Tag Archives: silk

Food sensor made from of silk microneedles looks like velco

These sensors really do look like velcro,

The Velcro-like food sensor, made from an array of silk microneedles, can pierce through plastic packaging to sample food for signs of spoilage and bacterial contamination. Image: Felice Frankel

A September 9, 2020 news item on Nanowerk announces some research from the Massachusetts Institute (MIT),

MIT engineers have designed a Velcro-like food sensor, made from an array of silk microneedles, that pierces through plastic packaging to sample food for signs of spoilage and bacterial contamination.

The sensor’s microneedles are molded from a solution of edible proteins found in silk cocoons, and are designed to draw fluid into the back of the sensor, which is printed with two types of specialized ink. One of these “bioinks” changes color when in contact with fluid of a certain pH range, indicating that the food has spoiled; the other turns color when it senses contaminating bacteria such as pathogenic E. coli.

A Sept. 9, 2020 MIT news release (also on EurekAlert), which originated the news item, delves further into the research,

The researchers attached the sensor to a fillet of raw fish that they had injected with a solution contaminated with E. coli. After less than a day, they found that the part of the sensor that was printed with bacteria-sensing bioink turned from blue to red — a clear sign that the fish was contaminated. After a few more hours, the pH-sensitive bioink also changed color, signaling that the fish had also spoiled.

The results, published today in the journal Advanced Functional Materials, are a first step toward developing a new colorimetric sensor that can detect signs of food spoilage and contamination.

Such smart food sensors might help head off outbreaks such as the recent salmonella contamination in onions and peaches. They could also prevent consumers from throwing out food that may be past a printed expiration date, but is in fact still consumable.

“There is a lot of food that’s wasted due to lack of proper labeling, and we’re throwing food away without even knowing if it’s spoiled or not,” says Benedetto Marelli, the Paul M. Cook Career Development Assistant Professor in MIT’s Department of Civil and Environmental Engineering. “People also waste a lot of food after outbreaks, because they’re not sure if the food is actually contaminated or not. A technology like this would give confidence to the end user to not waste food.”

Marelli’s co-authors on the paper are Doyoon Kim, Yunteng Cao, Dhanushkodi Mariappan, Michael S. Bono Jr., and A. John Hart.

Silk and printing

The new food sensor is the product of a collaboration between Marelli, whose lab harnesses the properties of silk to develop new technologies, and Hart, whose group develops new manufacturing processes.

Hart recently developed a high-resolution floxography technique, realizing microscopic patterns that can enable low-cost printed electronics and sensors. Meanwhile, Marelli had developed a silk-based microneedle stamp that penetrates and delivers nutrients to plants. In conversation, the researchers wondered whether their technologies could be paired to produce a printed food sensor that monitors food safety.

“Assessing the health of food by just measuring its surface is often not good enough. At some point, Benedetto mentioned his group’s microneedle work with plants, and we realized that we could combine our expertise to make a more effective sensor,” Hart recalls.

The team looked to create a sensor that could pierce through the surface of many types of food. The design they came up with consisted of an array of microneedles made from silk.

“Silk is completely edible, nontoxic, and can be used as a food ingredient, and it’s mechanically robust enough to penetrate through a large spectrum of tissue types, like meat, peaches, and lettuce,” Marelli says.

A deeper detection

To make the new sensor, Kim first made a solution of silk fibroin, a protein extracted from moth cocoons, and poured the solution into a silicone microneedle mold. After drying, he peeled away the resulting array of microneedles, each measuring about 1.6 millimeters long and 600 microns wide — about one-third the diameter of a spaghetti strand.

The team then developed solutions for two kinds of bioink — color-changing printable polymers that can be mixed with other sensing ingredients. In this case, the researchers mixed into one bioink an antibody that is sensitive to a molecule in E. coli. When the antibody comes in contact with that molecule, it changes shape and physically pushes on the surrounding polymer, which in turn changes the way the bioink absorbs light. In this way, the bioink can change color when it senses contaminating bacteria.

The researchers made a bioink containing antibodies sensitive to E. coli, and a second bioink sensitive to pH levels that are associated with spoilage. They printed the bacteria-sensing bioink on the surface of the microneedle array, in the pattern of the letter “E,” next to which they printed the pH-sensitive bioink, as a “C.” Both letters initially appeared blue in color.

Kim then embedded pores within each microneedle to increase the array’s ability to draw up fluid via capillary action. To test the new sensor, he bought several fillets of raw fish from a local grocery store and injected each fillet with a fluid containing either E. coli, Salmonella, or the fluid without any contaminants. He stuck a sensor into each fillet. Then, he waited.

