This study presents the fabrication and characterization of a piezoelectric micromachined ultrasonic transducer (pMUT; radius: 40 µm) using a patterned aluminum nitride (AlN) thin film as the active piezoelectric material. A 20 × 20 array of pMUTs using a 1 µm thick AlN thin film was designed and fabricated on a 2 × 2 mm² footprint for a high fill factor. Based on the electrical impedance and phase of the pMUT array, the electromechanical coefficient was ~1.7% at the average resonant frequency of 2.82 MHz in air. Dynamic displacement of the pMUT surface was characterized by scanning laser Doppler vibrometry. The pressure output while immersed in water was 19.79 kPa when calculated based on the peak displacement at the resonant frequency. The proposed AlN pMUT array has potential applications in biomedical sensing for healthcare, medical imaging, and biometrics.

Background: The phase correction on transcranial focused ultrasound is essential to regulate unwanted focal point shift caused by skull bone aberration. The aim of the current study was to design and investigate the feasibility of a ray-based phase correction toolkit for transcranial focused ultrasound. Results: The peak pressure at focal area was improved by 140.5 ± 7.0% on target I and 134.8 ± 19.1% on target II using proposed phase correction toolkit, respectively. A total computation time of 402.1 ± 24.5 milliseconds was achieved for each sonication. Conclusion: The designed ray-based phase correction software can be used as a lightweight toolkit to compensate aberrated phase within clinical environment.

Underwater sensors that detect the distance and direction of acoustic sources are critical for surveillance monitoring and target detection in the water. Here, we propose an axial vector sensor that utilizes a small (~1 cm³) compressive-type piezoelectric accelerometer using piezoelectric single crystals. Initially, finite element analysis (FEA) was used to optimize the structure that comprised piezoelectric Pb(Mb_1/3Nb_2/3)O₃-28%PbTiO₃ single crystals on a tungsten seismic mass. The receiving voltage sensitivity (RVS) was enhanced through geometric optimization of the thickness and sensing area of the piezoelectric material and the seismic mass. The estimated maximum RVS of the optimized vector sensor was −212 dB. FEA simulations and practical measurements were used to verify the directivity of the vector sensor design, which exhibited a dipole pattern. The dipole beam pattern was used to obtain cardioid patterns using the simulated and measured results for comparison. The results clearly showed the feasibility of using the proposed piezoelectric single-crystal accelerometer for a compressive-type vector sensor.

The potential improvement in sonication efficiency achieved by tilting the focused ultrasound (FUS) transducer of the transcranial MR-guided FUS system is presented. A total of 56 cases of patient treatment data were used. The relative position of the clinical FUS transducer to the patient’s head was reconstructed, and region-specific skull density and porosity were calculated based on the patient’s CT volume image. The total transmission coefficient of acoustic waves emitted from each channel was calculated. Then, the total energy penetrating the human skull—which represents the sonication efficiency—was estimated. As a result, improved sonication efficiency was by titling the FUS transducer to a more appropriate angle achieved in all 56 treatment cases. This simulation result suggests the potential improvement in transcranial-focused ultrasound treatment by simply adjusting the transducer angle.

Multibeam echosounder (MBES) backscatter data are influenced by underwater sound absorption, which is dependent on environmental parameters such as temperature, salinity, and depth. This study leverages CTD datasets from the Korea Oceanographic Data Center (KODC) to analyze and visualize the spatiotemporal variations in absorption parameters in the East Sea of Korea, which are subject to pronounced variability over time and space. The legacy MBES backscatter data, originally processed using generalized absorption parameters that neglected spatiotemporal variations, were compared with the calibrated data. The calibration process included inverse calculation of water temperature with depth-specific average salinity values from the nearest KODC stations. This calibration revealed discrepancies of up to 2.1 dB in backscatter intensity across survey lines, highlighting the potential misrepresentation of legacy MBES backscatter data due to site-specific absorption variability having been overlooked. By addressing these discrepancies, this study underscores the importance of incorporating spatiotemporal absorption variability into MBES calibration workflows. This integrated approach not only enhances the reliability of legacy MBES data but also provides valuable insights for marine resource management, seafloor mapping, and environmental monitoring in highly dynamic marine environments such as the East Sea of Korea.

The blood–brain barrier (BBB) severely restricts the delivery of neuroprotective compounds to the brain, limiting therapeutic strategies for Parkinson's disease (PD). Ginsenoside Rg3, a bioactive component of ginseng, has demonstrated neuroprotective potential, but its efficacy is constrained by poor BBB permeability. Here, we evaluated focused ultrasound (FUS)-mediated BBB opening (FUS BBBO) to enhance delivery of Rg3-loaded nanoparticles in a rotenone-induced mouse model of PD. Localized FUS sonications were applied to induce transient BBB disruption, followed by intraperitoneal administration of FITC-labeled Rg3 nanoparticles. In vivo and Ex vivo fluorescence imaging confirmed a significant increase in brain accumulation of nanoparticles after FUS BBBO. While Rg3 nanoparticle treatment alone showed moderate increases in ATP levels and Complex I activity, FUS alone produced comparable trends with slightly higher recovery. The combination treatment with FUS-mediated BBBO demonstrated higher mean values (ATP: 0.27 ± 0.06; Complex I: 1.98 ± 0.41) compared to the PD group, along with improvements in motor performance. These findings suggest that FUS-BBBO may enhance the delivery of Rg3 nanoparticles to the brain and support mitochondrial function. Overall, the combination approach showed a trend toward improved outcomes; however, further studies are required to confirm these effects and establish therapeutic potential for solid statistical analysis.