Chemistry Reference
In-Depth Information
Fig. 6.8
The decay of the swimmer speed with time.
To p
the normalised speed of the squirmers
for various surfactant concentration as a function of time. The normalisation is done with the
initial (
peak
) speed at each concentration. The decay of the velocity is different for each surfactant
concentration. The
black dashed lines
are exponential fits to the data.
Bottom
the decay exponent
of the normalised speed as a function of surfactant concentration
dependance of concentrations on the behavior of the B-Z reaction, we again look
for the decay at different concentrations of the external fuel i.e. the surfactant. As
we increase the surfactant fuel outside the droplet to a concentration much above
the concentration of bromine source within the droplets, we expect that the decay
rate slows down and eventually tends towards a saturation since the bromine runs
out much before the surfactant. That this is indeed the case is shown in Fig.
6.8
.In
the top panel, we show the speed of the droplet, normalised by the initial speed, as
a function of time together with exponential fits to the data shown in black dotted
lines. The decay exponent plotted against surfactant concentration indeed shows this
saturation behaviour as we just discussed.
The very simple model above predicts the locomotion speed to be independent of
the bromine release rate. This can of course not be strictly true in general, and it is
instructive to demonstrate this experimentally. We take advantage again of the B-Z
reaction, this time creating an oscillating bromine concentration inside the droplet
