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Northwestern University in Illinois has a new way to etch microscopic channels on silicon for use in future “lab-on-a-chip” devices (US patent application 2004/37959). The method involves harnessing the precision positioning system in a scanning probe microscope – a device used to map surface contours by measuring current between a fine metal tip and a surface. A thin layer of water condenses onto the surface to be etched, while acid is applied to the tip of the probe. When the tip is brought near to the water, capillary action draws acid onto the surface, and as the probe is moved along, the acid carves channels as narrow as 10 nanometres wide.