  Interparticle friction plays a governing role in the mechanics of particulate
materials. However, virtually all experimental studies to date rely on
measuring macroscopic responses, and as such it remains largely unknown how
frictional effects emerge at the microscopic level. This is particularly
challenging in systems subject to thermal fluctuations due to the transient
nature of interparticle contacts. Here, we directly relate particle-level
frictional arrest to local coordination in an attractive colloidal model
system. We reveal that the orientational dynamics of particles slows down
exponentially with increasing coordination number due to the emergence of
frictional interactions, the strength of which can be tuned simply by varying
the attraction strength. Using a simple computer simulation model, we uncover
how the interparticle interactions govern the formation of frictional contacts
between particles. Our results establish quantitative relations between
friction, coordination and interparticle interactions. This is a key step
towards using interparticle friction to tune the mechanical properties of
particulate materials.
