IEEE Trans Ultrason Ferroelectr Freq Control. 2021 Jul;68(7):2532-2542. doi: 10.1109/TUFFC.2021.3062071. Epub 2021 Jun 29.
Dual-frequency capacitive micromachined ultrasonic transducers (CMUTs) are introduced for multiscale imaging applications, where a single array transducer can be used for both deep low-resolution imaging and shallow high-resolution imaging. These transducers consist of low- and high-frequency membranes interlaced within each subarray element. They are fabricated using a modified sacrificial release process. Successful performance is demonstrated using wafer-level vibrometer testing, as well as acoustic testing on wirebonded dies consisting of arrays of 2- and 9-MHz elements of up to 64 elements for each subarray. The arrays are demonstrated to provide multiscale, multiresolution imaging using wire phantoms and can span frequencies from 2 MHz up to as high as 17 MHz. Peak transmit sensitivities of 27 and 7.5 kPa/V are achieved with the low- and high-frequency subarrays, respectively. At 16-mm imaging depth, lateral spatial resolution achieved is 0.84 and 0.33 mm for low- and high-frequency subarrays, respectively. The signal-to-noise ratio of the low-frequency subarray is significantly higher for deep targets compared to the high-frequency subarray. The array achieves multiband imaging capabilities difficult to achieve with current transducer technologies and may have applications to multipurpose probes and novel contrast agent imaging schemes.
双频电容式微机械超声换能器（CMUT）被引入用于多尺度成像应用，其中单个阵列换能器可用于深低分辨率成像和浅高分辨率成像。这些换能器由低频率和高频率薄膜在每个子阵元内交错组成。它们采用改进的牺牲释放工艺制造。使用晶圆级振动计测试以及对由多达 64 个每个子阵元的 2MHz 和 9MHz 元件组成的键合线裸片进行的声学测试成功证明了其性能。该阵列被证明可以使用线 phantom 进行多尺度、多分辨率成像，并且可以覆盖从 2MHz 到高达 17MHz 的频率。低频和高频子阵分别实现了 27 和 7.5 kPa/V 的峰值发射灵敏度。在 16mm 的成像深度下，低频和高频子阵的横向空间分辨率分别为 0.84mm 和 0.33mm。与高频子阵相比，低频子阵的深目标信噪比显著更高。该阵列实现了多波段成像能力，这是当前换能器技术难以实现的，可能适用于多用途探头和新型对比剂成像方案。
