Nanotechnology in Smart Textiles and Wearables



The number and variety of smart textiles and wearable electronic devices has increased significantly in the past few years, as they offer significant enhancements to human comfort, health and well-being.

Wearable low-power silicon electronics, light-emitting diodes (LEDs) fabricated on fabrics, textiles with integrated Lithium-ion batteries (LIB) and electronic devices such as smart glasses, watches and lenses have been widely investigated and commercialized (e.g. Google glass, Apple Watch).

There is increasing demand for wearable electronics from industries such as:
Medical and healthcare monitoring and diagnostics.

Sportswear and fitness monitoring (bands).

Consumer electronics such as smart watches, smart glasses and headsets.

Military GPS trackers, equipment (helmets) and wearable robots.

Smart apparel and footwear in fashion and sport.

Workplace safety and manufacturing.

However, improvements in sensors, flexible & printable electronics and energy devices are necessary for wider implementation and nanomaterials and/or their hybrids are enabling the next phase convergence of textiles, electronics and informatics.

They  are opening the way for the integration of electronic components and sensors (e.g. heat and humidity) in high strength, flexible and electrically conductive textiles with energy storage and harvesting capabilities, biological functions, antimicrobial properties, and many other new functionalities.

The industry is now moving towards the development of electronic devices with flexible, thin, and large-area form factors.

Electronic devices that are fabricated on flexible substrates for application in flexible displays, electronic paper, smart packages, skin-like sensors, wearable electronics, implantable medical implements etc. is a fast growing market. Their future development depends greatly on the exploitation of advanced materials. (See Our YouTube Video – below)


Nanomaterials such as carbon nanotubes (CNT), silver nanowires graphene and other 2D materials are viewed as key materials for the future development of wearable electronics for implementation in healthcare and fitness monitoring, electronic devices incorporated into clothing and ‘smart skin’ applications (printed graphene-based sensors integrated with other 2D materials for physiological monitoring).

 


Genesis Nanotechnology Inc.

“Great Things from Small Things”

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Perovskite solar cells hit new world efficiency record


Dr. Anita Ho-Baillie, a Senior Research Fellow at the Australian Centre for Advanced Photovoltaics at UNSW, with the new perovskite cell. Credit: Rob Largent/UNSW

They’re flexible, cheap to produce and simple to make – which is why perovskites are the hottest new material in solar cell design. And now, engineers at Australia’s University of New South Wales in Sydney have smashed the trendy new compound’s world efficiency record.

Speaking at the Asia-Pacific Solar Research Conference in Canberra on Friday 2 December, Anita Ho-Baillie, a Senior Research Fellow at the Australian Centre for Advanced Photovoltaics (ACAP), announced that her team at UNSW has achieved the highest efficiency rating with the largest perovskite solar cells to date.

The 12.1% efficiency rating was for a 16 cm2 perovskite solar cell, the largest single perovskite photovoltaic cell certified with the highest energy conversion efficiency, and was independently confirmed by the international testing centre Newport Corp, in Bozeman, Montana.
The new cell is at least 10 times bigger than the current certified high-efficiency perovskite solar cells on record.

Her team has also achieved an 18% efficiency rating on a 1.2 cm2 single perovskite cell, and an 11.5% for a 16 cm2 four-cell perovskite mini-module, both independently certified by Newport.

“This is a very hot area of research, with many teams competing to advance photovoltaic design,” said Ho-Baillie. “Perovskites came out of nowhere in 2009, with an efficiency rating of 3.8%, and have since grown in leaps and bounds.

These results place UNSW amongst the best groups in the world producing state-of-the-art high-performance perovskite solar cells. And I think we can get to 24% within a year or so.”


Perovskite is a structured compound, where a hybrid organic-inorganic lead or tin halide-based material acts as the light-harvesting active layer. They are the fastest-advancing solar technology to date, and are attractive because the compound is cheap to produce and simple to manufacture, and can even be sprayed onto surfaces.

“The versatility of solution deposition of perovskite makes it possible to spray-coat, print or paint on solar cells,” said Ho-Baillie. “The diversity of chemical compositions also allows cells be transparent, or made of different colours. Imagine being able to cover every surface of buildings, devices and cars with solar cells.”

