Review - Nanomechanical Calorimetric Infrared Spectroscopy using Bi-Material Microfluidic Cantilevers

Receptor-free, in-situ sensing of chemical and biological analytes with high selectivity and sensitivity is a highly sought-after goal. While a resonating microfluidic, hollow channel microcantilever is an ideal platform for sensing pico liters (pL) of liquid analytes based on changes in the specific gravity it does not offer any chemical selectivity. Fabricating these hollow channel cantilevers as bi-material beams allows them to be extremely sensitive to small changes in temperature as well. When a liquid confined in such a cantilever is illuminated with tunable IR radiation, it undergoes bending whenever the liquid analyte absorbs the light at a particular wavelength. Monitoring the cantilever bending as a function of illuminating wavelength provides IR spectrum of the analyte confined in the channel. This method combines the selectivity of IR spectroscopy and the sensitivity of a cantilever for molecular recognition of pL volume of liquid samples. This nanomechanical calorimetric infrared spectroscopy is an ideal technique for physical and chemical characterization of pico liter volumes of liquid analytes.