KAUST – Putting the ‘Sense’ in Materials – Say Goodbye to Batteries as You Know Them


KAUST 5c6a94542b7e32661e7f8b63An interdisciplinary initiative is helping KAUST be at the forefront of a digital revolution, where sensors can find a use just about anywhere.

 

The ability to track minuscule but important changes across a range of systems—from the body to the borough and beyond—seems limitless with the emerging array of novel devices that are tiny, self-powering and wirelessly connected. KAUST’s Sensor Initiative comprises a broad range of experts, from marine scientists to electrical engineers, who are innovating solutions to some of the most challenging obstacles in sensor technology. Together, they are powering up to transform the exciting intersection between small interconnected devices and the world around us.

Capacity to monitor our surroundings also reveals new potential in environmental and community protection. For example, a sensor that can detect a flood or a fire can save lives; a sensor that can track animals could help to better manage an ecosystem; and a sensor that can read plant condition could promote sustainable farming.

To take advantage of the market opportunities for sensors in both medical and environmental fields, KAUST holds an annual meeting of biologists, engineers and chemists to discuss technology development. Since 2015, these meetings have produced ambitious collaborations that aim to improve the science that underpins next-gen sensors as well as to take them to the market.

Get ready to plug and play

Khaled Salama, professor of electrical engineering and director of the Sensor Initiative, explains that what sets KAUST apart are the University’s human resources and outstanding lab facilities that underpin its innovative sensor technologies. With the onslaught of data coming from the hundreds of billions of sensors in our cities, cars, homes and offices, we need machine learning to help us understand the data, the supercomputing power to manage it and the expertise to make sure the machines do it all effectively.

“KAUST has strength in materials research, which is where our expertise can be used for developing sensors with transducer components that can be quickly swapped out and replaced with ones customized for different biological or environmental applications,” says Salama.

“Some can stick to your skin and monitor your vital signs through changes in your sweat while others can be placed in petroleum installations to monitor hazardous gases,” says Salama. “We’re not bound to one specific application, and each new development gives us a chance to answer some fundamental scientific questions along the way.”

Say goodbye to batteries, as you know them

KAUST is deploying tiny sensors across the University’s campus to model future smart cities that can continuously monitor air quality or help self-driving cars navigate. Implementing this vision means making devices that are as self-sufficient as possible.

“If you have sensors containing regular batteries, they might last a thousand cycles,” says Husam Alshareef, professor of materials science. “We have to get them to last millions of times longer.”

Alshareef and several international collaborators are building a technology known as microsupercapacitors—next-generation batteries—to resolve challenges around energy storage. Through a special vacuum deposition process, the team has transformed ruthenium oxide into a thin-film electrode that can hold massive amounts of charge and quickly release it on demand.

Get plant smart with winged sensors

Professor Muhammad Hussain is a strong believer in the importance of availability in the sensor market. He insists that his sensors not only provide solutions to everyday problems but also that they be affordable to all. That said, he does not forgo creativity for affordability. Hussain’s plant sensors are flexible, inexpensive and range in size from 1-20 mm in diameter. When placed on a plant leaf, they can detect temperature, humidity and growth, data that can be used to help farmers farm smart—minimizing nutrient and water waste. But what makes them especially remarkable is their beautiful butterfly shape. When asked why he chose the butterfly shape Hussain told us, “Butterflies are aesthetically beautiful and natural in a plant environment. Their large wings allow us to integrate many different sensors, which is especially useful for the artificial intelligence chip we are currently integrating into the system. Ultimately, we aim to create a fully interactive system such that the butterfly can deliver nutrients or gather more data.”

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Sherjeel Khan, ph.D. student with Mohammed Hussain, fabricates the plant-monitoring sensors shaped like butterflies. © 2018 KAUST

Learn to talk effectively

One of the advanced sensors being developed at KAUST is the smart bandage from the group of Atif Shamim in the electrical engineering program. This gadget uses carbon-based transducers to directly contact chronic wounds and to predict signs of infection based on blood pH levels.

Shamim notes that wireless communication is crucial if sensors and other components of the Internet of things are to be integrated with everyday items. His team has pioneered the use of low-energy Bluetooth radio networks to help connect smart devices with each other and also with network servers.

“Even though the Internet of things is about inanimate objects, they have to make decisions for you,” says Shamim. “They need to sense and they need to communicate.”

