High frequency ultrasound 2D array design and fabrication with 3D printed interposers at 200 μm pitch.

High-frequency 2D ultrasound arrays (10-50 MHz) can adjust the focus position in three-dimensional space to produce highly focused beams and have potential use in ultrasound elastography and ophthalmology applications. However, these applications remain unfulfilled due to the difficulty in realizing the array element pitch requirements of high-frequency ultrasound 2D arrays with existing technologies. In recent years, the rapid development of 3D printing technology has made complex and fine structures possible. By utilizing high-resolution 3D printing technology, we can effectively solve the connection problem between circuits and acoustic modules in the ultrasound 2D array fabrication process, making it possible to fabricate high-frequency ultrasound 2D arrays. In this work, we demonstrate two alternative fabrication processes for high-frequency 2D ultrasound arrays with a realized pitch of 200 µm and 256 elements per array. The fabricated arrays achieved a yield of 82 % and 75 %, with an average fractional bandwidth of 43 %. The element-to-element variability in bandwidth was 18 %, which reflects the inherent challenges of fine-pitch high-frequency array fabrication. These results highlight the feasibility of scalable fabrication techniques while identifying areas for future optimization.