  In granular physics experiments, it is a persistent challenge to obtain the
boundary stress measurements necessary to provide full a rheological
characterization of the dynamics. Here, we describe a new technique by which
the outer boundary of a 2D Couette cell both confines the granular material and
provides spatially- and temporally- resolved stress measurements. This key
advance is enabled by desktop laser-cutting technology, which allows us to
design and cut linearly-deformable walls with a specified spring constant. By
tracking the position of each segment of the wall, we measure both the normal
and tangential stress throughout the experiment. This permits us to calculate
the amount of shear stress provided by basal friction, and thereby determine
accurate values of $\mu(I)$.
