Chemistry Reference
In-Depth Information
Fig. 5.5
Droplet oscillators in a hexagonal packing geometry within a PDMS microchannel.
To p
The different intensities of the droplets show the different BZ reaction states within each droplet
for two different droplet sizes. Each droplet acts like an isolated individual oscillator without any
coupling with its neighbours. Image contrast is enhanced for better visualization. Scale bar is 150
.
Bottom
The intensity trace for a single droplet is shown as a function of time. The constancy of the
frequency and amplitude of the oscillations can be clearly seen
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soon as bilayers form between droplets, their interfaces touch each other very closely
such that the droplets are not perfectly spherical anymore. Due to this, the packing
fraction increases as seen in Fig.
5.6
. Once the bilayers are formed, completely dif-
ferent oscillatory dynamics are seen. Often, waves of synchronised activity such as
travelling waves are seen as in Fig.
5.6
. Therefore we see a switch from the individ-
ual to collective dynamics of the oscillators when bilayer networks are formed. We
discuss this aspect in greater detail in the next section.
5.3.2 Membrane Formation Triggers Oscillator Coupling
As soon as a bilayer has formed, coupling is expected to commence rapidly. Most of
the mono-olein molecules forming the membrane have been exposed to the reaction
products of the BZ system before and will thus be brominated already when the
membrane forms. But even if the latter was formed with fresh mono-olein, it would
be readily saturated with bromine given its minute thickness, and thus would let
further bromine compounds pass easily.
The strong variation in coupling strength by membrane formation can be seen
most impressively in excitatory waves propagating in rafts of BZ droplets with a
yet incomplete network of bilayer membrane contacts. Figure
5.7
shows snapshots
