Adding a layer of air in a thermal actuator?

I am modeling a thermal actuator and would like to account for conduction through air between the small gap of two beams however I cannot get it to converge. I'm tryied to add a layer using heat transfer in fluids, but Comsol is asking for and elastic modulus and poissons ratio.... I've included a screenshot of where I'm at. The large planar area is the air and the outline is the thermal actuator. Thank you for your time!! !
Image Link - https://ibb.co/YW66Wyf