Most of the world’s commercial solar cells are made from a refined, highly purified silicon crystal and, like the most efficient commercial silicon cells (known as PERC cells and invented at UNSW), need to be baked above 800?C in multiple high-temperature steps.

Perovskites, on the other hand, are made at low temperatures and 200 times thinner than silicon cells.

But although perovskites hold much promise for cost-effective solar energy, they are currently prone to fluctuating temperatures and moisture, making them last only a few months without protection. Along with every other team in the world, Ho-Baillie’s is trying to extend its durability.

Thanks to what engineers learned from more than 40 years of work with layered silicon, they’re are confident they can extend this.

 

Nevertheless, there are many existing applications where even disposable low-cost, high-efficiency solar cells could be attractive, such as use in disaster response, device charging and lighting in electricity-poor regions of the world.
Perovskite solar cells also have the highest power to weight ratio amongst viable photovoltaic technologies.

“We will capitalise on the advantages of perovskites and continue to tackle issues important for commercialisation, like scaling to larger areas and improving cell durability,” said Martin Green, Director of the ACAP and Ho-Baillie’s mentor. The project’s goal is to lift perovskite solar cell efficiency to 26%.

The research is part of a collaboration backed by $3.6 million in funding through the Australian Renewable Energy Agency’s (ARENA) ‘solar excellence’ initiative. ARENA’s CEO Ivor Frischknecht said the achievement demonstrated the importance of supporting early stage renewable energy technologies:
“In the future, this world-leading R&D could deliver efficiency wins for households and businesses through rooftop solar as well as for big solar projects like those being advanced through ARENA’s investment in large-scale solar.”

To make a perovskite solar cells, engineers grow crystals into a structure known as ‘perovskite’, named after Lev Perovski, the Russian mineralogist who discovered it. They first dissolve a selection of compounds in a liquid to make the ‘ink’, then deposit this on a specialised glass which can conduct electricity. When the ink dries, it leaves behind a thin film that crystallises on top of the glass when mild heat is applied, resulting in a thin layer of perovskite crystals.

The tricky part is growing a thin film of perovskite crystals so the resulting solar cell absorbs a maximum amount of light.

Worldwide, engineers are working to create smooth and regular layers of perovskite with large crystal grain sizes in order to increase photovoltaic yields.

Ho-Baillie, who obtained her PhD at UNSW in 2004, is a former chief engineer for Solar Sailor, an Australian company which integrates solar cells into purpose-designed commercial marine ferries which currently ply waterways in Sydney, Shanghai and Hong Kong.

WEARABLE NANOTECHNOLOGY ~ Imagine Charging Your Phone by “Plugging it Into Your Jacket” …


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Imagine plugging your phone into your jacket to charge it up or recharging your electric car just by leaving it in a sunny parking lot.

Associate Professor Jayan Thomas teaches nanotechnology at the University of Central Florida. He is working on a filament that can store the energy of the sun and could one day be woven into clothing or coat the roof of a car.wearable-textiles-100616-0414_powdes_ti_f1

To demonstrate how his project might work, Thomas had to learn how to use some old technology – a loom.

“Listen-In” to the Audio Link Below

 

Using Scalable Quantum Dot Light-Emitting Diodes (LEDs) to produce entangled photons ~ Underpinning for Quantum Computing


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Quantum computing is heralded as the next revolution in terms of global computing. Google, Intel and IBM are just some of the big names investing millions currently in the field of quantum computing which will enable faster, more efficient computing required to power the requirements of our future computing needs.

 

Now a researcher and his team at Tyndall National Institute in Cork have made a ‘quantum leap’ by developing a technical step that could enable the use of quantum computers sooner than expected.

 

Conventional digital computing uses ‘on-off’ switches, but quantum computing looks to harness quantum state of matters – such as entangled photons of light or multiple states of atoms – to encode information. In theory, this can lead to much faster and more powerful computer processing, but the technology to underpin quantum computing is currently difficult to develop at scale.
Researchers at Tyndall have taken a step forward by making quantum dot light-emitting diodes (LEDs) that can produce entangled photons (whose actions are linked), theoretically enabling their use to encode information in quantum computing.

