We are developing a sensor capable of detecting biological species such as cells, proteins, toxins, and DNA at concentrations as low as 10−18M. The force amplified biological sensor will take advantage of the high sensitivity of force microscope cantilevers to detect the presence of as little as one superparamagnetic particle bound to a cantilever by a sandwich immunoassay technique. The device, which will ultimately be small enough for hand‐held use, will perform an assay in about 10 min. Lock‐in detection and use of a reference cantilever will provide a high degree of vibration immunity. An array of ten or more cantilevers will provide greater sensitivity and the capability to detect multiple species simultaneously. The force amplified biological sensor also offers the potential of distinguishing and studying chemical species via its ability to measure binding forces.