Most piezoelectric biosensors use thin piezoelectric crystals, either as longitudinal acoustic waves devices (e.g. quartz crystal microbalances, QCM), or as bulk/surface acoustic waves (SAW) devices. A novel system is described in which acoustic waves are launched in very thin polymer films to produce an oscillatory resonant device for the detection of proteins. The device uses a polymeric material in two distinct forms: common PVDF (which has good piezoelectric properties) and the Immobilon-P membrane (a porous type of PVDF with a high protein binding capacity). Current work with this system is presented.