 

This is not the first time that LEDs have been made that can produce entangled photons, but the methods and materials described in the new paper (Nature Photonics, “Selective carrier injection into patterned arrays of pyramidal quantum dots for entangled photon light-emitting diodes”) have important implications for the future of quantum technologies, explains researcher Dr Emanuele Pelucchi, Head of Epitaxy and Physics of Nanostructures and a member of the Science Foundation Ireland-funded Irish Photonic Integration Centre (IPIC) at Tyndall National Institute in Cork.

 

Dr Emanuele Pelucchi
Dr Emanuele Pelucchi.

 

“The new development here is that we have engineered a scalable array of electrically driven quantum dots using easily-sourced materials and conventional semiconductor fabrication technologies, and our method allows you to direct the position of these sources of entangled photons,” he says.

 

“Being able to control the positions of the quantum dots and to build them at scale are key factors to underpin more widespread use of quantum computing technologies as they develop.”

 

qd-computing-2-120215-quantum-100631144-primary-idgeThe Tyndall technology uses nanotechnology to electrify arrays of the pyramid-shaped quantum dots so they produce entangled photons. “We exploit intrinsic nanoscale properties of the whole “pyramidal” structure, in particular, an engineered self-assembled vertical quantum wire, which selectively injects current into the vicinity of a quantum dot,” explains Dr Pelucchi. 

 

“The reported results are an important step towards the realization of integrated quantum photonic circuits designed for quantum information processing tasks, where thousands or more sources would function in unison.”
“It is exciting to see how research at Tyndall continues to break new ground, particularly in relation to this development in quantum computing. The significant breakthrough by Dr Pelucchi advances our understanding of how to harness the opportunity and power of quantum computing and undoubtedly accelerates progress in this field internationally. Photonics innovations by the IPIC team at Tyndall are being commercialized across a number sectors and as a result, we are directly driving global innovation through our investment, talent and research in this area,” said Dr Kieran Drain, CEO at Tyndall National Institute.
Source: Tyndall National Institute

 

New way to make low-cost perovskite solar cell technology


 

efficiently-photo-charging-lithium-ion-batteries-by-perovskite-solar-cell“By combining these two cells, the perovskite cell and the silicon cell, we are able to make much better use of the solar energy and achieve higher efficiencies than either cell on its own.”

Researchers at The Australian National University (ANU) have found a new way to fabricate high efficiency semi-transparent perovskite solar cells in a breakthrough that could lead to more efficient and cheaper solar electricity (Advanced Energy Materials, “Efficient Indium-Doped TiOxElectron Transport Layers for High-Performance Perovskite Solar Cells and Perovskite-Silicon Tandems”).

 

Dr Tom White from the ANU Research School of Engineering said the new fabrication method significantly improved the performance of perovskite solar cells, which can combine with conventional silicon solar cells to produce more efficient solar electricity.

 

ANU Ph.D. student The Duong, Dr.Tom White and Ph.D. student Jun Peng
 

ANU Ph.D. student The Duong, Dr.Tom White and Ph.D. student Jun Peng.

 

He said perovskite solar cells were extremely good at making electricity from visible light – blue, green and red – while conventional silicon solar cells were more efficient at converting infrared light into electricity.

“The prospect of adding a few additional processing steps at the end of a silicon cell production line to make perovskite cells is very exciting and could boost solar efficiency from 25 per cent to 30 per cent,” Dr White said.
“By combining these two cells, the perovskite cell and the silicon cell, we are able to make much better use of the solar energy and achieve higher efficiencies than either cell on its own.”
While perovskite cells can improve efficiency, they are not yet stable enough to be used on rooftops. Dr White said the new fabrication technique could help develop more reliable perovskite cells.
The new fabrication method involves adding a small amount of the element indium into one of the cell layers during fabrication. That could increase the cell’s power output by as much as 25 per cent.
“We have been able to achieve a record efficiency of 16.6 per cent for a semi-transparent perovskite cell, and 24.5 per cent for a perovskite-silicon tandem, which is one of the highest efficiencies reported for this type of cell,” said Dr White.
Dr White said the research placed ANU in a small group of labs around the world with the capability to improve silicon solar cell efficiency using perovskites.
The development builds on the state-of-the-art silicon cell research at ANU and is part of a $12.2 million “High-efficiency silicon/perovskite solar cells” project led by University of New South Wales and supported by $3.6 million of funding from the Australian Renewable Energy Agency.
Research partners include Monash University, Arizona State University, Suntech R&D Australia Pty Ltd and Trina Solar.
Source: The Australian National University

