Science, Acting Chair, Department of Biomedical Engineering, Khalifa University, along with Dr Herbert F. Jelinek, Associate Professor, Dr. Ahsan Khandoker, Associate Professor, and Dr. Kinda Khalaf, Associate Professor and Associate Chair, Department of Biomedical Engineering, Khalifa University, for the metadata and physiological signal analysis, when they will be obtained from the users.

Khalifa University is also collaborating with the research Lab, Signal Processing and Biomedical Technology Unit, Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece, involving the development team of Tsoumalis George, Zafiris Bampos, and Iakovakis Dimitrios, for implementing the functional versions of CovidSense in both operational systems of Android and iPhone. For more information about the app please visit

Clarence Michael
English Editor Specialist
17 January 2021

The post Khalifa University Researchers Launching App to Identify CoVid-19 ‘High Risk’ Category Users from Smartphone Data appeared first on Khalifa University.

Electricity and water consumption play a crucial role in the sustainable development of desert regions. In countries with arid climates like the United Arab Emirates, water-energy efficiency and conservation in agriculture are critical issues.

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The Middle East is one of the most water-scarce regions in the world, accounting for 6.3 percent of the world’s population with access to only 1.4 percent of the world’s renewable fresh water. Food, energy, and water supplies are essential to life in every community, particularly those that rely heavily upon electricity and water infrastructures. In arid MENA countries like the United Arab Emirates, economic development results in increasingly intensive demands on energy and water resources, especially in the context of climate change.

One activity in the UAE that requires significant amounts of both water and electricity: agriculture. The areas suited to agriculture in the UAE are determined by the availability of water and cultivable soil, with groundwater the main natural source of water. Due to increasing food demand and rapid population growth, and the goal to achieve food security, the UAE has invested in the agricultural sector, potentially resulting in more stress on water and electricity resources.

To suggest policies for water-energy efficiency and conservation in the UAE, a team from Khalifa University in collaboration with MIT investigated the links between electricity and water consumption on UAE farms. Abdullah Khamis Banhidarah, recent KU graduate, Dr. Ameena Saad Al-Sumaiti, Assistant Professor of Electrical Engineering and Computer Science; Dr. James Wescoat Jr., Professor of Landscape Architecture and Geography at MIT; and Dr. Hoach The Nguyen, Postdoctoral Fellow, published their findings in.

Their analysis showed that water use is more important than electricity use in rural areas, with the cost and reliability of water more important than the cost and reliability of electricity.

“In rapidly urbanizing countries like the UAE, heavy emphasis is given to municipal, industrial, and urban resource uses, but we wanted to draw attention to the importance and nature of agricultural water and electricity use in the UAE,” explained Dr. Al-Sumaiti. “Two-thirds of all Emirates’ water consumption is taken by agriculture and agricultural water conservation is a matter of high priority for the UAE’s sustainable development. Understanding water and electricity use in agriculture can help increase efficiency and develop coherent usage policies.”

The researchers surveyed farms in the five different regions of the UAE, focusing on the variables that could explain the different levels of water and electricity use. They found that variables such as farm owner characteristics and farm worker salaries are associated with the levels of resource use. Gender, education level, and family visits to the farms in the winter influenced electricity consumption, while worker salary, the total number of palm trees, and the number of animals influenced water consumption.

“Interestingly, none of the farm owners reported that they are employing any renewable energy or distributed generation technologies, but they accepted the possibility of connecting to common water-electricity networks with other farms,” explained Dr. Al-Sumaiti. “Importantly, we also found that worker salary has a strong influence on both water and electricity consumption, meaning policies on water-energy efficiency should take this into account.”

There have been many changes to the UAE’s agriculture sector over the past few decades as the sector modernizes. These changes include the development of modern irrigation systems, organic farming, and hydroponics for plant growth with minimum water. Additionally, major efforts have been made to preserve water resources and harvest renewable energy, with the government focusing on sustainable usage and management of water and energy resources, particularly as the number of farms continues to grow.