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Shamim’s smart bandage may help to predict signs of infection in a wound by reading blood pH levels. © 2018 KAUST 

Be prepared to dive deep

Shamim is partnering with other KAUST researchers, including Jürgen Kosel, who specializes in using the property of magnetism in his sensor work to track animal behavior in the Red Sea. The team created stickers—each containing a self-powered, Bluetooth-connected position sensor—that are small enough to be attached to crabs, turtles and giant clams in the Red Sea.

Kosel and his group aimed to tackle the primary challenge associated with remote tracking of marine life—the tendency for water to scatter the radiofrequency waves used by most sensors for geolocation. Working with the KAUST Nanofabrication Core Lab to fabricate thin-film structures, the team created flexible sensors that reveal their global position using magnetic signals that easily access subsurface environments.

“Magnetic fields can penetrate many materials without affecting them, and that includes humans and other animals,” says Kosel. “We’ve shown that you can even derive how much energy a marine animal consumes using magnetic sensors that monitor water flow.”

Sense the future of sensors

For the Emeritus Senior Vice President for Research, Jean Frechet, the possibilities are great: “With our expertise and resources, we have built bridges across disciplines by bringing together researchers from KAUST and other institutions. They inspire each other to solve challenges as diverse as the survival of marine life, communications for the 21st century, and the exploitation of big data. The KAUST Sensor Initiative will stimulate the next generation and contribute to diversifying the country’s economy as we design and engineer sensors that collect the data we need to address global challenges.”

 

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Colorful solution to a chemical industry bottleneck – KAUST Researchers Develop an “hourglass shape” Graphene-Oxide Membrane to rapidly separate chemical mixtures – Application Pharmaceuticals (other chemical mixtures)


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A graphene-oxide membrane design inspired by nature swiftly separates solvent molecules.

The nanoscale water channels that nature has evolved to rapidly shuttle water molecules into and out of cells could inspire new materials to clean up chemical and pharmaceutical production. KAUST researchers have tailored the structure of graphene-oxide layers to mimic the hourglass shape of these biological channels, creating ultrathin membranes to rapidly separate chemical mixtures.

“In making pharmaceuticals and other chemicals, separating mixtures of organic molecules is an essential and tedious task,” says Shaofei Wang, postdoctoral researcher in Suzana Nuñes lab at KAUST. One option to make these chemical separations faster and more efficient is through selectively permeable membranes, which feature tailored nanoscale channels that separate molecules by size.

But these membranes typically suffer from a compromise known as the permeance-rejection tradeoff. This means narrow channels may effectively separate the different-sized molecules, but they also have an unacceptably low flow of solvent through the membrane, and vice versa—they flow fast enough, but perform poorly at separation.

Nuñes, Wang and the team have taken inspiration from nature to overcome this limitation. Aquaporins have an hourglass-shaped channel: wide at each end and narrow at the hydrophobic middle section. This structure combines high solvent permeance with high selectivity. Improving on nature, the team has created channels that widen and narrow in a synthetic membrane.

The membrane is made from flakes of a two-dimensional carbon nanomaterial called graphene oxide. The flakes are combined into sheets several layers thick with graphene oxide. Organic solvent molecules are small enough to pass through the narrow channels between the flakes to cross the membrane, but organic molecules dissolved in the solvent are too large to take the same path. The molecules can therefore be separated from the solvent.

To boost solvent flow without compromising selectivity, the team introduced spacers between the graphene-oxide layers to widen sections of the channel, mimicking the aquaporin structure. The spacers were formed by adding a silicon-based molecule into the channels that, when treated with sodium hydroxide, reacted in situ to form silicon-dioxide nanoparticles. “The hydrophilic nanoparticles locally widen the interlayer channels to enhance the solvent permeance,” Wang explains.

When the team tested the membrane’s performance with solutions of organic dyes, they found that it rejected at least 90 percent of dye molecules above a threshold size of 1.5 nanometers. Incorporating the nanoparticles enhanced solvent permeance 10-fold, without impairing selectivity. The team also found there was enhanced membrane strength and longevity when chemical cross-links formed between the graphene-oxide sheets and the nanoparticles.

“The next step will be to formulate the nanoparticle graphene-oxide material into hollow-fiber membranes suitable for industrial applications,” Nuñes says.

