Tag Archives: sensors

Swelling sensors and detecting gases at the nanoscale

A June 17, 2014 news item on Nanowerk features a new approach to sensing gases from the Massachusetts Institute of Technology (MIT),

Using microscopic polymer light resonators that expand in the presence of specific gases, researchers at MIT’s Quantum Photonics Laboratory have developed new optical sensors with predicted detection levels in the parts-per-billion range. Optical sensors are ideal for detecting trace gas concentrations due to their high signal-to-noise ratio, compact, lightweight nature, and immunity to electromagnetic interference.

Although other optical gas sensors had been developed before, the MIT team conceived an extremely sensitive, compact way to detect vanishingly small amounts of target molecules.

A June 17, 2014 American Institute of Physics (AIP) news release by John Arnst, which originated the news item, describes the new technique in some detail,

The researchers fabricated wavelength-scale photonic crystal cavities from PMMA, an inexpensive and flexible polymer that swells when it comes into contact with a target gas. The polymer is infused with fluorescent dye, which emits selectively at the resonant wavelength of the cavity through a process called the Purcell effect. At this resonance, a specific color of light reflects back and forth a few thousand times before eventually leaking out. A spectral filter detects this small color shift, which can occur at even sub-nanometer level swelling of the cavity, and in turn reveals the gas concentration.

“These polymers are often used as coatings on other materials, so they’re abundant and safe to handle. Because of their deformation in response to biochemical substances, cavity sensors made entirely of this polymer lead to a sensor with faster response and much higher sensitivity,” said Hannah Clevenson. Clevenson is a PhD student in the electrical engineering and computer science department at MIT, who led the experimental effort in the lab of principal investigator Dirk Englund.

PMMA can be treated to interact specifically with a wide range of different target chemicals, making the MIT team’s sensor design highly versatile. There’s a wide range of potential applications for the sensor, said Clevenson, “from industrial sensing in large chemical plants for safety applications, to environmental sensing out in the field, to homeland security applications for detecting toxic gases, to medical settings, where the polymer could be treated for specific antibodies.”

The thin PMMA polymer films, which are 400 nanometers thick, are patterned with structures that are 8-10 micrometers long by 600 nanometers wide and suspended in the air. In one experiment, the films were embedded on tissue paper, which allowed 80 percent of the sensors to be suspended over the air gaps in the paper. Surrounding the PMMA film with air is important, Clevenson said, both because it allows the device to swell when exposed to the target gas, and because the optical properties of air allow the device to be designed to trap light travelling in the polymer film.

The team found that these sensors are easily reusable since the polymer shrinks back to its original length once the targeted gas has been removed.

The current experimental sensitivity of the devices is 10 parts per million, but the team predicts that with further refinement, they could detect gases with part-per-billion concentration levels.

The researchers have provided an image illustrating the sensor’s response to a target gas,

High-sensitivity detection of dilute gases is demonstrated by monitoring the resonance of a suspended polymer nanocavity. The inset shows the target gas molecules (darker) interacting with the polymer material (lighter). This interaction causes the nanocavity to swell, resulting in a shift of its resonance. CREDIT: H. Clevenson/MIT

High-sensitivity detection of dilute gases is demonstrated by monitoring the resonance of a suspended polymer nanocavity. The inset shows the target gas molecules (darker) interacting with the polymer material (lighter). This interaction causes the nanocavity to swell, resulting in a shift of its resonance.
CREDIT: H. Clevenson/MIT

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

High sensitivity gas sensor based on high-Q suspended polymer photonic crystal nanocavity by  Hannah Clevenson, Pierre Desjardins, Xuetao Gan, and Dirk Englund. Appl. Phys. Lett. 104, 241108 (2014); http://dx.doi.org/10.1063/1.4879735

This is an open access paper.

Graphene-based sensor mimics pain (mu-opioid) receptor

I once had a job where I had to perform literature searches and read papers on pain research as it related to morphine tolerance. Not a pleasant task, it has left me eager to encourage and write about alternatives to animal testing, a key component of pain research. So, with a ‘song in my heart’, I feature this research from the University of Pennsylvania written up in a May 12, 2014 news item on ScienceDaily,

Almost every biological process involves sensing the presence of a certain chemical. Finely tuned over millions of years of evolution, the body’s different receptors are shaped to accept certain target chemicals. When they bind, the receptors tell their host cells to produce nerve impulses, regulate metabolism, defend the body against invaders or myriad other actions depending on the cell, receptor and chemical type.

Now, researchers from the University of Pennsylvania have led an effort to create an artificial chemical sensor based on one of the human body’s most important receptors, one that is critical in the action of painkillers and anesthetics. In these devices, the receptors’ activation produces an electrical response rather than a biochemical one, allowing that response to be read out by a computer.

By attaching a modified version of this mu-opioid receptor to strips of graphene, they have shown a way to mass produce devices that could be useful in drug development and a variety of diagnostic tests. And because the mu-opioid receptor belongs to the most common class of such chemical sensors, the findings suggest that the same technique could be applied to detect a wide range of biologically relevant chemicals.

