Superlubricity coating could reduce economic losses from friction and wear Posted on 7 Jun 16:11

Superlubricity coating could reduce economic losses from friction and wear

Superlubricity coating could reduce economic losses from friction, wear
ORNL's vertically aligned carbon nanotubes reduce friction to nearly zero to improve energy efficiency. Credit: Chanaka Kumara/ORNL, U.S. Dept. of Energy

Scientists at the Department of Energy's Oak Ridge National Laboratory have invented a coating that could dramatically reduce friction in common load-bearing systems with moving parts, from vehicle drive trains to wind and hydroelectric turbines. It reduces the friction of steel rubbing on steel at least a hundredfold. The novel ORNL coating could help grease a U.S. economy that each year loses more than $1 trillion to friction and wear—equivalent to 5% of the gross national product.


"When components are sliding past each other, there's friction and wear," said Jun Qu, leader of ORNL's Surface Engineering and Tribology group. Tribology, from the Greek word for rubbing, is the science and technology of interacting surfaces in relative motion, such as gears and bearings. "If we reduce friction, we can reduce energy consumption. If we reduce wear, we can elongate the lifespan of the system for better durability and reliability."

With ORNL colleagues Chanaka Kumara and Michael Lance, Qu led a study published in Materials Today Nano about a coating composed of  nanotubes that imparts superlubricity to sliding parts. Superlubricity is the property of showing virtually no resistance to sliding; its hallmark is a coefficient of friction less than 0.01. In comparison, when dry metals slide past each other, the coefficient of friction is around 0.5. With an oil lubricant, the coefficient of friction falls to about 0.1. However, the ORNL coating reduced the coefficient of friction far below the cutoff for superlubricity, to as low as 0.001.

"Our main achievement is we make superlubricity feasible for the most common applications," Qu said. "Before, you'd only see it in either nanoscale or specialty environments."

For the study, Kumara grew carbon nanotubes on steel plates. With a machine called a tribometer, he and Qu made the plates rub against each other to generate carbon-nanotube shavings.

The  coat the steel, repel corrosive moisture, and function as a lubricant reservoir. When they are first deposited, the vertically aligned carbon nanotubes stand on the surface like blades of grass. When steel parts slide past each other, they essentially "cut the grass." Each blade is hollow but made of multiple layers of rolled , an atomically thin sheet of carbon arranged in adjacent hexagons like chicken wire. The fractured  debris from the shaving is redeposited onto the contact surface, forming a graphene-rich tribofilm that reduces friction to nearly zero.

Making the carbon nanotubes is a multistep process. "First, we need to activate the steel surface to produce tiny structures, on the size scale of nanometers. Second, we need to provide a  to grow the carbon nanotubes," Kumara said. He heated a stainless-steel disk to form metal-oxide particles on the surface. Then he used  to introduce carbon in the form of ethanol so that metal-oxide particles can stitch carbon there, atom by atom in the form of nanotubes.

  • Superlubricity coating could reduce economic losses from friction, wear
    A stainless-steel disk was heated to create iron and nickel oxide particles on its surface. The particles catalyzed carbon nanotube growth during chemical vapor deposition. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
  • Superlubricity coating could reduce economic losses from friction, wear
    ORNL researchers used a tribometer for friction testing to show that carbon nanotubes in the presence of even one drop of oil could sustain superlubricity over 500,000 cycles. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
  • Superlubricity coating could reduce economic losses from friction, wear
    A stainless-steel disk was heated to create iron and nickel oxide particles on its surface. The particles catalyzed carbon nanotube growth during chemical vapor deposition. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
  • Superlubricity coating could reduce economic losses from friction, wear
    ORNL researchers used a tribometer for friction testing to show that carbon nanotubes in the presence of even one drop of oil could sustain superlubricity over 500,000 cycles. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

The new nanotubes do not provide superlubricity until they are damaged. "The carbon nanotubes are destroyed in the rubbing but become a new thing," Qu said. "The key part is those fractured carbon nanotubes are pieces of graphene. Those graphene pieces are smeared and connected to the contact area, becoming what we call tribofilm, a coating formed during the process. Then both contact surfaces are covered by some graphene-rich coating. Now, when they rub each other, it's graphene on graphene."

The presence of even one drop of oil is crucial to achieving superlubricity. "We tried it without oil; it didn't work," Qu said. "The reason is, without oil, friction removes the carbon nanotubes too aggressively. Then the tribofilm cannot form nicely or survive long. It's like an engine without oil. It smokes in a few minutes, whereas one with oil can easily run for years."

The ORNL coating's superior slipperiness has staying power. Superlubricity persisted in tests of more than 500,000 rubbing cycles. Kumara tested the performances for continuous sliding over three hours, then one day and later 12 days. "We still got superlubricity," he said. "It's stable."

Using , Kumara examined the mowed fragments to prove that tribological wear had severed the carbon nanotubes. To independently confirm that rubbing had shortened the nanotubes, ORNL co-author Lance used Raman spectroscopy, a technique that measures vibrational energy, which is related to the atomic bonding and crystal structure of a material.

"Tribology is a very old field, but modern science and engineering provided a new scientific approach to advance technology in this area," Qu said. "The fundamental understanding has been shallow until the last maybe 20 years, when tribology got a new life. More recently, scientists and engineers really came together to use the more advanced material characterization technologies—that's an ORNL strength. Tribology is very multidisciplinary. No one is an expert in everything. Therefore, in tribology, the key to success is collaboration."

He added, "Somewhere, you can find a scientist with expertise in carbon nanotubes, a scientist with expertise in tribology, a scientist with expertise in materials characterization. But they are isolated. Here at ORNL, we are together."

  • Superlubricity coating could reduce economic losses from friction, wear
    Chanaka Kumara of ORNL used a chemical vapor deposition system, in the background, to coat a stainless-steel disc, in the foreground, with carbon nanotubes. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
  • Superlubricity coating could reduce economic losses from friction, wear
    Jun Qu of ORNL shows stainless-steel disks before (silver) and after (black) coating with carbon nanotubes that provide superlubricity. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
  • Superlubricity coating could reduce economic losses from friction, wear
    Chanaka Kumara of ORNL used a chemical vapor deposition system, in the background, to coat a stainless-steel disc, in the foreground, with carbon nanotubes. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
  • Superlubricity coating could reduce economic losses from friction, wear
    Jun Qu of ORNL shows stainless-steel disks before (silver) and after (black) coating with carbon nanotubes that provide superlubricity. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

ORNL's tribology teams have done award-winning work that has attracted industrial partnerships and licensing. In 2014, an ionic anti-wear additive for fuel-efficient engine lubricants, developed by ORNL, General Motors, Shell Global Solutions and Lubrizol, won an R&D 100 award. ORNL's collaborators were Qu, Huimin Luo, Sheng Dai, Peter Blau, Todd Toops, Brian West and Bruce Bunting.

Similarly, the work described in the current paper was a finalist for an R&D 100 award in 2020. The researchers have applied for a patent of their novel superlubricity coating.

