Bowel sounds contain some important human physiological parameters which can reflect information about intestinal function. In this work, in order to realize real-time monitoring of bowel sounds, a portable and wearable bowel sound electronic monitor based on piezoelectric micromachined ultrasonic transducers (PMUTs) is proposed. This prototype consists of a sensing module to collect bowel sounds and a GUI (graphical user interface) based on LabVIEW to display real-time bowel sound signals. The sensing module is composed of four PMUTs connected in parallel and a signal conditioning circuit. The sensitivity, noise resolution, and non-linearity of the bowel sound monitor are measured in this work. The result indicates that the designed prototype has high sensitivity (−142.69 dB), high noise resolution (50 dB at 100 Hz), and small non-linearity. To demonstrate the characteristic of the designed electronic monitor, continuous bowel sound monitoring is performed using the electronic monitor and a stethoscope on a healthy human before and after a meal. Through comparing the experimental results and analyzing the signals in the time domain and frequency domain, this bowel sound monitor is demonstrated to record bowel sounds from the human intestine. This work displays the potential of the sensor for the daily monitoring of bowel sounds.

This Letter introduces an innovative electrically tunable suspended acoustic waveguide utilizing aluminum scandium nitride thin film. This design allows for dynamic modulation of the phase of traveling acoustic waves through the application of a vertical electric field. With both simulation and experimental approaches, the study explores how the waveguide width and inherent dispersion properties influence phase modulation. Results indicate that broader waveguides demonstrate more significant phase lag, with phase shifts of 37.2°, 40.8°, and 44.7° for waveguide widths of 10, 20, and 30 μm, respectively, measured in 200 μm-long segments under a ±40 V DC bias at 1.05 GHz. The exceptionally low Vπ·L of 6.44 V·cm underscores the system's ability to control phase efficiently with minimal power consumption. The exceptional properties of the waveguide make it a promising candidate for advanced acoustic signal processing, enabling precise phase control to enhance both device performance and energy efficiency.

This article presents lithium niobate (LiNbO₃) based on shear horizontal (SH0) resonators, utilizing a suspended structure, for radio frequency (RF) applications. It demonstrates the design, analysis, and fabrication of SH0 resonators based on a 36Y-cut LiNbO₃ thin film. The spurious-free SH0 resonator achieves an electromechanical coupling coefficient ($k_t^2$) of 42.67% and a quality factor (Q_r) of 254 at the wave-propagating orientation of 0° in the 36Y-cut plane.

Thermo-optic (TO) phase shifter serves as a fundamental component in large-scale integrated photonic chips, where its power consumption and response time significantly impact system performance. Various structures have been explored to enhance the performance of TO phase shifters, including spiral waveguide, suspended structures, and slow-light configurations. However, these structures often come with trade-offs in terms of footprint, robustness, bandwidth, or insertion loss. In this paper, we present a high-performance CMOS-compatible TO phase shifter that maintains a small footprint and minimal optical loss. Leveraging the high thermal conductivity of aluminum nitride (AlN), we achieve a π-phase shifting power of 14 mW for Mach–Zehnder interferometers (MZI) and 1.7 mW for ring resonators. The bandwidth of both MZI and ring resonator TO phase shifters reach 145 kHz. The proposed TO phase shifter demonstrates significant potential for large-scale integration into photonics chips, offering high power efficiency and broad bandwidth.

This work explores the infrared (IR) detection capabilities of 750 nm thick Z-cut lithium niobate (LN) thin film resonator at asymmetric modes of various orders: the first, third, fifth, and seventh order asymmetric (A1, A3, A5, and A7), with resonant frequencies of 2.35, 6.68, 11.09, and 15.49 GHz. Under the infrared radiation of 0.575 mW, the responses about admittance minima and frequency drift corresponding to these modes have been experimentally validated. Notably, the A1 mode exhibits the most significant admittance dip response with 2.62 dB, while the A7 mode demonstrates a maximum frequency drift response of 670 kHz. The optimal parameter for noise equivalent power reaches 15.41 pW/Hz1/2, and the optimal detectivity achieves 7.40 × 106 m Hz1/2/W. These findings indicate the immense potential of LN thin-film resonators for infrared sensing applications.

This work presents a comprehensive band analysis for calculating the S₂₁ and bandwidth (BW) of acoustic delay lines (ADLs) based on single-phase unidirectional transducers (SPUDTs). Focusing on the electrode layout, the amplitude and phase relationships of the incident fundamental symmetric (S0) Lamb wave and reflected waves at electrode centers (ECs) of Double SPUDT and Bottom Floating (BF) SPUDT unit cells across different frequencies are first investigated. Subsequently, ADLs are conceptualized as a model consisting of unit cells with transduction centers (TCs) and reflection centers (RCs) on each port, with an intermediate gap that introduces propagation loss (PL). Utilizing 1-μm-thick aluminum nitride (AlN) and scandium-doped aluminum nitride (Al_0.7Sc_0.3N) thin films, theoretical modeling and finite element method (FEM) assisted calculations are conducted to compute the reflection (Γ) and transmission (T) coefficients for both Double SPUDT and BF SPUDT unit cells. The S₂₁ and 5-dB BW in the center frequency (f_c) vicinity of the ADLs, with cell count (N) ranging from 3 to 13 and gap length (L_g) ranging from 50 to 300 μm, are theoretically computed. The comparison with time-gated measurements demonstrates that the calculation errors are consistently below 5 dB⋅MHz. This analysis provides theoretical insight into the relationships among the ADL’s spectrum, PL, N, SPUDT structure, and piezoelectric film, offering valuable guidance for ADL performance optimization. 2024-0197