Small and extremely small molecules and ions or atoms may be detected with the novel device with exceptional sensitivity. The detection is implemented in a simple manner by the known acoustic resonator FBAR or by means of other technologies that measure the physical properties of the filled layer. The permeability of substances (e.g. active ingredients) through membranes such as cell membranes, lipid bilayers, and cell walls can be examined by combining a sensor with the reservoir and the membrane.