A sensor for detecting an analyte of interest in a fluid sample includes (i) a structure having a plurality of surficial walls that define a plurality of air gaps in the structure and (ii) a binding material. The structure is configured such that both a fluid sample lacking the analyte of interest and a fluid sample containing the analyte of interest are able to penetrate the plurality of air gaps. The binding material, which is present on the plurality of surficial walls, is able to bind the analyte of interest. The sensor is configured such that, when the analyte of interest binds to the binding material, a change in surface energy results within the plurality of surficial walls.