A May 6, 2014 University of Pennsylvania news release, which originated the news item, describes the main teams involved in this research along with why and how they worked together (Note: Links have been removed),

The study, published in the journal Nano Letters, was led by A.T. Charlie Johnson, director of Penn’s Nano/Bio Interface Center and professor of physics in Penn’s School of Arts & Sciences; Renyu Liu, assistant professor of anesthesiology in Penn’s Perelman School of Medicine; and Mitchell Lerner, then a graduate student in Johnson’s lab. It was made possible through a collaboration with Jeffery Saven, professor of chemistry in Penn Arts & Sciences. The Penn team also worked with researchers from the Seoul National University in South Korea.

Their study combines recent advances from several disciplines.

Johnson’s group has extensive experience attaching biological components to nanomaterials for use in chemical detectors. Previous studies have involved wrapping carbon nanotubes with single-stranded DNA to detect odors related to cancer and attaching antibodies to nanotubes to detect the presence of the bacteria associated with Lyme disease.

After Saven and Liu addressed these problems with the redesigned receptor, they saw that it might be useful to Johnson, who had previously published a study on attaching a similar receptor protein to carbon nanotubes. In that case, the protein was difficult to grow genetically, and Johnson and his colleagues also needed to include additional biological structures from the receptors’ natural membranes in order to keep them stable.

In contrast, the computationally redesigned protein could be readily grown and attached directly to graphene, opening up the possibility of mass producing biosensor devices that utilize these receptors.

“Due to the challenges associated with isolating these receptors from their membrane environment without losing functionality,” Liu said, “the traditional methods of studying them involved indirectly investigating the interactions between opioid and the receptor via radioactive or fluorescent labeled ligands, for example. This multi-disciplinary effort overcame those difficulties, enabling us to investigate these interactions directly in a cell free system without the need to label any ligands.”

With Saven and Liu providing a version of the receptor that could stably bind to sheets of graphene, Johnson’s team refined their process of manufacturing those sheets and connecting them to the circuitry necessary to make functional devices.

The news release provides more technical details about the graphene sensor,

“We start by growing a piece of graphene that is about six inches wide by 12 inches long,” Johnson said. “That’s a pretty big piece of graphene, but we don’t work with the whole thing at once. Mitchell Lerner, the lead author of the study, came up with a very clever idea to cut down on chemical contamination. We start with a piece that is about an inch square, then separate them into ribbons that are about 50 microns across.

“The nice thing about these ribbons is that we can put them right on top of the rest of the circuitry, and then go on to attach the receptors. This really reduces the potential for contamination, which is important because contamination greatly degrades the electrical properties we measure.”

Because the mechanism by which the device reports on the presence of the target molecule relies only on the receptor’s proximity to the nanostructure when it binds to the target, Johnson’s team could employ the same chemical technique for attaching the antibodies and other receptors used in earlier studies.

Once attached to the ribbons, the opioid receptors would produce changes in the surrounding graphene’s electrical properties whenever they bound to their target. Those changes would then produce electrical signals that would be transmitted to a computer via neighboring electrodes.

The high reliability of the manufacturing process — only one of the 193 devices on the chip failed — enables applications in both clinical diagnostics and further research. [emphasis mine]

“We can measure each device individually and average the results, which greatly reduces the noise,” said Johnson. “Or you could imagine attaching 10 different kinds of receptors to 20 devices each, all on the same chip, if you wanted to test for multiple chemicals at once.”

In the researchers’ experiment, they tested their devices’ ability to detect the concentration of a single type of molecule. They used naltrexone, a drug used in alcohol and opioid addiction treatment, because it binds to and blocks the natural opioid receptors that produce the narcotic effects patients seek.

“It’s not clear whether the receptors on the devices are as selective as they are in the biological context,” Saven said, “as the ones on your cells can tell the difference between an agonist, like morphine, and an antagonist, like naltrexone, which binds to the receptor but does nothing. By working with the receptor-functionalized graphene devices, however, not only can we make better diagnostic tools, but we can also potentially get a better understanding of how the bimolecular system actually works in the body.”

“Many novel opioids have been developed over the centuries,” Liu said. “However, none of them has achieved potent analgesic effects without notorious side effects, including devastating addiction and respiratory depression. This novel tool could potentially aid the development of new opioids that minimize these side effects.”

Wherever these devices find applications, they are a testament to the potential usefulness of the Nobel-prize winning material they are based on.

“Graphene gives us an advantage,” Johnson said, “in that its uniformity allows us to make 192 devices on a one-inch chip, all at the same time. There are still a number of things we need to work out, but this is definitely a pathway to making these devices in large quantities.”

There is no mention of animal research but it seems likely to me that this work could lead to a decreased use of animals in pain research.

This project must have been quite something as it involved collaboration across many institutions (from the news release),

Also contributing to the study were Gang Hee Han, Sung Ju Hong and Alexander Crook of Penn Arts & Sciences’ Department of Physics and Astronomy; Felipe Matsunaga and Jin Xi of the Department of Anesthesiology at the Perelman School of Medicine, José Manuel Pérez-Aguilar of Penn Arts & Sciences’ Department of Chemistry; and Yung Woo Park of Seoul National University. Mitchell Lerner is now at SPAWAR Systems Center Pacific, Felipe Matsunaga at Albert Einstein College of Medicine, José Manuel Pérez-Aguilar at Cornell University and Sung Ju Hong at Seoul National University.