In 2011, there were 35,704 farms in the UAE. The farms surveyed by the research team used the electricity distribution networks as their electricity source, but received their water from two sources, the water distribution network or water tankers, especially in remote areas where the distribution network is unavailable.

“All farms use water tanks for storage with an average of two tanks per farm and an average capacity of 2,740 gallons per farm,” explained Dr. Al-Sumaiti. “All the farms are grid-connected and pay monthly electricity bills. From surveying the owners, we found that the farms prioritize water cost and reliability over electricity, with relatively equal importance given to water usage for households, animals, and irrigation. These results indicate a strong rural pattern of resource preferences, and a recognition of water supply as crucial for farming sustainability.”

The researchers found five common factors affecting the consumption of both electricity and water: the farmer owner’s age, workers’ salary, farm owner’s visits to the farm in the summer, the number of buildings, and the number of rooms.

“The last two items are not too surprising, but the significance of the owner’s age and workers’ wages deserve further inquiry,” added Dr. Al-Sumaiti. “Additionally, gender, education level, and visits of the family to the farm in the winter influenced the electricity consumption in ways that need to be studied in relation to attitudes towards resource consumption and conservation. Less surprising is that income, total numbers of palm trees, and total numbers of animals affect water consumption. Farm water and energy budgets are a logical extension of this research.”

The team suggests that a variety of policies should be considered to achieve a significant effect on water and electricity consumption. Policies could aim at increasing the efficiency of water and electricity consumption, as well as developing isolated networks, micro-grids, and distributed generation to emphasize the benefits of technologies connected to other farms.Ìę

Jade Sterling
Science Writer
7 December 2021

The post Electricity Water Usage for Sustainable Development on UAE Farms appeared first on Khalifa University.

Researchers from Khalifa University have developed a simple method to produce catalysts more efficiently and precisely, which could help accelerate the development of super effective catalysts for numerous industries.

A team of researchers led by Dr. Yasser Al Wahedi, Assistant Professor of Chemical Engineering at Khalifa University and a member of the Center for Catalysis and Separations (CeCaS), and Dr. Georgia Basina, Post-Doctoral Fellow in the same department, have developed a new way of making catalysts that is more precise and effective. This simple and effective method involves embedding nanoparticles in a material dotted with ultra-small pores, known as the ‘NEMMs’ approach. The team recently published their work in.

A catalyst is a substance that can be added to a reaction to increase the reaction rate without being consumed in the process. They typically speed up a reaction by reducing the energy needed to activate the process by providing an alternate reaction pathway.

Heterogeneous catalysts, commonly used in the oil and gas industries, are catalysts that exist in a different state than the reactants—for example, the catalyst may be in a solid state, while the reactants are liquid or gas.

“Heterogeneous catalysts are crucial in many industries such as oil, gas, petrochemicals, and pharmaceuticals,” explained Dr. Al Wahedi. “A typical heterogeneous catalyst is composed of an active phase, which performs the catalytic function, and a support which enhances the active phase and its stability.”

One such example is the catalytic converter in a gasoline or diesel-fueled car. Transition metal catalysts are embedded on a solid phase support, which comes into contact with gases from the car’s exhaust stream, increasing the rate of reactions to produce fewer toxic products from pollutants in this exhaust stream. The catalytic converter is also an example of surface catalysis, where the reactant molecules are adsorbed onto a solid surface before they react with the catalyst. The rate of a surface-catalyzed reaction increases with the surface area of catalyst in contact with the reactants, and so the solid support is designed to have a very high surface area with a porous structure and honeycomb-like appearance.

“Typically, the support structure accounts for 60 to 99 percent of the weight of the total catalyst, while its role is limited to stabilizing the active component nanoparticles,” said Dr. Al Wahedi. “To enhance the catalytic performance, we need to increase the amount of active component in the structure, while keeping particle size and state optimal.”

Conventional methods to prepare catalysts often start with the support structure and then introduce the active ingredient via insertion methods such as impregnation, chemical vapor deposition or ion exchange. When manufacturers want to increase the amount of the active ingredient using these methods, it often results in poor dispersions, or a lack of control over the size of the ingredient particles.

