Biomedical subjects

C D Ohl

Publications and source records attributed to C D Ohl.

5 recordsLinked to original sources

PubMed2003

Shock-wave-induced jetting of micron-size bubbles.

Free gas bubbles in water with radii between 7 and 55 microm subjected to a shock wave exhibit a liquid jetting phenomenon with the jet pointing in the direction of the propagating shock wave. With increasing bubble radius, the length of the jet tip increases and a lower estimate of the averaged jet velocity increases linearly from 20 to 150 m/s. At a later stage, the jet breaks up and releases micron-size bubbles. In the course of shock wave permeabilization and transfection of biological cells, this observation suggests a microinjection mechanism when the cells are near bubbles exposed to a shock wave.

Cell Membrane↗

PubMed2003

Cell detachment method using shock-wave-induced cavitation.

The detachment of adherent HeLa cells from a substrate after the interaction with a shock wave is analyzed. Cavitation bubbles are formed in the trailing, negative pressure cycle following the shock front. We find that the regions of cell detachment are strongly correlated with spatial presence of cavitation bubbles. It is shown that the cavitation bubble collapse generates a transient high-speed flow along the substrate surface leading to rapid detachment of the cells. Flow trajectories are reconstructed from the video recordings using robust image-processing methods. From these trajectories, an estimate of the shear stress acting on the cells is obtained and the area of detachment is estimated with a kinetic model. Furthermore, it is suggested that the application of shock waves extends the known methods of cell detachment with the ability to control the process in space and time.

Cell Adhesion↗

PubMed2001

Spiraling bubbles: how acoustic and hydrodynamic forces compete.

Experiments to study the effect of acoustic forces on individual bubbles in shear flows have been carried out. In the system that we have used, the competition between acoustic and fluid dynamical forces results in a spiraling bubble trajectory. This dynamics is modeled by expressing the balance between Bjerknes and hydrodynamic forces in terms of an ordinary differential equation model, to which a separation of time scales is applied. The success of this model shows that the simple force-balance approach is still meaningful when bubbles are subjected to sound fields.

Journal Article↗

PubMed1999

Acoustic cavitation structures and simulations by a particle model.

Cavitation bubbles in acoustic resonators are observed to arrange in branch-like patterns. We give a brief review of the anatomy of such structures and outline an approach for simulation by individual, moving bubbles. This particle model can reproduce an experimentally observed transition between different structure types in a rectangular resonator cell.

Journal Article↗

PubMed1997

Cavitation bubble dynamics.

The dynamics of cavitation bubbles on water is investigated for bubbles produced optically and acoustically. Single bubble dynamics is studied with laser produced bubbles and high speed photography with framing rates up to 20.8 million frames per second. Examples for jet formation and shock wave emission are given. Acoustic cavitation is produced in water in the interior of piezoelectric cylinders of different sizes (up to 12 cm inner diameter). The filementary structure composed of bubbles is investigated and their light emission (sonoluminescence) studied for various driving strengths.

Journal Article↗