Design, Fabrication, and Characterization of Capacitive Micromachined Ultrasonic Transducers for Transcranial, Multifocus Neurostimulation.

In a recent study using 3-D fullwave simulations, it was shown for a nonhuman primate model that a helmet-shaped 3D array of 128 transducer elements can be assembled for neurostimulation in an optimized configuration with the accommodation of an imaging aperture. Considering all acoustic losses, according to this study, for a nonhuman primate skull, the assembly of the proposed transducers was projected to produce sufficient focusing gain in two different focal positions at deep and shallow brain regions, thus providing sufficient acoustic intensity at these distinct focal points for neural stimulation. This array also has the ability to focus on multiple additional brain regions.

Comparative Assessment of the Influence of Embolizing Agents on the Adrenal Parenchyma.

A comparative analysis of morphological and functional changes in the adrenal glands after embolization of supplying arteries with Lifepearl microspheres (100±25 μm; Terumo) and with a solution of polidocanol (Aethoxysklerol, Kreussler Pharma) was performed in male Vietnamese Lop-Bellied pigs (n=20). The introduction of the microspheres into the arterial bed did not affect the adrenal parenchyma. However, the injection of the liquid sclerosing agent caused foci of productive inflammation leading to the formation of sclerotic tissue and reduction of the volume of glandular tissue.

Design and Fabrication of 1-D CMUT Arrays for Dual-Mode Dual-Frequency Acoustic Angiography Applications.

When microbubble contrast agents are excited at low frequencies (less than 5 MHz), they resonate and produce higher-order harmonics due to their nonlinear behavior. We propose a novel scheme with a capacitive micromachined ultrasonic transducer (CMUT) array to receive high-frequency microbubble harmonics in collapse mode and to transmit a low-frequency high-pressure pulse by releasing the CMUT plate from collapse and pull it back to collapse again in the same transmit-receive cycle. By patterning and etching the substrate to create glass spacers in the device cavity we can reliably operate the CMUT in collapse mode and receive high-frequency signals.

An Ultrasonic Energy Harvesting IC Providing Adjustable Bias Voltage for Pre-Charged CMUT.

Ultrasonic wireless power transmission (WPT) using pre-charged capacitive micromachined ultrasonic transducers (CMUT) is drawing great attention due to the easy integration of CMUT with CMOS techniques. Here, we present an integrated circuit (IC) that interfaces with a pre-charged CMUT device for ultrasonic energy harvesting. We implemented an adaptive high voltage charge pump (HVCP) in the proposed IC, which features low power, overvoltage stress (OVS) robustness, and a wide output range.