  A common feature of biological self-organization is how active agents
communicate with each other or their environment via chemical signaling. Such
communications, mediated by self-generated chemical gradients, have
consequences for both individual motility strategies and collective migration
patterns. Here, in a purely physicochemical system, we use self-propelling
droplets as a model for chemically active particles that modify their
environment by leaving chemical footprints, which act as chemorepulsive signals
to other droplets. We analyze this communication mechanism quantitatively both
on the scale of individual agent-trail collisions as well as on the collective
scale where droplets actively remodel their environment while adapting their
dynamics to that evolving chemical landscape. We show in experiment and
simulation how these interactions cause a transient dynamical arrest in active
emulsions where swimmers are caged between each other's trails of secreted
chemicals. Our findings provide new insight into the collective dynamics of
chemically active particles and yield principles for predicting how negative
autochemotaxis shapes their navigation strategy.