References

Wang, S., Mahalingam, D., Sutisna, B. & Nunes, S.P. 2D-dual-spacing channel membranes for high performance organic solvent nanofiltration. Journal of Materials Chemistry Aadvance online publication, 10 January 2019.| article

 

‘Smart’ Orthodontic Technology from KAUST – Flexible microbattery enables smart dental braces


Nano Dental Bracesid48660

Flexible, non-cytotoxic battery concept. Optical images of an intra-oral implantable device that relies on millimeter-sized flexible, biocompatible lithium-ion battery as a rapid powering solution. (© Nature Publishing Group)

Researchers have demonstrated a novel approach toward smart orthodontics based on near-infrared red light from a mechanically flexible LED powered by flexible bio-safe batteries all integrated in a single 3D-printed dental brace.

As the team from King Abdullah University of Science and Technology (KAUST) demonstrates in their paper in NPJ Flexible Electronics (“Flexible and biocompatible high-performance solid-state micro-battery for implantable orthodontic system”), integration of red light therapy enhances bone regeneration, reducing overall time to wear the dental brace and unburdening users from expense. Furthermore, 3D printing allows personalized (instead of one size fits all) transparent dental brace.
“Integration of electronic devices in 3D printed dental aligners, as we have demonstrated here, is a pragmatic approach towards implementing a flexible electronic technology in personalized advanced healthcare, particularly in orthodontics,” Muhammad Mustafa Hussain, an Associate Professor of Electrical Engineering at KAUST, tells Nanowerk. ” The next stage of our work will be to demonstrate diagnostics in the smart dental brace in which sensors are able to detect the pressure exerted by aligners on teeth. This might help orthodontists estimate the force required by aligners; thus providing both diagnostic and treatment capabilities in dental braces. “
Flexible, non-cytotoxic battery concept
The scientific core of the team’s findings is to approach flexible energy storage solutions in a way that is pragmatic, fast and well integrated with other components. A major challenge to integrate any traditional lithium-based energy storage is their toxicity. The scientists circumvented this issue by introducing non-toxic micro-scale flexible batteries to be used as on-demand power supply.
Furthermore, they integrated near-infrared (NIR) capability as well as an optoelectronic system of light emitting diodes (LED) arrays in a personalized, 3D-printed semi-transparent dental brace. Of course, such a device would not have been possible without an appropriate energy storage solution.
Key to this smart brace is the use of a high-performance flexible solid-state microbattery. A standalone all thin-film lithium-ion battery already can be readily thinned down to about 30 microns thickness to achieve flexibility. The team’s flexing process for thin-film-based micro-batteries achieves two major objectives: 1) utilization of mature and reliable CMOS process with 90% yield and repeated electrochemical measurements on multiple devices, and 2) the ability to withstand high annealing temperatures of cathode material or soldering that are unachievable using direct film deposition on plastic substrates.
“Our flexile biocompatible lithium-ion battery can be transferred on polyethylene terephthalate (PET) and interconnected via aluminum engraved interconnections to create a battery module,” explains Hussain. “During testing we found that the battery module exhibits minimal strain while most of the stress is experienced by the PET film.”
Continuous intra-oral NIR light therapy for patients is becoming a growing necessity for accelerating the rate of the bone remodeling process. Near-infrared light can be absorbed by bone cells to stimulate the bone regeneration for faster orthodontic treatment.
That’s why the team integrated near-infrared LEDs with the flexible batteries and interconnected them on a soft PET substrate. The whole device is embedded in semi-transparent 3D-printed brace.
To summarize, this smart dental brace relies on two main functionalities: Firstly, a customizable, personalized, and semitransparent brace, which provides required external loading to stimulate healthy rebuilding of bone structures. Secondly, a miniaturized, soft, biocompatible optoelectronic system for an intraoral (conformable on the mouth) near-infrared light therapy, which allows rapid, temporally specific control of osteogenic cell activity via targeted exposure and light sensitive proteins present in bone cells.
“The combination of both strategies in one single platform provides affordable, multifunctionality dental braces,” concludes Hussain. “Such capability enhances the bone regeneration significantly and reduces the overall cost and discomfort. Our future work will include integration of compliant soft-substrate-based LEDs and miniaturized ICs with enhanced wireless capability for smart gadget-based remote control for cleaning and therapy.”

 

@ Michael Berger © Nanowerk

Better photovoltaic efficiency grows from enormous solar crystals: MH Perovskites 


In-depth analysis of the mechanisms that generate floating crystals from hot liquids could lead to large-scale, printable solar cells


New evidence of surface-initiated crystallization may improve the efficiency of printable photovoltaic materials.

In the race to replace silicon in low-cost solar cells, semiconductors known as metal halide perovskites are favored because they can be solution-processed into thin films with excellent photovoltaic efficiency. 

