This work demonstrates the use of fluorescent molecular rotors as a method to directly measure the viscosity of aqueous and lipophilic aerosol in the micron size range. Analysis of particles deposited on surfaces potentially suffers from interferences due to the surface they are deposited on. Therefore fluorescence lifetime imaging (FLIM) of the fluorescent molecular rotors dissolved in aerosol systems of interest is applied here to particles trapped with optical tweezers, which allows for measurements of viscosity changes in a single suspended aerosol droplet in a contact-free environment.