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

Scalable Production of Highly Sensitive Nanosensors Based on Graphene Functionalized with a Designed G Protein-Coupled Receptor by Mitchell B. Lerner, Felipe Matsunaga, Gang Hee Han, Sung Ju Hong, Jin Xi, Alexander Crook, Jose Manuel Perez-Aguilar, Yung Woo Park, Jeffery G. Saven, Renyu Liu, and A. T. Charlie Johnson.Nano Lett., Article ASAP
DOI: 10.1021/nl5006349 Publication Date (Web): April 17, 2014
Copyright © 2014 American Chemical Society

This paper is behind a paywall.

Monitoring air pollution at home, at work, and in the car—the nano way

Meagan Clark, in an April 18, 2014  article for International Business Times, writes about a project in the EU (European Union) where researchers are working to develop nanotechnology-enabled sensors for air quality at home, at work, and in the car,

Poor indoor and outdoor air quality is linked to one in eight deaths worldwide or 7 million, making it the world’s most dangerous environmental health risk, according to a March [2014?] report by the World Health Organization.

That is the reasoning behind the European Union’s decision to fund a new nanotechnology project [IAQSENSE] that would allow people to gauge air quality real-time at home, work and in cars with low cost, mini sensor systems, the EU’s community research and development information service announced Friday [April 18, 2014].

“The control of indoor air quality and the related comfort it provides should have a huge societal impact on health, presence at work and economic-related factors,” Claude Iroulart, coordinator of IAQSENSE, said in a statement. …

The IAQSENSE homepage provides more details about itself,

The indoor air quality (IAQ) influences the health and well-being of people. For the last 20 years, there has been a growing concern regarding pollutants in closed environments and the difficulty in identifying these pollutants and their critical levels, without heavy, expensive equipment.

IAQSense aims to develop new nanotechnology based sensor systems that will precisely monitor the composition of the air in terms of both chemical and bio contaminants. This system will be miniaturized, low cost and adapted to mass production.

A major challenge consists of a gaz [sic] sensor system which must be at the same time low cost and highly sensitive and selective.  IAQSense relies on three patented technologies, of which one is based on surface ion mobility dynamics separating each gas component. Working like a spectrometer it allows high sensitivity fast multi-gas detection in a way never seen before.

IAQSense Project will characterize, monitor and improve indoor air quality in an innovative way.

The consortium is composed of 4 SMEs [small to medium enterprises[, 3 industrial companies and 3 research institutes. The project will last 3 years (01.09.2013 – 31.08.2016) and will deliver a complete sensor system.

The IAQSense research project has received funding from the European Community´s 7th Framework Programme under grant agreement n° 6043125.

As someone who has suffered from breathing problems from time to time, I wish them the best with this project .

‘Ship in a bottle’ concept helps to create an artificial nose

I love the description of this latest artificial nose, ,as being based on a ‘ship in a bottle’ concept, from an Oct. 10, 2013 Rice University news release (also on EurekAlert),

Rice University scientists took a lesson from craftsmen of old to assemble microscopic compounds that warn of the presence of dangerous fumes from solvents.

The researchers combined a common mineral, zeolite, with a metallic compound based on rhenium to make an “artificial nose” that can sniff out solvent gases. They found that in the presence of the compound, each gas had a photoluminescent “fingerprint” with a specific intensity, lifetime and color.

The challenge for Martí and his team was to get their large metallic particles through the much smaller pores of a zeolite cage. The answer: Do it old-school. In their process, small chemical components enter the cage, find each other and self-assemble into rhenium complexes. Then they’re stuck — like a ship in a bottle.

The news release goes on to relate how the researchers created their ‘ship in a bottle’ or zeolite cage,

“We sequentially load the individual parts of the complex into the zeolite,” Martí said. “The parts are smaller than the pores, but when they self-assemble inside the zeolite, they’re trapped.” Once washed to eliminate complexes that form outside the zeolites, the compound is ready for use.

The relatively simple technique, which was initially developed and studied by two Rice alumni while they were undergraduate students in Martí’s lab, could provide a scalable, inexpensive platform to monitor toxic vapors from industrial solvents.

Solvents are liquid chemicals, often petroleum-based, that are widely used to dissolve solid materials. They are found in paints, thinners, aerosol sprays, dyes, marking pens, adhesives and many other products.

They also evaporate quickly. Solvent vapors, which are hazardous to inhale and can be highly flammable, are often denser than air and gather at floor level, where they can build to dangerous amounts unless detected.

Martí said platinum, gold, palladium and copper salts are often used to detect vapors, because they change color in the presence of solvents. The rhenium-based supramolecular complex was known to fluoresce in the presence of some solvents, but dealing with vapors is a different story.

“If the complexes are in a solid state, they are too close to each other and gases can’t interact with them,” he said. “So we started thinking of ways to create space between them.”

Enter zeolites. “These zeolites are cages with big cavities and small pores,” Martí said. “The pores are big enough — at about 7.4 angstroms — for most gas-phase molecules to enter. The question was how to trap the bigger rhenium complexes inside.”