A collaboration between King Abdullah University of Science and Technology (KAUST) and Oxford University researchers has now uncovered a strategy that grows perovskites into centimeter-scale, highly pure crystals thanks to the effect of surface tension (ACS Energy Letters, “The role of surface tension in the crystallization of metal halide perovskites”).

In their natural state, perovskites have difficultly moving solar-generated electricity because they crystallize with randomly oriented grains. 

Osman Bakr from KAUST’s Solar Center and coworkers are working on ways to dramatically speed up the flow of these charge carriers using inverse temperature crystallization (ITC). This technique uses special organic liquids and thermal energy to force perovskites to solidify into structures resembling single crystals—the optimal arrangements for device purposes.

While ITC produces high-quality perovskites far faster than conventional chemical methods, the curious mechanisms that initiate crystallization in hot organic liquids are poorly understood. Ayan Zhumekenov, a PhD student in Bakr’s group, recalls spotting a key piece of evidence during efforts to adapt ITC toward large-scale manufacturing. “At some point, we realized that when crystals appeared, it was usually at the solution’s surface,” he says. “And this was particularly true when we used concentrated solutions.”

The KAUST team partnered with Oxford theoreticians to identify how interfaces influence perovskite growth in ITC. They propose that metal halides and solvent molecules initially cling together in tight complexes that begin to stretch and weaken at higher temperatures. With sufficient thermal energy, the complex breaks and perovskites begin to crystallize.

But interestingly, the researchers found that complexes located at the solution surface can experience additional forces due to surface tension—the strong cohesive forces that enable certain insects to stride over lakes and ponds. The extra pull provided by the surface makes it much easier to separate the solvent-perovskite complexes and nucleate crystals that float on top of the liquid.

Exploiting this knowledge helped the team produce centimeter-sized, ultrathin single crystals and prototype a photodetector with characteristics comparable to state-of-the-art devices. Although the single crystals are currently fragile and difficult to handle due to their microscale thicknesses, Zhumekenov explains that this method could help direct the perovskite growth onto specific substrates.

“Taking into account the roles of interfaces and surface tension could have a fundamental impact,” he says, “we can get large-area growth, and it’s not limited to specific metal cations—you could have a library of materials with perovskite structures.”

Source: King Abdullah University of Science and Technology

KAUST: Using Graphene Quantum Dots to Get More Energy from the Solar Spectrum


Graphene quantum dots can improve the efficiency of silicon solar cells.

 

A graphene quantum dot (white) on top of a solar cell formed by silicon (Si) insulating (ITO) and metal (Au) layers. 
Reproduced with permission from ref 1. © 2016 American Chemical Society

Small flakes of graphene could1 expand the usable spectral region of light in silicon solar cells to boost their efficiency, new research from KAUST shows1.

Solar cell materials have become significantly cheaper to produce in recent years, yet further cost savings are needed to make solar technologies commercially attractive. The prevalence of silicon in solar cells makes them a good target for efficiency enhancement.

“By improving the efficiency of silicon solar cells, we can provide a more cost-effective way for energy production,” said Jr-Hau He, KAUST associate professor of electrical engineering, who also led the research team.

Graphene quantum dots are small flakes of graphene that are useful because of their interaction with light. One of these interactions is optical downconversion, which is a process that transforms light of high energies into lower energy (for example, from the ultraviolet to the visible).

Downconversion can be used to boost solar cells. Silicon absorbs light very efficiently in the visible part of the spectrum, and therefore appears black. However, the absorption strength of silicon for ultraviolet light is much smaller, meaning that less of this light is absorbed, reducing the efficiency of solar cells in that part of the spectrum.
One way to circumvent this problem is the downconversion of ultraviolet light to energies where silicon is a more efficient absorber.

Graphene quantum dots are ideal candidates for this purpose. They are easy to manufacture using readily-available materials such as sugar and by then heating them with microwave radiation. While the dots are almost transparent to visible light, which is important to pass that light through to the solar cell, they are efficient in converting UV light to lower energies.

The researchers integrated the quantum dots on a silicon solar cell device. The efficiency of the solar cells increased in comparison to control samples. For a mature technology to show a clear improvement in efficiency is promising, because it can be produced using an easy manufacturing process.

