Category Archives: water

Controlling water with ‘stick-slip surfaces’

Controlling water could lead to better designed microfluidic devices such as ‘lab-on-a-chip’. A July 27, 2015 news item on Nanowerk announces a new technique for controlling water,

Coating the inside of glass microtubes with a polymer hydrogel material dramatically alters the way capillary forces draw water into the tiny structures, researchers have found. The discovery could provide a new way to control microfluidic systems, including popular lab-on-a-chip devices.

Capillary action draws water and other liquids into confined spaces such as tubes, straws, wicks and paper towels, and the flow rate can be predicted using a simple hydrodynamic analysis. But a chance observation by researchers at the Georgia Institute of Technology [US] will cause a recalculation of those predictions for conditions in which hydrogel films line the tubes carrying water-based liquids.

“Rather than moving according to conventional expectations, water-based liquids slip to a new location in the tube, get stuck, then slip again – and the process repeats over and over again,” explained Andrei Fedorov, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. “Instead of filling the tube with a rate of liquid penetration that slows with time, the water propagates at a nearly constant speed into the hydrogel-coated capillary. This was very different from what we had expected.”

A July 27, 2015 Georgia Institute of Technology (Georgia Tech) news release (also on EurekAlert) by John Toon, which originated the news item, describes the work in more detail,

When the opening of a thin glass tube is exposed to a droplet of water, the liquid begins to flow into the tube, pulled by a combination of surface tension in the liquid and adhesion between the liquid and the walls of the tube. Leading the way is a meniscus, a curved surface of the water at the leading edge of the water column. An ordinary borosilicate glass tube fills by capillary action at a gradually decreasing rate with the speed of meniscus propagation slowing as a square root of time.

But when the inside of a tube is coated with a very thin layer of poly(N-isopropylacrylamide), a so-called “smart” polymer (PNIPAM), everything changes. Water entering a tube coated on the inside with a dry hydrogel film must first wet the film and allow it to swell before it can proceed farther into the tube. The wetting and swelling take place not continuously, but with discrete steps in which the water meniscus first sticks and its motion remains arrested while the polymer layer locally deforms. The meniscus then rapidly slides for a short distance before the process repeats. This “stick-slip” process forces the water to move into the tube in a step-by-step motion.

The flow rate measured by the researchers in the coated tube is three orders of magnitude less than the flow rate in an uncoated tube. A linear equation describes the time dependence of the filling process instead of a classical quadratic equation which describes filling of an uncoated tube.

“Instead of filling the capillary in a hundredth of a second, it might take tens of seconds to fill the same capillary,” said Fedorov. “Though there is some swelling of the hydrogel upon contact with water, the change in the tube diameter is negligible due to the small thickness of the hydrogel layer. This is why we were so surprised when we first observed such a dramatic slow-down of the filing process in our experiments.”

The researchers – who included graduate students James Silva, Drew Loney and Ren Geryak and senior research engineer Peter Kottke – tried the experiment again using glycerol, a liquid that is not absorbed by the hydrogel. With glycerol, the capillary action proceeded through the hydrogel-coated microtube as with an uncoated tube in agreement with conventional theory. After using high-resolution optical visualization to study the meniscus propagation while the polymer swelled, the researchers realized they could put this previously-unknown behavior to good use.

Water absorption by the hydrogels occurs only when the materials remain below a specific transition temperature. When heated above that temperature, the materials no longer absorb water, eliminating the “stick-slip” phenomenon in the microtubes and allowing them to behave like ordinary tubes.

This ability to turn the stick-slip behavior on and off with temperature could provide a new way to control the flow of water-based liquid in microfluidic devices, including labs-on-a-chip. The transition temperature can be controlled by varying the chemical composition of the hydrogel.

“By locally heating or cooling the polymer inside a microfluidic chamber, you can either speed up the filling process or slow it down,” Fedorov said. “The time it takes for the liquid to travel the same distance can be varied up to three orders of magnitude. That would allow precise control of fluid flow on demand using external stimuli to change polymer film behavior.”

The heating or cooling could be done locally with lasers, tiny heaters, or thermoelectric devices placed at specific locations in the microfluidic devices.

That could allow precise timing of reactions in microfluidic devices by controlling the rate of reactant delivery and product removal, or allow a sequence of fast and slow reactions to occur. Another important application could be controlled drug release in which the desired rate of molecule delivery could be dynamically tuned over time to achieve the optimal therapeutic outcome.

In future work, Fedorov and his team hope to learn more about the physics of the hydrogel-modified capillaries and study capillary flow using partially-transparent microtubes. They also want to explore other “smart” polymers which change the flow rate in response to different stimuli, including the changing pH of the liquid, exposure to electromagnetic radiation, or the induction of mechanical stress – all of which can change the properties of a particular hydrogel designed to be responsive to those triggers.

“These experimental and theoretical results provide a new conceptual framework for liquid motion confined by soft, dynamically evolving polymer interfaces in which the system creates an energy barrier to further motion through elasto-capillary deformation, and then lowers the barrier through diffusive softening,” the paper’s authors wrote. “This insight has implications for optimal design of microfluidic and lab-on-a-chip devices based on stimuli-responsive smart polymers.”

In addition to those already mentioned, the research team included Professor Vladimir Tsukruk from the Georgia Tech School of Materials Science and Engineering and Rajesh Naik, Biotechnology Lead and Tech Advisor of the Nanostructured and Biological Materials Branch of the Air Force Research Laboratory (AFRL).

Here’s a link to and a citation for the paper,

Stick–slip water penetration into capillaries coated with swelling hydrogel by J. E. Silva, R. Geryak, D. A. Loney, P. A. Kottke, R. R. Naik, V. V. Tsukruk, and A. G. Fedorov. Soft Matter, 2015,11, 5933-5939 DOI: 10.1039/C5SM00660K First published online 23 Jun 2015

This paper is behind a paywall.

