40 MHz PMN-PT Single-Crystal Kerfless Phased Array

This miniature 32-element kerfless phased array is designed for forward-looking intravascular ultrasound (IVUS) and endoscopic ultrasound (EUS) imaging applications. Fabricated from a ⟨001⟩-oriented PMN-PT single crystal lapped to 40 µm thickness, the array achieves a center frequency of 40 MHz with 34% bandwidth and 20 dB insertion loss. The kerfless design—wherein elements are defined solely by photolithographically patterned electrodes without mechanical dicing between elements—enables an extremely compact active aperture of 1.0 × 1.0 mm² with 33 µm element pitch. This configuration supports electronic beam steering over a ±30° field of view, providing forward-looking capability not available in commercial side-looking IVUS catheters. Compared to PZT ceramic-based arrays, the PMN-PT single crystal offers higher dielectric constant and piezoelectric coefficient, yielding improved sensitivity for small-aperture, high-frequency imaging. Both ultrasound and photoacoustic imaging modes have been demonstrated with this device.

Parameter	Value
Array Type	Kerfless phased array
Number of Elements	32
Center Frequency	42.6 ± 0.4 MHz
Bandwidth (‑6 dB)	34.1 ± 2.2%
Piezoelectric Material	PMN‑PT single crystal ((001) oriented)
Element Thickness	40 μm
Element Pitch	33 μm (0.9λ in water)
Active Array Area	1.0 × 1.0 mm²
Electromechanical Coupling (kₜ)	0.56 ± 0.02
Electrical Impedance (at 40 MHz)	69.9 ± 2.9 Ω
Insertion Loss	20.0 ± 1.3 dB
Matching Layer	Parylene (12 μm)
Backing Material	E‑Solder 3022 (conductive epoxy)
Imaging Field of View	±30° (steered)
Measured Lateral Resolution (FWHM)	467 μm
Measured Axial Resolution (FWHM)	118 μm