Other groups have trapped ruthenium complexes in zeolites, but these complexes were not ideal to detect solvents. Then-undergraduates Ty Hanna and, later, Zack Panos developed the method to put rhenium complexes inside zeolites. The results were outstanding, Martí said.

Like canaries in a coalmine, the caged complexes strongly signal the presence of a vapor by the color and intensity of their photoluminescent glow in ultraviolet light.

Martí said nobody had studied the third key property — the amount of time the complex remains in an excited state. That ranges from less than 1,000 nanoseconds for water and ammonia to “a quite long” 4,000-plus nanoseconds for pyridine. It’s different for every type of vapor, he said.

“We concluded that every individual vapor has a set of photophysical properties that is unique for that solvent,” he said. “Each one has a unique fingerprint.”

With the ability to detect three distinct characteristics for each vapor, a team led by graduate student Avishek Saha built a three-dimensional plot to map the fingerprints of 17 types of solvents. They found categories of solvents — nonpolar, alcohols, protics (which include water) and aprotics — tended to gather in their own areas.

“That’s another interesting thing,” Martí said. “Different solvent groups occupy different areas in the map. So even if a solvent hasn’t been studied, our material will help people recognize the category it falls into.”

He said the group plans to test more solvents and suggested the material may also be useful for detecting the presence of other volatile species like explosives.

Here’s a link to and a citation for the research article,

Three-Dimensional Solvent-Vapor Map Generated by Supramolecular Metal-Complex Entrapment by Avishek Saha, Zack Panos, Ty Hanna, Kewei Huang, Mayra Hernández-Rivera, and Prof. Angel A. Martí.
Angewandte Chemie International Edition Article first published online: 2 OCT 2013 DOI: 10.1002/anie.201305762

Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

The article is behind a paywall.

The reference to a ‘ship in a bottle’ brought me back to my childhood. Our parents had a ‘ship in a bottle’ but neither my sister nor I were allowed to touch it. In fact, it was brought out for viewing purposes only on special occasions. I no longer remember what made it so precious but I do recall how magical it seemed. Luckily the internet has made satisfying one’s curiosity easy; I found a picture and instructions on how to make ‘a ship in a bottle’,

Credit: Goaly (?) [downloaded from http://www.instructables.com/id/Building-A-Ship-In-A-Bottle/]

Credit: Goaly (?) [downloaded from http://www.instructables.com/id/Building-A-Ship-In-A-Bottle/]

You can find instructions by Goaly for Building a Ship in a Bottle here.

Happy Thanksgiving Weekend!

Carbon nanotubes one way: gas and other flexible sensors

A Sept. 24, 2013 Technische Universitaet Muenchen (TUM) press release (also on EurekAlert) promises that flexible sensors are on the horizon,

Carbon nanotube-based gas sensors created at TUM offer a unique combination of characteristics that can’t be matched by any of the alternative technologies. They rapidly detect and continuously respond to extremely small changes in the concentrations of gases including ammonia, carbon dioxide, and nitrogen oxide. They operate at room temperature and consume very little power. Furthermore, as the TUM researchers report in their latest papers, such devices can be fabricated on flexible backing materials through large-area, low-cost processes.

Thus it becomes realistic to envision plastic food wrap that incorporates flexible, disposable gas sensors, providing a more meaningful indicator of food freshness than the sell-by date. Measuring carbon dioxide, for example, can help predict the shelf life of meat. “Smart packaging” – assuming consumers find it acceptable and the devices’ non-toxic nature can be demonstrated – could enhance food safety and might also vastly reduce the amount of food that is wasted. Used in a different setting, the same sort of gas sensor could make it less expensive and more practical to monitor indoor air quality in real time.

Dexter Johnson in a Sept. 26, 2013 posting on Nanoclast (an IEEE [Institute of Electrical and Electronics Engineers] blog) warns (Note: Links have been removed),

While this sounds great, the obstacle preventing this from becoming a reality has always been cost. Thin-film sensory packaging may make sense for a high-cost item, but for an inexpensive grocery store product, it’s hard to justify an additional cost that may be as much as the product itself. I made this point nearly a decade ago in report I authored titled, “The Future of Nanotechnology in Printing and Packaging”.

This doesn’t even take into account the often biased opinion people have about nanotechnology in relation to food.

Dexter recommends the researchers focus their commercialization efforts on robotic skins and other high ticket applications.

In reading the description of how the researchers created these flexible sensors, Dexter’s concerns are brought int high relief,

The most basic building block for this technology is a single cylindrical molecule, a rolled-up sheet of carbon atoms that are linked in a honeycomb pattern. This so-called carbon nanotube could be likened to an unimaginably long garden hose: a hollow tube just a nanometer or so in diameter but perhaps millions of times as long as it is wide. Individual carbon nanotubes exhibit amazing and useful properties, but in this case the researchers are more interested in what can be done with them en masse.

