Two new and exciting scanning-probe techniques have been developed recently. The field is moving closer to being able to build 3D engineered atom-precise structures. Neither of these techniques does this yet, and one may not be able to, but... read on and see why this is an exciting time to be in nanotech.
Superionic stamping is a technique that uses a solid material in which metal ions can move around when directed by electricity. Push the stamp into a substrate, run a current, and some metal moves from the stamp onto the substrate.
I suspected that this would be useful in a scanning-probe system as well: draw lines in metal from a single sharp probe tip. I speculated that a sharp enough tip might even be able to transfer one atom at a time, and with the right metal (one that didn't slump/flow at the nanoscale, like gold does) might even be able to build 3D structures. So I wrote to Nicholas Fang, one of the researchers who developed the technique. His answer, quoted with permission:
In fact the direct writing approach already exists and we found we can grow a variety of patterns with high aspect ratio. We haven't worked on Tungsten or Iridium, they might be some new materials to explore in our study. In the past STM already can deposit Au, Cu and Ag with sub-10nm features so I believe it is very feasible to push it down to atomic level.
This is very exciting stuff! I also speculate that multiple tips with different metals might be used to build nano-coupons of metal alloys with every atom in an engineered position. Although this would be extremely slow, it might be useful for metallurgical testing and research--if anyone knows how to test sub-micron coupons of metal.
And of course, between stamps and massively parallel tip arrays, this may be useful for building high-performance computer chips without photon lithography. So that may drive the development of the technique.
The second technique uses dip-pen nanolithography to build artificial lipid bilayers, like the ones that make up cell membranes. The developers, which include Chad Mirkin, inventor of DPN, have been able to "deposit multiple phospholipids in precise patterns." The story continues, "The investigators note that they should be able to use dip-pen nanolithography to design the type of complex physical and chemical networks of materials that are found in cell membranes."
While trying to re-find that story, I found two related stories. This one describes a tool that is showing just how complex cell membranes really are. It points out that atomic force microscopes can't see the molecular composition, just the surface profile. Well, this other story describes a way to make AFMs sensitive to molecular composition: tether an antibody to the tip.
Back to molecular placement: I don't know if the dip-pen technique is capable of atomic precision; my impression is that for the foreseeable future, it'll have trouble getting down below nanometer precision. Of course I could be wrong. But as researchers become more comfortable thinking about directly building nanoscale structures out of scanning-probe-placed molecules, molecular manufacturing will seem more and more reasonable.
Tags: nanotechnology nanotech nano science technology weblog blog
Comments