After about 16 hours, the team observed that the “E” turned from blue to red, only in the fillet contaminated with E. coli, indicating that the sensor accurately detected the bacterial antigens. After several more hours, both the “C” and “E” in all samples turned red, indicating that every fillet had spoiled.

The researchers also found their new sensor indicates contamination and spoilage faster than existing sensors that only detect pathogens on the surface of foods.

“There are many cavities and holes in food where pathogens are embedded, and surface sensors cannot detect these,” Kim says. “So we have to plug in a bit deeper to improve the reliability of the detection. Using this piercing technique, we also don’t have to open a package to inspect food quality.”

The team is looking for ways to speed up the microneedles’ absorption of fluid, as well as the bioinks’ sensing of contaminants. Once the design is optimized, they envision the sensor could be used at various stages along the supply chain, from operators in processing plants, who can use the sensors to monitor products before they are shipped out, to consumers who may choose to apply the sensors on certain foods to make sure they are safe to eat.

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

A Microneedle Technology for Sampling and Sensing Bacteria in the Food Supply Chain by Doyoon Kim, Yunteng Cao, Dhanushkodi Mariappan, Michael S. Bono Jr., A. John Hart, Benedetto Marelli. DOI: https://doi.org/10.1002/adfm.202005370 First published: 09 September 2020

This paper is behind a paywall.

‘Smart’ fabric that’s bony

Researchers at Australia’s University of New South of Wales (UNSW) have devised a means of ‘weaving’ a material that mimics *bone tissue, periosteum according to a Jan. 11, 2017 news item on ScienceDaily,

For the first time, UNSW [University of New South Wales] biomedical engineers have woven a ‘smart’ fabric that mimics the sophisticated and complex properties of one nature’s ingenious materials, the bone tissue periosteum.

Having achieved proof of concept, the researchers are now ready to produce fabric prototypes for a range of advanced functional materials that could transform the medical, safety and transport sectors. Patents for the innovation are pending in Australia, the United States and Europe.

Potential future applications range from protective suits that stiffen under high impact for skiers, racing-car drivers and astronauts, through to ‘intelligent’ compression bandages for deep-vein thrombosis that respond to the wearer’s movement and safer steel-belt radial tyres.

A Jan. 11, 2017 UNSW press release on EurekAlert, which originated the news item, expands on the theme,

Many animal and plant tissues exhibit ‘smart’ and adaptive properties. One such material is the periosteum, a soft tissue sleeve that envelops most bony surfaces in the body. The complex arrangement of collagen, elastin and other structural proteins gives periosteum amazing resilience and provides bones with added strength under high impact loads.

Until now, a lack of scalable ‘bottom-up’ approaches by researchers has stymied their ability to use smart tissues to create advanced functional materials.

UNSW’s Paul Trainor Chair of Biomedical Engineering, Professor Melissa Knothe Tate, said her team had for the first time mapped the complex tissue architectures of the periosteum, visualised them in 3D on a computer, scaled up the key components and produced prototypes using weaving loom technology.

“The result is a series of textile swatch prototypes that mimic periosteum’s smart stress-strain properties. We have also demonstrated the feasibility of using this technique to test other fibres to produce a whole range of new textiles,” Professor Knothe Tate said.

In order to understand the functional capacity of the periosteum, the team used an incredibly high fidelity imaging system to investigate and map its architecture.

“We then tested the feasibility of rendering periosteum’s natural tissue weaves using computer-aided design software,” Professor Knothe Tate said.

The computer modelling allowed the researchers to scale up nature’s architectural patterns to weave periosteum-inspired, multidimensional fabrics using a state-of-the-art computer-controlled jacquard loom. The loom is known as the original rudimentary computer, first unveiled in 1801.

“The challenge with using collagen and elastin is their fibres, that are too small to fit into the loom. So we used elastic material that mimics elastin and silk that mimics collagen,” Professor Knothe Tate said.

In a first test of the scaled-up tissue weaving concept, a series of textile swatch prototypes were woven, using specific combinations of collagen and elastin in a twill pattern designed to mirror periosteum’s weave. Mechanical testing of the swatches showed they exhibited similar properties found in periosteum’s natural collagen and elastin weave.

First author and biomedical engineering PhD candidate, Joanna Ng, said the technique had significant implications for the development of next-generation advanced materials and mechanically functional textiles.

While the materials produced by the jacquard loom have potential manufacturing applications – one tyremaker believes a titanium weave could spawn a new generation of thinner, stronger and safer steel-belt radials – the UNSW team is ultimately focused on the machine’s human potential.

