A novel single-element dual-frequency ultrasound transducer for image-guided precision medicine

Multi-Transduction-Mechanism Technology, an Emerging Approach to Enhance Sensor Performance

“…The technology of multi-transduction mechanisms involves more than one transduction mechanism within a single sensor structure, thereby enabling the sensor to detect and simultaneously distinguish between different types of stimuli for greater degrees of freedom [10,11]. The utilization of multi-transduction-mechanism technology allows a multi-parameter response and individual operation in different ranges, leading to an expanded range of operating conditions and improved performance [49][50][51]. Moreover, this technology has the potential to achieve miniaturization by reducing the number of utilized sensors in an array [13].…”

“…Ultrasound transducers operating at higher frequencies (in the MHz range) suffer from low penetration depths, frequency-dependent attenuation, and low depth of field [56]. Using low-frequency transducers that operate in the kHz range can overcome this disadvantage but leads to issues of reduced resolution [50,56]. The idea of dual-frequency ultrasonic transducers capable of operating in both high and low frequencies has therefore been explored to overcome these issues by utilizing arrays of PMUTs [6] or CMUTs [7] with different dimensions fabricated on the same substrate.…”

“…The combination of the CMUT and PMUT operation modes in a dual-frequency ultrasonic transducer (DFUT) has been proposed by Sun et al [50] to overcome this challenge. The three-layer device comprises of a piezoelectric layer placed atop the flexible membrane of a CMUT, enabling both high-and low-frequency modes of operation.…”

“…The dual-frequency ultrasound transducer is composed of a large elastic layer with a small, etched cavity, a piezoelectric layer on top of the elastic layer, and three conductive metal layers serving as electrodes on the top, middle, and bottom, as shown in Figure 3 [50]. When a low-frequency AC voltage with a DC bias is applied between the middle and bottom electrodes, the device functions as a CMUT with an operating frequency of 5.9 MHz.…”

Numerical Study and Optimisation of a Novel Single-Element Dual-Frequency Ultrasound Transducer

“…Benefiting from deep penetration and high resolution, dual-frequency ultrasound transducers (DFUTs) have been studied in recent years for applications in medical therapy and imaging, such as non-destructive testing, transdermal drug release, photoacoustic imaging, and acoustic cavitation enhancement [ 1 , 2 , 3 , 4 , 5 ]. In order to achieve a dual-frequency ultrasound operation, so far there are four main approaches: (1) interleaving two different single-frequency elements in the horizontal plane of one chip [ 6 , 7 , 8 , 9 ], (2) stacking two different single-frequency elements in the vertical plane of one chip [ 10 , 11 , 12 , 13 , 14 ], (3) combining the thickness-bending (TB) and thickness-expansion (TE) modes in one transducer element [ 15 ], and (4) combining the fundamental and harmonic/superharmonic vibration modes in one transducer element [ 16 , 17 , 18 ]. In general, the first two DFUT configurations typically tend to be adopted because of their advantages in individual optimization for each frequency band and low coupling between the adjacent elements.…”