In laterally homogeneous samples, the surface expansion is proportional to the temperature change of the sample after a laser pulse, hence for such samples the signal can fairly accurately be described if only sample heating and thermal conduction are taken into account. However, to study spatial resolution in AFM-IR, models that describe laterally heterogeneous samples are required. Here, surface displacement also depends on the elastic response of the sample, as the inhomogeneous, absorber distribution dependent heating and creates inhomogeneous strain in the neighboring material. There ple, heat conduction within the sample and thermo-elastic deformation of the sample.