"Next, we hope to partner with industry to write a joint proposal to DOE to test, mature and license the technology," Qu said. "In a decade we'd like to see improved high-performance vehicles and power plants with less energy lost to friction and wear."

More information: Chanaka Kumara et al, Macroscale superlubricity by a sacrificial carbon nanotube coating, Materials Today Nano (2022). DOI: 10.1016/j.mtnano.2022.100297

Bearings Can Fail Because There's Not Enough Load! Posted on 16 Mar 11:35

Insufficient load

Bearings need a minimum load to function properly. Inadequate load can be as damaging as excessive load. Damage from insufficient load appears as smearing on the rolling elements and races. This is especially important with cylindrical roller bearings since they are designed for larger loads. 

This Is Your Bearing On Drugs! Posted on 19 Jan 13:37

By: Steve Kroll, Intech Bearing Inc.

This Is Your Bearing On Drugs - Bearing Maintenance Or A Lack Thereof

Have a regular maintenance program for your machines? If not, this can happen:

This was once the center roller bearing in a planetary gear box. The I.D. measures about 100mm, give or take about 30mm.

The shop that this machine was in had fired their previous maintenance manager because, according to them, "They were experiencing too much downtime because of his excessive maintenance of the machines". 

So this is the result of what is called, "deferred maintenance"

So if you want to upgrade your bearings to square rollers, keep on deferring maintenance. It helps OUR business!





A Heat Engine Without Moving Parts-As Efficient as a Steam Turbine? Posted on 20 Jul 13:11

Heat engine cell with no moving parts is as efficient as a steam turbine


A thermophotovoltaic (TPV) cell (size 1 cm x 1 cm) mounted on a heat sink designed to measure the TPV cell efficiency. To measure the efficiency, the cell is exposed to an emitter, and simultaneous measurements of electric power and heat flow through the device are taken. [Credit: Photo by Felice Frankel]

 By Jennifer Chu, MIT

Engineers at MIT and the National Renewable Energy Laboratory (NREL) have designed a heat engine with no moving parts. Their new demonstrations show that it converts heat to electricity with over 40% efficiency -- a performance better than that of the average turbine-based heat engine system efficiency in the United States.

The heat engine is a thermophotovoltaic (TPV) cell, similar to a solar panel's photovoltaic cells, that passively captures high-energy photons from a white-hot heat source and converts them into electricity. The team's design can generate electricity from a heat source of between 1,900 to 2,400 C, or up to about 4,300 F.

The researchers plan to incorporate the TPV cell into a grid-scale thermal battery. The system would absorb excess energy from renewable sources such as the sun and store that energy in heavily insulated banks of hot graphite. When the energy is needed, such as on overcast days, TPV cells would convert the heat into electricity, and dispatch the energy to a power grid.

With the new TPV cell, the team has now successfully demonstrated the main parts of the system in separate, small-scale experiments. They are working to integrate the parts to demonstrate a fully operational system. From there, they hope to scale up the system to replace fossil-fuel-driven power plants and enable a fully decarbonized power grid, supplied entirely by renewable energy.

"Thermophotovoltaic cells were the last key step toward demonstrating that thermal batteries are a viable concept," says Asegun Henry, the Robert N. Noyce Career Development Professor in MIT's Department of Mechanical Engineering. "This is an absolutely critical step on the path to proliferate renewable energy and get to a fully decarbonized grid."

Henry and his collaborators published their results April 13 in the journal Nature.

Jumping the gap
More than 90% of the world's electricity comes from sources of heat such as coal, natural gas, nuclear energy, and concentrated solar energy. For a century, steam turbines have been the industrial standard for converting such heat sources into electricity.

On average, steam turbine systems reliably convert about 35% of a heat source into electricity, with about 60% representing the highest efficiency of any heat engine to date. But the machinery depends on moving parts that are temperature limited. Heat sources higher than 2,000 C, such as Henry's proposed thermal battery system, would be too hot for turbines.

In recent years, scientists have looked into solid-state alternatives -- heat engines with no moving parts that could potentially work efficiently at higher temperatures.

"One of the advantages of solid-state energy converters are that they can operate at higher temperatures with lower maintenance costs because they have no moving parts," Henry says. "They just sit there and reliably generate electricity."

Thermophotovoltaic cells offered one exploratory route toward solid-state heat engines. Much like solar cells, TPV cells could be made from semiconducting materials with a particular bandgap -- the gap between a material's valence band and its conduction band. If a photon with a high enough energy is absorbed by the material, it can kick an electron across the bandgap, where the electron can then conduct, and thereby generate electricity -- doing so without moving rotors or blades.

To date, most TPV cells have only reached efficiencies of around 20%, with the record at 32%, as they have been made of relatively low-bandgap materials that convert lower-temperature, low-energy photons, and therefore convert energy less efficiently.

Catching light
In their new TPV design, Henry and his colleagues looked to capture higher-energy photons from a higher-temperature heat source, thereby converting energy more efficiently. The team's new cell does so with higher-bandgap materials and multiple junctions, or material layers, compared with existing TPV designs.

The cell is fabricated from three main regions: a high-bandgap alloy, which sits over a slightly lower-bandgap alloy, underneath which is a mirror-like layer of gold. The first layer captures a heat source's highest-energy photons and converts them into electricity, while lower-energy photons that pass through the first layer are captured by the second and converted to add to the generated voltage. Any photons that pass through this second layer are then reflected by the mirror, back to the heat source, rather than being absorbed as wasted heat.

The team tested the cell's efficiency by placing it over a heat flux sensor -- a device that directly measures the heat absorbed from the cell. They exposed the cell to a high-temperature lamp and concentrated the light onto the cell. They then varied the bulb's intensity, or temperature, and observed how the cell's power efficiency -- the amount of power it produced, compared with the heat it absorbed -- changed with temperature. Over a range of 1,900 to 2,400 C, the new TPV cell maintained an efficiency of around 40%.

"We can get a high efficiency over a broad range of temperatures relevant for thermal batteries," Henry says.

The cell in the experiments is about one square centimeter. For a grid-scale thermal battery system, Henry envisions the TPV cells would have to scale up to about 10,000 sq ft (about a quarter of a football field), and would operate in climate-controlled warehouses to draw power from huge banks of stored solar energy. He points out that an infrastructure exists for making large-scale photovoltaic cells, which could also be adapted to manufacture TPVs.

"There's definitely a huge net positive here in terms of sustainability," Henry says. "The technology is safe, environmentally benign in its life cycle, and can have a tremendous impact on abating carbon dioxide emissions from electricity production."

This research was supported, in part, by the U.S. Department of Energy.

Published May 2022

GE Aviation's Adaptive Cycle Engine with Ceramic Parts withstands even HIGHER Temps Posted on 30 Nov 11:54

By introducing rotating CMC parts into its hardest-working sections, the GE Adaptive Cycle Engine (ACE) can withstand higher temperatures than ever before..

