The viscosity of DMF is 0.802 mPa•s and the surface tension is 25.7 dyne/cm, while the viscosity of water is 2.98 mPa•s and the surface tension is 72.8 mN/m. According to the research of C.E.Ejim et al. , when other conditions remained the same, the size of liquid atomized particles would increase with the increase of viscosity or surface tension. Therefore, when the atomizer was powered on, the atomized particles generated by DMF liquid were much smaller than those generated by water, so at the initial stage of atomization, the DMF atomized particles would be too small to be observed by naked eyes until a period, which was longer than the time required for water atomization. After testing, the project determined that the DMF solution sampling time was approximately 50 seconds.