Controlled cavitation in microfluidics

by
Ed Zwaan, Severine Le Gac, Kinko Tsuji, and Claus-Dieter Ohl

The manuscript is now in press for publication in Physical Review Letters. Here, we want to share some more information and movies on this work. For contact please email c.d.ohl@utwente.nl .
bubble generation A laser pulse focused from below in a microfluidic device (20 microns high, PDMS=polydimethylsiloxane) creates a pan-cake shaped and short lived bubble.
picture of a system A picture of  two identical systems on the rubber like substrate (PDMS). The large holes are reservoirs for filling the lines.
radil flow Vapor bubble dynamics in a large chamber with no nearby boundaries. The bubble essentially oscillates radially and the flow stops shortly after the bubble collapse. The movie is taken with 1 million frames/s, and the image width is 140microns.

radil flow The bubble expands and collapses in a complex geometry. Here, two feeding capillaries connect with a round (left) and rectangular shaped (right) container. A jet flow is created which accelerates the flow towards the left. Please note that the flow doesn't stop after the bubble collapse but two persisting vortex rings are created. The movie is taken with 1 million frames/s, and the image width is 140microns.

With increasing numbers of boundaries more fluid jets are observed:
one wall
close to a boundary		 two walls
In a rectangular channel:
note the transport of vorticity towards the walls
three walls
triangular structure		 four walls
square: 4-leafed clover