Nanomaterials and UV (ultraviolet) light for environmental cleanups

I think this is the first time I’ve seen anything about a technology that removes toxic materials from both water and soil; it’s usually one or the other. A July 22, 2015 news item on Nanowerk makes the announcement (Note: A link has been removed),

Many human-made pollutants in the environment resist degradation through natural processes, and disrupt hormonal and other systems in mammals and other animals. Removing these toxic materials — which include pesticides and endocrine disruptors such as bisphenol A (BPA) — with existing methods is often expensive and time-consuming.

In a new paper published this week in Nature Communications (“Nanoparticles with photoinduced precipitation for the extraction of pollutants from water and soil”), researchers from MIT [Massachusetts Institute of Technology] and the Federal University of Goiás in Brazil demonstrate a novel method for using nanoparticles and ultraviolet (UV) light to quickly isolate and extract a variety of contaminants from soil and water.

A July 21, 2015 MIT news release by Jonathan Mingle, which originated the news item, describes the inspiration and the research in more detail,

Ferdinand Brandl and Nicolas Bertrand, the two lead authors, are former postdocs in the laboratory of Robert Langer, the David H. Koch Institute Professor at MIT’s Koch Institute for Integrative Cancer Research. (Eliana Martins Lima, of the Federal University of Goiás, is the other co-author.) Both Brandl and Bertrand are trained as pharmacists, and describe their discovery as a happy accident: They initially sought to develop nanoparticles that could be used to deliver drugs to cancer cells.

Brandl had previously synthesized polymers that could be cleaved apart by exposure to UV light. But he and Bertrand came to question their suitability for drug delivery, since UV light can be damaging to tissue and cells, and doesn’t penetrate through the skin. When they learned that UV light was used to disinfect water in certain treatment plants, they began to ask a different question.

“We thought if they are already using UV light, maybe they could use our particles as well,” Brandl says. “Then we came up with the idea to use our particles to remove toxic chemicals, pollutants, or hormones from water, because we saw that the particles aggregate once you irradiate them with UV light.”

A trap for ‘water-fearing’ pollution

The researchers synthesized polymers from polyethylene glycol, a widely used compound found in laxatives, toothpaste, and eye drops and approved by the Food and Drug Administration as a food additive, and polylactic acid, a biodegradable plastic used in compostable cups and glassware.

Nanoparticles made from these polymers have a hydrophobic core and a hydrophilic shell. Due to molecular-scale forces, in a solution hydrophobic pollutant molecules move toward the hydrophobic nanoparticles, and adsorb onto their surface, where they effectively become “trapped.” This same phenomenon is at work when spaghetti sauce stains the surface of plastic containers, turning them red: In that case, both the plastic and the oil-based sauce are hydrophobic and interact together.

If left alone, these nanomaterials would remain suspended and dispersed evenly in water. But when exposed to UV light, the stabilizing outer shell of the particles is shed, and — now “enriched” by the pollutants — they form larger aggregates that can then be removed through filtration, sedimentation, or other methods.

The researchers used the method to extract phthalates, hormone-disrupting chemicals used to soften plastics, from wastewater; BPA, another endocrine-disrupting synthetic compound widely used in plastic bottles and other resinous consumer goods, from thermal printing paper samples; and polycyclic aromatic hydrocarbons, carcinogenic compounds formed from incomplete combustion of fuels, from contaminated soil.

The process is irreversible and the polymers are biodegradable, minimizing the risks of leaving toxic secondary products to persist in, say, a body of water. “Once they switch to this macro situation where they’re big clumps,” Bertrand says, “you won’t be able to bring them back to the nano state again.”

The fundamental breakthrough, according to the researchers, was confirming that small molecules do indeed adsorb passively onto the surface of nanoparticles.

“To the best of our knowledge, it is the first time that the interactions of small molecules with pre-formed nanoparticles can be directly measured,” they write in Nature Communications.

Nano cleansing

Even more exciting, they say, is the wide range of potential uses, from environmental remediation to medical analysis.

The polymers are synthesized at room temperature, and don’t need to be specially prepared to target specific compounds; they are broadly applicable to all kinds of hydrophobic chemicals and molecules.

“The interactions we exploit to remove the pollutants are non-specific,” Brandl says. “We can remove hormones, BPA, and pesticides that are all present in the same sample, and we can do this in one step.”

And the nanoparticles’ high surface-area-to-volume ratio means that only a small amount is needed to remove a relatively large quantity of pollutants. The technique could thus offer potential for the cost-effective cleanup of contaminated water and soil on a wider scale.

“From the applied perspective, we showed in a system that the adsorption of small molecules on the surface of the nanoparticles can be used for extraction of any kind,” Bertrand says. “It opens the door for many other applications down the line.”

This approach could possibly be further developed, he speculates, to replace the widespread use of organic solvents for everything from decaffeinating coffee to making paint thinners. Bertrand cites DDT, banned for use as a pesticide in the U.S. since 1972 but still widely used in other parts of the world, as another example of a persistent pollutant that could potentially be remediated using these nanomaterials. “And for analytical applications where you don’t need as much volume to purify or concentrate, this might be interesting,” Bertrand says, offering the example of a cheap testing kit for urine analysis of medical patients.

The study also suggests the broader potential for adapting nanoscale drug-delivery techniques developed for use in environmental remediation.

“That we can apply some of the highly sophisticated, high-precision tools developed for the pharmaceutical industry, and now look at the use of these technologies in broader terms, is phenomenal,” says Frank Gu, an assistant professor of chemical engineering at the University of Waterloo in Canada, and an expert in nanoengineering for health care and medical applications.

“When you think about field deployment, that’s far down the road, but this paper offers a really exciting opportunity to crack a problem that is persistently present,” says Gu, who was not involved in the research. “If you take the normal conventional civil engineering or chemical engineering approach to treating it, it just won’t touch it. That’s where the most exciting part is.”