“Our longer term goal is to weave biological tissues – essentially human body parts – in the lab to replace and repair our failing joints that reflect the biology, architecture and mechanical properties of the periosteum,” Ms Ng said.

An NHMRC development grant received in November [2016] will allow the team to take its research to the next phase. The researchers will work with the Cleveland Clinic and the University of Sydney’s Professor Tony Weiss to develop and commercialise prototype bone implants for pre-clinical research, using the ‘smart’ technology, within three years.

In searching for more information about this work, I found a Winter 2015 article (PDF; pp. 8-11) by Amy Coopes and Steve Offner for UNSW Magazine about Knothe Tate and her work (Note: In Australia, winter would be what we in the Northern Hemisphere consider summer),

Tucked away in a small room in UNSW’s Graduate School of Biomedical Engineering sits a 19th century–era weaver’s wooden loom. Operated by punch cards and hooks, the machine was the first rudimentary computer when it was unveiled in 1801. While on the surface it looks like a standard Jacquard loom, it has been enhanced with motherboards integrated into each of the loom’s five hook modules and connected to a computer. This state-of-the-art technology means complex algorithms control each of the 5,000 feed-in fibres with incredible precision.

That capacity means the loom can weave with an extraordinary variety of substances, from glass and titanium to rayon and silk, a development that has attracted industry attention around the world.

The interest lies in the natural advantage woven materials have over other manufactured substances. Instead of manipulating material to create new shades or hues as in traditional weaving, the fabrics’ mechanical properties can be modulated, to be stiff at one end, for example, and more flexible at the other.

“Instead of a pattern of colours we get a pattern of mechanical properties,” says Melissa Knothe Tate, UNSW’s Paul Trainor Chair of Biomedical Engineering. “Think of a rope; it’s uniquely good in tension and in bending. Weaving is naturally strong in that way.”


The interface of mechanics and physiology is the focus of Knothe Tate’s work. In March [2015], she travelled to the United States to present another aspect of her work at a meeting of the international Orthopedic Research Society in Las Vegas. That project – which has been dubbed “Google Maps for the body” – explores the interaction between cells and their environment in osteoporosis and other degenerative musculoskeletal conditions such as osteoarthritis.

Using previously top-secret semiconductor technology developed by optics giant Zeiss, and the same approach used by Google Maps to locate users with pinpoint accuracy, Knothe Tate and her team have created “zoomable” anatomical maps from the scale of a human joint down to a single cell.

She has also spearheaded a groundbreaking partnership that includes the Cleveland Clinic, and Brown and Stanford universities to help crunch terabytes of data gathered from human hip studies – all processed with the Google technology. Analysis that once took 25 years can now be done in a matter of weeks, bringing researchers ever closer to a set of laws that govern biological behaviour. [p. 9]

I gather she was recruited from the US to work at the University of New South Wales and this article was to highlight why they recruited her and to promote the university’s biomedical engineering department, which she chairs.

Getting back to 2017, here’s a link to and citation for the paper,

Scale-up of nature’s tissue weaving algorithms to engineer advanced functional materials by Joanna L. Ng, Lillian E. Knothe, Renee M. Whan, Ulf Knothe & Melissa L. Knothe Tate. Scientific Reports 7, Article number: 40396 (2017) doi:10.1038/srep40396 Published online: 11 January 2017

This paper is open access.

One final comment, that’s a lot of people (three out of five) with the last name Knothe in the author’s list for the paper.

*’the bone tissue’ changed to ‘bone tissue’ on July 17,2017.

Drip dry housing

This piece on new construction materials does have a nanotechnology aspect although it’s not made clear exactly how nanotechnology plays a role.

From a Dec. 28, 2016 news item on phys.org (Note: A link has been removed),

The construction industry is preparing to use textiles from the clothing and footwear industries. Gore-Tex-like membranes, which are usually found in weather-proof jackets and trekking shoes, are now being studied to build breathable, water-resistant walls. Tyvek is one such synthetic textile being used as a “raincoat” for homes.

You can find out more about Tyvek here.on the Dupont website.

A Dec. 21, 2016 press release by Chiara Cecchi for Youris ((European Research Media Center), which originated the news item, proceeds with more about textile-type construction materials,

Camping tents, which have been used for ages to protect against wind, ultra-violet rays and rain, have also inspired the modern construction industry, or “buildtech sector”. This new field of research focuses on the different fibres (animal-based such as wool or silk, plant-based such as linen and cotton and synthetic such as polyester and rayon) in order to develop technical or high-performance materials, thus improving the quality of construction, especially for buildings, dams, bridges, tunnels and roads. This is due to the fibres’ mechanical properties, such as lightness, strength, and also resistance to many factors like creep, deterioration by chemicals and pollutants in the air or rain.