Laid down in thin films, randomly oriented carbon nanotubes form conductive networks that can serve as electrodes; patterned and layered films can function as sensors or transistors. “In fact,” Prof. Lugli [Prof. Paolo Lugli, director of TUM's Nanoelectronics Institute] explains, “the electrical resistivity of such films can be modulated by either an applied voltage (to provide a transistor action) or by the adsorption of gas molecules, which in turn is a signature of the gas concentration for sensor applications.” And as a basis for gas sensors in particular, carbon nanotubes combine advantages (and avoid shortcomings) of more established materials, such as polymer-based organic electronics and solid-state metal-oxide semiconductors. What has been lacking until now is a reliable, reproducible, low-cost fabrication method.

Spray deposition, supplemented if necessary by transfer printing, meets that need. An aqueous solution of carbon nanotubes looks like a bottle of black ink and can be handled in similar ways. Thus devices can be sprayed – from a computer-controlled robotic nozzle – onto virtually any kind of substrate, including large-area sheets of flexible plastic. There is no need for expensive clean-room facilities.

“To us it was important to develop an easily scalable technology platform for manufacturing large-area printed and flexible electronics based on organic semiconductors and nanomaterials,” Abdellah says. “To that end, spray deposition forms the core of our processing technology.”

Remaining technical challenges arise largely from application-specific requirements, such as the need for gas sensors to be selective as well as sensitive.

Here are citations for and links to three of the researchers’ papers,

Fabrication of carbon nanotube thin films on flexible substrates by spray deposition and transfer printing. Ahmed Abdelhalim, Alaa Abdellah, Giuseppe Scarpa, Paolo Lugli. Carbon, Vol. 61, September 2013, 72-79. DOI: 10.1016/j.carbon.2013.04.069

Flexible carbon nanotube-based gas sensors fabricated by large-scale spray deposition.
Alaa Abdellah, Zubair Ahmad, Philipp Köhler, Florin Loghin, Alexander Weise, Giuseppe Scarpa, Paolo Lugli. IEEE Sensors Journal, Vol. 13 Issue 10, October 2013, 4014-4021. DOI: 10.1109/JSEN.2013.2265775

Scalable spray deposition process for high performance carbon nanotube gas sensors. Alaa Abdellah, Ahmed Abdelhalim, Markus Horn, Giuseppe Scarpa, and Paolo Lugli. IEEE Transactions on Nanotechnology 12, 174-181, 2013. DOI: 10.1109/TNANO.2013.2238248

All three papers are behind paywalls.

In one of those coincidences that take place from time to time, I wrote about an upcoming event taking place in the Guardian’s London offices, a panel discussion on nanotechnology and food,in a Sept.  26, 2013 posting.

Detecting date rape drugs before you drink

A July 3, 2013 article by Gail Weinreb for Globes.co features an Israeli company’s (Drink Science) nanotechnology-enabled date rape sensor,

Date rape drugs are anesthetics used by the pharmaceutical industry. Users of the drug obtain them illegally, but do not develop them at home, so there is little variability between the different versions, and they can be detected by a single test. However, a test for detecting date rape drugs does not solve the problem of the rape of a victim who has ingested the drug or other drugs such as Ecstasy (or rape that does involve the use of drugs at all), but only the specific use of anesthetics.

The chemical part of the test uses a solvent, which when it comes in contract with a date rape drug, precipitates making the beverage turbid. The product is designed like a drinks mix or cosmetics (such as eyeliner). A woman drops the product into the glass and waits for a reaction. In cases of a dark nightclub, for example, where it is impossible to see whether the drink has become turbid or remained clear, the test includes another trick – it has an LED light. The light diminishes in turbidity. “We found 100% accuracy in the drinks we tested,” Avidor [CEO Dr. Yoav Avidor] said. “The product works on many kinds of drinks.”

According to Weinrreb’s article, Avidor expects the product to be on the market in nine months.

Unfortunately, there’s not much information about the company or the product on its website although you can find news coverage dating from August 2011 about the product. The company does offer this description of itself and the product on its Facebook page,

Drink Sciences is a start-up that’s developing a straw/stirrer that detects date rape drugs in drinks. We are focused on helping prevent Drug Facilitated Sexual Assault, a crime with growing incidence rates in the US and globally.

I wish them good luck with launching their product into the marketplace when, presumably, they’ll have a name for it.

Luminous bacteria sense pharmaceuticals and metals in wastewater

Scientists at the Helmholtz Association of German Research Centres have conceptualized a technique using luminescent bacterial proteins for sensing pharmaceuticals and metals in waste water. From the Helmholtz Association of German Research Centres June 12, 2013 press release,

While residual medications don’t belong in the water, trace metals from industrial process waters handled by the recycling industry are, in contrast, valuable resources. Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have developed a simple color sensor principle which facilitates the easy detection of both materials as well as many other substances. This is the concept: If the analyzed sample shines red, then the water is ‘clean;’ if its color turns green, however, then it contains the substances the scientists wish to detect. The researchers recently published their concept in the scientific journal Sensors and Actuators B: Chemical (DOI: 10.1016/j.snb.2013.05.051).