The three key innovations of the engine combine to deliver new performance capabilities and efficiencies:

  • An adaptive engine cycle that provides both a high-thrust mode for maximum power and a high-efficiency mode for optimum fuel savings and loiter time;
  • A third-stream architecture that provides a step-change in thermal management capability, enabling future mission systems for increased combat effectiveness; and
  • Extensive use of advanced component technologies, including ceramic matrix composites (CMC), polymer matrix composites (PMC), and additive manufacturing.

Coronavirus Is Destroyed On Contact with Copper Surfaces Posted on 4 Apr 12:11

Logo of aem Link to Publisher's site
. 2011 Mar; 77(5): 1541–1547.
Published online 2010 Dec 30. doi: 10.1128/AEM.02766-10
PMCID: PMC3067274
PMID: 21193661

Metallic Copper as an Antimicrobial Surface


Bacteria, yeasts, and viruses are rapidly killed on metallic copper surfaces, and the term “contact killing” has been coined for this process. While the phenomenon was already known in ancient times, it is currently receiving renewed attention. This is due to the potential use of copper as an antibacterial material in health care settings. Contact killing was observed to take place at a rate of at least 7 to 8 logs per hour, and no live microorganisms were generally recovered from copper surfaces after prolonged incubation. The antimicrobial activity of copper and copper alloys is now well established, and copper has recently been registered at the U.S. Environmental Protection Agency as the first solid antimicrobial material. In several clinical studies, copper has been evaluated for use on touch surfaces, such as door handles, bathroom fixtures, or bed rails, in attempts to curb nosocomial infections. In connection to these new applications of copper, it is important to understand the mechanism of contact killing since it may bear on central issues, such as the possibility of the emergence and spread of resistant organisms, cleaning procedures, and questions of material and object engineering. Recent work has shed light on mechanistic aspects of contact killing. These findings will be reviewed here and juxtaposed with the toxicity mechanisms of ionic copper. The merit of copper as a hygienic material in hospitals and related settings will also be discussed.

The use of copper by human civilizations dates back to between the 5th and 6th millennia B.C. It was the first metal used, presumably because it could be found in a native, metallic form which did not require smelting. Its use remained scattered throughout Europe and the Middle East, and the archeological evidence remains scarce. With the invention of smelting, the metallurgic age began and the advantage of combining copper with tin to form bronze was discovered. The earliest bronze artifacts originated from the Middle East and China and date to before 3000 B.C., but it was not until the second millennium B.C. that bronze was used throughout Europe. The ability to smelt and forge iron from about 1000 B.C. marks the end of the Bronze Age and the beginning of the Iron Age.

The oldest recorded medical use of copper is mentioned in the Smith Papyrus, one of the oldest books known (). This Egyptian medical text, written between 2600 and 2200 B.C., describes the application of copper to sterilize chest wounds and drinking water (). Greeks, Romans, Aztecs, and others also used copper or copper compounds for the treatment of such ailments as headaches, burns, intestinal worms, and ear infections and for hygiene in general. In the 19th century, a new awareness of copper's medical potency was spawned by the observation that copper workers appeared to be immune to cholera in the 1832 and subsequent outbreaks in Paris, France (). The use of copper in medicine became widespread in the 19th and early 20th centuries, and a variety of inorganic copper preparations were used to treat chronic adenitis, eczema, impetigo, scrofulosis, tubercular infections, lupus, syphilis, anemia, chorea, and facial neuralgia (). The use of copper as an antimicrobial agent continued until the advent of commercially available antibiotics in 1932. The spread of antibiotic resistance through selective pressure began and today has made antibiotic-resistant bacteria ubiquitous in hospitals, nursing homes, food processing plants, and animal breeding facilities. This has raised the need for different approaches to keep pathogenic microorganisms at bay. One such alternative is the use of copper surfaces in hygiene-sensitive areas. While this approach is not novel (), it had lost importance and acceptance in the last few decades. A 1983 report documenting the beneficial effects of using brass and bronze on doorknobs to prevent the spread of microbes in a hospitals remained largely unnoticed (). Similarly, the idea of using copper vessels to render water drinkable has been revived only very recently as a low-cost alternative for developing countries (). Currently, there is an intense interest in the use of copper as a self-sanitizing material, and many recent publications deal with mechanistic aspects of “contact killing” (contact-mediated killing) by copper.


Copper is an essential trace element in most living organisms, and more than 30 types of copper-containing proteins are known today. Prominent examples are lysyl oxidase, which is involved in the cross-linking of collagen, tyrosinase, required for melanin synthesis, dopamine β-hydroxylase, which functions in the catecholamine pathway, cytochrome c oxidase, the terminal electron acceptor of the respiratory chain, and superoxide dismutase, required for defense against oxidative damage. In these enzymes, copper serves as an electron donor/acceptor by alternating between the redox states Cu(I) and Cu(II) (). Other copper proteins, such as plastocyanins or azurins, act as electron carriers. Depending on the type of coordination of the copper to the protein, the redox potential of copper can vary over the range +200 mV to +800 mV. On the other hand, the redox properties of copper can also cause cellular damage. A number or mechanisms have been suggested. Reactive hydroxyl radicals can be generated in a Fenton-type reaction:

equation M1

The extremely reactive hydroxyl radical can participate in a number of reactions detrimental to cellular molecules, such as the oxidation of proteins and lipids (). Copper ions can also lead to depletion of sulfhydryls, such as in cysteines or glutathione, in a cycle between reactions 2 and 3:

equation M2


equation M3

The hydrogen peroxide thus generated can in turn participate in reaction 1 and lead to further generation of toxic hydroxyl radicals. It is still not clear to what extent reactions 1 to 3 cause copper toxicity. Cells try to keep H2O2 at very low levels, and reaction 1 may not be the chief toxic mechanism, although this has been frequently claimed. An alternative route of copper ion toxicity has been shown to be the displacement of iron from iron-sulfur clusters (). Similarly, copper ions may compete with zinc or other metal ions for important binding sites on proteins. The toxic effect of copper on microbes is utilized in agriculture for the control of bacterial and fungal diseases (), which in fact led to the first thorough investigation of bacterial resistance to copper ions ().

Bacteria evolved a range of mechanisms to protect themselves from the toxic effects of copper ions: extracellular sequestration of copper ions, relative impermeability of the outer and inner bacterial membranes to copper ions, metallothionein-like copper-scavenging proteins in the cytoplasm and periplasm, and active extrusion of copper from the cell. The latter appears to be the chief mechanism of copper tolerance in bacteria and has been extensively studied in Gram-positive and Gram-negative bacteria. In Escherichia coli, the CopA copper-transporting ATPase resides in the cytoplasmic membrane and pumps excess Cu(I) from the cytoplasm to the periplasm (). In the periplasmic space, the multicomponent copper efflux system CusCFBA and the multicopper oxidase CueO control the copper level and redox state, respectively. In addition to these chromosomally encoded systems, E. coli strains can harbor related, plasmid-encoded systems which further increase copper tolerance (). All the components of this copper detoxification machinery are transcriptionally upregulated by copper via two regulatory circuits. In Gram-positive bacteria, which are devoid of a periplasmic space and an outer membrane, only CopA-type copper exporters are present and a single regulatory circuit usually controls their expression (, ). A number of other components, like copper-binding proteins, copper reductases, etc., support these basic defense systems against copper and have been described elsewhere (, , , ).