“Textiles play an important role in the modernisation of infrastructure and in sustainable buildings”, explains Andrea Bassi, professor at the Department of Civil and Environmental Engineering (DICA), Politecnico of Milan, “Nylon and fiberglass are mixed with traditional fibres to control thermal and acoustic insulation in walls, façades and roofs. Technological innovation in materials, which includes nanotechnologies [emphasis mine] combined with traditional textiles used in clothes, enables buildings and other constructions to be designed using textiles containing steel polyvinyl chloride (PVC) or ethylene tetrafluoroethylene (ETFE). This gives the materials new antibacterial, antifungal and antimycotic properties in addition to being antistatic, sound-absorbing and water-resistant”.

Rooflys is another example. In this case, coated black woven textiles are placed under the roof to protect roof insulation from mould. These building textiles have also been tested for fire resistance, nail sealability, water and vapour impermeability, wind and UV resistance.

Photo: Production line at the co-operative enterprise CAVAC Biomatériaux, France. Natural fibres processed into a continuous mat (biofib) – Martin Ansell, BRE CICM, University of Bath, UK

In Spain three researchers from the Technical University of Madrid (UPM) have developed a new panel made with textile waste. They claim that it can significantly enhance both the thermal and acoustic conditions of buildings, while reducing greenhouse gas emissions and the energy impact associated with the development of construction materials.

Besides textiles, innovative natural fibre composite materials are a parallel field of the research on insulators that can preserve indoor air quality. These bio-based materials, such as straw and hemp, can reduce the incidence of mould growth because they breathe. The breathability of materials refers to their ability to absorb and desorb moisture naturally”, says expert Finlay White from Modcell, who contributed to the construction of what they claim are the world’s first commercially available straw houses, “For example, highly insulated buildings with poor ventilation can build-up high levels of moisture in the air. If the moisture meets a cool surface it will condensate and producing mould, unless it is managed. Bio-based materials have the means to absorb moisture so that the risk of condensation is reduced, preventing the potential for mould growth”.

The Bristol-based green technology firm [Modcell] is collaborating with the European Isobio project, which is testing bio-based insulators which perform 20% better than conventional materials. “This would lead to a 5% total energy reduction over the lifecycle of a building”, explains Martin Ansell, from BRE Centre for Innovative Construction Materials (BRE CICM), University of Bath, UK, another partner of the project.

“Costs would also be reduced. We are evaluating the thermal and hygroscopic properties of a range of plant-derived by-products including hemp, jute, rape and straw fibres plus corn cob residues. Advanced sol-gel coatings are being deposited on these fibres to optimise these properties in order to produce highly insulating and breathable construction materials”, Ansell concludes.

You can find Modcell here.

Here’s another image, which I believe is a closeup of the processed fibre shown in the above,

Production line at the co-operative enterprise CAVAC Biomatériaux, France. Natural fibres processed into a continuous mat (biofib) – Martin Ansell, BRE CICM, University of Bath, UK [Note: This caption appears to be a copy of the caption for the previous image]

Coat fruit with silk to keep it fresh

A May 6, 2016 news item on ScienceDaily describes a way to keep fruit fresh without refrigeration,

Half of the world’s fruit and vegetable crops are lost during the food supply chain, due mostly to premature deterioration of these perishable foods, according to the Food and Agriculture Organization (FAO) of the United Nations.

Tufts University biomedical engineers have demonstrated that fruits can stay fresh for more than a week without refrigeration if they are coated in an odorless, biocompatible silk solution so thin as to be virtually invisible. The approach is a promising alternative for preservation of delicate foods using a naturally derived material and a water-based manufacturing process.

A May 6, 2016 Tufts University news release (also on EurekAlert), which originated the news item, describes the work,

Silk’s unique crystalline structure makes it one of nature’s toughest materials. Fibroin, an insoluble protein found in silk, has a remarkable ability to stabilize and protect other materials while being fully biocompatible and biodegradable.

For the study, researchers dipped freshly picked strawberries in a solution of 1 percent silk fibroin protein; the coating process was repeated up to four times.  The silk fibroin-coated fruits were then treated for varying amounts of time with water vapor under vacuum (water annealed) to create varying percentages of crystalline beta-sheets in the coating. The longer the exposure, the higher the percentage of beta-sheets and the more robust the fibroin coating. The coating was 27 to 35 microns thick.