The test sample solar cells measured so far have not yet been optimized to be closer to the record-breaking performances seen in silicon. The researchers therefore plan to combine some other enhancement technologies previously achieved in similar devices.
He noted. “We have been successfully utilized surface engineering treatments, including fabricating nanostructures and passivation layers, to improve the light harvesting and the electrical properties of solar cells. By integrating these techniques all together, we hope that in the next few years the world record can be broken at KAUST,” he said.

Reference
Tsai, M.-L., Tu, W.-C., Tang, L., Wei, T.-C., Wei, W.-R., Lau, S.P., Chen, L.-J. & He, J.-H. Efficiency enhancement of silicon heterojunction solar cells via photon management using graphene quantum dot as downconverters. Nano Letters 16, 309−313 (2016).| article

Perovskite phosphor boosts visible light communication: Flashy nanocrystals help LEDs send data in the blink of an eye


Flashy NP Perovskite 1466097172999A green-emitting perovskite nanocrystal phosphor mixed with a red-emitting nitride phosphor looks yellow under ambient light (left). When excited by blue laser light, the phosphor combination produces white light (right).
Credit: Osman Bakr

 

Light-emitting diodes (LEDs) are increasingly used to illuminate homes and offices; soon, the same lights could also transmit data to your computer or smartphone in photon pulses so fast the eye can’t see them. But this form of visible light communication faces two key challenges: The light must flicker fast enough to carry sizeable amounts of data; and at the same time it should provide the warm, balanced color tones needed for pleasant ambient lighting.

 

Nanocrystals of cesium lead bromide (CsPbBr3) could help to solve both problems, according to a team led by Boon S. Ooi and Osman M. Bakr at King Abdullah University of Science & Technology (KAUST). They have found that LEDs coated with the material can reach high data transmission rates of 2 gigabits per second, comparable to the fastest Wi-Fi, while producing a quality of light that matches commercial white-light LEDs (ACS Photonics 2016, DOI: 10.1021/acsphotonics.6b00187).

 

Visible light communication, sometimes called Li-Fi, is already finding real-world applications. Last year, for example, Dutch company Phillips installed a smart LED system in a French supermarket that uses Li-Fi to transmit discount offers to shoppers’ cellphones, based on their location in the store. If data rates could be increased significantly, Li-Fi might add much-needed capacity to congested Wi-Fi networks that rely on radio waves.

 

And since the smart LEDs are doing double duty, by providing both lighting and communication, they offer an economical solution, says Bakr. Ooi adds that these systems do not even need a direct line of sight between LED and computer: “As long as your device can see light, you can detect a signal,” he says.

 

White-light LEDs typically contain a blue LED coated with phosphors that turn some of the light into green and red. But most phosphors take too long to recover between excitation and emission, pulsing no more than a few million times per second. Last year, other researchers showed that polymer semiconductors could reach more than 200 MHz (ACS Photonics2015, DOI: 10.1021/ph500451y).

 

The KAUST team instead turned to CsPbBr3, part of a family of materials known as perovskites that have become the darling of the photovoltaic research community. Perovskite solar cells have seen remarkable efficiency gains over the past seven years, and the materials are cheap and relatively easy to prepare in solution.

 

The team created nanocrystals of the perovskite, roughly 8 nm across, and found that their green emission faded in just seven nanoseconds. This allowed them to pulse reliably at almost 500 MHz, setting what the researchers believe is a new record for LED phosphors. “It is an extremely impressive and important achievement,” says Ted Sargent of the University of Toronto, who works on optoelectronic materials and has collaborated with the KAUST group in the past.

 

The rapid response is partly due to the size of the crystals, Bakr explains. When blue light excites an electron in the material, it forms an electron-hole pair called an exciton. The confines of the tiny crystal change the exciton’s energy levels, making the electron more likely to recombine with its hole and emit a photon.

 

When the researchers teamed the perovskite phosphor with a commercial red-emitting phosphor and a blue gallium nitride LED, the device produced a warm white light with a color rendering index of 89, as good as white LEDs already on the market (natural sunlight itself is rated at 100). “This quality makes this material ideal for low-power indoor illumination,” Sargent says.

 

Jakoah Brgoch of the University of Houston, who develops novel phosphors for LED lighting, says that it is relatively easy to fine-tune the chemistry of perovskites by substituting different halides or metal ions. “That means there’s a lot of potential to improve these properties,” he says.

Chemical & Engineering News ISSN 0009-2347 Copyright © 2016 American Chemical Society

Toronto’s QD (Quantum Dot) Solar sole Canadian among five winners of solar technology challenge


QD Solar untitledFive North American solar start-up companies have been selected to receive further support in developing their technology and moving them closer to market under the SunRISE TechBridge Challenge, which had 56 team entries.

