Silver Membrane Filters Play a Part in Antimatter Trapping

If you fastidiously watch “Through the Wormhole” like I do, chances are you’ll find this application for silver membrane filters fascinating – they’re being used to assist in the collection of antimatter! Now if your main reference for antimatter is a certain Dan Brown novel, you should know that separating and collecting antimatter is a much, much more difficult process than the entertainment industry would have you believe. In fact, “If you take all the antimatter produced in the history of the world and annihilated it all at once, you wouldn't have enough energy to boil a pot of tea,” according to Harvard physicist Gerald Gabrielse. Professor Gabrielse is a leader in antimatter trapping methodology and a co-author of the paper Pumped Helium System for Cooling Positron and Electron Traps to 1.2 K, which details how our filters are used to trap antimatter.

Antimatter is composed of the exact opposite particles (particles of the same mass but opposite electrical charges) as its traditional counterpart. So whereas a hydrogen atom is made of one electron and one proton, an antihydrogen atom (called H-Bar) is comprised of a positron and an antiproton. When antimatter comes into contact with matter, even air, both particles annihilate and release energy in the form of photons (light particles) and/or radiation. Because of the extreme instability of antimatter, one of the major challenges with studying it is gathering enough of the material in a lab. To store any amount of antimatter requires an extremely powerful vacuum to prevent it from coming into any contact with matter. To this end, scientists are experimenting with all manner of “traps” in order to separate and analyze the antimatter.

It is one of these traps that pure silver membranes have found a role in the antimatter collection process. The paper referenced above explains how in order to collect antihydrogen the scientists must cool the trap apparatus to temperatures close to absolute zero. To cool the apparatus to such an extreme degree the scientists here use liquid helium (which is about -269°C), this is also where the silver filters come into play. In order to remove any impurities that could cause clogging in the apparatus, the liquid helium is twice filtered through silver filters, first through a 5 micron filter and then a 3 micron filter before continuing through the pumping system.

A popular misconception about antimatter is that it has potential as an alternative energy source. On his website Professor Gabrielse points out that “No antimatter energy source will ever be possible since it takes much more energy to make antimatter than can ever be recovered from antimatter annihilation…Our motivation for trapping antimatter is to study is basic properties and to compare them with the properties of ordinary hydrogen atoms.” So while this research isn’t going to solve our energy problems, it could help physicists answer some of the biggest mysteries regarding the makeup of the universe.

That last part would sound better coming from Morgan Freeman…

Visit here to find the full paper.

To learn more about antimatter trapping, including separating the myths from the facts, see Gabriel Gabrielse’s website.

Silver, Silver Everywhere!

Check out this interesting article from the NIST Tech Beat explaining how nature may be manufacturing silver nanoparticles all by itself. The article also discusses some ideas as to why it is that silver is such a good antibacterial agent.

Read the NIST article here.

Silver Membrane Filters to Collect Wood Dust

A new study by NIOSH found a more effective method for testing occupational exposure to airborne wood dust, which is known to cause cancer. This new practice incorporates silver membrane filters along with a mid-infrared diffuse reflection method for direct on-filter determination of wood dust mass instead of gravimetric analysis and glass fiber filters, creating a more specific test.

To learn more, you can view the article abstract here.

EPA Creates 4 New Clean Air Research Centers

Today the Environmental Protection Agency awarded $32 million to 4 universities around the country to study the health impacts of air pollution. These centers will answering questions like, "does air pollution effect a child's learning ability?" "Are obese people more susceptible to health effects of air pollution?" "How does your commute effect your health?"

We work with a number of environmental labs to provide filtration materials, and one of the most common requests we get from them is for our 0.45 micron, 25mm silver membranes to comply with NIOSH methods for testing airborne contaminants such as silica and bromine. 