The strawberries were then stored at room temperature. Uncoated berries were compared over time with berries dipped in varying numbers of coats of silk that had been annealed for different periods of time. At seven days, the berries coated with the higher beta-sheet silk were still juicy and firm while the uncoated berries were dehydrated and discolored.

Tests showed that the silk coating prolonged the freshness of the fruits by slowing fruit respiration, extending fruit firmness and preventing decay.

“The beta-sheet content of the edible silk fibroin coatings made the strawberries less permeable to carbon dioxide and oxygen. We saw a statistically significant delay in the decay of the fruit,” said senior and corresponding study author Fiorenzo G. Omenetto, Ph.D. Omenetto is the Frank C. Doble Professor in the Department of Biomedical Engineering and also has appointments in the Department of Electrical Engineering and in the Department of Physics in the School of Arts and Sciences.

Similar experiments were performed on bananas, which, unlike strawberries, are able to ripen after they are harvested. The silk coating decreased the bananas’ ripening rate compared with uncoated controls and added firmness to the fruit by preventing softening of the peel.

The thin, odorless silk coating did not affect fruit texture.  Taste was not studied.

“Various therapeutic agents could be easily added to the water-based silk solution used for the coatings, so we could potentially both preserve and add therapeutic function to consumable goods without the need for complex chemistries,” said the study’s first author, Benedetto Marelli, Ph.D., formerly a post-doctoral associate in the Omenetto laboratory and now at MIT.

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

Silk Fibroin as Edible Coating for Perishable Food Preservation by B. Marelli, M. A. Brenckle, D. L. Kaplan & F. G. Omenetto. Scientific Reports 6, Article number: 25263 (2016) doi:10.1038/srep25263 Published online: 06 May 2016

This is an open access paper.

Norway and degradable electronics

It’s a bit higgledy-piggledy but a Nov. 20, 2014 news item on Nanowerk highlights some work with degradable electronics taking place in Norway,

When the FM frequencies are removed in Norway in 2017, all old-fashioned radios will become obsolete, leaving the biggest collection of redundant electronics ever seen – a mountain of waste weighing something between 25,000 and 30,000 tonnes.

The same thing is happening with today’s mobile telephones, PCs and tablets, all of which are constantly being updated and replaced faster than the blink of an eye. The old devices end up on waste tips, and even though we in the west recover some materials for recycling, this is only a small proportion of the whole.

And nor does the future bode well with waste in mind. Technologists’ vision of the future is the “Internet of Things”. Electronics are currently printed onto plastics. All products are fitted with sensors designed to measure something, and to make it possible to talk to other devices around them. Davor Sutija is General Manager at the electronics firm Thin Film, and he predicts that in the course of a few years each of us will progress from having a single sensor to having between a hundred and a thousand. This in turn will mean that billions of devices with electronic bar codes will be released onto the market.

Researchers are now getting to grips with this problem. Their aim is to develop processes in which electronics are manufactured in such a way that their entire life cycle is controlled, including their ultimate disappearance.

A Nov. 20, 2014 article by Åse Dragland for the Gemini newsletter (also found as a Nov. 20, 2014 news release on SINTEF [Norwegian: Stiftelsen for industriell og teknisk forskning]), describes the inspiration for the work in Norway while pointing out some signficant differences from US researchers in the approach to creating a commercial application,

In New Orleans in the USA, researchers have made electronic circuits which they implant into surgical wounds following operations on rats. Each wound is sewn up and the electricity in the circuits then accelerates the healing process. After a few weeks, the electronics are dissolved by the body fluids, making it unnecessary to re-open the wound to remove them manually.

In Norway, researchers at SINTEF have now succeeded in making components containing magnesium circuits designed to transfer energy. These are soluble in water and disappear after a few hours.

“We make no secret of the fact that we are putting our faith in the research results coming out of the USA”, says Karsten Husby at SINTEF ICT. “The Americans have made amazing contributions both in relation to medical applications, and towards resolving the issue of waste. We want to try to find alternative approaches to the same problem”, he says.

The circuit containing the small components is printed on a silicon wafer. At only a few nanometres thick, the circuits are extremely thin, and this enables them to dissolve more effectively. Some of the circuit components are made of magnesium, others of silicon, and others of silicon with a magnesium additive.

But the journey to the researchers’ goal from their current position leaves them with more than enough work to do. Making the ultra-thin circuits is a challenge enough in itself, but they also have to find a “coating” or “film” which will act as a protective packaging around the circuits.

The Americans use silk as their coating material, but the Norwegians are not in favour of this. The silk used is made as part of a process which involves the substance lithium, which is banned at MiNaLab – the laboratory where the SINTEF researchers work.