The researchers have made this illustration of their work available,

Nanoparticles that lose their stability upon irradiation with light have been designed to extract endocrine disruptors, pesticides, and other contaminants from water and soils. The system exploits the large surface-to-volume ratio of nanoparticles, while the photoinduced precipitation ensures nanomaterials are not released in the environment. Image: Nicolas Bertrand Courtesy: MIT

Nanoparticles that lose their stability upon irradiation with light have been designed to extract endocrine disruptors, pesticides, and other contaminants from water and soils. The system exploits the large surface-to-volume ratio of nanoparticles, while the photoinduced precipitation ensures nanomaterials are not released in the environment.
Image: Nicolas Bertrand Courtesy: MIT

Here’s a link to and a citation for the paper,

Nanoparticles with photoinduced precipitation for the extraction of pollutants from water and soil by Ferdinand Brandl, Nicolas Bertrand, Eliana Martins Lima & Robert Langer. Nature Communications 6, Article number: 7765 doi:10.1038/ncomms8765 Published 21 July 2015

This paper is open access.

Graphene and water (G20 Water commentary)

Tim Harper’s, Chief Executive Officer (CEO) of G2O Water, July 13, 2015 commentary was published on Nanotechnology Now. Harper, a longtime figure in the nanotechnology community (formerly CEO of Cientifica, an emerging technologies consultancy and current member of the World Economic Forum, not unexpectedly focused on water,

In the 2015 World Economic Forum’s Global Risks Report survey participants ranked Water Crises as the biggest of all risks, higher than Weapons of Mass Destruction, Interstate Conflict and the Spread of Infectious Diseases (pandemics). Our dependence on the availability of fresh water is well documented, and the United Nations World Water Development Report 2015 highlights a 40% global shortfall between forecast water demand and available supply within the next fifteen years. Agriculture accounts for much of the demand, up to 90% in most of the world’s least-developed countries, and there is a clear relationship between water availability, health, food production and the potential for civil unrest or interstate conflict.

The looming crisis is not limited to water for drinking or agriculture. Heavy metals from urban pollution are finding their way into the aquatic ecosystem, as are drug residues and nitrates from fertilizer use that can result in massive algal blooms. To date, there has been little to stop this accretion of pollutants and in closed systems such as lakes these pollutants are being concentrated with unknown long term effects.

Ten years ago, following discussions with former Israeli Prime Minister Shimon Peres, I organised a conference in Amsterdam called Nanowater to look at how nanotechnology could address global water issues. [emphasis mine] While the meeting raised many interesting points, and many companies proposed potential solutions, there was little subsequent progress.

Rather than a simple mix of one or two contaminants, most real world water can contain hundreds of different materials, and pollutants like heavy metals may be in the form of metal ions that can be removed, but are equally likely to be bound to other larger pieces of organic matter which cannot be simply filtered through nanopores. In fact the biggest obstacle to using nanotechnology in water treatment is the simple fact that small holes are easily blocked, and susceptibility to fouling means that most nanopore membranes quickly become barriers instead of filters.

Fortunately some recent developments in the ‘wonder material’ graphene may change the economics of water. One of the major challenges in the commercialisation of graphene is the ability to create large areas of defect-free material that would be suitable for displays or electronics, and this is a major research topic in Europe where the European Commission is funding graphene research to the tune of a billion euros. …

Tim goes on to describe some graphene-based solutions including a technology developed at the University of South Carolina, which is also mentioned in a July 16, 2015 G20 Water press release,

Fouling of nano/ultrafiltration membranes in oil/water separation is a longstanding issue and a major economic barrier for their widespread adoption. Currently membranes typically show severe fouling, resulting from the strong adhesion of oil on the membrane surface and/or oil penetration inside the membranes. This greatly degrades their performance and shortens service lifetime as well as increasing the energy usage.

G2O™s bio inspired approach uses graphene oxide (GO) for the fabrication of fully-recoverable membranes for high flux, antifouling oil/water separation via functional and structural mimicking of fish scales. The ultra-thin, amphiphilic, water-locking GO coating mimics the thin mucus layer covering fish scales, while the combination of corrugated GO flakes and intrinsic roughness of the porous supports successfully reproduces the hierarchical roughness of fish scales. Cyclic membrane performance evaluation tests revealed circa 100% membrane recovery by facile surface water flushing, establishing their excellent easy-to-recover capability.

The pore sizes can be tuned to specific applications such as water desalination, oil/water separation, storm water treatment and industrial waste water recovery. By varying the GO concentration in water, GO membranes with different thickness can be easily fabricated via a one-time filtration process.
G2O™s patented graphene oxide technology acts as a functional coating for modifying the surface properties of existing filter media resulting in:
Higher pure water flux;
High fouling resistance;
Excellent mechanical strength;
High chemical stability;
Good thermal stability;
Low cost.

We’re going through a water shortage here in Vancouver, Canada after a long spring season which distinguished itself with a lack of rain and the introduction of a heatwave extending into summer. It is by no means equivalent to the situation in many parts of the world but it does give even those of us who are usually waterlogged some insight into what it means when there isn’t enough water.

For more insight into water crises with a special focus on the Middle East (notice Harper mentioned Israel’s former Prime Minister Shimon Peres in his commentary), I have a Feb. 24, 2014 posting (Water desalination to be researched at Oman’s newly opened Nanotechnology Laboratory at Sultan Qaboos University) and a June 25, 2013 post (Nanotechnology-enabled water resource collaboraton between Israel and Chicago).

You can check out the World Economic Forum’s Outlook on the Global Agenda 2015 here.

The Outlook on the Global Agenda 2015 features an analysis of the Top 10 trends which will preoccupy our experts for the next 12-18 months as well as the key challenges facing the world’s regions, an overview of global leadership and governance, and the emerging issues that will define our future.