In contrast to copper defense, copper utilization by bacteria is much less well understood. In Synechocystis, it appears that a special copper uptake ATPase serves in supplying copper to the photosynthetic components in the thylakoid membranes (). On the other hand, methanotrophic bacteria that require copper for particulate methane monooxygenase secrete siderophore-like substances, the methanobactins, to scavenge extracellular copper (). In Gram-negative bacteria, like E. coli, it is believed that the metalation of cuproenzymes takes place in the periplasmic space and does not require special copper uptake systems across the cytoplasmic membrane. Finally, many novel proteins of unknown function which are regulated by copper have been identified in the Gram-positive organism Lactococcus lactis (), and further efforts will be required for an in-depth understanding of copper handling by bacteria.


The study of the antimicrobial properties of metallic copper surfaces is a relatively recent development and gained momentum when the Environmental Protection Agency (EPA) registered almost 300 different copper surfaces as antimicrobial in 2008 ( Prior to that, a number of studies have already dealt with the kinetics of contact killing upon exposure of bacteria to copper and copper alloy surfaces (, , , , ). Table Table11 summarizes the species tested, test procedures, and killing kinetics. In general, microbes were inactivated on copper within hours, but such parameters as the inoculation technique, incubation temperature, and copper content of the alloy used were not usually investigated in a systematic way and are difficult to compare between studies. Nevertheless, a few general principles appear clear: higher copper content of alloys (), higher temperature (), and higher relative humidity () increased the efficacy of contact killing. Treatments that lowered corrosion rates, e.g., application of corrosion inhibitors or a thick copper oxide layer, lowered the antimicrobial effectiveness of copper surfaces ().


Contact killing of microbes by copper surfaces

Species Application method Killing time, RTa Reference
Salmonella enterica Wet, 4.5 × 106 CFUb 4 h
Campylobacter jejuni Wet, 4.5 × 106 CFUb 8 h
Escherichia coli O157 Wet, (3-4) × 107 CFUc 65 min
Escherichia coli O157 Wet, 2.7 × 107 CFUc 75 min
MRSAd (NCTC10442) Wet, (1-1.9) × 107 CFUc 45 min
EMRSA-1e (NCTC11939) Wet, (1-1.9) × 107 CFUc 60 min
EMRSA-16e (NCTC13143) Wet, (1-1.9) × 105 CFUc 90 min
Listeria monocytogenes Scott A Wet, 107 CFUc 60 min
Mycobacterium tuberculosis Wet, 2.5 × 107 CFUf 5 to 15 daysg
Candida albicans Wet, >105 CFUf 60 min
Klebsiella pneumoniae Wet, >107 CFUf 60 min
Pseudomonas aeruginosa Wet, >107 CFUf 180 min
Acinetobacter baumannii Wet, >107 CFUf 180 min
MRSA Wet, >107 CFUf 180 min
Influenza A virus (H1N1) Wet, 5 × 105 virusesh 6 h, 4-log decrease
C. difficile (ATCC 9689) vegetative cells and spores Wet, 2.2 × 105 CFUc 24-48 h
C. difficile NCTC11204/R20291 vegetative cells Wet, (1-5) × 106 CFUi 30 min
C. difficile dormant spores Wet, 8 × 106 CFUi Unaffected in 3 h
C. difficile germinating spores Wet, 8 × 106 CFUi 3 h, 3-log decrease
Pseudomonas aeruginosa PAO1 Wet, 2.2 × 107 CFUj 120 min
MRSA NCTC 10442 Wet, 2 × 107 CFU 75 min, 7 log decrease
Escherichia coli W3110 Dry, 109 CFUi 1 min
Acinetobacter johnsonii DSM6963 Dry, 109 CFUk A few minutes
Pantoea stewartii DSM30176 Dry, 109 CFUi 1 min
Pseudomonas oleovorans DSM 1045 Dry, 109 CFUk 1 min
Staphylococcus warnerii DSM20316 Dry, 109 CFUk A few minutes
Brachybacterium conglomeratum DSM 10241 Dry, 109 CFUk A few minutes
Aspergillus flavus Wet, (2-300) × 105 sporesc 120 h
Aspergillus fumigatus Wet, (2-300) × 105 sporesc >120 h
Aspergillus niger Wet, (2-300) × 105 sporesc > 576 h
Fusarium culmonium Wet, (2-300) × 105 sporesc 24 h
Fusarium oxysporum Wet, (2-300) × 105 sporesc 24 h
Fusarium solani Wet, (2-300) × 105 sporesc 24 h
Penicillium crysogenum Wet, (2-300) × 105 sporesc 24 h
Candida albicans Wet, (2-300) × 105 sporesc 24 h
Enterococcus hirae ATCC 9790 Wet, 107 CFUc 90 min
Different Enterococcus spp. Wet, 106 CFUf 60 min
Candida albicans Dry, 106 CFUk 5 min
Saccharomyces cerevisiae Dry, 106 CFUk 30 s
aRT, room temperature; only the values for the most efficient alloy are reported.
bInoculation with 1.5 ml of culture (4.5 × 106 CFU), kept under humid conditions.
cInoculation with a 20-μl drop of culture.
dMethicillin-resistant Staphylococcus aureus.
eEpidemic methicillin-resistant Staphylococcus aureus.
fTwenty microliters of culture spread on coupons.
gTime before strain became culture positive in Bactec 12B growth medium after exposure to copper.
hInoculation with 20 μl of virion suspension.
iOne hundred microliters of dilute culture.
jTwenty-five microliters of culture spread on coupons with a glass spreader.
kThin film applied with a cotton swab.

In most studies on contact killing, a “wet” inoculation technique was used by applying typically 20 μl of cell suspensions to coupons. While this is a valid approach for laboratory testing, it might not mimic well the dry copper surfaces encountered in health care environments. In an alternative “dry” method, a small volume of liquid is applied to coupons with a cotton swab. The thin film of liquid evaporates within seconds and allows direct contact of all cells with the metal surface. Under these conditions, E. coli and other bacteria were inactivated within a few minutes of exposure (-). This suggests that dry metallic copper surfaces are even more antimicrobial than moist ones, which raises interesting questions about the mechanism of contact killing.

Certain Gram-positive bacteria, such as members of the Bacilli and Clostridia, form endospores which can resist heat, radiation, desiccation, denaturing chemicals, etc. Thus, endospores pose a real challenge to aseptic procedures. Clostridium difficile is an important pathogen of the group of spore-forming bacteria and leads to diseases like diarrhea and colitis. Excretion of endospores by infected persons might contaminate surfaces and generate a long-term reservoir for transmission. In spite of the robustness of these spores, killing by metallic copper has been reported in some cases. In one study, viable spores were found to be diminished by 99.8% in 3 h on solid copper (), while complete inactivation of spores in 24 to 48 h was reported in a second study (). Clearly, endospores are more resilient to contact killing by copper than vegetative cells, but killing may still occur and thus warrant the strategic use of copper to curb spreading of C. difficile.