Here is a breakdown of what the four new centers are focusing on:

• University of Washington - Effects of roadway pollution on on cardiovascular health.
• Michigan State University - The relationships between obesity and air pollution.
• Emory University / Georgia Institute of Technology - Characterize health risks of air pollution mixtures, research how social factors (living location, commute, etc.) impact health. 
• Harvard University - Investigate health effects of short-term and long-term exposure to pollutants on specific health functions, including cognitive function, birth weight, and mortality. 

See also:
"EPA Awards $32 Million to Understand Health Impacts of Air Pollution"

EPA Clean Air Research Centers Home

See How Nano-Water Filters are Made

We've previously discussed how the combination of silver and carbon nanotubes can be used to create more efficient water purification filters, now you can see a little bit about how this filter is made thanks to Technology Review and Stanford University. You can read more about the process here.

Putting on a Shiny Suit: Polycarbonate Membranes get Sputtered!

Polycarbonate (PCTE) track-etch membranes, created decades ago, are finding some new uses in the development of nanotechnology applications.  They owe this new application to their precise pore geometry and organization.  PCTE membranes were previously utilized in the manufacture of single-walled nanotubes (SWNT) due to the relative ease of depositing metal ions on the inside of their pores, then selectively dissolving the PCTE; leaving behind nanotubes for use as super-conducting wires, micro-diode arrays, or magnetic-data storage devices.  

PCTE membranes are traditionally sputter coated with gold for use in scanning electron microscopy (SEM) imaging because it is easier to capture samples on their smooth membrane surface.  Now scientists are developing new ways to utilize PCTE membranes by sputter-coating metal ions on the membrane.  One new use is to construct a biocompatible glucose sensor¹ that can be implanted inside a diabetic’s body.  The membrane is sputter coated with platinum and the pores filled with an enzyme chemically anchored inside the pore.  When excess glucose enters the pores, an electrochemical reaction is started, traveling down the pore to the thin sputtered metal layer, where the signal is picked up and sent to a microprocessor inside the sensor.  The amount of glucose triggering inside each pore determines the strength of the electrical response.  The size of the entire sensor area might be as small as 0.15cm²!  There’s even work filling PCTE pores with photosensitive materials to turn the membrane into flexible solar cells.   

Sputtered membranes are also finding niches in synthesizing catalysts to help make ethanol from syngas (CO and H₂) as this ethanol can be used as an inexpensive and environmentally friendly fuel and fuel additive².  PCTE sheets can be sputter coated with gold and sandwiched onto a Zn sheet to make the necessary anode and cathode for electrodepositing Mn-Cu-ZnO nanowires/tubes.  These nanotubes can then be successfully used as catalysts in CO hydrogenation reaction to produce alcohols.  With so many industrial nations moving towards ethanol as an alternative to petroleum fuels, the need for synthesizing ethanol from available materials may have a new ally in track-etch membranes.

1: A. Kros, M. Gerritsen, V.S.I. Sprakel, N.A.J.M. Sommerdijk, J. Jansen, R.J.M. Nolte, Silica-based hybrid materials as biocompatible coatings for glucose sensors. Sensors and Actuators B, (2001) 68-75.

2: M.Gupta1, V. Kalpathi and J. J. Spivey, Electrodeposition of Cu-ZnO and Mn-Cu-ZnO Nanowires/tubes for Synthesis of Ethanol [abstract] In: Proceedings of the Electrochemical Society, 214^th Meeting Honolulu, Hawaii. October 12-17, 2008.  Abstract no. 0281

Silver Nanoparticles to Reduce Membrane Biofouling

Scientists at Michigan State University and the PERMEANT Group describes how they are infusing membranes with nanotechnology in order to improve membrane performance, particularly in the field of water purification.  While the use of nanotechnology to expand membrane permeability, selectivity, and resistance has grown more frequent over the last 20 or so years, the new research by these groups is taking this approach in interesting directions.  For instance, on one project they have demonstrated that by adding silver nanoparticles into the polymer matrix of the membrane that the mixture is effective at reducing intrapore biofouling.  Experimentation also shows that this method could also be used to inhibit the biofilm growth on downstream membrane surfaces.  