G20 Water can be found here.

Crowd computing for improved nanotechnology-enabled water filtration

This research is the product of a China/Israel/Switzerland collaboration on water filtration with involvement from the UK and Australia. Here’s some general information about the importance of water and about the collaboration in a July 5, 2015 news item on Nanowerk (Note: A link has been removed),

Nearly 800 million people worldwide don’t have access to safe drinking water, and some 2.5 billion people live in precariously unsanitary conditions, according to the Centers for Disease Control and Prevention. Together, unsafe drinking water and the inadequate supply of water for hygiene purposes contribute to almost 90% of all deaths from diarrheal diseases — and effective water sanitation interventions are still challenging scientists and engineers.

A new study published in Nature Nanotechnology (“Water transport inside carbon nanotubes mediated by phonon-induced oscillating friction”) proposes a novel nanotechnology-based strategy to improve water filtration. The research project involves the minute vibrations of carbon nanotubes called “phonons,” which greatly enhance the diffusion of water through sanitation filters. The project was the joint effort of a Tsinghua University-Tel Aviv University research team and was led by Prof. Quanshui Zheng of the Tsinghua Center for Nano and Micro Mechanics and Prof. Michael Urbakh of the TAU School of Chemistry, both of the TAU-Tsinghua XIN Center, in collaboration with Prof. Francois Grey of the University of Geneva.

A July 5, 2015 American Friends of Tel Aviv University news release (also on EurekAlert), which originated the news item, provides more details about the work,

“We’ve discovered that very small vibrations help materials, whether wet or dry, slide more smoothly past each other,” said Prof. Urbakh. “Through phonon oscillations — vibrations of water-carrying nanotubes — water transport can be enhanced, and sanitation and desalination improved. Water filtration systems require a lot of energy due to friction at the nano-level. With these oscillations, however, we witnessed three times the efficiency of water transport, and, of course, a great deal of energy saved.”

The research team managed to demonstrate how, under the right conditions, such vibrations produce a 300% improvement in the rate of water diffusion by using computers to simulate the flow of water molecules flowing through nanotubes. The results have important implications for desalination processes and energy conservation, e.g. improving the energy efficiency for desalination using reverse osmosis membranes with pores at the nanoscale level, or energy conservation, e.g. membranes with boron nitride nanotubes.

Crowdsourcing the solution

The project, initiated by IBM’s World Community Grid, was an experiment in crowdsourced computing — carried out by over 150,000 volunteers who contributed their own computing power to the research.

“Our project won the privilege of using IBM’s world community grid, an open platform of users from all around the world, to run our program and obtain precise results,” said Prof. Urbakh. “This was the first project of this kind in Israel, and we could never have managed with just four students in the lab. We would have required the equivalent of nearly 40,000 years of processing power on a single computer. Instead we had the benefit of some 150,000 computing volunteers from all around the world, who downloaded and ran the project on their laptops and desktop computers.

“Crowdsourced computing is playing an increasingly major role in scientific breakthroughs,” Prof. Urbakh continued. “As our research shows, the range of questions that can benefit from public participation is growing all the time.”

The computer simulations were designed by Ming Ma, who graduated from Tsinghua University and is doing his postdoctoral research in Prof. Urbakh’s group at TAU. Ming catalyzed the international collaboration. “The students from Tsinghua are remarkable. The project represents the very positive cooperation between the two universities, which is taking place at XIN and because of XIN,” said Prof. Urbakh.

Other partners in this international project include researchers at the London Centre for Nanotechnology of University College London; the University of Geneva; the University of Sydney and Monash University in Australia; and the Xi’an Jiaotong University in China. The researchers are currently in discussions with companies interested in harnessing the oscillation knowhow for various commercial projects.

 

Here’s a link to and a citation for the paper,

Water transport inside carbon nanotubes mediated by phonon-induced oscillating friction by Ming Ma, François Grey, Luming Shen, Michael Urbakh, Shuai Wu,    Jefferson Zhe Liu, Yilun Liu, & Quanshui Zheng. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.134 Published online 06 July 2015

This paper is behind a paywall.

Final comment, I find it surprising that they used labour and computing power from 150,000 volunteers and didn’t offer open access to the paper. Perhaps the volunteers got their own copy? I certainly hope so.

Tanzanian research into nanotechnology-enabled water filters

Inexpensive 99.9999…% filtration of metals, bacteria, and viruses from water is an accomplishment worthy of a prize as the UK’s Royal Academy of Engineering noted by awarding its first ever International Innovation Prize of £25,000 ($38,348 [USD?]) to Askwar Hilonga, a Tanzanian academic and entrepreneur. A June 11, 2015 article by Sibusiso Tshabalala for Quartz.com describes the water situation in Tanzania and Hilonga’s accomplishment (Note: Links have been removed),

Despite Tanzania’s proximity to three major lakes almost half of it’s population cannot access potable water.

Groundwater is often the alternative, but the supply is not always clean. Mining waste (pdf, pg 410) and toxic drainage systems easily leak into fresh groundwater, leaving the water contaminated.

Enter Askwar Hilonga: a 38-year old chemical engineer PhD and entrepreneur. With 33 academic journal articles on nanotechnology to his name, Hilonga aims to solve Tanzania’s water contamination problems by using nanotechnology to customize water filters.

There are other filters available (according to Tshabalala’s article) but Hilonga’s has a unique characteristic in addition to being highly efficient and inexpensive,

Purifying water using nanotechnology is hardly a new thing. In 2010, researchers at the Yi Cui Lab at Stanford University developed a synthetic “nanoscanvenger” made out of two silver layers that enable nanoparticles to disinfect water from contaminating bacteria.

What makes Hilonga’s water filter different from the Stanford-developed “nanoscavenger”, or the popular LifeStraw developed by the Swiss-based health innovation company Vestergaard 10 years ago?

