Proximal Probes: Exploration and Manipulation of Matter at the Atomic ScaleTo achieve true nanotechnology that which will be commercially viable and which will drastically change the world, we need small self-sufficient and replicating machines. But we are incapable of designing anything that small and complex right now because we are forced to use bulk technology, that which is built from the top to bottom (eg. parts made from large bulk material), rather than bottom to top (eg. atom by atom).Although this bulk technology is extremely crude compared to what we will have in the future, we are making steady progress in the tools used to manipulate matter at the nano-scale. One of today's most popular venues of research toward nanotechnology involves proximal probe machinery. The glossary from Unbounding the Future by Eric Drexler defines proximal probes as "A family of devices capable of fine positional control and sensing, including scanning tunneling and atomic force microscopes; an enabling technology for nanotechnology.". Right now the two most popular proximal probe devices seem to be the Atomic Force Microscope (AFM) and the Scanning Tunneling Microscope (STM).
The Scanning Tunneling Microscope The STM is capable of precisely mapping the surface of conductive materials. It does this by placing a very, very fine needle with an electrically charged tip over the surface. A current, like in a circuit, is established between the needle tip and the surface of the material. The needle is drawn across the material, moving up and down with the curve of the atoms, and from the charge and needle movement the surface is mapped. The tip gets so close to the surface that the atoms of the tip and material are actually overlapping. This is due to the ambiguity of the locations of electrons in the atoms. The Atomic Force Microscope The ATM works by simply dragging a needle, somewhat similar to the one used in an STM, across the surface of the material. Rather than mapping the atoms via an electric current, the ATM maps by optically sensing the movement of a spring, which is connected to the needle and exerts a small force for the needle to press against the surface. The tip of the ATM also moves up and down along the curvatures of the atoms. Moving Small Stuff around Right now STMs and ATMs can do very limited unprecise manipulation of nano-scale matter, but the technology is steadily progressing. Sources: Chapter 4 of Unbounding the Future by Eric Drexler: http://foresight.org/UTF/Unbound_LBW/chapt_4.html Digital Instruments Page: http://www.di.com/Products/ScanMethods/scanMain.html main |