Here’s the concept, from the press release,

The sensor principle is based on a red and a green fluorescent dye. If a substance to be detected is present in a water sample, then the sensor shines green; a red color, however, indicates that the substance is not present. What is the reason for the color difference? “The color molecules are located on a nanostructured surface consisting of bacterial proteins. The dyes are so close to one another that energy is transferred from the green to the red dye if these dyes are irradiated with light at a specific wavelength, for example, the light emitted by a laser. Then the sample shines red. This energy transfer, though, only occurs if the water sample is ‘clean.’ If, however, any foreign substances such as, for example, the pharmaceuticals or pollutants to be detected accumulate between the color molecules at specific binding sites, then the transfer is interrupted and only the green dyes shine,” explains Ulrike Weinert. Her doctoral dissertation revolves around the binding of color molecules on nano surfaces.

The network project (“AptaSens”) was subsidized by the Federal Ministry of Education and Research (BMBF). Nanostructured surfaces are an important part of the project. They are extracted from the envelope proteins of bacteria which are cultivated by the researchers in a lab. “The proteins form regular lattice structures at the nano level. They are ideally suited to evenly arrange functional groups and other molecules,” notes Weinert.

Another essential component of the sensor principle are the binding sites on the nano surface of the substances which are to be detected. That’s why so-called aptamers are used. These aptamers are short, single-stranded DNA oligonucleotides; the DNA segments can be designed in such a way that they are capable of specifically binding the most diverse substances such as the pharmaceuticals or the pollutants mentioned above. Dr. Beate Strehlitz from the Leipzig-based Helmholtz Centre for Environmental Research (UFZ) has specialized in this field. Within the scope of the AptaSens project, her team developed such a receptor for the antibiotic kanamycin which is used, for example, for the treatment of such bacterial infections of the eye as conjunctivitis, or in veterinary medicine.

The next step will be testing, from the press release,

What remains to be done now is to combine the kanamycin receptor with the dyes to test the color sensor principle with a sample substance. “From there, it’s just a small step to the development of a complete color sensor,” notes Katrin Pollmann [Dr. Katrin Pollmann, Team Leader Biotechnology at the HZDR {Holtzman Centres}]. For this, the researchers need to integrate the individual components – which include bacterial proteins, dyes, and aptamers – into a sensor chip. They have actually conducted a number of experiments with suitable substrates such as, for example, glass or silicon dioxide. “The sensor chip could be as small as a thumbnail. It could be wetted on site with the water sample to be analyzed. This would also include a laser light source which activates the chip as well as a detector that measures the change in color,” adds Pollmann. The scientists are now applying for a follow-up project.

I’d love to get a little more information about which metals (gold nanoparticles? silver nanoparticles? zinc oxide nanoparticles? etc.) could be detected in the water. If the information is in the research team’s published paper, that is available only behind a paywall.  H/T to Nanowerk (June 12, 2013 news item) for alerting me to this research work.

Here’s a citation (the link was provided earlier in this post),

U. Weinert, K. Pollmann, J. Raff. “Fluorescence Resonance Energy Transfer by S-layer coupled fluorescence dyes”, in Sensors and Actuators B: Chemical (2013), DOI: 10.1016/j.snb.2013.05.051

For anyone who’s interested in more information about aptamers, there’s my Oct. 25, 2011 posting which featured an interview with Dr. Maria DeRosa about her work with them.

CeNSE (Central Nervous System of the Earth) and billions of tiny sensors from HP plus a memristor update

Mike Thacker’s Feb. 1, 2013 (?) post features an HP Labs video trumpeting what is described as their most progressive work, from the official HP Labs blog,

… HP Labs in Palo Alto, for example, which is using nanotechnology capabilities to create low-cost censors that act as a central nervous system for the earth. The technology can be used to closely monitor — and quickly respond to — changes in agriculture, food supply and architectural infrastructure around the world.

CeNSE (Central Nervous System of the Earth) sounds like something new, eh? Almost three years ago, Greg Lindsay wrote about CeNSE and its first customer, Shell Oil, in a Feb. 12, 2010 article for Fast Company (Note: Links have been removed),

Just days after Cisco signaled it will horn into IBM’s turf by rewiring an aging city in Massachusetts, Hewlett Packard announced this morning the first commercial application of its own holistic blueprint–the torturously acronymed “CeNSE” (short for Central Nervous System for the Earth). Much like IBM’s “Smarter Planet” campaign, HP proposes sticking billions of sensors on everything in sight and boiling down the resulting flood of data into insights for making the world a better, greener place. But what sets HP apart from its rivals is its determination to create a smarter planet almost entirely within house, from sensors of its own design and manufacture to servers to software to the consultants who will tie it all together. And its first customer could not be less green: Shell Oil.

The Shell deal also unintentionally explodes the myth that a smarter planet is necessarily a greener one. HP’s bleeding-edge accelerometers are being deployed for the least green thing you can think of: sucking every last drop of oil out of the ground. While absolutely necessary for the current trajectory of our way of life (and buying us more time to develop alternatives), it’s hard to argue that technology for more efficiently recovering fossil fuels is in any way sustainable. (Although Wacker [Jeff Wacker, the leader of services innovation at HP and the head of its efforts to commercialize CeNSE] gamely argues the same technology is needed for finding empty pockets suitable for carbon sequestration.) While corporate-sponsored smarter cities can, in fact, be greener ones, their charter is the same as it ever was: profit. [emphasis mine]

Lindsay’s article echoes some of what I noted in the context of the Carbon Management Canada (CMC) network (government- and industry-funded) in my Feb. 4, 2013 posting about ultra-sensitive nanosensors and attempts to reduce carbon emissions in the Alberta oil sands. While the industry may work to reduce emissions, its raison d’être is profit and that can lead to complex situations with conflicting agendas.