“It is customized. The filter can be tailored for specific individual, household and communal use,” says Hilonga.

A June 2, 2015 news item about the award on BBC (British Broadcasting Corporation) online describes how the filter works,

The sand-based water filter that cleans contaminated drinking water using nanotechnology has already been trademarked.

“I put water through sand to trap debris and bacteria,” Mr Hilonga told the BBC’s Newsday programme about the filter.

“But sand cannot remove contaminants like fluoride and other heavy metals so I put them through nano materials to remove chemical contaminants.”

Hilonga describes the filter in a little more detail in his May 30, 2014 video submitted for for the UK Royal Academy of Engineering’s prize (Africa Prize for Engineering Innovation)

Finalists for the prize (there were four) received a six month mentorship which included help to develop the technology further and with business plans. Hilonga has already enabled 23 entrepreneurs to develop nanofilter businesses, according to the Tshabalala article,

Through the Gongali Model Company, a university spin-off company which he co-founded, Hilonga has already enabled 23 entrepreneurs in Karatu to set up their businesses with the filters, and local schools to provide their learners with clean drinking water.

With this prize money, Hilonga will be able to lower the price of his filter ($130 [USD?) according to the BBC news item.

Congratulations to Dr. Hilonga and his team! For anyone curious about the Gongali Model Company, you can go here.

Water-fueled computer

A computer fueled by water? A fascinating concept as described in a June 9, 2015 news item on ScienceDaily,

Computers and water typically don’t mix, but in Manu Prakash’s lab, the two are one and the same. Prakash, an assistant professor of bioengineering at Stanford, and his students have built a synchronous computer that operates using the unique physics of moving water droplets.

A June 8, 2015 Stanford University news release by Bjorn Carey, which originated the news item, details the ideas (new applications) and research (open access to the tools for creating water droplet-fueled circuits) further,

The computer is nearly a decade in the making, incubated from an idea that struck Prakash when he was a graduate student. The work combines his expertise in manipulating droplet fluid dynamics with a fundamental element of computer science – an operating clock.

“In this work, we finally demonstrate a synchronous, universal droplet logic and control,” Prakash said.

Because of its universal nature, the droplet computer can theoretically perform any operation that a conventional electronic computer can crunch, although at significantly slower rates. Prakash and his colleagues, however, have a more ambitious application in mind.

“We already have digital computers to process information. Our goal is not to compete with electronic computers or to operate word processors on this,” Prakash said. “Our goal is to build a completely new class of computers that can precisely control and manipulate physical matter. Imagine if when you run a set of computations that not only information is processed but physical matter is algorithmically manipulated as well. We have just made this possible at the mesoscale.”

The ability to precisely control droplets using fluidic computation could have a number of applications in high-throughput biology and chemistry, and possibly new applications in scalable digital manufacturing.

The crucial clock

For nearly a decade since he was in graduate school, an idea has been nagging at Prakash: What if he could use little droplets as bits of information and utilize the precise movement of those drops to process both information and physical materials simultaneously. Eventually, Prakash decided to build a rotating magnetic field that could act as clock to synchronize all the droplets. The idea showed promise, and in the early stages of the project, Prakash recruited a graduate student, Georgios “Yorgos” Katsikis, who is the first author on the paper.

Computer clocks are responsible for nearly every modern convenience. Smartphones, DVRs, airplanes, the Internet – without a clock, none of these could operate without frequent and serious complications. Nearly every computer program requires several simultaneous operations, each conducted in a perfect step-by-step manner. A clock makes sure that these operations start and stop at the same times, thus ensuring that the information synchronizes.

The results are dire if a clock isn’t present. It’s like soldiers marching in formation: If one person falls dramatically out of time, it won’t be long before the whole group falls apart. The same is true if multiple simultaneous computer operations run without a clock to synchronize them, Prakash explained.

“The reason computers work so precisely is that every operation happens synchronously; it’s what made digital logic so powerful in the first place,” Prakash said.

A magnetic clock

Developing a clock for a fluid-based computer required some creative thinking. It needed to be easy to manipulate, and also able to influence multiple droplets at a time. The system needed to be scalable so that in the future, a large number of droplets could communicate amongst each other without skipping a beat. Prakash realized that a rotating magnetic field might do the trick.

Katsikis and Prakash built arrays of tiny iron bars on glass slides that look something like a Pac-Man maze. They laid a blank glass slide on top and sandwiched a layer of oil in between. Then they carefully injected into the mix individual water droplets that had been infused with tiny magnetic nanoparticles.

Next, they turned on the magnetic field. Every time the field flips, the polarity of the bars reverses, drawing the magnetized droplets in a new, predetermined direction, like slot cars on a track. Every rotation of the field counts as one clock cycle, like a second hand making a full circle on a clock face, and every drop marches exactly one step forward with each cycle.

A camera records the interactions between individual droplets, allowing observation of computation as it occurs in real time. The presence or absence of a droplet represents the 1s and 0s of binary code, and the clock ensures that all the droplets move in perfect synchrony, and thus the system can run virtually forever without any errors.

“Following these rules, we’ve demonstrated that we can make all the universal logic gates used in electronics, simply by changing the layout of the bars on the chip,” said Katsikis. “The actual design space in our platform is incredibly rich. Give us any Boolean logic circuit in the world, and we can build it with these little magnetic droplets moving around.”

The current paper describes the fundamental operating regime of the system and demonstrates building blocks for synchronous logic gates, feedback and cascadability – hallmarks of scalable computation. A simple-state machine including 1-bit memory storage (known as “flip-flop”) is also demonstrated using the above basic building blocks.

A new way to manipulate matter

The current chips are about half the size of a postage stamp, and the droplets are smaller than poppy seeds, but Katsikis said that the physics of the system suggests it can be made even smaller. Combined with the fact that the magnetic field can control millions of droplets simultaneously, this makes the system exceptionally scalable.

