Piezoelectric microbalances are devices which uses piezoelectric crystal resonators as mass sensitive sensor elements. The microbalances are mainly used for thin film monitoring, chemical and biological sensors. Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress. ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... Thin-film optics is the branch of optics which deals with very thin structured layers of different materials. ... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology is the science of life (from the Greek words bios = life and logos = word). ...