Claus-Dieter OHL
Associate Professor
Division of Physics and Applied Physics
School of Physical and Mathematical Sciences
Dipl. Phys, University of Darmstadt, Germany
PhD (Physics), University of Göttingen, Germany
Major Research Interest: Experimental Fluid Dynamics
Other Interests: Acoustics and Cavitation
Email: CDOhl@ntu.edu.sg
http://www1.spms.ntu.edu.sg/~cdohl/home.html
Tel: (65) 6513 8039
Selected Publications
Gonzalez-Avila, S.R., Huang, X., Quinto-Su,
P.A., Wu, T., Ohl, C.D., “Motion of
Micrometer Sized Spherical Particles
Exposed to a Transient Radial Flow:
Attraction, Repulsion, and Rotation”, Phys.
Rev. Lett. 2011, 107, 074503. Covered by
Physical Review Focus August 2011
Tandiono, Ohl, S.W., Ow, D.S.W., Klaseboer,
E., Wong, V.V., Dumke, R., Ohl, C.D.,
“Sonochemistry and sonoluminescence in
microfluidics”, Proc. Nat. Acad. Sci. 2011,
108, 5996–5998.
Huang, X., Quinto-Su, P.A., Gonzalez-A.,
S.R., Wu, T., Ohl, C.D., “Controlled
manipulation and measurement of single
Co nanowire with a laser-induced cavitation
bubble”, Nano Lett. 2010, 10, 3846–3851.
Quinto-Su, P.A., Huang, X.H., Gonzalez, R.,
Wu, T., Ohl, C.D, “Manipulation and
microrheology of carbon nanotubes with
laser-induced cavitation bubbles”,
Phys. Rev. Lett. 2010, 104, 014501.
Lim, K.Y., Quinto-Su, P.A., Klaseboer, E.,
Khoo, B.C., Venugopalan, V., Ohl C.D.
“Non-spherical laser-induced cavitation
bubbles”, Phys. Rev E. 2010, 81, 016308.
Covered by Physical Review Focus February
2010
Zhao, X., Quinto-Su, P.A., Ohl, C.D.
“Dynamics of magnetic bubbles in Acoustic
and Magnetic Fields”, Phys. Rev. Lett. 2009,
102 024501.
Physical Review Letters Editor's Suggestion
Covered by Physics Todays March Issue
2009 page 18.
Fast flows are in general observed on large scales;
examples of fast natural flows include avalanches,
volcanic eruptions, or tornados. Yet, not only on large
scales but also on very small scales rapid flow can
occur.
What is able to drive flows with speeds of more than
100Êm/s on microscopic scales? The answer is
bubbles; more precisely it is a special type of bubbles
known as cavitation bubbles. These are largely empty
bubbles in a liquid. Cavitation can be generated by
boiling, by depositing energy, e.g. with a pulsed laser,
or by pulling the liquid apart with intense acoustic
waves till the liquid ruptures and voids are formed.
The flow when the cavitation bubbles explode and
shrink can be as damaging as their larger
counterparts. They are known to erode ship propellers,
pump blades, and fuel injection nozzles. On the other
hand, cavitation can be beneficial. It can remove
unwanted material from surfaces, such as grease
from jewelry and particulate contamination from
fragile silicon wafers; further applications of cavitation
are fragmentation of kidney stones, drug delivery into
cells, and the non-invasive treatment of tumors.
Our research interest is the small scale fluid dynamics
at high Reynolds numbers. In particular, we are
studying the process of cavitation nucleation, thus
working on the puzzle where do the bubbles originate
from. Here, we found that particles are acting as
nucleation sites, and accelerate to high velocities.
Furthermore, we are interested on the interaction of
bubbles with ultrasound and shock waves and
discovered the formation of microscopic fluid needles.
Oscillating bubbles close to surfaces develop by flow
focusing a fast jet which impacts on the surface. The
spreading of this jet on the surface is creates very
high levels of wall shear stress. Here, we are analyzing
the importance of this flow for cleaning applications
and for drug delivery into adherent cells.
We have demonstrated that microscopic bubbles can
be generated in lab-on-a-chip systems. They are able
to actuate flows in microscopic channels rapidly
allowing new approaches to surpass the current limits
of low Reynolds number microfluidics.
Two examples showing the richness of fluid mechanics
we experience in our lab (price winner of the Gallery
of Fluid Motion APS/DFD 2009 and 2010). The figure
on the left shows the formation of a rapid jet pointing
upwards and a slower annular jet; both forming
droplets on their tips The figure on the right is created
in a microfluidic device where 25 bubbles are
generated with the help of laser and a digital hologram.
Photonics, fluids, and high speed photography reveal
the beautiful symmetry of a cluster of bubbles
expanding and collapsing in concert.
132 DIVISION OF
PHYSICS AND
APPLIED PHYSICS