“We can keep making it smaller and smaller so that it can do more operations per time, so that it can work with smaller droplet sizes and do more number of operations on a chip,” said graduate student and co-author Jim Cybulski. “That lends itself very well to a variety of applications.”

Prakash said the most immediate application might involve turning the computer into a high-throughput chemistry and biology laboratory. Instead of running reactions in bulk test tubes, each droplet can carry some chemicals and become its own test tube, and the droplet computer offers unprecedented control over these interactions.

From the perspective of basic science, part of why the work is so exciting, Prakash said, is that it opens up a new way of thinking of computation in the physical world. Although the physics of computation has been previously applied to understand the limits of computation, the physical aspects of bits of information has never been exploited as a new way to manipulate matter at the mesoscale (10 microns to 1 millimeter).

Because the system is extremely robust and the team has uncovered universal design rules, Prakash plans to make a design tool for these droplet circuits available to the public. Any group of people can now cobble together the basic logic blocks and make any complex droplet circuit they desire.

“We’re very interested in engaging anybody and everybody who wants to play, to enable everyone to design new circuits based on building blocks we describe in this paper or discover new blocks. Right now, anyone can put these circuits together to form a complex droplet processor with no external control – something that was a very difficult challenge previously,” Prakash said.

“If you look back at big advances in society, computation takes a special place. We are trying to bring the same kind of exponential scale up because of computation we saw in the digital world into the physical world.”

Here’s a link to and a citation for the paper,

Synchronous universal droplet logic and control by Georgios Katsikis, James S. Cybulski, & Manu Prakash. Nature Physics (2015) doi:10.1038/nphys3341 Published online 08 June 2015

This paper is behind a paywall.

For anyone interested in creating a water-fueled circuit, you could try contacting Manu Prakash, Bioengineering: manup@stanford.edu

Tiny Science. Big Impacts. Cool Videos. Winners announced and new call for submissions.

The US National Nanotechnology Coordination Office (NNCO) on behalf of the National Nanotechnology Initiative (NNI) has announced the winners for its first, ‘Tiny Science. Big Impacts. Cool Videos.’ contest in a June 5, 2015 news item on Nanowerk,

The National Nanotechnology Coordination Office (NNCO) is pleased to announce the winners of the first Tiny Science. Big Impacts. Cool Videos. nanotechnology video contest for students. Abelardo Colon and Jennifer Gill from the University of Puerto Rico, Rio Piedras, Nanoscience and Nanotechnology Research Lab won the top honors for their video entitled Chlorination-less. The video explains a new method for disinfecting drinking water using a nanodiamond powder. This nanotechnology-enabled method can kill bacteria, is biocompatible, and is reusable, making it a good alternative to traditional chlorination. Congratulations Abelardo and Jennifer!

A June 5, 2015 NNCO news release on EurekAlert, which originated the news item, describes the judging process and plans for the video,

Videos submitted by students from universities across the United States and U.S. territories, were posted on NanoTube, the official National Nanotechnology Initiative (NNI) YouTube channel, for public voting. The winning video was chosen by representatives from the NNI member agencies from the top two videos identified by public voting. This video will be featured on Nano.gov for the next month. For more information on the Tiny Science. Big Impacts. Cool Videos. contest rules and judges, visit the student video contest page on Nano.gov.

Here is Chlorination-less,

From the Chlorination-less YouTube page,

Published on Apr 28, 2015

“Access to clean water is a major international issue that must not be ignored. Our research is finding a new method for the disinfection of drinking water. Even so, chlorination is the most common treatment for the disinfection of drinking water, but has a lot of disadvantages. Disinfectant by-products (DBP’s) produced by the chlorine disinfection process can cause health problems such as cancer to humans that drink water or inhale vapor. Also some bacteria are able to adapt to this chemical treatment. This is why we are proposing a physical treatment using Ultra Dispersed Diamond (UDD) for the disinfection of drinking water. The UDD is a nanodiamond powder, which has bactericidal properties and is biocompatible. After applying the UDD material to the contaminated water we have promising results. There was a reduction of fecal E. coli colonies as time passed and the density of the material increases. This process will be healthier, cheaper, and more environmentally friendly since it is reusable.”

University of Puerto Rico , Rio Piedras Campus

As for the next contest, that begins July 1, 2015 (from the Tiny Science. Big Impacts. Cool Videos. contest webpage), Note: Links have been removed,

Graduate students, will your research lead to nanotechnologies that impact our daily lives? Submit videos that demonstrate how your nanotechnology research will bring solutions to real-world problems. …

Email submissions information to NNCOvideos@gmail.com and include:

Name and affiliation:

Submissions will be accepted from teams and from individuals. A lead contact person must be designated for team submissions. The order in which names are listed in the submission is the order in which they will appear on the NNI public voting page, the NNI YouTube channel, and on Nano.gov.

Description (150 words or less): Explain your research, use plain language and avoid jargon. Concentrate on what problem your research will help to solve.

Title of uploaded video: It should be the same as the video file name you upload using Google Drive.

Releases for people appearing in the video: A release form is available here; print, collect signatures, scan, and email us electronic copies.

Laboratory website: Include link to the lab where you work, if available

Funding source: Include funding agency, program manager, and award/grant number, if possible

Upload videos using Google Drive to NNCOvideos@gmail.com:

Video Criteria

Video length should be between 2.5 and 3 minutes.

Maximum file size is 2 GB

File type must be H.264, MP4, FLV, or MOV

Use a camera that can shoot videos at least 1280 x 720 pixels in size.

Save video file as the title listed on emailed submission information

Remember to avoid jargon while explaining your research

Collect signed releases (available here) from any recognizable individual appearing in your video

You are allowed to have others (e.g., film students) produce the video. If you put your own video together make sure everything is well lit. Fluorescent overhead lights aren’t the best, try to use natural or focused light if you can. Pay attention to sound quality; use a good microphone and listen for background noise. Watch for too much clutter in the background of your scenes, this can be distracting.

