  Several experimental demonstrations of the Casimir force between two closely
spaced bodies have been realized over the past two decades. Extending the
theory to incorporate the behavior of the force between two superconducting
films close to their transition temperature has resulted in competing
predictions. To date, no experiment exists that can test these theories, partly
due to the difficulty in aligning two superconductors in close proximity, while
still allowing for a temperature-independent readout of the arising force
between them. Here we present an on-chip platform based on an optomechanical
cavity in combination with a grounded superconducting capacitor, which
overcomes these challenges and opens up the possibility to probe modifications
to the Casimir effect between two closely spaced, freestanding superconductors
as they transition into a superconducting state. We also perform preliminary
force measurements that demonstrate the capability of these devices to probe
the interplay between two widely measured quantum effects: Casimir forces and
superconductivity.
