  We develop and thoroughly test a stress-controlled, parallel plates shear
cell that can be coupled to an optical microscope or a small angle light
scattering setup, for simultaneous investigation of the rheological properties
and the microscopic structure of soft materials under an imposed shear stress.
In order to minimize friction, the cell is based on an air bearing linear
stage, the stress is applied through a contactless magnetic actuator, and the
strain is measured through optical sensors. We discuss the contributions of
inertia and of the small residual friction to the measured signal and
demonstrate the performance of our device in both oscillating and step stress
experiments on a variety of viscoelastic materials.
