A piezoelectric strain sensor and method thereof for detecting strain, vibration, and/or pressure. The sensor incorporates a sequence of piezoelectric and semiconductor layers in a thin-film transistor structure. The thin-film transistor structure can be configured on a flexible substrate via a low-cost fabrication technique. The piezoelectric layer generates an electric charge resulting in a modulation of a transistor current, which is a measure of external strain. The sensor can be formed as a single gate field-effect piezoelectric sensor and a dual gate field-effect piezoelectric sensor. The semiconductor layer can be configured from a nanowire array resulting in a metal-piezoelectric-nanowire field effect transistor. The single and dual gate field-effect piezoelectric sensor offer increased sensitivity and device control due to the presence of the piezoelectric layer in the transistor structure and low cost manufacturability on large area flexible substrates.