“To overcome this issue, we can encapsulate the active nanoparticles in a mesoporous matrix comprised of the supporting material to produce a structure we term the NEMMs,” explained Dr. Basina. “This approach allows us to develop catalysts with high active component loadings while keeping the size optimal for efficient catalysis.”

The NEMMs approach involves growing a porous support material around nanoparticles of the active ingredient. They use nanoparticles that are the perfect size to serve as nucleation centers, around which a mesoporous silicon oxide (a material containing pores with diameters between 2 and 50 nanometres) matrix grows. The approach also uses surfactant molecules to create a ‘crown’ around the active component particles, which is removed after the matrix has been grown in order to leave an empty space between the active component and the mesoporous material. It is in this empty space that the catalysis reactants can be adsorbed.

The research team tested their catalyst on the selective oxidation of hydrogen sulphide, an important industrial reaction whereby toxic hydrogen sulphide is oxidized to produce sulphur.

“Our approach circumvents the limitations rooted in conventional catalyst design by allowing complete independent control over the active component nanoparticle shapes and size,” said Dr. Al Wahedi. “ We have investigated this approach on the selective oxidation of H2S reaction (commercially denoted as SuperClausTM). Compared with previous studies, our catalysts achieve near complete conversions and more than 95 percent selectivity at a fraction of the catalyst mass required.”

The ease of this synthesis method and the stability and efficiency of the resulting catalyst promise a wide spectrum of applications beyond the selective oxidation of hydrogen sulphide in myriad industries.

Jade Sterling
Science Writer
29 September 2020

The post Turning Catalyst Production Inside Out appeared first on Khalifa University.

Khalifa University researchers leverage 3D printing to better image the fluid dynamics in underground rocks

Researchers at Khalifa University have developed a new way to 3D print reservoir rock replicas that have complex porous structures and mimic a carbonate rock’s natural mineralogy. The 3D printed rocks are transparent, and allow researchers to image precisely how fluid flows through the ultra-tiny pores of rock – information which could help develop effective strategies for hydrocarbon and geothermal energy extraction, carbon sequestration, and even ice mining and water extraction from the ground during planetary exploration.

“While recent improvements in 3D printing enable scientists to fabricate 3D structures that have complicated porous structures by using polymeric materials, these structures ultimately lack in surface functionality. We overcame this problem by integrating high-resolution 3D printing with an internal coating to create structures that functionally replicate the natural rock,” explained Dr. TieJun Zhang, Associate Professor of Mechanical Engineering, and the principal investigator of a reservoir characterization and modeling project.

His team, which includes, Hongxia Li, Aikifa Raza, Qiaoyu Ge, and Jin-You Lu, recently published describing the new micro-3D printing and mineral coating technique. This approach has been filed as both International PCT and GCC Patents.

Highly porous materials exist in all sorts of applications, from concrete and filtration to biology and oil and gas extraction. Engineers have been studying how fluids flow through porous materials for some time – a branch of study known as microfluidics. Because pore sizes can be as small as a single micrometer, and the porous material being studied can be in hard to reach places, like underground or within the human body, creating devices that can be used to simulate the way fluids flow through porous materials has been the primary way that scientists have advanced understanding of microfluidics.

Even better microfluidic devices, like the 3D printed porous structure developed by Dr. Zhang’s team, could open the door to a vast array of opportunities in quickly modelling and predicting microfluidic flow behaviors in applications such as geology and hydrocarbon extraction.

Traditional microfluidic chips show how fluids move through the pores of the rock and are typically made from glass or silicon. For some applications, this is enough, but carbonate rock is a material susceptible to fluids underground, and the microfluidic model needs to take into account the strong interactions between the fluid and the rock.

3D printing has emerged as one solution to this but many of the issues in fabricating complicated porous networks arise from the limitations in printing materials.

