Abstract: A piezoelectric patch sensor for measuring muscle movement of contraction and extension is disclosed. The sensor is elongated and directly attached to a skin site of a user for the measuring via an interface circuit connected to a host processor. The piezoelectric patch sensor has an adhesive layer with an adhesive bottom surface for firmly attaching to the skin site. An elastic sheet is integrated on top of the adhesive layer. A piezoelectric thread is further integrated on top of the elastic sheet and has a bundle of aligned piezoelectric fibers. The thread is electrically coupled to the interface circuit via a pair of conductive wires, forming a piezoelectric measurement circuitry. Muscle movement under the skin site shrinks or extends the piezoelectric patch sensor in its entirety along the direction of muscle movement due to a corresponding shrinking or extending movement of the skin firmly attached to the adhesive layer.