Timeline:

NNCO will begin accepting submissions for the Tiny Science. Big Impacts. Cool Videos. video contest on July 1, 2015.

The Tiny Science. Big Impacts. Cool Videos. video contest will close on November 12, 2015.

The deadline for submissions is 12:00 p.m. PST November 12, 2015.

Semifinalist judging for videos submitted before 12:00 p.m. PST on November 12, 2015 takes place from 12:00 p.m. November 19, 2015 to 12:00 p.m. November 30, 2015.

The winning video will be announced on December 15, 2015.

Good luck!

Computer modeling of engineered nanoparticles in surface water, the NanoDUFLOW model

A June 4, 2015 news item on phys.org features research that could be very helpful in understanding the impact that engineered nanoparticles (ENP) have on the water in our environment,

Researchers of Wageningen University (Netherlands) provide the world’s first spatiotemporally explicit model that simulates the behaviour and fate of engineered nanoparticles (ENPs) in surface waters. Wageningen researcher Bart Koelmans: “This is important in order to assure safe nanotechnology. We do need to have an assessment of the risks of ENPs to man and the environment.”

Nanotechnology is developing fast, with the fast growing emission of less than 100 nm engineered nanoparticles as a consequence. ENPs are hard to measure in the environment so that exposure assessments have to rely on modelling. Previous models could only predict average background concentrations on a continental or national scale.

A June 3, 2015 Wageningen University press release, which originated the news item, describes the computer model,

The new NanoDUFLOW model however, developed by Joris Quik, Jeroen de Klein and Bart Koelmans and recently described in Water Research magazine, is capable of simulating the concentrations of ENPs, and their homo- and heteroaggregates in space and time, for any hydrological flow regime of a river. Under the hood of NanoDUFLOW is an ‘engine’ that calculates all relevant interactions among 35 types of particles including the ENPs, and that decides upon aggregation, settling or prolonged flow in the river. The rate of these interactions depends on the flow conditions in the river, which are calculated in the hydrology module of NanoDUFLOW. This module can be set to match the channel structure of any catchment as defined by the user, allowing for a great flexibility.

Development of the model

Development of the model took a long and winding road. ENPs are emerging chemicals with unique properties, which implies that some new process descriptions needed to be developed. One of the main parameters in this new type of models is the attachment efficiency. The attachment efficiency is the chance that two particles stay together when they collide, a chance that depends on the nature of the colliding particles and the chemistry of the water. A smart calculation method needed to be developed that enabled the estimation of the attachment efficiency from laboratory experiments with ENPs and natural particles and waters collected in the field.

Using NanoDUFLOW for the risk assessment of nanomaterials

In order to assure safe nanotechnology, society calls for an assessment of the risks of ENPs to man and the environment. A risk assessment for ENPs requires an assessment of ENP exposure, and of the effects caused by ENPs, which then can be compared in a risk characterisation. Whereas previous screening-level models still may be first choice for lower tiers in the risk assessment, NanoDUFLOW is believed to be useful for higher tiers of the risk assessment, where site specific risks need to be addressed. Simulations with NanoDUFLOW showed the occurrence of clear ENP contamination ‘hot spots’ in the water column and in sediments. Furthermore, NanoDUFLOW was capable of simulating the speciation of ENPs over different size fractions. This speciation defines the ecotoxicologically relevant fractions of ENPs, for a variety of species traits. Also in this respect NanoDUFLOW will add to refining the risk assessment for ENPs.

Here’s a link to and a citation for the paper,

Spatially explicit fate modelling of nanomaterials in natural waters by Joris T. K. Quika, Jeroen J.M. de Klein, & Albert A. Koelmans. Water Research Volume 80, 1 September 2015, Pages 200–208  doi:10.1016/j.watres.2015.05.025

This paper is behind a paywall.

A GEnIuS approach to oil spill remediation at 18th European Forum on Eco-innovation

In light of recent local events (an oil spill in Vancouver’s [Canada] English Bay, a popular local beach [more details in my April 16, 2015 post]), it seems appropriate to mention a environmentally friendly solution to mopping up oil spills (oil spill remediation). A May 21, 2015 news item on Azonano features a presentation on the topic at hand (Note: A link has been removed),

Directa Plus at 18th European Forum on Eco-innovation to present GEnIuS, the innovative project that leads to the creation of a graphene-based product able to remove hydrocarbons from polluted water and soil.

The Forum untitled “Boosting competitiveness and innovation” is being held by the European Commission on 20th and 21st of May in Barcelona. The main purpose of this event is presenting the last developments in the eco-innovation field: an important moment where emerging and cutting-edge innovators will get in contact with new promising solutions under political, financial and technological point of view.

Directa Plus research has driven to the creation of an ecologic, innovative and highly effective oil-adsorbent, characterized by unique performances in oil adsorbency, and at the same time absence of toxicity and flammability, and the possibility to recover oil.

The creation of this graphene-based oil-adsorbent product, commercialized as Grafysorber, has been promoted by GEnIuS project and already approved by the Italian Ministry of Enviroment to be used in occasion of oil spills clean-up activities.

Giulio Cesareo, Directa Plus President and CEO, commented:

“Grafysorber embodies the nano-carbon paradox -in fact, with a nano-carbon material we are able to cut down part of damages caused by hydrocarbons, derived from carbon itself.

“Moreover, our product, once exhausted after depuration of water, finishes positively its life cycle inside the asphalt and bitumen, introducing new properties as thermal conductivity and mechanical reinforcement. I believe that every company is obliged to work following a sustainable approach to guarantee a balanced use of resources and their reuse, where possible.”

