Biomedical subjects

Yoseph Bar-Cohen

Publications and source records attributed to Yoseph Bar-Cohen.

3 recordsLinked to original sources

PubMed2005

The mechanical and thermal effects of focused ultrasound in a model biological material.

This paper is motivated by possible medical applications of focused ultrasound in the minimally invasive treatment of a variety of musculoskeletal disorders that are responsive to thermal treatment. A model-based analysis of the interaction of high-intensity focused ultrasound with biological materials is carried out in an effort to predict the path of the sound waves and the temperature field in the focal region. A finite-element-based general purpose code called PZFlex is used to determine the effects of nonlinearity and geometrical complexity of biological structures. It was found that at frequencies of interest in therapeutic applications, the nonlinear effects are usually negligible and the geometrical complexities can be handled through a substructuring procedure. An approximate analytical method with acceptable accuracy is developed as an alternative to the purely numerical approach used in PZFlex. The mechanical and thermal effects in two-layered fluid material systems induced by high-frequency focused ultrasound are calculated through this analytical method. The results are compared with those obtained using PZFlex as a benchmark.

Biomechanical Phenomena↗

PubMed2005

Current and future developments in artificial muscles using electroactive polymers.

For decades, electroactive polymers received relatively little attention due to their limited actuation capability. However, in the last 15 years, a series of electroactive polymer materials have emerged that produce a significant shape or size change in response to electrical stimulation. These materials have the closest functional similarity to biologic muscles, enabling the engineering of novel capabilities that were, up until recently, impossible to achieve. Efforts are underway to address the many challenges that are hampering the practical application of these materials, and recent progress has already led to dramatic capability improvements. Various novel mechanisms and devices were demonstrated including robotic fish, catheter steering elements, robotic arms, miniature grippers, loudspeakers, active diaphragms, Braille display and dust-wipers. For developers of future medical devices, these materials are offering numerous advantages for their flexibility, fracture toughness and controllability, as well as low mass and low power requirements. This article provides a review of the current status, challenges and potential near-future applications of these materials.

Biocompatible Materials↗

PubMed2003

Modeling and computer simulation of ultrasonic/sonic driller/corer (USDC).

Simulation and analytical models for the ultrasonic/sonic drill/corer (USDC) are described in this paper. The USDC was developed as a tool for in-situ rock sampling and analysis in support of the NASA planetary exploration program. The USDC uses a novel drive mechanism, which transfers ultrasonic vibrations of a piezoelectric actuator into larger oscillations of a free-flying mass (free-mass). The free-mass impact on the drill bit creates a stress pulse at the drill tip/rock interface causing fracture in the rock. The main parts of the device (transducer, free-mass, bit, and rock) and the interactions between them were analyzed and numerically modeled to explore the drive mechanism. Each of these interactions is normally described by a time-dependent 2- or 3-D model involving slowly converging solutions, which makes the conventional approach unsuitable for USDC optimization studies. A simplified integrated model using tabulated data was developed to simulate the operation of the USDC on desktop PC and successfully predicted the characteristics of the device under a variety of conditions. The simulated results of the model and the experimental data used to verify the model are presented.

Journal Article↗