Polarized composite-polymer materials PVDF-TrFE/Bi2O3 for fabricating broadband high frequency ultrasound and photoacoustic transducers

In this work, we have demonstrated the fabrication of a lead-free high frequency ultrasound and photoacoustic transducers by using the composite polymer material PVDF-TrFE and $Bi_{2}O_{3}$ as a polarizing nanofiller. We have used the drop-casting method for developing composite polymer and nanofiller based sensor film. The FTIR data analysis of the synthesized composite sensor film shows that the $\beta$ phase of the composite material sensor film has advanced after adding the nanofiller. Several transducers have been fabricated and we have performed experiments for both pulse-echo and photoacoustic signal acquisition with our fabricated transducers. The fabricated transducers show ultrasound central frequency around 32MHz with bandwidth approximately 19MHz in pulse-echo mode, whereas a photoacoustic signal from human hair shows a central frequency of 11MHz and the bandwidth found to be more than 12MHz i.e., 114% of central frequency at -6dB. These results show that lead free composite polymer PVDF-TrFE and $Bi_{2}O_{3}$ as a nanofiller can be used for fabricating high frequency sensor and signal acquisition for high-resolution ultrasound and photoacoustic imaging.