“Lithium generates a technical problem for our lab”, says Geir Uri Jensen, “so we’re considering alternatives, including a variety of plastics”, he says. “In order to achieve this, we’ve brought in some materials scientists here at SINTEF who are very skilled in this field”, he says.

The nature of the coating must be tailored to the time at which the electronics are required to degrade. In some cases this is just one week – in others, four. For example, if the circuit package is designed to be used in seawater, and fitted with sensors for taking measurements from oil spills, the film must be made so that it remains in place for the weeks in which the measurements are being taken.

“When the external fluids penetrate to the “guts” inside the packaging, the circuits begin to degrade. The job must be completed before this happens”, says Karsten Husby.

Geir Uri Jensen makes a sketch and explains how the nano researchers use horizontal and vertical etching processes in the lab to deposit all the layers onto the silicon circuits. And then – how they have to etch and lift the circuit loose from the silicon wafer in order later to transfer it across to the film.

“This works well enough using sensors at full scale”, he says, “but when the wafers are as thin as this, things become more tricky”. Jensen shrugs. “Even if the angle is just a little off, the whole assembly will snap”, he says.

There’s no doubt that as the use of consumer electronics increases, so too does the need to remove obsolete electronic products. Just think of all the cheap electronics built into children’s toys which are thrown away every year.

The removal of “outdated electronics” can also be a very labour-intensive process. Every day, surgeons place implants fitted with sensors into our bodies in order to measure everything from blood pressure and pressure on the brain, to how our hip implants are working. Some weeks later they have to operate again in order to remove the electronics.

But not everyone is interested in the new technologies developing in this field. Electronics companies which manufacture circuits are more interested in selling their products than in investing in research that results in their products disappearing. And companies which rely on recycling for their revenues may regard these new ideas as a threat to their existence.
Eco-friendly electronics are on the way

“It’s important to make it clear that we’re not manufacturing a final product, but a demo that can show that an electronic component can be made with properties that make it degradable”, says Husby. “Our project is now in its second year, but we’ll need a partner active in the industry and more funding in the years ahead if we’re to meet our objectives. There’s no doubt that eco-friendly electronics is a field which will come into its own, also here in Norway. And we’ve made it our mission to reach our goals”, he says.

Here’s an image of dissolving electronic circuits made available by the researchers,

Electronic circuits can be implanted into surgical wounds and assist the healing process by accelerating wound closure. After a few weeks, the electronics are dissolved by the body fluids, making it unnecessary to re-open the wound to remove them manually. Photos: Werner Juvik/SINTEF - See more at: http://gemini.no/en/2014/11/tomorrows-degradable-electronics/#sthash.Erh1sZp2.dpuf

Electronic circuits can be implanted into surgical wounds and assist the healing process by accelerating wound closure. After a few weeks, the electronics are dissolved by the body fluids, making it unnecessary to re-open the wound to remove them manually. Photos: Werner Juvik/SINTEF – See more at: http://gemini.no/en/2014/11/tomorrows-degradable-electronics/#sthash.Erh1sZp2.dpuf

The researcher most associated with this kind of work is John Rogers at the University of Illinois at Urbana-Champaign and you can read more about biodegradable/dissolving electronics in a Sept. 27, 2012 article (open access) by Katherine Bourzac for Nature magazine. You can find more information about Thin Film Electronics or Thinfilm Electronics (mentioned in the third paragraph of the news item on Nanowerk) website here.

Tooth tattoos at Tufts University

In spring 2012, there was a fluttering in the blogosphere about tooth tattoos with the potential for monitoring dental health. As sometimes happens, I put off posting about the work until it seemed everyone else had written about it (e.g. Mar. 30, 2012 posting by Dexter Johnson for his Nanoclast blog on the IEEE website) and there was nothing left for me to say.  Happily, the researchers at Tufts University (where part of this research [Princeton University is also involved] is being pursued) have released more information in a Nov. 1, 2012 news article by David Levin,

The sensor, dubbed a “tooth tattoo,” was developed by the Princeton nanoscientist Michael McAlpine and Tufts bioengineers Fiorenzo Omenetto, David Kaplan and Hu Tao. The team first published their research last spring in the journal Nature Communications.

The sensor is relatively simple in its construction, says McAlpine. It’s made up of just three layers: a sheet of thin gold foil electrodes, an atom-thick layer of graphite known as graphene and a layer of specially engineered peptides, chemical structures that “sense” bacteria by binding to parts of their cell membranes.

