Sensors in mid-infrared spectroscopy based on attenuated total reflection (ATR) sensing with internal reflection elements (IREs) facilitate easier measurements of aqueous solutions or other opaque analytes. Micromachined silicon (Si) elements are an attractive alternative to conventional IREs, as they can be produced cheaply with silicon processing. Techniques for surface modifications are also easily integrated into the wafer process, and surface structures such as micropillars or nanoparticles can thereby be used for signal enhancement.