New Potassium Sodium Niobate Single Crystal with Thickness-independent High-performance for Photoacoustic Angiography of Atherosclerotic Lesion

Abstract

The synthesis of (K0.45Na0.55)0.96Li0.04NbO3 (KNLN) single crystals with a <100>-orientation, using a seed-free solid state crystal growth method, is described here. With the thickness of the crystals decreasing down to the order of tens of micrometers, this new lead-free single crystal exhibits thickness-independent electrical behavior, and maintains superior piezoelectric constant (d33 = 670 pC N−1) and electromechanical coupling factor (kt = 0.55). The successful fabrication of a tiny intravascular photoacoustic probe, with a 1 mm outside diameter, is achieved using a single crystal with a thickness of around 60 μm, in combination with a 200 μm core multimode fiber. Wire phantom photoacoustic images show that the axial resolution and lateral resolution of the single crystal based probe are 60 and 220 μm, respectively. In addition, intravascular photoacoustic imaging of the atherosclerotic lesion of a human artery is presented. In the time-domain and frequency-domain images, calcified regions are clearly distinguishable from surrounding tissue. These interesting results demonstrate that KNN-based lead-free piezoelectric single crystals are a promising candidate to substitute for lead-based piezoelectric materials for photoacoustic imaging in the future.

Post-Voltage-Boost Circuit-Supported Single-Ended Class-B Amplifier for Piezoelectric Transducer Applications

“…The input signal of the amplifier was a 5-cycle, 100-mV P-P sinusoidal waveform at 15 MHz. The expander used in the experiment had a pair of diodes, which were used to reduce the ring-down signal [ 38 , 76 ]. In the limiter used in the experiment, a pair of diodes were connected in parallel with a resistor, and it was used to reduce the high-voltage signal to protect the oscilloscope and pre-amplifier [ 35 , 77 , 78 ].…”

“…Nonlinear amplifiers such as the class-B amplifier are preferable for mobile ultrasound instruments owing to their lower DC power consumption [ 19 ]. For typical ultrasound applications, a single-ended-type class-B amplifier is preferable compared to a differential-ended amplifier for piezoelectric transducers, because some piezoelectric transducers have large undesirable capacitances in their equivalent circuit models [ 36 , 37 , 38 ]. A differential-ended amplifier scheme can change the resonant frequency of piezoelectric transducers because the change from a differential path to a single path requires the use of large inductive-type transformers [ 39 , 40 ].…”

Wide Bandwidth Class-S Power Amplifiers for Ultrasonic Devices

“…The basic gain function can be obtained from Equation (22). The final gain of the two-stage power amplifiers can be obtained by multiplying the gain of the first stage with the gain of the second stage, as shown in Equation (25).…”

“…The transfer functions ω in,A , ω out,A , ω in,B , and ω out,B are then substituted into Equation (22). This power amplifier circuit consists of two stages, and the total gain of V out /V in of each stage can be obtained as follows.…”

“…However, large size material, which has high acoustic impedance, could increase the bandwidth, and lower the sensitivity of the ultrasonic devices, because the mechanical damping absorb the part of the acoustic powers [20,21]. In addition, proper acoustic matching layers of the ultrasonic devices are used to increase the bandwidth, but also lower the sensitivity of the ultrasonic devices [22]. The electrical matching circuits are also useful to maximize energy transmission or increase the bandwidth of the ultrasonic systems by placing the matching circuits between the transducers and electronics [23,24].…”