GRAPHENE CONDUCTIVITY VARIATION DURING DRYING OF SUSPENSION DROPLETS ON THE SURFACE OF GRAPHENE FILM

In the present work, we study the evaporation of droplets of various suspensions on the surface of graphene film. Graphene sensors are silicon dioxide substrates with graphene film deposited on them with copper electrodes. Graphene conductivity changes while droplets deposited on the surface dry. The dependences of the resistance of graphene sensors on the geometric parameters of the droplets (heights, contact angles, contact areas of the droplets with the surface) are found. The sensitivity of the sensors to the presence of soot particles in the droplets, as well as to the presence and hydrophilic-lipophilic balance of surfactants is demonstrated. The variation of conductivity is associated with a change in the structure of the liquid near the graphene surface. The presence of water molecules and soot particles reduces conductivity by creating a tangentially directed electric field. The presence of surfactants, in turn, increases the conductivity of graphene by creating an electric field normal to graphene surface.