Ultrasonic Transducer From Piezoelectric Polymer Multilayer Through Electrophoretic Deposition for Photoacoustic Imaging.

Emerging ultrasound imaging modality based on optical-generated acoustic waves, such as photoacoustic (PA) imaging, has enabled novel functional imaging on biological samples. The performance of the ultrasonic transducer plays a critical role in producing higher quality PA images. However, the high electrical impedance of the small piezoelectric elements in the transducer array causes an electrical mismatch with external circuitry and results in degraded sensitivity. One effective method for reducing the electrical impedance is to implement a piezoelectric multilayer configuration instead of the conventional single layer for the transducer. In this work, we introduced an ultrasonic transducer comprising a piezoelectric polymer multilayer structure produced by an innovative multicycle powder-based electrophoretic deposition, using a suspension of polymer nanoparticles. The multicycle electrophoretic deposition overcomes the redissolution issue in solution-based methods. The ultrasonic transducer comprising the piezoelectric polymer multilayer exhibits significantly enhanced receiving sensitivity as compared to the ultrasonic transducer using a single layer. Ultrasonic transducer with multielement array configuration is obtained using the piezoelectric polymer multilayer, and PA imaging with improved resolution is demonstrated. Theoretical analysis shows that the enhanced transducer performance is mainly attributed to the improved electrical impedance match between the piezoelectric polymer element in the transducer and external receiving circuit.