Controlling movement of nano-objects on surfaces is important for molecular electronics and nanomachi-nery. One way of doing this is to make paths or tracks that the target object wants to follow, and excluding the rest of the surface to stop them wanderingrnoff. Graded polymer layers, where one parameter (e.g., chemical composition) is varied laterally, allow systematic control of surface properties, but up till now the lengthscale of the gradients (millimeters) achieved have not been small enough for manipulation of nano-objects. Now, researchers at Freiburg University have overcome this size hurdle, developing a method that produces well-defined gradients on the nanoscale. A surface is coated with photoinitiator and then irradiated with a UV interference pattern. This destroys parts of the layer, leaving a pattern of active sites that can then be polymerized to give the desired functionality. More complex patterns can be achieved by using multiple UV interference patterns.
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