Suspended ceramic structures with nanometer-scale thickness, as well as 2D materials, serve as mechanically resonant structures with low mechanical energy loss, making them excellent candidates for thermal sensing applications. At TU Wien, our group explores photothermal IR detection, microscopy, and spectroscopy using nanomechanical resonators, commonly referred to as nanoelectromechanical systems (NEMS). These resonators are highly sensitive to temperature changes, which manifest as shifts or de-tuning of their resonant frequency. Consequently, any material placed on these resonators—whether a thin film for broadband IR absorption, dispersed molecules, or single molecules—can be detected if it absorbs light and dissipates heat. This means that the absorbing material, the analyte, becomes an integral part of the detection system itself, with no wavelength limitations, allowing for in situ measurements across the entire spectrum that the analyte can absorb. The choice of resonator material and its geometric design is crucial in minimizing noise and optimizing the resonator's response, which in turn enhances its noise equivalent power (NEP). We have successfully measured IR light in the range from 1 to 25 µm with an NEP of 7 pW/√Hz,[1] localized single dye molecules and determined the orientation of single nanorods,[2,3] measured and separated the IR spectra of nanograms of simultaneously desorbing species,[4] and opened new avenues for studying ultrafine particles, proteins, and catalysis.[5] 1. Piller, Markus, et al. "Thermal IR detection with nanoelectromechanical silicon nitride trampoline resonators." IEEE Sensors Journal 23.2 (2022): 1066-1071. 2. Chien, Miao-Hsuan, et al. "Single-molecule optical absorption imaging by nanomechanical photothermal sensing." Proceedings of the National Academy of Sciences 115.44 (2018): 11150-11155. 3. Kanellopulos, Kostas, Robert G. West, and Silvan Schmid. "Nanomechanical photothermal near infrared spectromicroscopy of individual nanorods." ACS photonics 10.10 (2023): 3730-3739. 4. Luhmann, Niklas, et al. "Nanoelectromechanical infrared spectroscopy with in situ separation by thermal desorption: Nems-ir-td." ACS sensors 8.4 (2023): 1462-1470. 5. West, Robert G., Kostas Kanellopulos, and Silvan Schmid. "Photothermal microscopy and spectroscopy with nanomechanical resonators." The Journal of Physical Chemistry C 127.45 (2023): 21915-21929.