I have mentioned a Romanian project employing Directa Plus’s solution, Grafysorber in a December 30, 2014 post. At the time, the product name was called Graphene Plus and Grafysorber was a constituent of the product.

You can find more information about Graphene Eco Innovative Sorbent (GENIUS) here and about Directa Plus here. The company is located in Italy.

One final bit about oil spills and remediation, the Deepwater Horizon/Gulf/BP oil spill has spawned, amongst many others, a paper from the University of Georgia (US) noting that we don’t know that much about the dispersants used to clean up, from a May 14, 2015 University of Georgia news release on EurekAlert,

New commentary in Nature Reviews Microbiology by Samantha Joye of the University of Georgia and her colleagues argues for further in-depth assessments of the impacts of dispersants on microorganisms to guide their use in response to future oil spills.

Chemical dispersants are widely used in emergency responses to oil spills in marine environments as a means of stimulating microbial degradation of oil. After the Deepwater Horizon spill in 2010, dispersants were applied to the sea surface and deep waters of the Gulf of Mexico, the latter of which was unprecedented. Dispersants were used as a first line of defense even though little is known about how they affect microbial communities or the biodegradation activities they are intended to spur.

The researchers document historical context for the use of dispersants, their approval by the Environmental Protection Agency and the uncertainty about whether they stimulate or in fact inhibit the microbial degradation of oil in marine ecosystems.

One challenge of testing the toxicity from the use of dispersants on the broader ecosystem is the complex microbial communities of the different habitats represented in a large marine environment, such as the Gulf of Mexico. Development of model microbial communities and type species that reflect the composition of surface water, deep water, deep-sea sediments, beach sediments and marsh sediments is needed to evaluate the toxicity effects of dispersants.

“The bottom line is that we do not truly understand the full range of impacts that dispersants have on microbial communities, and we must have this knowledge in hand before the next marine oil spill occurs to support the decision-making process by the response community,” Joye said.

I hope the Canadians who are overseeing our waterways are taking note.

Nanopollution of marine life

Concerns are being raised about nanosunscreens and nanotechnology-enabled marine paints and their effect on marine life, specifically, sea urchins. From a May 13, 2015 news item on Nanowerk (Note: A link has been removed),

Nanomaterials commonly used in sunscreens and boat-bottom paints are making sea urchin embryos more vulnerable to toxins, according to a study from the University of California, Davis [UC Davis]. The authors said this could pose a risk to coastal, marine and freshwater environments.

The study, published in the journal Environmental Science and Technology (“Copper Oxide and Zinc Oxide Nanomaterials Act as Inhibitors of Multidrug Resistance Transport in Sea Urchin Embryos: Their Role as Chemosensitizers”), is the first to show that the nanomaterials work as chemosensitizers. In cancer treatments, a chemosensitizer makes tumor cells more sensitive to the effects of chemotherapy.

Similarly, nanozinc and nanocopper made developing sea urchin embryos more sensitive to other chemicals, blocking transporters that would otherwise defend them by pumping toxins out of cells.

A May 12, 2015 UC Davis news release, which originated the news item, includes some cautions,

Nanozinc oxide is used as an additive in cosmetics such as sunscreens, toothpastes and beauty products. Nanocopper oxide is often used for electronics and technology, but also for antifouling paints, which prevent things like barnacles and mussels from attaching to boats.

“At low levels, both of these nanomaterials are nontoxic,” said co-author Gary Cherr, professor and interim director of the UC Davis Bodega Marine Laboratory, and an affiliate of the UC Davis Coastal Marine Sciences Institute. “However, for sea urchins in sensitive life stages, they disrupt the main defense mechanism that would otherwise protect them from environmental toxins.”

Science for safe design

Nanomaterials are tiny chemical substances measured in nanometers, which are about 100,000 times smaller than the diameter of a human hair. Nano-sized particles can enter the body through the skin, ingestion, or inhalation. They are being rapidly introduced across the fields of electronics, medicine and technology, where they are being used to make energy efficient batteries, clean up oil spills, and fight cancer, among many other uses. However, relatively little is known about nanomaterials with respect to the environment and health.

Here’s a link to and a citation for the paper,

Copper Oxide and Zinc Oxide Nanomaterials Act as Inhibitors of Multidrug Resistance Transport in Sea Urchin Embryos: Their Role as Chemosensitizers by Bing Wu, Cristina Torres-Duarte, Bryan J. Cole, and Gary N. Cherr. Environ. Sci. Technol., 2015, 49 (9), pp 5760–5770 DOI: 10.1021/acs.est.5b00345 Publication Date (Web): April 7, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

While this research into nanoparticles as chemosensitizers is, according to UC Davis, the first of its kind, the concern over nanosunscreens and marine waters has been gaining traction over the last few years. For example, there’s  research featured in a June 10, 2013 article by Roberta Kwok for the University of Washington’s ‘Conservation This Week’ magazine,

Sunscreen offers protection from UV rays, reduces the risk of skin cancer, and even slows down signs of aging. Unfortunately, researchers have found that sunscreen also pollutes the ocean.

Although people have been using these products for decades, “the effect of sunscreens, as a source of introduced chemicals to the coastal marine system, has not yet been addressed,” a research team writes in PLOS ONE. Sunscreens contain chemicals not only for UV protection, but also for coloring, fragrance, and texture. And beaches are becoming ever-more-popular vacation spots; for example, nearly 10 million tourists visited Majorca Island in the Mediterranean Sea in 2010.

Here’s a link to the 2013 PLOS ONE paper,

Sunscreen Products as Emerging Pollutants to Coastal Waters by Antonio Tovar-Sánchez, David Sánchez-Quiles, Gotzon Basterretxea, Juan L. Benedé, Alberto Chisvert, Amparo Salvador, Ignacio Moreno-Garrido, and Julián Blasco. PLOS ONE DOI: 10.1371/journal.pone.0065451 Published: June 5, 2013

This is an open access journal.