Dynamic acoustic focusing in photoacoustic transmitter

Qi Li,Jiapu Li,Haobo Zhu,Yujie Chen,Benpeng Zhu,Hongbin Yu

doi:10.1016/j.pacs.2020.100224

Abstract

Photoacoustic transmitter represents a promising substitute for conventional piezoelectric counterparts. However, lack of easy and effective method for dynamically manipulating the focused acoustic field is a common and tricky problem faced by current photoacoustic technology. In this paper, a new strategy for constructing focus tunable photoacoustic transmitter is proposed. Different from existed prevailing device architecture, a sandwich like photoacoustic conversion layer is innovatively designed into a suspending elastic membrane with clamped boundary and it can be deformed using integrated pneumatic actuator. Owing to the membrane deflection property, concave spherical contours with variable radius of curvature can be obtained. Considering the shape determined sound emission characteristic, continuous tuning on the axial focusing length of the acoustic field has been successfully demonstrated in the photoacoustic transmitter for the first time. Besides, acoustic signal with significantly improved negative pressure has also been achieved especially at the focus, bringing additional advantage for applications.

Highlights

Benefit from the non-ionized radiation and large penetration depth characteristics, ultrasound has been widely used especially in biomed ical applications as medical imaging [1,2,3], drug delivery [4], cell manipulation [5,6,7], lithotripsy [8] and sonothrombolysis [9]
When combining the shape determined sound emission distribution characteristic associated with PA technology, we experimentally demonstrate, to the best of our knowledge, the first dynamic acoustic focusing capability in PA transmitter
Considering the PA conversion layer shape determined sound field distribution, dynamic acoustic focusing along axial direction has been successfully achieved with simple hardware configuration and easy control, providing a feasible and prospective solution to address the technical challenge faced by the PA society

Summary

Introduction

Benefit from the non-ionized radiation and large penetration depth characteristics, ultrasound has been widely used especially in biomed ical applications as medical imaging [1,2,3], drug delivery [4], cell manipulation [5,6,7], lithotripsy [8] and sonothrombolysis [9]. As for the PA technology, the most commonly adopted method is to directly coat a PA conversion layer onto a solid transparent substrate with concave surface contour (such as glass concave lens) [21,22,23]. In order to capture the entire 3D image, the axial scan of the focal plane is essential and it has to be achieved through moving the ultra sound probe due to its fixed focal length and limited depth of focus. It puts forward higher requirement for operators and largely lowers the operation efficiency as well as accuracy. When combining the shape determined sound emission distribution characteristic associated with PA technology, we experimentally demonstrate, to the best of our knowledge, the first dynamic acoustic focusing capability in PA transmitter

Device fabrication

Experiment results

Conclusions