“We created a new type of peptide that can serve as an intermediary between bacteria and the sensor,” says McAlpine. “At one end is a molecule that can bond with the graphene, and at the other is a molecule that bonds with bacteria,” allowing the sensor to register the presence of bacteria, he says.

Because the layers of the device are so thin and fragile, they need to be mounted atop a tough but flexible backing in order to transfer them to a tooth. The ideal foundation, McAlpine says, turns out to be silk—a substance with which Kaplan and Omenetto have been working for years.

By manipulating the proteins that make up a single strand of silk, it’s possible to create silk structures in just about any shape, says Omenetto, a professor of biomedical engineering at Tufts. Since 2005, he’s created dozens of different structures out of silk, from optical lenses to orthopedic implants. Silk is “kind of like plastic, in that we can make [it] do almost anything,” he says. “We have a lot of control over the material. It can be rigid. It can be flexible. We can make it dissolve in water, stay solid, become a gel—whatever we need.”

Omenetto, Kaplan and Tao created a thin, water-soluble silk backing for McAlpine’s bacterial sensor—a film that’s strong enough to hold the sensor components in place, but soft and pliable enough to wrap easily around the irregular contours of a tooth.

To apply the sensor, McAlpine says, you need only to wet the surface of the entire assembly—silk, sensor and all—and then press it onto the tooth. Once there, the silk backing will dissolve within 15 or 20 minutes, leaving behind the sensor, a rectangle of interwoven gold and black electrodes about half the size of a postage stamp and about as thick as a sheet of paper. The advantage of being attached directly to a tooth means that the sensor is in direct contact with bacteria in the mouth—an ideal way to monitor oral health.

Because the sensor doesn’t carry any onboard batteries, it must be both read and powered simultaneously through a built-in antenna. Using a custom-made handheld device about the size of a TV remote, McAlpine’s team can “ping” that antenna with radio waves, causing it to resonate electronically and send back information that the device then uses to determine if bacteria are present.

The sensor (A), attached to a tooth (B) and activated by radio signals (C), binds with certain bacteria (D). Illustration: Manu Mannoor/Nature Communications (downloaded from http://now.tufts.edu/articles/tooth-tattoo)

In addition to its potential for  monitoring dental health, the tooth tattoo could replace some of the more invasive health monitoring techniques (e.g., drawing blood), from the Tufts University article,

In addition to monitoring oral health, Kugel [Gerard Kugel, Tufts professor of prosthodontics and operative dentistry and associate dean for research at Tufts School of Dental Medicine] believes the tooth tattoo might be useful for monitoring a patient’s overall health. Biological markers for many diseases—from stomach ulcers to AIDS—appear in human saliva, he says. So if a sensor could be modified to react to those markers, it potentially could help dentists identify problems early on and refer patients to a physician before a condition becomes serious.

“The mouth is a window to the rest of the body,” Kugel says. “You can spot a lot of potential health problems through saliva, and it’s a much less invasive way to do diagnostic tests than drawing blood.”

Before monitoring of any type can take place, there is at least one major hurdle still be overcome. Humans are quite sensitive to objects being placed in their mouths. According to one of the researchers, we can sense objects that are 50 to 60 microns wide, about the thickness piece of paper, and that may be too uncomfortable to bear.

H/T Nov. 9, 2012 news item on Nanowerk for pointing me towards the latest information about these tooth tattoos.

Microneedles from Tufts University

Here’s some very exciting news from Tufts University in a Dec. 21, 2011 news item on Nanowerk,

Bioengineers at Tufts University School of Engineering have developed a new silk-based microneedle system able to deliver precise amounts of drugs over time and without need for refrigeration. The tiny needles can be fabricated under normal temperature and pressure and from water, so they can be loaded with sensitive biochemical compounds and maintain their activity prior to use. They are also biodegradable and biocompatible.

I have previously written about a micro needle project at the Georgia Institute of Technology in Nov. 9, 2011 posting and about Mark Kendall’s nano vaccine patch on more than one occasion, most recently in my Aug. 3, 2011 posting.

This new drug delivery project surprised me; I didn’t realize that horesradish could also be a drug,

The Tufts researchers successfully demonstrated the ability of the silk microneedles to deliver a large-molecule, enzymatic model drug, horseradish peroxidase (HRP), at controlled rates while maintaining bioactivity. In addition, silk microneedles loaded with tetracycline were found to inhibit the growth of Staphylococcus aureus, demonstrating the potential of the microneedles to prevent local infections while also delivering therapeutics.

