Surface-to-Surface Bridges Formed by Reversibly Assembled Polymers

Self-assembled polymers whose main chains are defined by reversible DNA base pairing form bridges between the tip of an atomic force microscope and substrate. The forces associated with the rupture of these assemblies are independent of polymer bridge length, and they resemble those expected for the isolated associations defining the polymer bridges. The assembly is reversible and is inhibited by a competitive, nonpolymerizing oligonucleotide. Noncomplementary polymer brush layers do not bridge, and therefore, the forces result from specific molecular recognition events. The length distribution of the bridges differs greatly from that of the polymers in solution, and thus the bridging is responsive to the spatial constraints of the environment.