The illustrated embodiments include a method of operating a SAW sensor to detect a sample in a fluid which includes the steps of: providing a SAW sensor with a functionalized detection lane in a handheld, portable assay and sensor system； maintaining the functionalized detection lane of the SAW sensor dry until the sample is fluidicly disposed in the detection lane； fluidicly disposing the sample in the functionalized detection lane； removing fluid the functionalized detection lane to concentrate the sample in the functionalized detection lane to increase the probability of a specific antibody-antigen interaction； washing the functionalized detection lane so that substantially only the specific antigen-antibody interaction remains in the functionalized detection lane； removing fluid from the functionalized detection lane again； and measuring concentration of the sample while the functionalized detection lane is fluid-free.