Of the five winners, one is Canadian colloidal quantum dot cell developerQD Solar, which will gain support from Greentown Launch acceleration and DSM Partnership/Investment, as well as desk and lab space at Greentown Labs in Somerville, MA, and networking and coaching to accelerate their business and networking in the cleantech community in the Greater Boston area.

QD Solar uses low-cost, nano-engineered particles to produce solar cells that can capture wasted infrared light, resulting in a 20% increase in efficiency over conventional solar panels, based on research conducted at the Nanomaterials for Energy Laboratory in the University of Toronto’s Department of Electrical and Computer Engineering.

The SunRISE TechBridge Challenge challenged companies to present innovative solutions and new materials that will lower the levelized cost of energy (LCOE) for photovoltaic (PV) systems, including novel materials for existing and emerging high performance PV modules, technologies enabling non-traditional solar deployment, and business models that integrate solar PV with energy storage.

QD Solar started life at the University of Toronto and MaRS Innovation, and in March received $2.55 million from Sustainable Development Technology Canada (SDTC).

QDSolar

Conventional solar panels waste a large portion of available sun energy because their silicon solar cells can’t capture infrared light energy, a problem that QD Solar set out to solve with their proprietary quantum dot-based solar cells using nano-engineered, low-cost materials that can absorb infrared light.

QD Solar CEO Dan Shea is a former executive with Celestica and Blackberry.

In 2009, co-founder Edward Sargent and his team at the University of Toronto received a grant from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia to advance their research into colloidal quantum dots for solar power applications.

The SunRISE TechBridge Challenge was organized by Fraunhofer TechBridge and the SunRISE Partners, which include Royal DSM and Greentown Labs.

The Fraunhofer TechBridge Challenge is an offering of the Fraunhofer Center for Sustainable Energy Systems (CSE), which organizes several industry-sponsored annual challenges to accelerate promising technologies through targeted industry-driven validation projects, including the SunRISE Challenge, Advanced Industrial Surfaces, the Microgrid Challenge, and the Innovation Ecosystem Program.

Fraunhofer Gesellschaft is a German applied R&D organization which has 66 institutes and independent research units throughout Germany and 80 institutes and centers around the world.

Nicola Bettio, a member of QD Solar’s Board of Directors, manages the KAUST Innovation Fund and anticipates the establishment of the company’s presence in a significant development facility in KAUST’s Research & Technology Park in the near future.

KAUST University: Partnering for sustainable fresh water production: Video


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Published online Jun 7, 2016

Combining methods for water desalination results in low-cost, highly efficient water production.

Innovative solutions to improve the efficiency of water desalination are a major focus in countries such as Saudi Arabia, where fresh water for industrial, agricultural and human use is scarce. A research partnership between KAUST and the National University of Singapore has won global acclaim for its unique and efficient yet low-cost method of conducting desalination called hybrid multi-effect adsorption desalination.

In a world of dwindling freshwater supply, how can we meet the demands of a growing population? This video explains a new hybrid process which can double the freshwater output of traditional thermally-driven desalination without requiring additional energy. Developed by the King Abdullah University of Science and Technology (KAUST) and the National University of Singapore (NUS), this desalination method is now being piloted for wider implementation by MEDAD, a KAUST-supported startup company. For more information on the new hybrid technology.

Video explains the hybrid process of adsorption desalination using animations.

© 2016 KAUST

The collaboration has resulted in two desalination pilot schemes—one at KAUST itself and the other at a second location also in Saudi Arabia—as well as a spin-off company called MEDAD that will help to commercialize the hybrid desalination technology. The project is led by Kim Choon Ng from the University’s Water Desalination and Reuse Center. Ng has devoted his career to finding ways of reducing the cost of desalination through novel technologies.

Traditional desalination techniques use membranes and pressure to separate salt and other minerals from seawater, but these techniques are expensive, energy intensive and inefficient.

“Desalination is particularly complicated in the challenging environment of the Gulf, where high salinity, silt levels and increased water temperatures make working with the seawater quite difficult,” Ng said. “The frequent occurrence of hazardous algal blooms has also contributed to high pre-treatment costs and severe fouling of membranes. These elements combine to considerably increase the overall unit cost of producing desalinated water.”

Ng and his team recognized that the only viable option to overcome these challenges was to base their system on thermal desalination rather than membrane-based techniques.