A “Smart-Solar” Window ~ Privacy and light control on demand: YouTube Video


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Smart windows get darker to filter out the sun’s rays on bright days, and turn clear on cloudy days to let more light in. This feature can help control indoor temperatures and offers some privacy without resorting to aids such as mini-blinds.Now scientists report a new development in this growing niche: solar smart windows that can turn opaque on demand and even power other devices. The study appears in ACS Photonics (“Electrically Controllable Light Trapping for Self-Powered Switchable Solar Windows”).

 

Smart windows get darker to filter out the sun’s rays on bright days, and turn clear on cloudy days to let more light in. This feature can help control indoor temperatures and offers some privacy without resorting to mini-blinds. Now scientists report a new development in this growing niche: solar smart windows that can turn opaque on demand and even power other devices.

Most existing solar-powered smart windows are designed to respond automatically to changing conditions, such as light or heat. But this means that on cool or cloudy days, consumers can’t flip a switch and tint the windows for privacy.
Also, these devices often operate on a mere fraction of the light energy they are exposed to while the rest gets absorbed by the windows. This heats them up, which can add warmth to a room that the windows are supposed to help keep cool. Jeremy Munday and colleagues wanted to address these limitations.
The researchers created a new smart window by sandwiching a polymer matrix containing microdroplets of liquid crystal materials, and an amorphous silicon layer — the type often used in solar cells — between two glass panes.

 

When the window is “off,” the liquid crystals scatter light, making the glass opaque. The silicon layer absorbs the light and provides the low power needed to align the crystals so light can pass through and make the window transparent when the window is turned “on” by the user.

The extra energy that doesn’t go toward operating the window is harvested and could be redirected to power other devices, such as lights, TVs or smartphones, the researchers say.
Source: American Chemical Society

 

Splitting Water ~ Using a novel non-precious metal catalyst ~ For Low Cost Hydrogen Cell


water-splitting-id45120A new research, affiliated with Ulsan National Institute of Science and Technology (UNIST) has presented a novel strategy for non-precious metal catalyst that can replace rare and expensive platinum(Pt)-based catalyst, currently used in hydrogen fuel cell.
In their study, published in the November issue of the Journal of the American Chemical Society (“A General Approach to Preferential Formation of Active Fe–Nx Sites in Fe–N/C Electrocatalysts for Efficient Oxygen Reduction Reaction”), Professor Sang Hoon Joo of Energy and Chemical Engineering and his team have devised a new synthetic strategy to boost the activity of iron- and nitrogen-doped carbon (Fe-N/C) catalyst that can realize low-cost hydrogen fuel cell.

 

Synthetic scheme for the preparation of CNT/PC catalysts
Synthetic scheme for the preparation of CNT/PC catalysts. (Image: UNIST) (click on image to enlarge)
 

Hydrogen fuel cell generates electricity with hydrogen and oxygen, producing water as a byproduct. Precious platinum(Pt) has been used in commercialized fuel cell. However, the high cost of Pt (>40$ per g) hampers widespread application of the fuel cell.

 

The research team has attempted to develop high-performance non-precious metal catalyst which can substitute for state-of-the-art Pt-based catalysts. In this research, they focused on carbon-based catalyst with iron and nitrogen due to low cost and high activity (Fe-N/C catalyst). During the preparation of the Fe-N/C catalysts, high-temperature heat-treatment at over 700°C is commonly required to endow high catalystic activity, but unfortunately this treatment also diminishes the number of active site. The active site refers to the place where rate-determining catalytic reaction occurs.
To solve the problem, they have introduced ‘silica-protective-layer’ approach. The silica layer effectively preserved the active site at high-temperature, preventing the destruction of the active site.
The novel Fe-N/C catalyst prepared by ‘silica-protective-layer’ approach showed very high oxygen reduction reaction (ORR) activity which is comparable to Pt catalyst. ORR is an electrochemical reaction at the cathode of hydrogen fuel cell. Due to 1-million-times slower reaction kinetics of ORR at the cathode compared with hydrogen oxidation reaction at the anode, ORR is a major factor for a large drop of the efficiency of fuel cell. Up to date, expensive Pt has been used primarily as an efficient ORR catalyst.
The research team realized a record high activity by employing their catalyst as the cathode catalyst of alkaline membrane fuel cell (one type of hydrogen fuel cell). The team also demonstrated very high performance in proton exchange membrane fuel cell (PEMFC), in which the developed catalyst showed the activity of 320 A cm-3, exceeding 2020 US Department of Energy (DOE) activity target for non-precious metal catalyst (300 A cm-3).
“Our novel strategy for high-performance catalyst is expected to hasten the commercialization of hydrogen fuel cell, and the catalyst design can be also applied to other energy storage and conversion devices.” says Prof. Joo.
Source: Ulsan National Institute of Science and Technology