What is the mechanism of contact killing? This question cannot yet be answered clearly, but a number of factors contributing to contact killing have been identified. In wet inoculation of copper surfaces with bacteria, the copper homeostatic systems of the cell appear to play a role. Pseudomonas aeruginosa PAO1 deleted in the cinR gene, encoding a copper-responsive regulator, or the cinA gene, encoding an azurin-like protein involved in copper resistance, was more rapidly killed on copper surfaces than the wild type (). Similarly, an Enterococcus hirae mutant deleted in the gene for the copper export pump, copB, was killed after 75 min, while complete inactivation of the wild type took 90 min. In E. coli, finally, deletion of three systems, cueO (encoding periplasmic copper oxidase), cus (encoding a periplasmic copper efflux system), and copA (encoding a cytoplasmic copper extrusion pump), led to faster killing kinetics than for the wild type, preincubated with copper to express the copper-homeostatic genes (, ). Preincubation with copper also increased the killing time of E. coli carrying the plasmid-borne pco copper resistance system (). Clearly, bacterial copper resistance systems do not offer protection from contact killing, but they do prolong survival. This suggests the involvement of dissolved copper ions in the killing process (Fig. (Fig.1).1). This is further supported by the effect of medium composition on contact killing. Application of the cells to copper surfaces in Tris buffer dramatically enhanced contact killing, and much more copper was dissolved by Tris buffer than by water or phosphate buffer (). Although spent medium dissolved as much copper as Tris buffer, this copper was probably tightly bound to media components and not bioavailable and thus did not accelerate contact killing. For E. coli, it was shown that copper chelators protected cells from contact killing (). All these observations support a role of surface-released free copper ions in contact killing, but they are clearly not the sole determinant of the process.

Cartoon of the tentative events in contact killing. (A) Copper dissolves from the copper surface and causes cell damage. (B) The cell membrane ruptures because of copper and other stress phenomena, leading to loss of membrane potential and cytoplasmic content. (C) Copper ions induce the generation of reactive oxygen species, which cause further cell damage. (D) Genomic and plasmid DNA becomes degraded.

Recent studies showed that large amounts of copper ions were taken up by E. coli over 90 min, when cells were applied to copper coupons in a standing drop. When cells were plated on copper by the dry method, the accumulation of copper ions by cells was even more dramatic, reaching a low molar concentration, or 27-fold the level observed by wet plating, in a fraction of the time. The copper ion level of cells remained high throughout the killing phase, suggesting that cells become overwhelmed by their intracellular copper (). Another factor that influences cell survival on metallic copper is oxidative stress. Generation of reactive oxygen species (ROS) is probably mediated by redox cycling between the different copper species, Cu(0), Cu(I), and Cu(II). The absence of oxygen did not inhibit contact killing of E. coli but doubled the time required for complete killing of 109 cells from 1 to 2 min in the dry plating method (). This indicates that stress caused by reactive oxygen species is another factor contributing to contact killing.

The fate of DNA during contact killing by copper has also been investigated. According to one study, DNA is a major target of copper toxicity, leading to rapid DNA fragmentation and cell death (). This contrasts with recent findings by Espirito Santo et al., which suggest that the primary damage to cells in contact killing is membrane damage (). It is likely that DNA damage ensues only as a secondary event following cell death. It could be shown that membrane damage by copper was not accompanied by an increase in the mutation rate or DNA fragmentation. Deinococcus radiodurans is a bacterium that is exceptionally resistant to ionizing radiation because of its ability to repair even highly fragmented DNA. Remarkably, D. radiodurans was as sensitive as E. coli to contact killing by copper (). At the current state of knowledge, it appears that contact killing proceeds by successive membrane damage, copper influx into the cells, oxidative damage, cell death, and DNA degradation (cf. Fig. Fig.1).1). Clearly, this sequence of events is still tentative, and further work on contact killing is required to offer more-detailed molecular insight into the process.

How soiling, cleaning, exposure to chemicals, and tarnishing affect the antimicrobial properties of copper has not yet been studied in detail. In a study where copper surfaces were inoculated with bacteria in 1% solutions of albumin, dried, and subsequently cleaned with 70% ethanol or 1% sodium hypochlorite, there was a build-up of residues and a concomitant decrease in killing efficiency (). On the other hand, it was reported that copper surfaces remained active when soiled (). Also, it was found that there was no reduction in killing efficiency over 30 cycles of bacterial inoculation, followed by cleaning with a 1% nonionic detergent solution (M. Solioz and C. Molteni, unpublished observations). From what is known about the mechanism of contact killing, it appears clear that a clean copper surface, free of oxide, wax, or other coating agents, will always be active in contact killing. A future task will be to establish reproducible protocols for cleaning copper surfaces such that they maintain maximal efficacy in contact killing.


Touch surfaces commonly found in hospitals, such as door handles, touch plates, bed rails, call buttons, toilet seats, etc., can be highly contaminated with microbes. It was shown that germs such as Staphylococcus aureus and Acinetobacter spp. can persist on such surfaces for months (). Frequent and efficient cleaning, combined with proper hand hygiene, diminishes transmission of infections, but complete elimination appears impossible (). With the worldwide spread of such antibiotic-resistant organisms as methicillin-resistant S. aureus (MRSA) or more recently New Delhi metallo-beta-lactamase (NDM)-harboring strains, dangerous nosocomial infections have become a primary concern for hospitals. It can be approximated that in 2006 there were about 720,000 hospital-acquired infections in the United States, causing $125 billion in extra hospital charges and more than 74,000 fatalities (database on hospital-acquired infections in Pennsylvania []). These numbers emphasize the need for new approaches to hospital hygiene, and antimicrobial copper promises to provide one such approach to supplement the current hygiene measures.

Stainless steel is the metal predominantly used in health care environments because of its “clean” appearance and corrosion resistance. However, there is no inherent antimicrobial advantage to using this metal (). Copper surfaces, with their self-sanitizing properties, could be envisioned as making an important contribution to infection control. Thus, the use of antimicrobial metallic copper surfaces is likely to provide protection from infectious microbes by reducing surface contamination, as was recently shown in successful hospital trials. Hospital trials are now ongoing worldwide, and the first results have been reported (, , ).

The 10-week Selly Oak Hospital trial in Birmingham, United Kingdom, was carried out with both copper and control surfaces in the same ward. This approach was chosen to decrease potential bias in the microbial challenge to copper and control surfaces (). In addition, after 5 weeks, the copper-containing and non-copper-containing surfaces and items were interchanged to further diminish bias. Bacterial contamination of a copper-coated (70% Cu) composite toilet seat, brass tap handles (60% Cu), and a brass door push plate (70% Cu) was compared against that of equivalent items with plastic, chrome-plated, or aluminum surfaces. Median numbers of bacteria recovered from surfaces of copper-containing items were between 90% and 100% lower than those from control surfaces. While MRSA and C. difficile were not isolated in this study, methicillin-sensitive S. aureus (MSSA), vancomycin-resistant Enterococcus (VRE), and E. coli were found only on control surfaces but not on copper surfaces.