They investigated a combined technique and utilized an existing industrially-proven method called multi-effect distillation (MED). This involves spraying saline water over the outer surfaces of a series of tubes (or stages) arranged in a tower. At the top of the tower, saline water is fed in and heated by a steam-driven compressor. The resulting water vapor is collected while the salt is left behind. This process is repeated over subsequent stages, and the vapor from each stage is channeled through the tubes to the bottom of the tower, where it condenses to generate fresh water as it cools.

Ng’s team combined MED with a thermally-driven process called adsorption desalination (AD), which uses low-cost silica gel adsorbents with a very high affinity for water vapor. The researchers adapted the last stage of MED so that the vapor uptake is carried out by AD.

The water vapor is attracted to designated adsorption gel beds while the remaining gel beds undergo desorption, removing the water and preparing the silica gel for the next round. Crucially, there are no major moving parts in the AD cycle, meaning it uses far less energy than some other techniques, and it can run on waste heat from other industrial processes.

“The best part about AD is that it can be run at low temperatures and low pressures,” explained Ng. “In fact, we can run cycles at only 7°C and at a pressure of 2 kPa. This presents a unique opportunity to exploit the renewable energy resources that the Kingdom has—namely solar and geothermal energy—to run the system. Also, because we are producing cooling as part of the process, we can link into air-conditioning systems.”

Simulations on the hybrid MEDAD system indicate that it could double or even triple desalinated water production. Experiments conducted at the pilot plant at KAUST have already increased fresh water production by more than 50 percent. This represents the highest water production ever reported for a desalination technique and earned the team a GE-Aramco “Global Innovation Challenge” award in January 2015. The breakthrough also helps extend the lower end of the temperature range at which the system can operate, which has been a major limitation with MED in the past.

“This represents a major leap forward in water production using thermally-driven cycles, and it is attributed to the excellent thermodynamic synergy between MED and AD cycles,” noted Ng. “We believe it can be developed fully to an extent where the energy efficiency of desalination can meet the target needed for sustainability.”

————–

The technology has been licensed by the NUS Industry Liasion Office, part of the NUS Enterprise, and the University’s Innovation and Economic Development Office, to MEDAD.

 

Kim Choon Ng and Muhammad Wakil inspect the MEDAD hybrid desalination pilot at KAUST.

Kim Choon Ng and Muhammad Wakil inspect the MEDAD hybrid desalination pilot at KAUST.

© 2015 KAUST

Kim Choon Ng (left) explains the hybrid cycle to visitors at KAUST, including Ahmad Khowaiter from Saudi Aramco (center), Dr. Abdulrahman from the Saline Water Conversion Commission (SWCC) (right) and Dr. Ahmed Al Arifi from SWCC (far right).

Kim Choon Ng (left) explains the hybrid cycle to visitors at KAUST, including Ahmad Khowaiter from Saudi Aramco (center), Dr. Abdulrahman from the Saline Water Conversion Commission (SWCC) (right) and Dr. Ahmed Al Arifi from SWCC (far right).

© 2015 KAUST

 

Catching more “Sun”


 

catchingmore sun 041316Combining quantum dots and organic molecules can enable solar cells to capture more of the sun’s light.

Light from the sun is our most abundant source of renewable energy, and learning how best to harvest this radiation is key for the world’s future power needs. Researchers at KAUST have discovered that the efficiency of solar cells can be boosted by combining inorganic semiconductor nanocrystals with .

Quantum dots are nano-crystals that only measure roughly 10 nanometers across. An electron trapped by the dot has quite different properties from those of an electron free to move through a larger material.

“One of the greatest advantages of for solar cell technologies is their optical properties’ tunability,” explained KAUST Assistant Professor of Chemical Science Omar Mohammed. “They can be controlled by varying the size of the quantum dot.”

Mohammed and his colleagues are developing lead sulfide quantum dots for optical energy harvesting; these tend to be larger than dots made from other materials. Accordingly, lead sulfide quantum dots can absorb light over a wider range of frequencies. This means they can absorb a greater proportion of the light from the sun when compared to other smaller dots.

QD Images Scale and Size quantum_dots_c

To make a fully functioning solar cell, electrons must be able to move away from the quantum dot absorption region and flow toward an electrode. Ironically, the property of large lead sulfide quantum dots that makes them useful for broadband absorption—a smaller electron energy bandgap—also hinders this energy harvesting process. Previously, efficient electron transfer had only been achieved for lead sulfide quantum dots smaller than 4.3 nanometers across, which caused a cut-off in the frequency of light converted.

