  The Casimir effect arises when long-ranged fluctuations are geometrically
confined between two surfaces, leading to a macroscopic force. Traditionally,
these forces have been observed in quantum systems and near critical points in
classical systems. Here we show the existence of Casimir-like forces between
two pinned particles immersed in two-dimensional systems near the jamming
transition. We observe two components to the total force: a short-ranged,
depletion force and a long-ranged, repulsive Casimir-like force. The
Casimir-like force dominates as the jamming transition is approached, and when
the pinned particles are much larger than the ambient jammed particles. We show
that this repulsive force arises due to a clustering of particles with strong
contact forces around the perimeter of the pinned particles. As the separation
between the pinned particles decreases, a region of high-pressure develops
between them, leading to a net repulsive force.