“Conventionally, we can enhance the thermal, electrical, and mechanical properties of 3D-printed devices by adding nanomaterials into polymer ink,” explained Dr. Li, the leading author of this work. “However, these added particles often cause severe light scattering, which impacts printing precision.

It’s then much harder to create the microstructures of natural porous materials like rock. Another issue is that this composite material has poor light transparency, meaning seeing the fluid flow through the device is much more difficult.”

To overcome these issues, the KU researchers used an alternative to polymer ink: in-situ mineral growth in 3D-printed device.

“On complex surfaces, putting a thin layer of a mineral coating on the inner surface of the micromodel mimics the natural surface mineralogy, but can mean that the crystal growth isn’t uniform,” explained Dr. Li. “To overcome this, we coated a seed layer of calcite nanoparticles on the inner surface. This facilitated calcite crystals to grow uniformly, resulting in a device that functioned precisely like carbonate rock. We made a ‘real’, yet transparent, rock.”

This device can then be used as a sort of ‘rock-on-a-chip’ to analyze how various fluids move through the pores and can be readily tailored to test, observe and analyze fluidics in biological, soft robotics, aerospace, and other emerging applications. This ‘rock-on-a-chip’ use has also been demonstrated by the team in another publication.

The transparent, 3D printed rock created at Khalifa University makes microfluidic technology more accessible to researchers in various fields and accelerates innovation. It could also be used to gain key insights into how to extract more hydrocarbons from the UAE’s oil fields in a more sustainable and cost-effective way.

Jade Sterling
Science Writer
25 August 2020

The post 3D Printed Transparent Rocks with Fluid Imaging Could Help Extract Energy from the Ground appeared first on Khalifa University.

Despite how frequent dust storms are in the Middle East, little is known about how and why they are so much more common in the summer months. A team from Khalifa University set out to better understand this phenomenon by examining the intense dust activity that occurred in July 2018.

The Arabian Peninsula is one of the world’s major sources of dust year round, contributing substantially to the total amount of dust in the air in the Northern Hemisphere. Frequent dust storms occur here, between 15 to 20 per year, impacting all aspects of life for its human population, as well as affecting marine ecosystems and the climate.

Despite this, little is known about how and why dust storms are much more common in the summer months. A team from Khalifa University set out to better understand this phenomenon by examining the intense dust activity that occurred in July 2018.
Dr. Diana Francis, Senior Research Scientist, Dr. Narendra Nelli, Postdoctoral Fellow, and Dr. Marouane Temimi, Associate

Professor of Civil Infrastructure and Environmental Engineering, all from Khalifa University, published their findings in the journal of along with Dr. Jean-Pierre Chaboureau, University of Toulouse, France, Dr. Juan Cuesta, Université Paris-Est Creteil, France, Noor Alshamsi, UAE National Center for Meteorology, Dr. Olivier Pauluis, New York University, and Dr. Lulin Xue, US National Center for Atmospheric Research. The team investigated the dust storms of July 2018 to identify the underlying atmospheric dynamics and assess how much impact the radiative effects of dust had on cloud and rain development.

“Despite originating from relatively few areas around the world, atmospheric dust is an important component of the Earth’s climate system,” explained Dr. Francis. “Atmospheric dust particles can serve as cloud condensation nuclei and ice nucleating particles, thereby altering cloud development and properties and associated precipitation.”

The amount of dust in the air also influences radiative effects as dust particles can scatter and absorb shortwave radiation, and absorb and re-emit longwave radiation. This has repercussions for atmospheric thermodynamics as the local temperature, winds and rainfall are affected.

“The dust in the air interacts with radiation from the sun and increases the mass of water in the atmosphere, causing a greenhouse effect and further increasing the ground temperature and humidity,” explained Dr. Francis. “This then has implications on the development of weather features such as sea breezes.”

Though the dust does reduce the amount of solar energy reaching the surface by absorbing and scattering the radiation, this absorption can contribute to localized heating by directly warming the dust-filled atmospheric layer and emitting longwave radiation towards the surface of the Earth. This, however, depends on where the dust layer is located, such as whether it is situated over water, vegetated areas or desert regions.