As for what these billions and billions of tiny sensors might do for us, it seems there might be alternatives to at least one of the capabilities claimed by HP Labs and its sensors, ‘sensing changes in architectural infrastructures’. My Jan. 3, 2013 post, Signal danger with smart paint, mentioned a much more modest effort,

An innovative low-cost smart paint that can detect microscopic faults in wind turbines, mines and bridges before structural damage occurs is being developed by researchers at the University of Strathclyde in Glasgow, Scotland. [emphasis mine]

The environmentally-friendly paint uses nanotechnology to detect movement in large structures, and could shape the future of safety monitoring.

I digress slightly. The reference to the ‘central nervous system of the earth’ and Stanley Williams’ presence in the video reminded me of the memristor and an announcement (mentioned in my April 19, 2012 posting) that HP Labs would be rolling out some memristor-enabled products in 2013. Sadly, later in the year I missed this announcement, from a July 9, 2012 posting by Chris Mellor for TheRegister.co.uk,

Previously he (Stanley Williams) has said that HP and fab partner Hynix would launch a memristor product in the summer of 2013. At the Kavli do [Kavli Foundation Roundtable, June 2012], Williams said: “In terms of commercialisation, we’ll have something technologically viable by the end of next year.”

But that doesn’t mean a commercial product launch, and Hynix’s concerns about memristor device effect on flash are relevant: “Our partner, Hynix, is a major producer of flash memory, and memristors will cannibalise its existing business by replacing some flash memory with a different technology. So the way we time the introduction of memristors turns out to be important. There’s a lot more money being spent on understanding and modeling the market than on any of the research,” said Williams. [emphasis mine]

We might see a memristor product by summer 2014 but it could be later, as Hynix balances memristor device revenues, starting from zero, cutting into flash revenues in the millions of dollars.

I think the reason innovation is often introduced by outsiders is that they have no vested interest in maintaining the status quo as per the situation with Hynix and HP Labs, i.e., not wanting to cannibalize a current and profitable product line by introducing something new and, one gathers, an improvement.

University of Toronto’s (Canada) smiley face tattoo/sensor

Researchers at the University of Toronto have created a medical sensor that can be applied to the skin like a temporary tattoo.

University of Toronto Scarborough student Vinci Hung helped create the smiley face sensor shown here in the box at upper right (photo by Ken Jones)

The Dec. 3, 2012 news item on ScienceDaily notes,

A medical sensor that attaches to the skin like a temporary tattoo could make it easier for doctors to detect metabolic problems in patients and for coaches to fine-tune athletes’ training routines. And the entire sensor comes in a thin, flexible package shaped like a smiley face.

“We wanted a design that could conceal the electrodes,” says Vinci Hung, a PhD candidate in the Department of Physical & Environmental Sciences at UTSC [University of Toronto Scarborough], who helped create the new sensor. “We also wanted to showcase the variety of designs that can be accomplished with this fabrication technique.”

The Dec. 3, 2012 University of Toronto news release by Kurt Kleiner, which originated the news item, provides details about how the sensor/tattoo is fabricated and how it functions on the skin,

The new tattoo-based solid-contact ion-selective electrode (ISE) is made using standard screen printing techniques and commercially available transfer tattoo paper, the same kind of paper that usually carries tattoos of Spiderman or Disney princesses. In the case of the smiley face sensor, the “eyes” function as the working and reference electrodes, and the “ears” are contacts to which a measurement device can connect.

The sensor Hung helped make can detect changes in the skin’s pH levels in response to metabolic stress from exertion. Similar devices, called ion-selective electrodes (ISEs), are already used by medical researchers and athletic trainers. They can give clues to underlying metabolic diseases such as Addison’s disease, or simply signal whether an athlete is fatigued or dehydrated during training. The devices are also useful in the cosmetics industry for monitoring skin secretions.

But existing devices can be bulky, or hard to keep adhered to sweating skin. The new tattoo-based sensor stayed in place during tests, and continued to work even when the people wearing them were exercising and sweating extensively. The tattoos were applied in a similar way to regular transfer tattoos, right down to using a paper towel soaked in warm water to remove the base paper.

To make the sensors, Hung and her colleagues used a standard screen printer to lay down consecutive layers of silver, carbon fibre-modified carbon and insulator inks, followed by electropolymerization of aniline to complete the sensing surface.

By using different sensing materials, the tattoos can also be modified to detect other components of sweat, such as sodium, potassium or magnesium, all of which are of potential interest to researchers in medicine and cosmetology.

