A novel gas flow sensing application using piezoelectric ZnO thin films deposited on Phynox alloy

We report on the novel flow sensing application of piezoelectric ZnO thin film deposited on Phynox alloy sensing element. Characterization of piezoelectric ZnO films deposited on Phynox (Elgiloy) substrate at different RF powers is discussed. ZnO films deposited at RF power of 100 W were found to have fine c-axis orientation, possesses excellent surface morphology with lower rms surface roughness of 1.87 nm and maximum d31 coefficient value 4.7 pm V−1. The thin cantilever strip of Phynox alloy with ZnO film as a sensing layer for flow sensing has been tested for flow rates ranging from 2 to 18 L min−1. A detailed theoretical analysis of the experimental set-up showing the relationship between output voltage and force at a particular flow rate has been discussed. The sensitivity of flow sensing element is ∼18 mV/(L min−1) and typical response time is of the order of 20 m s. The sensing element is calibrated using in-house developed testing set-up.