Understanding the thermal and mechanical properties of thin polymers is important because of their relevance in microfabrication and additive manufacturing. Polymers such as PMMA, PDMS, PVA and SU-8 are widely used for 3D printed microfluidic devices. We have used thin polymer films of thickness 100-200nm deposited on microfabricated cantilevers to investigate their thermal and mechanical properties. A silicon microcantilever, fabricated by depositing a thin metal film on one of its sides, shows a thermal sensitivity of 5mK at room temperature. Such a bi-material cantilever with a thin polymer film undergoes bending when the molecular bonds of the polymer are resonantly excited with infrared radiation. Non-radiative relaxation of polymer bonds results in minute changes in the cantilever temperature that can be observed as the bending of the cantilever. We have used a frequency-tunable quantum cascade laser (QCL) as the light source for irradiating the cantilever. Monitoring the cantilever bending as a function of illumination wavelength provides the IR absorption spectrum of the deposited polymer film. This nanomechanical photo-thermal spectrum in the mid-infrared regime is free from overtones and can be used for characterization of the polymer thin films. Thermal characterization of the deposited polymer film was carried out by pulsed illumination with IR wavelength that matches the absorption peak of the polymer and by monitoring its response as a function of time. The thermo-mechanical transient response is then used for calculating the thermal diffusivity of the polymer films. The measured thermal diffusivity shows excellent agreement with those reported in the literature. A computational model is developed with predictions for the thermal response of the coated cantilever that are in support of the experimental data. We have also investigated the mechanical effect of UV exposure to thin polymer films. Cantilever response shows that exposure to UV light results in mechanical as well as spectral changes in the polymer thin film.