“Given the sporadic nature of dust storms, this complex balance between their effects on radiation and the resulting impacts on climate has been difficult to assess,” explained Dr. Francis.

“Because of this, dust storms can’t be included in future climate projections with much accuracy, with current global climate models underestimating the warming effect of dust by underestimating the actual amount of dust in the atmosphere.”

An essential part of the dust cycle is the transportation of dust around the world. For this, the dust storm needs the atmospheric processes that determine all aspects of the storm—from its intensity to its duration­. For the Arabian Peninsula, the Shamal winds play a critical role. These northerly semi-permanent winds are thought to be the main meteorological driver for dust emissions year round but Dr. Francis is interested in why dust emissions over the southern parts of the Arabian Peninsula peak in the summer.

“This peak indicates the existence of a still-unknown but important mechanism for dust emissions,” explained Dr. Francis.

“Cyclogenesis, the formation of cyclone, has proven to be a major dust emission mechanism over other arid regions, capable of generating dramatic dust storms. However, little attention has been given to dust activity associated with cyclogenesis over the Arabian Peninsula”

In July 2018, a cyclone formed over southwestern UAE and generated intense dust emissions over the UAE and northwestern Oman due to strong cyclonic winds.

“A clear footprint of the cloud was visible in the radiation measurements at the surface, with the warming effect by up to 10°C induced by the dust especially at night,” explained Dr. Francis.

“On the second day of cyclogenesis, clouds started to develop in the warm sector of the cyclone,” explained Dr. Francis. “Localized rain was observed in the southwestern UAE, and as the cyclone intensified, more water vapor was drawn from the Arabian Gulf and the Arabian Sea, which caused further rain to develop. Daytime ground temperatures were two degrees higher compared to prior days, while at night, temperatures were ten degrees higher than the normal temperature before and after the dust storm. This was due to sustained emissions of longwave radiation during the entire lifetime of the dust storm.”

The researchers found that the dust over a major dust source region induces a significant net warming effect at the surface and in the atmosphere during the night, modifying the atmosphere at lower levels. Their results highlight the important role dust plays in the climate system of the Arabian Peninsula, proving that air quality and weather forecast systems need to account for the impacts of dust storms to achieve improved accuracy.

“Dust also needs to be considered when predicting, designing and conducting cloud-seeding operations in the UAE because of the impact on the circulation, which in turn impacts the development of clouds and their lifetime,” added Dr. Francis. “Dust is a quasi-permanent natural part of the atmosphere over the Arabian Peninsula, and its impact on the climate and environment of this region is more significant than anyone previously thought.”

Jade Sterling
Science Writer
13 August 2020

The post How Dust Impacts the Arabian Climate appeared first on Khalifa University.

Scientists at Khalifa University are researching how solar nanofluids can be stabilized for use in concentrating solar power plants to generate clean electricity.

Concentrating solar power (CSP) plants – which use energy from the sun in the form of heat to generate clean electricity – could one day be used to meet a significant share of the world’s energy needs. But CSP faces a challenge: many power plants still rely on heat transfer fluids that were developed in the 1980s and are limited to lower operating temperatures.

Heat transfer fluids bring the heat collected from solar energy to a generator, where it is transformed into electricity. The hotter the fluid can get, the more its particles move and the higher its thermal energy, which translates into more efficient power generation. Nanofluids have been eyed as advanced heat transfer fluids for some time now, as the nanoparticles suspended in the fluid increase the fluid’s absorption surface area and thermal conductivity. However, solar nanofluids are challenged by instability, mainly caused by the clustering of nanoparticles within the fluid.

Now, scientists at Khalifa University are researching how these nanofluids can be stabilized, which is key to accelerating their uptake in CSP plants, and other industrial applications, around the world.

Dr. Omar Sharaf, Post-Doctoral Fellow at Khalifa University, with Dr. Eiyad Abu-Nada, Professor of Mechanical Engineering, and Dr. Robert Taylor, Associate Professor of Mechanical and Manufacturing Engineering at University of New South Wales, Sydney, recently published a in Physics Reports covering the topic of solar nanofluids to investigate their colloidal and chemical stability in various applications.

