November in Seattle: Turkey and Bus Crashes

We just got blasted with our first winter storm of the year and it was a mean one for Seattle.  Take a look at the video and you can tell that while there are many things we do well here (computer programming, watching soccer), driving around in the snow clearly isn't one of them.  Even our own metro buses can't quite get the hang of it!

Just a reminder, but Sterlitech will be closed this Thursday and Friday for the Thanksgiving holiday (November 25th and 26th. We will open again on Monday the 29th. We wish you all a safe and happy Thanksgiving!

Beta Ratios and Filter Efficency

Here is an article that does a great job of explaining what efficiency ratings mean on a filter and how they are calculated, courtesy of the American Filtration & Separation Society.  This is very useful information for filter users and purchasing agents on the practical effects the filter efficiency will have in a real world setting. 

You can read the whole thing 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.