 

Dotz Nano makes stunning ASX debut: Commercializing Graphene Quantum Dots: Rice U Developed Technology


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Perth tech company Dotz Nano has made a stunning ASX debut with its shares reaching more than double their issue price on the company’s first day of trade.

The company, a backdoor listing through the shell of former explorer Northern Iron, focuses on the development, manufacture and commercialisation of Graphene Quantum Dots (GQDs).

The company raised $6 million at 20 cents a share. Its shares hit an intraday high of 49 cents before retracing to close up more than 75 per cent at 36.5 cents.

GQDs are nanoparticles which have applications in LED displays, pigments, dyes and detergents as well as energy, electrical and medical applications.

Non-graphene derived quantum dots are already widely used in products such as high-definition TVs, medical imaging and lighting products. However they have limited applications because of their toxicity and production costs.

Dotz Nano said it had exclusive capabilities to extract GQDs from coal rather than graphite, allowing it to produce inexpensive, non-toxic GQDs at ten times the production yield of conventional GQDs.

qds-from-coal-1006_gqd-2-rn-310x302Quantum Dots from Coal + Graphene Could Dramatically Cut the Cost of Energy from Fuel Cells

The company said its patented technology was developed by Professor James Tour of the William Marsh Rice University in Houston, Texas. It also has a strong partnership with the Ben-Gurion University in Israel.

Watch A Video On Graphene-Quantum Dots

Dotz Nano said it was not aware of any other party commercialising GQDs and that it holds five patents covering all major jurisdictions.

Chief executive Moti Gross said the company had first mover advantage in its field.

“We have had extremely encouraging discussions with potential customers, sub-licensees and distributors, as with the Mainami Group in Japan, and there will be no shortage of activity from our potential deal pipeline,” he said.

“We take the opportunity to welcome our new shareholders on board and we look forward to updating the market as we continue to scale our business.”

The company also announced today a memorandum of understanding to establish a $S 20 million research centre at the Nanyang Technological University in Singapore.

Quantum Dots with Impermeable Shell: A Powerful Tool for Nano-Engineering


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Unique optical features of quantum dots make them an attractive tool for many applications, from cutting-edge displays to medical imaging. Physical, chemical or biological properties of quantum dots must, however, be adapted to the desired needs. Unfortunately, up to now quantum dots prepared by chemical methods could be functionalized using copper-based click reactions with retention of their luminescence. This obstacle can be ascribed to the fact that copper ions destroy the ability of quantum dots to emit light.

 

Scientists from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw and the Faculty of Chemistry of the Warsaw University of Technology (FC WUT) have shown, however, that zinc oxide (ZnO) quantum dots prepared by an original method developed by them, after modification by the click reaction with the participation of copper ions, fully retain their ability to emit light.

“Click reactions catalyzed by copper cations have long attracted the attention of chemists dealing with quantum dots. The experimental results, however, were disappointing: after modification, the luminescence was so poor that they were just not fit for use. We were the first to demonstrate that it is possible to produce quantum dots from organometallic precursors in a way they do not lose their valuable optical properties after being subjected to copper-catalysed click reactions,” says Prof. Janusz Lewinski (IPC PAS, FC WUT).

