Development of a digital micro-manufacturing process for high frequency ultrasound transducers

Conventional methods for fabricating ultrasound imaging transducers especially for high frequency (>;20 MHz) range are expensive, time consuming and limited to relatively simple geometries. In this paper, the development of an additive digital micro-manufacturing method for piezomaterials and composites based on digital micromirror devices (DMD) to be used in HF ultrasound transducers is presented. Photocured piezoelectric materials with micro-scale features were fabricated. Different piezoelectric characteristics of the materials have been tested and compared with the bulk case. The Density of the fabricated samples was increased by applying hot uniaxial press and adding PZT composite sol-gel to the photocure solution. The dielectric constant (ε_r) and the tangent loss (tgθ) of the samples at 1 KHz were found to be around 610 and 0.025, respectively. The measured piezoelectric constant (d₃₃) of the fabricated samples was around 156×10^-12 C/N, and the sound velocity about 1850 m/s. The polarization (P_r) and the coercive field (E_c) were 18 μC/cm² and 80 kV/cm, respectively.