2026 Theses Doctoral

High Density CMOS-based Ultrasound Phased Array with Monolithically Fabricated Piezoelectric Transducers for Photoacoustic Imaging

Arslan, Volkan

Ultrasound imaging is among the most widely utilized diagnostic modalities due to its reliance on non-ionizing radiation and the accessibility of low-cost hardware implementations. Recent advancements have focused on achieving further miniaturization, enhanced power efficiency, and improved spatial resolution. The monolithic co-design of ultrasound transducers with complementary metal-oxide-semiconductor (CMOS) electronics represents a critical step toward realizing compact, high-density array architectures. This work presents a scalable, CMOS-compatible integration strategy for polyvinylidene fluoride (PVDF) transducers and front-end circuitry optimized for high-resolution operation.

By reducing interconnect length, suppressing capacitive parasitics, and minimizing the input capacitance of receiver amplifiers, the proposed architecture enables high-fractional-bandwidth transduction suitable for advanced imaging applications. The fabricated array comprises 206 receiver elements, each measuring 30 µm x 25 µm x 5.5 µm, corresponding to a volumetric reduction of over two orders of magnitude compared to conventional ceramic piezoelectric transducers. Device performance is validated through in-vitro and in-vivo photoacoustic imaging experiments, achieving lateral and axial resolutions better than 30 µm and 15 µm, respectively. The demonstrated fabrication and integration approach, together with co-designed electronics on thinned CMOS substrates, establishes a pathway toward scalable, high-density, and mechanically flexible two-dimensional ultra-high-resolution transducer arrays.