 

nanotechnology-used-to-make-medicine-inside-the-bodyQuantum dots are crystalline structures with size of a few nanometers (billionth parts of a meter). As semiconductor materials, they exhibit a variety of interesting features typical of quantum objects, including absorbing and emitting radiation of only a strictly defined energy. Since atoms interact with light in a similar way, quantum dots are often called artificial atoms. In some respects, however, quantum dots offer more possibilities than atoms. Optical properties of each dot actually depend on its size and the type of material from which it is formed. This means that quantum dots may be precisely designed for specific applications.

To meet the need of specific applications, quantum dots have to be tailored in terms of physico-chemical properties. For this purpose, chemical molecules with suitable characteristics are attached to their surface. Due to the simplicity, efficacy, and speed of the process, an exceptionally convenient method is the click reaction. Unfortunately, one of the most widely used click reactions takes place with the participation of copper ions, which was reported to result in the almost complete quenching of the luminescence of the quantum dots.

“Failure is usually a result of the inadequate quality of quantum dots, which is determined by the synthesis method. Currently, ZnO dots are mainly produced by the sol-gel method from inorganic precursors. Quantum dots generated in this manner are coated with a heterogeneous and probably leaky protective shell, made of various sorts of chemical molecules. During a click reaction, the copper ions are in direct contact with the surface of quantum dots and quench the luminescence of the dot, which becomes completely useless,” explains Dr. Agnieszka Grala (IPC PAS), the first author of the article in the Chemical Communications journal.

For several years, Prof. Lewinski’s team has been developing alternative methods for the preparation of high quality ZnO quantum dots. The method presented in this paper affords the quantum dots derived from organozinc precursors. Composition of the nanoparticles can be programmed at the stage of precursors preparation, which makes it possible to precisely control the character of their organic-inorganic interface.

“Nanoparticles produced by our method are crystalline and all have almost the same size. They are spherical and have characteristics of typical quantum dots. Every nanoparticle is stabilized by an impermeable protective jacket, built of organic compounds, strongly anchored on the surface of the semiconductor core. As a result, our quantum dots remain stable for a long time and do not aggregate, that is clump together, in solutions,” describes Malgorzata Wolska-Pietkiewicz, a PhD student at FC WUT.

“The key to success is producing a uniform stabilizing shell. Such coatings are characteristic of the ZnO quantum dots obtained by our method. The organic layer behaves as a tight protective umbrella protecting dots from direct influence of the copper ions,” says Dr. Grala and clarifies: “We carried out click reaction known as alkyne-azide cycloaddition, in which we used a copper(l) compound as catalysts. After functionalization, our quantum dots shone as brightly as at the beginning.”

Quantum dots keep finding more and more applications in various industrial processes and as nanomarkers in, among others, biology and medicine, where they are combined with biologically active molecules. Nanoobjects functionalized in this manner are used to label both individual cells as well as whole tissues.

The unique properties of quantum dots also enable long-term monitoring of the labelled item. Commonly used quantum dots, however, contain toxic heavy metals, including cadmium. In addition, they clump together in solutions, which supports the thesis of the lack of tightness of their shells. Meanwhile, the ZnO dots produced by Prof. Lewinski’s group are non-toxic, they do not aggregate, and can be bound to many chemical compounds – so they are much more suitable for medical diagnosis and for imaging cells and tissues.

Research on the methods of production of functionalized ZnO quantum dots was carried out under an OPUS grant from the Poland’s National Science Centre.

Nano-Fiber coating prevents infections of prosthetic joints: Johns Hopkins University


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A titanium implant (blue) without a nanofiber coating in the femur of a mouse. Bacteria are shown in red and responding immune cells in yellow. Credit: Lloyd Miller/Johns Hopkins Medicine

In a proof-of-concept study with mice, scientists at The Johns Hopkins University show that a novel coating they made with antibiotic-releasing nanofibers has the potential to better prevent at least some serious bacterial infections related to total joint replacement surgery.

A report on the study, published online the week of Oct. 24 in Proceedings of the National Academy of Sciences, was conducted on the rodents’ knee joints, but, the researchers say, the technology would have “broad applicability” in the use of orthopaedic prostheses, such as hip and knee total joint replacements, as well pacemakers, stents and other . In contrast to other coatings in development, the researchers report the new material can release multiple antibiotics in a strategically timed way for an optimal effect.

