A whole bunch of biomed applications is promised by researchers from the University of Rochester, who developed this nano-thin porous silicon membrane:
A newly designed porous membrane, so thin it’s invisible edge-on, may revolutionize the way doctors and scientists manipulate objects as small as a molecule.
The 50-atom thick filter can withstand surprisingly high pressures and may be a key to better separation of blood proteins for dialysis patients, speeding ion exchange in fuel cells, creating a new environment for growing neurological stem cells, and purifying air and water in hospitals and clean-rooms at the nanoscopic level…
Details on the membrane, developed at the University of Rochester, appear in today’s issue of the journal Nature.
“It’s amazing, we have a material as thin as some of the molecules it’s sorting, and even riddled with holes, but can withstand enough pressure to make real-world nano-filtering a practical reality,” says research associate Christopher Striemer, co-creator of the membrane. “That ultra-thinness means much higher efficiency and lower sample loss, so we can do things that can’t normally be done with current materials.”
The membrane is a 15-nanometer-thick slice of the same silicon that’s used every day in computer-chip manufacturing. In the lab of Philippe Fauchet, professor of electrical and computer engineering at the University, Striemer discovered the membrane as he was looking for a way to better understand how silicon crystallizes when heated.
He used such a thin piece of silicon–only about 50 atoms thick–because it would allow him to use an electron microscope to see the crystal structure in his samples, formed with different heat treatments.
Striemer found that as parts of the silicon contracted into crystals, holes opened up in their wakes. Imagine a party of people spread out evenly throughout a room, but as the evening progresses and people huddle into cliques, scattered areas of empty floor open up…
To test the membrane, Gaborski placed a solution of two blood proteins, albumin and IgG, behind the membrane and forced it gently through the nanoscopic holes. In just over six minutes, the albumin had passed through, but the larger IgG protein was stopped.
And as if filtering by nanoscale size weren’t enough, the Rochester team has found a way for the nano-filter to carry a fixed charge, effectively making the hole “smaller” for molecules of a certain charge than for others. In a single filter it’s now possible to quickly and easily separate molecules by their size and their charge–a serious boon for fuel cell researchers, who wish to move only certain ions from one part of a fuel cell to another.
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