“By adjusting the post-processing conditions of the silk protein and varying the drying time of the silk protein, we were able to precisely control the drug release rates in laboratory experiments,” said Fiorenzo Omenetto, Ph.D., senior author on the paper. “The new system addresses long-standing drug delivery challenges, and we believe that the technology could also be applied to other biological storage applications.”

If we’re all lucky, it won’t be too long before syringes are a museum item and we’ll be getting our medication with far less discomfort/pain and, in some cases, fear.

Bee silk; minnows and silver nanoparticles; David Cramb at U of Calgary finds way to measure nanoparticles in bloodstream; Rock Against Prisons

I had not realized that there’s an international drive to produce artificial insect silk until this morning. According to a news item on Nanowerk,

CSIRO [Australia’s Commonwealth Scientific and Industrial Research Organisation] scientist Dr Tara Sutherland and her team have achieved another important milestone in the international quest to artificially produce insect silk. They have hand-drawn fine threads of honeybee silk from a ‘soup’ of silk proteins that they had produced transgenically.

These threads were as strong as threads drawn from the honeybee silk gland, a significant step towards development of coiled coil silk biomaterials.

“It means that we can now seriously consider the uses to which these biomimetic materials can be put,” Dr Sutherland said.

“We used recombinant cells of bacterium E. coli to produce the silk proteins which, under the right conditions, self-assembled into similar structures to those in honeybee silk.

If I understand this rightly,  ‘tinkering’ with bacterium E. coli makes this a transgenic system and I believe it’s a GEO (genetically engineered organism) and not a GMO (genetically modified organism). In any event, it’s also biomimetic because this process mimics a biological system.

On the practical side of things, insect silk could potentially be used for tough, lightweight textiles and medical applications such as sutures. You can read more about this in the Nanowerk news item.

A Purdue University study has added more evidence that silver nanoparticles are toxic to fish. According to the news item on physorg.com,

Tested on fathead minnows ╨ an organism often used to test the effects of toxicity on aquatic life — nanosilver suspended in solution proved toxic and even lethal to the minnows. When the nanosilver was allowed to settle, the solution became several times less toxic but still caused malformations in the minnows.

“Silver nitrate is a lot more toxic than nanosilver, but when nanosilver was sonicated, or suspended, its toxicity increased tenfold,” said Maria Sepulveda, an assistant professor of forestry and natural resources whose findings were published in the journal Ecotoxicology. “There is reason to be concerned.”

Coincidentally, Dr. David Cramb, director of the Nanoscience Program and professor in the department of Chemistry at the University of Calgary, and his colleagues have published a paper about a new methodology they are developing to measure the impact of nanoparticles (no specifics about which ones) on human health and the environment. From the news release on Eureka Alert, [Mar.4.10 ETA since I think the Eureka doesn’t last long, here’s a link to the same news on Azonano]

Cramb, director of the Faculty of Science’s nanoscience program, and his researchers have developed a methodology to measure various aspects of nanoparticles in the blood stream of chicken embryos. Their discovery is published in the March online edition of Chemical Physics Letters.

“With the boom in nanomaterials production there is an increasing possibility of environmental and/or human exposure. Thus there is a need to investigate their potential detrimental effects,” says Cramb. “We have developed very specialized tools to begin measuring such impacts.”

To close today off, I got a news release from poet Heather Haley (Vancouver, Canada based) about her latest local appearance,

Heather Haley was a member of Vancouver punk bands, the all-girl Zellots and the .45s with Randy Rampage and Brad Kent. Long-lost video of the Zellots will be screened and Heather will interviewed for a live webcast. She will perform poetry from her new collection, “Three Blocks West of Wonderland.” Hope to *see* you there.

ROCK AGAINST PRISONS Live Video Retrospective         Tuesday, March 9, 2010         7:00pm – 11:55pm
Little Mountain Gallery         195 east 26th Ave         Vancouver, BC
On March 9th, the social forces will be mounting an assault on the staid and the bland. From a Punk Rock Swap Meet to a Celebrity Auction, from an ‘umplugged’ stage to a Grand Slam Poetry Karaoke by some of the big stars of 1979, we are getting the Old Gang Together. We review the fabulous footage by doreen grey from the seminal 1979 gig and plan out the 2010 resurgence of the Vancouver Explosion.
Come on out and celebrate Vancouver’s living heritage with those who made it happen: Rabid, Female Hands, Devices, Zellots, Tunnel Canary, AKA, Subhumans. Special appearances. Door Prizes. Live Webcast and Kissing Booth. Fishnet stockings. Oodles of prime swag and fixins. Your every 1979 Punk nightmare come beautifully true.

You can also check out Heather’s latest work on her website.