It is noteworthy that in contrast to laboratory studies, in which unused copper surfaces are usually tested, this hospital trial employed “aged” surfaces. The items to be tested were installed at least 6 months prior to commencement of the study. This also allowed domestic staff and health care workers to become accustomed to the copper-containing fixtures. In addition, it provides support for the notion that copper surfaces will not lose their antimicrobial activity over time. Nevertheless, long-term studies are still required to evaluate the sustainability of the antimicrobial properties of copper surfaces over the course of several years.

A second hospital trial was contracted at a walk-in primary health care clinic in Grabouw, a rural region of the Western Cape, South Africa (). Here, a consulting room rather than a medical ward was refitted with copper surfaces. In this room, items in frequent contact with patients and staff, such as desks, trolleys, the top of a cupboard, and windowsills, were covered with copper sheets. During 6 months, surfaces were sampled every 6 weeks for a 4.5-day period, with multiple samplings per day. An overall 71% reduction in the bacterial load of the copper surfaces was observed compared to that of the control surfaces, with significantly lower mean total colony counts during working days and overnight (). Interestingly, comparable numbers of bacteria were counted when surfaces remained untouched over the weekends (71 h), but this phenomenon was not investigated further.

Finally, in the German trial at the Asklepios Hospital, Hamburg, touch surfaces in patient bed rooms, rest rooms, and staff rooms in an oncological/pneumological and a geriatric ward were refitted with brass (a copper/zinc alloy). Control rooms retained aluminum door handles and push plates and plastic light switches (). The total duration of this trial was 32 weeks, equally divided into summer and winter months. The number of aerobic, heterotrophic bacteria on these surfaces was determined once or twice per week. The presence of ciprofloxacin-resistant Staphylococcus (CRS) as an indicator organism for multiple-drug-resistant nosocomial pathogens was determined. Following sampling each morning, all surfaces were cleaned with a disinfectant. Additional samples were taken immediately after cleaning and 3, 6, and 9 h later. Over both halves of the trial, there was an average 63% reduction in the bacterial load on copper surfaces compared to controls. Results were significant for door handles, which had the highest overall microbial load. Bacterial numbers recovered from copper and plastic light switches were similar. No significant differences in the survival of CRS on copper and noncopper surfaces were observed, but on average cell numbers from copper were lower. Interestingly, the repopulation of surfaces by microbes occurred at different rates. For copper surfaces, the average rate of repopulation was less than half of that for the control surfaces, documenting the antibacterial properties of copper surfaces.

Results are still awaited from trials at the Memorial Sloan-Kettering Cancer Center in New York City, NY, the Medical University of South Carolina in Charleston, SC, the Ralph H. Johnson VA Medical Center in Charleston, the Hospital del Cobre de Calama in Chile, and the Kitasato University Hospital in Japan. In the hospitals trials described so far, only heterotrophic, aerobic bacteria were assessed. It would be interesting to conduct similar trials in which anaerobic bacteria, including endospore formers and eukaryotic microbes, are also evaluated, since these microbes pose their own unique challenges.


The antimicrobial properties of copper surfaces have now been firmly established. Hospital trials have shown a reduction in bacterial counts, indicating that copper surfaces are a promising additional tool alongside other hygienic measures to curb the number and severity of hospital-acquired infections. At this point, additional studies would be helpful in determining the most cost-effective way to give maximal protection in hospitals. For example, should only highly frequented sites be made of copper, e.g., doorknobs, faucets, and bed rails, or should the majority of accessible surfaces be made of copper? In addition, different copper alloys should be tested not only for their effectiveness but also for their esthetic appeal. Finally, the antimicrobial properties of copper surfaces must be integrated with other methods of disinfection and the overall hygiene concept of a health care facility. Additional measures, such as the addition of spore germinants to cleaning solutions to improve killing of spores, also deserve further investigation.

Bacterial resistance is a major concern in infection control. Are there bacteria which are naturally refractory to contact killing by copper? It is known that live bacteria can be isolated from copper-containing surfaces, and in a recent study, 294 isolates from European 50-cent coins were investigated in regard to copper resistance. Some of the isolates indeed exhibited prolonged (1 to 3 days) survival on dry but not on moist copper surfaces, but none of the strains was exceptionally copper resistant in culture (). Survival on copper-containing coins appeared to be the consequence of either endospore formation, survival on patches of dirt, or a special ability to endure a dry metallic copper surface. While the latter, rare property is not yet understood, widespread appearance of bacterial resistant to contact killing appears unlikely for the following reasons: (i) plasmid DNA is completely degraded after cell death by contact killing, preventing the transfer of resistance determinants between organisms (), (ii) contact killing is very rapid, and cells are not dividing on copper surfaces, precluding the acquisition of resistance, and (iii) copper and copper alloys have been used by humans for thousands of years, yet no bacteria fully resistant to contact killing have been discovered.


Financial support from the Swiss National Foundation (grant 3100A0_122551 to M.S.), pilot NIH grant P20 RR-017675 from the National Center for Research Resources (to G.G.), National Institutes of Health grant GM079192 (to C.R.), grants from the International Copper Association to G.G., C.R., and M.S., and a grant from the Swiss State Secretary for Education & Research (to M.S.) are greatly appreciated. Equipment in the lab of G.G. was purchased with Nebraska Tobacco Settlement Biomedical Research Development Funds.

The contents of this work are solely the responsibility of the authors and do not necessarily represent the official views of the NIH.


An external file that holds a picture, illustration, etc.
Object name is zam9991018500002.jpgGregor Grass is Assistant Professor of Microbiology, University of Nebraska—Lincoln. After reunification of his home country, Dr. Grass studied biology at the Martin-Luther Universität Halle-Wittenberg (MLU) in Halle, former East Germany, and completed his Ph.D. in microbiology at MLU with Dietrich H. Nies in 2000 on the highly metal-resistant, ever name-changing bacterium better known as strain CH34. He then worked as a postdoctoral Fellow with Chris Rensing in Tucson, AZ, on metal homeostasis of E. coli. In 2002, he became an independent group leader at MLU, and in 2008, he accepted a position as Assistant Professor at the University of Nebraska—Lincoln. For the last 14 years, Dr. Grass's research interests have centered on the molecular mechanisms of how bacteria acquire essential transition metals from their environments and the cellular systems involved in detoxification of excess trace element cations. Recently, his research focused on the antimicrobial mode of action of metallic copper surfaces.

An external file that holds a picture, illustration, etc.
Object name is zam9991018500003.jpgChristopher Rensing is Associate Professor of Microbiology, University of Arizona. Dr. Rensing was born in Princeton, NJ, but grew up mainly in Germany. He studied and obtained his Ph.D. at the Freie Universität Berlin and later Martin-Luther Universität Halle-Wittenberg in 1996. His Ph.D. with Dietrich H. Nies sought to gain a better understanding of how Cupriavidus metallidurans CH34 can survive under extremely high concentrations of heavy metals. As a postdoc, he then joined Barry Rosen's lab at Wayne State University in Detroit, MI, working mainly on the biochemical characterization of two metal-transporting P-type ATPases, ZntA and CopA. In 1999 he joined the University of Arizona, and in 2007 he was promoted to Associate Professor. His research is looking at different aspects of metal-microbe interactions, encompassing both environmental and medical microbiology.

