Design of a flexible transducer array and characterisation of piezoelectric sensors for curvature compensation

Flexible ultrasound has emerged as the basis for wearable devices in healthcare. In this work, a flexible 1D phased transducer array has been proposed. This transducer array includes piezoelectric sensors underneath the transducer array, which detect its local curvature at different locations, corresponding to the positions of each piezoelectric sensor. Using FEA a simulation study was created, resulting in a deformed transducer array in which the number of curves and the number of sensors are varied. The piezoelectric sensors detect the local curvature resulting in a displacement map along the array. The sensing error of these sensors is calculated by taking the difference between the detected curvature from the sensors and the actual curvature the PCB was subjected to during the simulations. The results of these simulations show that, an increase of sensors results in a noticeable decrease in sensing error up to 9 sensors. Increasing the number of sensors after that point decreases the sensing error to a negligible value. The curvature information gathered from the piezoelectric sensors was then used to allow for the generation of focused ultrasound beams. To enable this, ultrasound beamforming algorithms were augmented to include curvature correction. These simulations showed that, despite a slight decrease in beam pressure of a curved transducer array compared to an uncurved array, the sensors can effectively detect and compensate for curvature in ultrasound transducer arrays.