Movie of a colony surfing event of a 2µl drop (OD=0.27) on a 1°
slope (corresponding to main article figure 1). Time is indicated in
hours:minutes, the time interval between two frames is 5min.
SM2
Movie showing induced drop sliding of a 10µl supernatant drop
(right) contaminated by a dendrite of swarming bacteria from a 1µl
drop of bacteria (OD = 1.5, left) at t = 10h. The inclination
angle is 1°. See main article figure 3 for details. Time is
indicated in hours:minutes, the time interval between two frames is
5min.
SM3
Movie showing induced drop sliding of a 50µl
water drop (left) contaminated by a dendrite of swarming
bacteria from a 30µl drop of bacteria (right) at t = 110min.
Here, to reduce initial drop spreading, the initial amount
of surfactin present in the drop was minimised through the
following procedure: the bacterial suspension was grown to OD = 1.5
and centrifuged; the supernatant was removed and the bacteria
resuspended in fresh nutrients (final OD = 1.5) before deposition.
The inclination angle is 1°. See supplementary figure SF1 for
details. Time is indicated in hours:minutes, the time interval
between two frames is 2.5min.
SM4
Movie showing how a 30µl water drop (left) starts to slide after
being reached by the surfactin ring emitted by a 30µl drop of
non-motile bacteria (right). As for movie~SM3, to reduce initial
drop spreading, the initial amount of surfactin present in the
drop was minimised through the following procedure: the bacterial
suspension was grown to OD = 1.5 and centrifuged; the supernatant
was removed and the bacteria resuspended in fresh nutrients (final
OD = 1.5) before deposition. See supplementary figure~SF2 for
details. Time is indicated in hours:minutes, the time interval
between two frames is 2.5min.
SM5
Movie showing the evolution of a 2µl drop of commercial surfactin
solution (0.5g/l) on the gel surface. As for bacterial suspensions,
we observe a volume increase, and the outward propagation of a
surfactin ring. The wetting hysteresis is reduced to Δcos θ = cos
θR - cos θA = 0.003 at the onset of motion.
As opposed to the drops of bacterial suspension the drop moves only
through a finite distance, probably because sustained surfactin
production is required to continuously modify the wetting properties
of the gel ahead of the sliding drop. Time is indicated in
hours:minutes, the time interval between two frames is 5min.
Last modified: 21 Nov 2020