The innovation by Mohammed and the team was to mix lead sulfide quantum dots of various sizes with molecules from a family known as porphyrins. The researchers showed that by changing the porphyrin used, it is possible to control the charge transfer from large lead sulfide dots; while one molecule switched off charge transfer altogether, another one enabled transfer at a rate faster than 120 femtoseconds.

The team believe this improvement in ability is due to the interfacial electrostatic interactions between the negatively charged quantum dot surface and the positively charged porphyrin.

“With this approach, we can now extend the quantum dot size for efficient charge transfer to include most of the near-infrared spectral region, reaching beyond the previously reported cut-off,” stated Mohammed. “We hope next to implement this idea in with different architectures to optimize efficiency.”

Explore further: Quantum dots with built-in charge boost solar cell efficiency by 50%

More information: Ala’a O. El-Ballouli et al. Overcoming the Cut-Off Charge Transfer Bandgaps at the PbS Quantum Dot Interface, Advanced Functional Materials (2015). DOI: 10.1002/adfm.201504035

 

KAUST:Nanoscale Polymer Membranes for ‘Selective’ Water Filtering


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The right blend of polymers enables rapid and molecule-selective filtering of tiny particles from water.

A method of fabricating polymer membranes with nanometer-scale holes that overcomes some practical challenges has been demonstrated by KAUST researchers.

Porous membranes can filter pollutants from a liquid, and the smaller the holes, the finer the particles the membrane can remove. The KAUST team developed a block copolymer membrane with pores as small as 1.5 nanometers but with increased water flux, the volume processed per hour by a membrane of a certain area.

A nanofilter needs to be efficient at rejecting specific molecules, be producible on a large scale, filter liquid quickly and be resistant to fouling or the build-up of removed micropollutants on the surface.

Block copolymers have emerged as a viable material for this application. Their characteristics allow them to self-assemble into regular patterns that enable the creation of nanoporous materials with pores as small as 10 nanometers.

However, reducing the size further to three nanometers has only been possible by post-treating the membrane (depositing gold, for example2). Moreover, smaller holes usually reduce the water flux.

Klaus-Viktor Peinemann from the KAUST Advanced Membranes & Porous Materials Center and Suzana Nunes from the KAUST Biological and Environmental Science and Engineering Division formed a multidisciplinary team to find a solution.

“We mixed two block copolymers in a casting solution, tuning the process by choosing the right copolymer systems, solvents, casting conditions,” explained Haizhou Yu, a postdoctoral fellow in Peinemann’s group. This approach is an improvement on alternatives because it doesn’t require material post-treatment.

Peinemann and colleagues blended polystyrene-b-poly(acrylic acid) and polystyrene-b-poly(4-vinylpyridine) in a ratio of six to one. This created a sponge-like layer with a 60 nanometer film on top. Material analysis showed that nanoscale pores formed spontaneously without the need for direct patterning1.

The researchers used their nanofiltration material to filter the biological molecule protoporphyrin IX from water. The filter simultaneously allowed another molecule, lysine, to pass through, demonstrating its molecular selectivity. The researchers were able to filter 540 liters per hour for every square meter of membrane, which is approximately 10 times faster than commercial nanofiltration membranes.

The groups teamed up with Victor Calo from the University’s Physical Science and Engineering Division to develop computer models to understand the mechanism of pore formation. They showed that the simultaneous decrease in pore size and increase in flux was possible because, while the pores are smaller, the pore density in the block copolymer is higher.

“In the future, we hope to optimize membranes for protein separation and other applications by changing the copolymer composition, synthesizing new polymers and mixing with additives,” said Nunes.


Story Source:

The above post is reprinted from materials provided by KAUST – King Abdullah University of Science and Technology. Note: Materials may be edited for content and length.


Journal References:

  1. Yu, H., Qiu, X., Moreno, N., Ma, Z., Calo, V. M., Nunes, S. P. & Peinemann, K.-V. Self-assembled asymmetric block copolymer membranes: Bridging the gap from ultra- to nanofiltration. Angewandte Chemie International Edition, December 2015
  2. Haizhou Yu, Xiaoyan Qiu, Suzana P. Nunes, Klaus-Viktor Peinemann. Self-Assembled Isoporous Block Copolymer Membranes with Tuned Pore Sizes. Angewandte Chemie International Edition, 2014; 53 (38): 10072 DOI: 10.1002/anie.201404491