“We can potentially coat any metallic implant that we put into patients, from prosthetic joints, rods, screws and plates to pacemakers, implantable defibrillators and dental hardware,” says co-senior study author Lloyd S. Miller, M.D., Ph.D., an associate professor of dermatology and orthopaedic surgery at the Johns Hopkins University School of Medicine.

Surgeons and biomedical engineers have for years looked for better ways —including antibiotic coatings—to reduce the risk of infections that are a known complication of implanting artificial hip, knee and shoulder joints.

Every year in the U.S., an estimated 1 to 2 percent of the more than 1 million hip and knee replacement surgeries are followed by infections linked to the formation of biofilms—layers of bacteria that adhere to a surface, forming a dense, impenetrable matrix of proteins, sugars and DNA. Immediately after surgery, an acute infection causes swelling and redness that can often be treated with intravenous antibiotics. But in some people, low-grade chronic infections can last for months, causing bone loss that leads to implant loosening and ultimately failure of the new prosthesis. These infections are very difficult to treat and, in many cases of chronic infection, prostheses must be removed and patients placed on long courses of antibiotics before a new prosthesis can be implanted. The cost per patient often exceeds $100,000 to treat a biofilm-associated prosthesis infection, Miller says.

Major downsides to existing options for local antibiotic delivery, such as antibiotic-loaded cement, beads, spacers or powder, during the implantation of medical devices are that they can typically only deliver one antibiotic at a time and the release rate is not well-controlled. To develop a better approach that addresses those problems, Miller teamed up with Hai-Quan Mao, Ph.D., a professor of materials science and engineering at the Johns Hopkins University Whiting School of Engineering, and a member of the Institute for NanoBioTechnology, Whitaker Biomedical Engineering Institute and Translational Tissue Engineering Center.

Over three years, the team focused on designing a thin, biodegradable plastic coating that could release multiple antibiotics at desired rates. This coating is composed of a nanofiber mesh embedded in a thin film; both components are made of polymers used for degradable sutures.

To test the technology’s ability to prevent infection, the researchers loaded the nanofiber coating with the antibiotic rifampin in combination with one of three other antibiotics: vancomycin, daptomycin or linezolid. “Rifampin has excellent anti-biofilm activity but cannot be used alone because bacteria would rapidly develop resistance,” says Miller. The coatings released vancomycin, daptomycin or linezolid for seven to 14 days and rifampin over three to five days. “We were able to deploy two antibiotics against potential infection while ensuring rifampin was never present as a single agent,” Miller says.

The team then used each combination to coat titanium Kirschner wires—a type of pin used in orthopaedic surgery to fix bone in place after wrist fractures—inserted them into the of anesthetized mice and introduced a strain of Staphylococcus aureus, a bacterium that commonly causes biofilm-associated infections in orthopaedic surgeries. The bacteria were engineered to give off light, allowing the researchers to noninvasively track infection over time.

Miller says that after 14 days of infection in mice that received an antibiotic-free coating on the pins, all of the mice had abundant bacteria in the infected tissue around the knee joint, and 80 percent had bacteria on the surface of the implant. In contrast, after the same time period in mice that received pins with either linezolid-rifampin or daptomycin-rifampin coating, none of the mice had detectable bacteria either on the implants or in the surrounding tissue.

“We were able to completely eradicate infection with this coating,” says Miller. “Most other approaches only decrease the number of bacteria but don’t generally or reliably prevent infections.”

After the two-week test, each of the rodents’ joints and adjacent bones were removed for further study. Miller and Mao found that not only had infection been prevented, but the bone loss often seen near infected joints—which creates the prosthetic loosening in patients—had also been completely avoided in animals that received pins with the antibiotic-loaded coating.

Miller emphasized that further research is needed to test the efficacy and safety of the coating in humans, and in sorting out which patients would best benefit from the coating—people with a previous prosthesis joint infection receiving a new replacement joint, for example.

The polymers they used to generate the nanofiber coating have already been used in many approved devices by the U.S. Food and Drug Administration, such as degradable sutures, bone plates and drug delivery systems.

Explore further: Early studies show microspheres may prevent bone infections after joint replacement

More information: Polymeric nanofiber coating with tunable combinatorial antibiotic delivery prevents biofilm-associated infection in vivo, Proceedings of the National Academy of Sciences, www.pnas.org/cgi/doi/10.1073/pnas.1613722113