Multichannel acoustic tool for sensing in liquid microdroplets

A novel tool for sensing micro samples of liquids, 1 nl to 10 μl in volume, is proposed and tested. It is based on the thermal effects produced by evaporating droplets on a substrate, which are detected by elastic wave propagation. Rayleigh, shear horizontal and surface skimming bulk waves are used at the same time to this purpose. The method relies on the measurement of the mass and temperature of the droplet, together with the time, velocity, heat and kinetics of the droplet evaporation as well as the thermal conductivity of the substrate material. Results of the measurements are in good agreement with the theoretical calculations performed using the heat equation together with the proper boundary and initial conditions