You can find the reserchers’ article in the Royal Society’s Analyst journal,

Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring
Amay J. Bandodkar ,  Vinci W. S. Hung ,  Wenzhao Jia ,  Gabriela Valdés-Ramírez ,  Joshua R. Windmiller ,  Alexandra G. Martinez ,  Julian Ramírez ,  Garrett Chan ,  Kagan Kerman and Joseph Wang in Analyst, 2013,138, 123-128 DOI: 10.1039/C2AN36422K

The article is open access but you do need to register for a free account with the Royal Society’s RSC [ublishing platform.

Cloud project for London 2012 Olympics includes Umberto Eco?; University of Toronto researchers work on nano nose; Nano safety research centre in Scotland

Shades of the 19th century! One of the teams competing to build a 2012 Olympics tourist attraction for London’s east end has proposed digital clouds. According to the article (Digital cloud plan for city skies) by Jonathan Fildes, online here at BBC News,

The construction would include 120m- (400ft-) tall mesh towers and a series of interconnected plastic bubbles that can be used to display images and data.

The Cloud, as it is known, would also be used [as] an observation deck and park

The idea of displaying images and data on clouds isn’t entirely new,

… the prospect of illuminated messages on the slate of the heavens … most fascinated experts and layman. “Imagine the effect,” speculated the Electrical Review [Dec. 31, 1892], “if a million people saw in gigantic characters across the clouds such words as ‘BEWARE OF PROTECTION’ and “FREE TRADE LEADS TO H–L!”

(The passage is from Carolyn Marvin’s book, When old technologies were new.) I’m not sure what protection refers to but the reference to free trade still feels fresh.

I always find technology connections to the past quite interesting as similar ideas pop up independently from time to time and I’d be willing to bet the 2012 cloud team has no idea that displaying messages on clouds had been proposed as far back as the 1890s.

The current project has some interesting twists. The team is proposing to fund it with micro-donations from millions of people. From the BBC article,

“It’s really about people coming together to raise the Cloud,” Carlo Ratti, one of the architects behind the design from the Massachusetts Institute of Technology (MIT) told BBC News.

“We can build our Cloud with £5m or £50m. The flexibility of the structural system will allow us to tune the size of the Cloud to the level of funding that is reached.”

The size of the structure will evolve depending on the number of contributions, he said.

The cloud will not consume power from the city’s grid.

“Many tall towers have preceded this, but our achievement is the high degree of transparency, the minimal use of material and the vast volume created by the spheres,” said professor Joerg Schleich, the structural engineer behind the towers.

Professor Schleich was responsible for the Olympic Stadium in Munich as well as numerous lightweight towers built to the same design as the Cloud.

The structure would also be used to harvest all the energy it produces according to Professor Ratti.

“It would be a zero power cloud,” he said.

The team in addition to designers, scientists, and engineers includes Umberto Eco, a philosopher, semiotician, novelist, medievalist, and literary critic.

Yes, they have a writer on the team for a truly interdisciplinary approach. Or not. Eco may have lent his name to the project and not been an active participant. Still, I’m much encouraged by Eco’s participation (regardless of the amount or type) in this project as I think writers have, for the most part, been fusty and slow to engage with the changes we’re all experiencing.

At the University of Toronto (U of T), researchers are working on a project that they hope will be of interest to NASA ([US] National Aeronautics and Space Administration). From the news item on Azonano,

Thankfully, there is no failure to launch at U of T’s new electron beam nanolithography facility where researchers are already developing smaller-than-tiny award-winning devices to improve disease diagnoses and enhance technology that impacts fields as varied as space exploration, the environment, health care and information and media technologies.

One of these novel nano-devices, being developed by PhD student Muhammad Alam, is an optical nose that is capable of detecting multiple gases. Alam hopes it will be used by NASA one day.

Alam is working on a hydrogen sensor which can be used to detect the gas. Hydrogen is used in many industries and its use is rising so there is great interest in finding ways to handle it more safely and effectively. As for NASA, sometimes those rockets don’t get launched because they detect a hydrogen leak that didn’t actually happen. The U of T ‘nose’ promises to be more reliable than the current sensors in use.

Scotland is hosting one of the first nanomaterials research centres in the UK. From the news item on Nanowerk,

Professor Anne Glover, Chief Scientific Adviser for Scotland officially launched the new centre today (Wednesday, November 11) at Edinburgh Napier’s Craighouse Campus.
She said: “Given the widespread use of nanomaterials in [a] variety of everyday products, it is essential for us to fully understand them and their potential impacts. This centre is one of the first in the UK to bring together nano-science research across human, environment, reproductive health and microbiology to ensure the safe and sustainable ongoing use of nanotechnology.”
Director of the Centre for Nano Safety, Professor Vicki Stone said: “Nanomaterials are used in a diverse range of products from medicines and water purifiers to make-up, food, paints, clothing and electronics. It is therefore essential that we fully understand their longterm impact. We are dedicated to understanding the ongoing health and environmental affects of their use and then helping shape future policy for their development. The launch of this new centre is a huge step forward in this important area of research.”

It’s hard to see these initiatives (I mentioned more in yesterday’s [Nov. 10, 2009] posting) in the UK and Europe and not contrast them harshly with the Canadian scene. There may be large scale public engagement, public awareness, safety initiatives, etc. for nanotechnology in Canada but nobody is giving out any information about it.