Hopefully with every little improvement that these teams make will lead them a step closer to their goal of making the world’s supply of drinking water safer for all of us.  

   

You can read more about this research here.

Water Sterilization & Silver

From this recent article in NanoLetters, the American Chemical Society Journal, comes information about a new form of water sterilization out of Stanford University that takes advantages of the unique bacteria-killing properties of silver (the vampire and werewolf killing properties of silver have yet to be proven).  Basically, the proposed multiscale device would perform high speed electrical sterilization of water using a combination of silver nanowires, carbon nanotubes, and cotton.  The end result is that when operating at 100,000 L/(h m²) this device can inactivate greater than 98% of bacteria with only several seconds of total incubation time.

The author’s of this paper mention two interesting reasons for why silver is used in the device.  The first:        

Taking advantage of silver nanowires’ (AgNWs) and CNTs’ [Carbon Nanotube] unique ability to form complex multiscale coatings on cotton to produce an electrically conducting and high surface area device for the active, high-throughput inactivation of bacteria in water.

The other reason described for using silver in water sterilization:

Silver is chosen since it is a very well-known bactericidal agent, and recently a large amount of interest has been spurred by the discovery that silver nanoparticles work extremely well at killing bacteria and can be attached to various surfaces with chemical techniques.    

The outcome of the silver treatment in the author’s experiment provides further evidence of these properties:

The results clearly show that filters not treated with silver, including CNT-only cotton, showed a robust growth of bacteria, while the bacteria concentration in the solutions incubated with AgNW-treated material was reduced to the detection limit of the absorbance system used, at least a 2 to 3 order of magnitude reduction.

All in all, the findings in this paper are encouraging that implementation of this approach can kill microorganisms which cause biofouling in downstream filters.  The authors of the paper state, “Such technology could dramatically lower the cost of a wide array of filtration technologies for water as well as food, air, and pharmaceuticals, where the need to frequently replace filters is a large cost and difficult challenge.”

Their next step is to expand their experimentation to other microorganisms beyond the E. coli that was used for this study.  In their conclusion the authors note that, “Silver is known to be an extremely general agent so it can be expected that this device will also work over a wide array of organisms.” 

We’ll continue to monitor their progress and hope for the best!

Silver Membranes: Your last line of defense?

We ran across an interesting patent that involves silver membranes – As part of a system designed to detect and identify chemical and biological contaminants in the air!  In the proposed sampling method and system, the silver membrane is used to capture liquid, solid, and gas constituents that would then be analyzed by means of spectroscopy for contaminants. 

For more versatility, the surface of the membrane can be modified physically or chemically in order to increase the surface area and/or provide specific affinity towards analytes of interest.   For instance, a pure length of silver membrane would trap solid particulate materials while a silver membrane treated with a metal oxide such as magnesium oxide would adsorb volatile organic compounds from a gas or liquid state.   The suitable thickness for the silver membranes is between 10 - 50 microns, with 30 microns being the preferred thickness.  The standard thickness for Sterlitech silver membranes is between 30 - 50 microns.   
         
The implications for this patent are intriguing to say the least.  It’s nice to know that there’s a possibility of our silver membranes being used to save lives…

You can look at the full patent here.

FAQ: Do Silver Membranes have a coating on them?

From time to time we hear from customers that they have "scratched" their silver membranes.  This occasionally leads them to ask: Is there some sort of coating on the membrane that is being rubbed off?

Answer: Our silver membranes are made of 99.97% pure silver and do not have any coating on them.  What may appear to be scratching is actually a polishing of the silver surface, which makes the silver reflective.  This can be done when the membrane is rubbed with a metal object, such as tweezers.  We also posted a brief video demonstrating the effect.  You can watch it here.