An external file that holds a picture, illustration, etc.
Object name is zam9991018500004.jpgMarc Solioz is Professor of Biochemistry, University of Bern. A native of Zurich, Switzerland, Dr. Solioz studied chemistry and engineering in Zurich. He then moved to the United States, where he obtained his Ph.D. in biochemistry at St. Louis University in 1975. The Ph.D. work focused on genetic transfer between photosynthetic bacteria. During postdoctoral studies at the University of Basel with Gottfried Schatz, he investigated the biogenesis of mitochondria and the role of the mitochondrial genome. This was followed by several years as an Assistant/Associate Professor at the Federal Institute of Technology in Zurich (ETH), where he investigated membrane proteins and ion transport by cytochrome oxidases and ATPases. In 1989 he became Professor of Biochemistry at the University of Bern. With the discovery of the first copper-pumping ATPase in 1992, Dr. Solioz's focus shifted to copper, which has remained the subject of his studies to this day.


Published ahead of print on 30 December 2010.


1. Airey, P., and J. Verran. 2007. Potential use of copper as a hygienic surface; problems associated with cumulative soiling and cleaning. J. Hosp. Infect. 67:272-278. [PubMed] []
2. Balasubramanian, R., and A. C. Rosenzweig. 2008. Copper methanobactin: a molecule whose time has come. Curr. Opin. Chem. Biol. 12:245-249. [PMC free article] [PubMed] []
3. Casey, A. L., et al. 2010. Role of copper in reducing hospital environment contamination. J. Hosp. Infect. 74:72-77. [PubMed] []
4. Cha, J. S., and D. A. Cooksey. 1991. Copper resistance in Pseudomonas syringae mediated by periplasmic and outer membrane proteins. Proc. Natl. Acad. Sci. U. S. A. 88:8915-8919. [PMC free article] [PubMed] []
5. Cooksey, D. A. 1994. Molecular mechanisms of copper resistance and accumulation in bacteria. FEMS Microbiol. Rev. 14:381-386. [PubMed] []
6. Dancer, S. J. 2008. Importance of the environment in meticillin-resistant Staphylococcus aureus acquisition: the case for hospital cleaning. Lancet Infect. Dis. 8:101-113. [PubMed] []
7. Dick, R. J., J. A. Wray, and H. N. Johnston. 1973. A literature and technology search on the bacteriostatic and sanitizing properties of copper and copper alloy surfaces. Battelle Columbus Laboratories, Columbus, OH.
8. Dollwet, H. H. A., and J. R. J. Sorenson. 1985. Historic uses of copper compounds in medicine. Trace Elem. Med. 2:80-87. []
9. Elguindi, J., et al. Metallic copper corrosion rates, moisture content, and growth medium influence survival of copper-resistant bacteria. Appl. Microbiol. Biotechnol., in press. [PMC free article] [PubMed]
10. Elguindi, J., J. Wagner, and C. Rensing. 2009. Genes involved in copper resistance influence survival of Pseudomonas aeruginosa on copper surfaces. J. Appl. Microbiol. 106:1448-1455. [PMC free article] [PubMed] []
11. Espirito Santo, C., et al. 2011. Bacterial killing by dry metallic copper surfaces. Appl. Environ. Microbiol. 77:794-802. [PMC free article] [PubMed]
12. Espirito Santo, C., P. V. Morais, and G. Grass. 2010. Isolation and characterization of bacteria resistant to metallic copper surfaces. Appl. Environ. Microbiol. 76:1341-1348. [PMC free article] [PubMed] []
13. Espirito Santo, C., N. Taudte, D. H. Nies, and G. Grass. 2008. Contribution of copper ion resistance to survival of Escherichia coli on metallic copper surfaces. Appl. Environ. Microbiol. 74:977-986. [PMC free article] [PubMed] []
14. Faundez, G., M. Troncoso, P. Navarrete, and G. Figueroa. 2004. Antimicrobial activity of copper surfaces against suspensions of Salmonella enterica and Campylobacter jejuni. BMC Microbiol. 4:19. [PMC free article] [PubMed] []
15. Karlin, K. D. 1993. Metalloenzymes, structural motifs, and inorganic models. Science 261:701-708. [PubMed] []
16. Kim, E. H., C. Rensing, and M. M. McEvoy. 2010. Chaperone-mediated copper handling in the periplasm. Nat. Prod. Rep. 27:711-719. [PubMed] []
17. Kramer, A., I. Schwebke, and G. Kampf. 2006. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infect. Dis. 6:130-138. [PMC free article] [PubMed] []
18. Kuhn, P. J. 1983. Doorknobs: a source of nosocomial infection? Copper Development Association, New York, NY.
19. Kusumaningrum, H. D., G. Riboldi, W. C. Hazeleger, and R. R. Beumer. 2003. Survival of foodborne pathogens on stainless steel surfaces and cross-contamination to foods. Int. J. Food Microbiol. 85:227-236. [PubMed] []
20. Macomber, L., and J. A. Imlay. 2009. The iron-sulfur clusters of dehydratases are primary intracellular targets of copper toxicity. Proc. Natl. Acad. Sci. U. S. A. 106:8344-8349. [PMC free article] [PubMed] []
21. Magnani, D., O. Barré, S. D. Gerber, and M. Solioz. 2008. Characterization of the CopR regulon of Lactococcus lactis IL1403. J. Bacteriol. 190:536-545. [PMC free article] [PubMed] []
22. Magnani, D., and M. Solioz. 2007. How bacteria handle copper, p. 259-285. In D. H. Nies and S. Silver (ed.), Molecular microbiology of heavy metals. Springer, Heidelberg, Germany.
23. Marais, F., S. Mehtar, and L. Chalkley. 2010. Antimicrobial efficacy of copper touch surfaces in reducing environmental bioburden in a South African community healthcare facility. J. Hosp. Infect. 74:80-82. [PubMed] []
24. Mehtar, S., I. Wiid, and S. D. Todorov. 2008. The antimicrobial activity of copper and copper alloys against nosocomial pathogens and Mycobacterium tuberculosis isolated from healthcare facilities in the Western Cape: an in-vitro study. J. Hosp. Infect. 68:45-51. [PubMed] []
25. Michels, H. T., J. O. Noyce, and C. W. Keevil. 2009. Effects of temperature and humidity on the efficacy of methicillin-resistant Staphylococcus aureus challenged antimicrobial materials containing silver and copper. Lett. Appl. Microbiol. 49:191-195. [PMC free article] [PubMed] []
26. Mikolay, A., et al. 2010. Survival of bacteria on metallic copper surfaces in a hospital trial. Appl. Microbiol. Biotechnol. 87:1875-1879. [PubMed] []
27. Molteni, C., H. K. Abicht, and M. Solioz. 2010. Killing of bacteria by copper surfaces involves dissolved copper. Appl. Environ. Microbiol. 76:4099-4101. [PMC free article] [PubMed] []
28. Noyce, J. O., H. Michels, and C. W. Keevil. 2006. Potential use of copper surfaces to reduce survival of epidemic meticillin-resistant Staphylococcus aureus in the healthcare environment. J. Hosp. Infect. 63:289-297. [PubMed] []
29. Noyce, J. O., H. Michels, and C. W. Keevil. 2006. Use of copper cast alloys to control Escherichia coli O157 cross-contamination during food processing. Appl. Environ. Microbiol. 72:4239-4244. [PMC free article] [PubMed] []
30. Noyce, J. O., H. Michels, and C. W. Keevil. 2007. Inactivation of influenza A virus on copper versus stainless steel surfaces. Appl. Environ. Microbiol. 73:2748-2750. [PMC free article] [PubMed] []
31. Quaranta, D., et al. 2011. Mechanisms of contact-mediated killing of yeast cells on dry metallic copper surfaces. Appl. Environ. Microbiol. 77:416-426. [PMC free article] [PubMed] []
32. Rensing, C., and G. Grass. 2003. Escherichia coli mechanisms of copper homeostasis in a changing environment. FEMS Microbiol. Rev. 27:197-213. [PubMed] []
33. Rouch, D., J. Camakaris, B. T. Lee, and R. K. Luke. 1985. Inducible plasmid-mediated copper resistance in Escherichia coli. J. Gen. Microbiol. 131:939-943. [PubMed] []
34. Solioz, M., H. K. Abicht, M. Mermod, and S. Mancini. 2010. Response of Gram-positive bacteria to copper stress. J. Biol. Inorg. Chem. 15:3-14. [PubMed] []
35. Solioz, M., S. Mancini, H. K. Abicht, and M. Mermod. The lactic acid bacteria response to metal stress. In K. Papadimitriou and E. Tsakalidou (ed.), Stress response of lactic acid bacteria, in press. Springer, Heidelberg, Germany.
36. Solioz, M., and J. V. Stoyanov. 2003. Copper homeostasis in Enterococcus hirae. FEMS Microbiol. Rev. 27:183-195. [PubMed] []
37. Sudha, V. B. P., K. O. Singh, S. R. Prasad, and P. Venkatasubramanian. 2009. Killing of enteric bacteria in drinking water by a copper device for use in the home: laboratory evidence. Transact. R. Soc. Trop. Med. Hyg. 103:819-822. [PubMed] []
38. Tottey, S., P. R. Rich, S. A. Rondet, and N. J. Robinson. 2001. Two Menkes-type ATPases supply copper for photosynthesis in Synechocystis PCC 6803. J. Biol. Chem. 276:19999-20004. [PubMed] []
39. Warnes, S. L., S. M. Green, H. T. Michels, and C. W. Keevil. 2010. Biocidal efficacy of copper alloys against pathogenic enterococci involves degradation of genomic and plasmid DNA. Appl. Environ. Microbiol. 76:5390-5401. [PMC free article] [PubMed] []
40. Weaver, L., H. T. Michels, and C. W. Keevil. 2008. Survival of Clostridium difficile on copper and steel: futuristic options for hospital hygiene. J. Hosp. Infect. 68:145-151. [PubMed] []
41. Weaver, L., H. T. Michels, and C. W. Keevil. 2010. Potential for preventing spread of fungi in air-conditioning systems constructed using copper instead of aluminium. Lett. Appl. Microbiol. 50:18-23. [PubMed] []
42. Wheeldon, L. J., et al. 2008. Antimicrobial efficacy of copper surfaces against spores and vegetative cells of Clostridium difficile: the germination theory. J. Antimicrob. Chemother. 62:522-525. [PubMed] []
43. Wilks, S. A., H. Michels, and C. W. Keevil. 2005. The survival of Escherichia coli O157 on a range of metal surfaces. Int. J. Food Microbiol. 105:445-454. [PubMed] []
44. Wilks, S. A., H. T. Michels, and C. W. Keevil. 2006. Survival of Listeria monocytogenes Scott A on metal surfaces: implications for cross-contamination. Int. J. Food Microbiol. 111:93-98. [PubMed] []
45. Yoshida, Y., S. Furuta, and E. Niki. 1993. Effects of metal chelating agents on the oxidation of lipids induced by copper and iron. Biochim. Biophys. Acta 1210:81-88. [PubMed] []

