The Force Amplified Biological Sensor (FABS) is a desktop or portable instrument currently under development at the Naval Research Laboratory. FABS will use a rapid, automated immunoassay to detect analytes such as proteins, viruses, and bacteria. The assay uses forces produced by micron-sized magnetic particles to pull on antibody-antigen bonds. Microfabricated piezoresistive cantilevers measure the resulting piconewton-level forces with sufficient sensitivity to detect single antibody-antigen bonds. These forces also serve to characterize the bonds, allowing FABS to distinguish specific antibody-antigen bonds from nonspecific interactions.