“Nanofluids are engineered colloidal dispersions with solid inorganic nanoparticles,” explained Dr. Sharaf. “They have superior thermophysical properties that make them excellent materials for numerous engineering applications, including solar power generation.”

“But while a few review articles have previously targeted the issue of stability for thermal nanofluids, which allow for more effective heat transfer, there are no review articles covering the stability of solar nanofluids, which function as both solar absorbers and heat carriers,” added Dr. Abu-Nada. “Therefore, our objective was to provide a much-needed, state-of-the-art review of the stability of solar nanofluids and investigate the modern techniques and strategies to overcome their limitations. We’ve made an important step towards understanding the state-of-the-art in the development of resilient, long-term stable solar nanofluids for use in photothermal conversion applications.”

Nanofluids are increasingly used in applications requiring quick and effective heat transfer, including in solar thermal applications. They absorb the solar irradiance passing through them, which allows the base fluid to effectively capture and transport solar radiation. The more solar energy the nanofluid absorbs, the more efficient the photothermal conversion process, with the solar thermal system’s efficiency governed by the effectiveness of the photothermal conversion and heat transfer processes.

An ideal direct-absorption solar collector will absorb the concentrated solar radiation, convert that into heat, and transfer the heat to the intended application. Nanoparticles allow for several orders of magnitude higher heat transfer when absorbing solar radiation directly within the surrounding fluid, simply due to the small size and huge specific surface area of the nanoparticles.

“Despite their favorable thermophysical properties, the key challenge still hindering the widespread use and commercialization of solar nanofluids are issues pertaining to their dispersion and chemical stability,” explained Dr. Sharaf. “This is a result of operating for prolonged periods of time under the rough outdoor conditions encountered in photothermal conversion devices, such as elevated temperature, intense solar radiation, and thermal and solar cycling. Such conditions destabilize the nanofluids, eventually leading to those prized properties being significantly altered.”

Nanoparticles have exceptionally high surface-to-volume ratios and remain in a high energy state. As the particles move to reduce their surface energies, they cluster together, which reduces their efficiency. A nanofluid’s ability to resist clustering is known as its colloidal stability. Its chemical stability is determined by the ability to resist undesired chemical transformations over time.

“In other words, a stable nanofluid is one that retains its optical and thermal properties of interest after frequent use in its intended application,” explained Dr. Abu-Nada. “Depending on the nature of the solar photothermal conversion device, a solar nanofluid can be exposed to a number of destabilizing factors. Understanding these factors is crucial for designing a stable nanofluid.”

The working temperature of a solar nanofluid could be high during the day and low during the night due to solar cycling, reaching very high temperatures of much more than 400C in photothermal devices operating under concentrated solar radiation. Temperature variations can trigger sharp transitions from stability to instability, with parts of the nanofluid known to partially or even completely decompose and detach from the particles at working temperatures as low as 60C.

“In sunny, desert climates, where solar collectors are likely to be deployed, the difference between nanofluid temperature at daytime and night time could be significant, especially when operating under concentrated solar radiation,” explained Dr. Abu-Nada.

“Additionally, although it constitutes a small portion of the solar radiation hitting the Earth, UV radiation can cause severe damage to the constituents of a nanofluid, especially if optically concentrated. Prolonged UV radiation exposure is more often than not overlooked as a major destabilizing factor, because upon testing under natural sunlight for a limited period of time, the levels of exposure are not usually enough to induce too much damage. However, upon prolonged exposure, it is clear that UV exposure can have hugely detrimental effects.”

As energy demand across the globe increases, harnessing renewable energy remains essential. Concentrating sunlight is an effective way to generate higher output and nanofluids can play a crucial role in the development of these technologies.

Jade Sterling
Science Writer
4 August 2020

The post Keeping Solar Nanofluids Stable appeared first on Khalifa University.