Embodiments of the present invention are directed to efficient sensors for detecting the presence and concentration of one or more particular target molecules in solutions, air or other gasses, or otherwise present in an environment or sample. Various embodiments of the present invention provide relatively large binding constants or, equivalently, relatively small dissociation constants for binding of target biopolymers or other target molecules with complementary probes bound to, or associated with, a sensor substrate. In addition, various embodiments of the present invention increase the area of the surface of the sensor affected by binding of a target biopolymer or other target molecules to the sensor which, in turn, produces a stronger signal and greater signal-to-noise ratio for a given number or concentration of bound target biopolymers or other target molecules. In certain embodiments of the present invention, large binding constants, large signal-to-noise ratios, and strong signals are achieved by including probe molecules on the surface of the sensor directed to multiple binding sites within a target biopolymer or other target molecules, so that each bound target biopolymer or other target molecule is bound to, or associated with multiple probes.