Here is some further info on the working principle and thought applications of our so
called aocustic scallop or robo-scallop. It is an acoustic only powered
device. Therefore, it does not need wires or a battery as an energy
source, but picks up the energy from the sound field and transforms it
into a translational motion. If you fix it, the device can act as a pump.
A bubble in a tube closed at one end is driven into resonant pulsations
with an acoustic field. When the pressure increases the bubble
compresses and when the pressure decreases the bubble expands.
During the compression of the gas bubble, liquid is sucked under a large angle
into the tube. However, at expansion the liquid leaves the tube as a
jet. The repulsive force on the tube is different for the suction and
the jetting, thereby a net force is generated acting towards the
The Acoustic Scallop in motion
Some still images of the device propelling from left to right. The length of the device is approximately 3mm.
or watch the movie.
Tapered mouth to increase the acceptance angle.
Acoustic scallop with fins.
Attaching six individual scallops on spikes and connecting them to a
bearing makes a motor, or call it an acoustic underwater windmill :-).
History of the name:
Initially, the device was called acoustic fish.
However, one of the referees mentioned that typically a fish propells
by shedding vorticies and not by jet propulsion. He is right and as
most fishes use low Reynolds number (visocisty dominated flow) we
followed his adivse and named it acousctis scallop. The scallop is a moussle that propells with the help of little jets.
Prof. Dr. Andrea Prosperetti: Had the original idea and did most of the calculations/dimensioning
Ir. Rory Dijkink: Did the initial experiments and
measured the force during his Master thesis. He is now working on a
different subject as PhD student in the group.
Ir. Johan van der Dennen: Made the experiments on the moving scallop, two
headed scallop, and many other cute things during his Master project.
Dr. Claus-Dieter Ohl: Supervising the experiments.