An apparatus for performing SERS includes a substrate and flexible nano-fingers, each of the nano-fingers having a first end attached to the substrate, a free second end, and a body portion extending between the first end and the second end, in which the nano-fingers are arranged in an array on the substrate. The apparatus also includes an active material layer disposed on each of the second ends of the plurality of nano-fingers, in which the nano-fingers are to be in a substantially collapsed state in which the active layers on at least two of the nano-fingers contact each other under dominant attractive forces between the plurality of nano-fingers and in which the active material layers are to repel each other when the active material layers are electrostatically charged.