Nanoscopic gold spheres can be reversibly bound to DNA strands reversibly bound to DNA strands

How can individual components be assembled into larger functional units? And how can robot arms, for example, be made to "grab" specific nano-objects-and to release them at the right moment? The field of biotechnology presents interesting approaches to these problems. Researchers at the University of Dortmund have now developed an elegant method to link nanoparticles reversibly: they use short DNA strands to cause gold spheres to aggregate "on demand" and then to separate again, also "on demand".