Articles from Applied and Environmental Microbiology are provided here courtesy of American Society for Microbiology (ASM)

Understanding Friction Posted on 1 Aug 11:04

Understanding Friction. On a molecular scale, almost all surfaces are rough.

The Largest Non-Nuclear Explosion in US History Posted on 17 Apr 14:17

Anniversary of the largest non-nuclear explosion in US history in Texas City Texas

One Way Friction Sticky Posted on 10 Apr 12:47

One Way Friction Created

Self Healing Composite Materials Posted on 6 Mar 14:37

Researchers from EPFL's Laboratory for Processing of Advanced Composites have developed a material that can easily heal after being damaged. This cutting-edge composite could be used in aircraft, wind turbines, cars and sports equipment.

When a wind turbine blade or an airplane is hit by something, the damaged part has to be either replaced or patched with resin. Replacing the part is expensive, while repairing it with resin can make it heavier and change its properties. But now, thanks to a new, patented technology, researchers at EPFL have found a way to quickly and easily repair cracks in composite structures.

"With our technology, a repair agent is incorporated in the composite material," says Amaël Cohades, a researcher at EPFL's Laboratory for Processing of Advanced Composites(LPAC). Cracks in the resin can be repaired on site in little time by simply heating the material to 150°C. The heating process activates the repair agent, and the damaged part quickly heals, without any change to the original properties. This new-to-the-market technology can be applied to all sorts of structures, extending their lifespan at least threefold. The material’s properties and initial crack resistance are the same as those of traditional composites. What’s more, the technology is compatible with current manufacturing processes, so production facilities do not need to be retooled.

This technology could be particularly useful for wind turbines and storage tanks. "The cost of maintaining the world's wind turbines alone is estimated at 13 billion Swiss francs in 2020," says Cohades. He says the technology could also be applied to "many parts that we don't bother to repair at present, like bikes and car bumpers." One limitation is that the material doesn't heal if the impact breaks the fibers. But since the resin is always damaged first, this heat-based self-healing system would still work in the majority of cases.

A prototype on display at the World Composites Show

Thanks to an EPFL enable grant, designed to help EPFL scientists move their ideas out of the lab, the researchers were able to create a standard aerospace prototype. This part, made from fiberglass-reinforced resin, demonstrates how the healing process works. It will be presented at the JEC World Composites Show in Paris from 12 to 14 March 2019. In addition, the researchers are now setting up a startup to market the new materials.

For more information:

Author: Sarah Aubort
Source: Mediacom


Sold Out

Liquid error (layout/theme line 344): Could not find asset snippets/wholesale-now.liquid