Stick nanoparticles together only when you want to! Researchers at NYU have announced a way to use DNA strands to make nanoparticles sticky only under certain conditions.
If you can make nanoparticles stick on command, you're a big step closer to building a simple nanofactory.
In the study that I did with Tee Toth-Fejel for NIAC a few years ago on Large-Product General-Purpose Design and Manufacturing Using Nanoscale Modules, I proposed that a primitive sort of nanofactory might be built with molecular building blocks that would bind together when pressed together, but otherwise float around in solution. The idea was that the blocks would bind weakly to the tip of a "tattoo needle" which would then press them into a workpiece, where they would stick. Given an appropriate set of building blocks, it should be possible to build arrays of tattoo needles.
DNA strands stick together when their sequences match up properly. Sticking nanoparticles together by coating them with matching DNA strands has been done for a while. But the innovation here is that a strand with the right sequence can fold back and stick to itself.
A particle coated with doubled-over DNA strands will not be very sticky. But heat can unstick the strands from themselves, making them able to stick to each other, linking the attached particles. The article implies that holding a particle in position long enough will allow the strands to randomly uncoil and stick - whereas particles that bumped into each other in solution would almost always drift away before this could happen.
Another interesting point in the article: by making use of reversible attachment and conditional attachment, it seems possible to make intricate building block arrangements that can template copies of themselves. This could allow exponential growth of the patterns, even without externally controlled mechanical guidance.
DNA is extremely versatile, and the strength of the attachment between strands can be fine-tuned. The main thing I don't know here is the time scales involved. If it takes an hour to deposit a molecular building block, then this may not be useful for construction. But if it takes a minute or less, then things get very interesting.
I don't know yet if this innovation will go down in history beside Rothemund staples. But it is certainly complementary to it (no pun intended) since suitable molecular building blocks can be very easily built out of Rothemund-stapled DNA.
It wouldn't surprise me at all to see a computer-controlled DNA-based molecular manufacturing system within a few years. The material properties would not be all that great, and it might or might not have fast actuation, and it would require expensive feedstock and carefully controlled laboratory conditions, so it would not be revolutionary in an economic or military sense. But it would be an awesome proof of concept, leading people to wonder what other materials and binding systems might be used to build higher-performance nanofactories.
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Posted by: medic | June 23, 2009 at 05:09 AM