Tartrazine ELISA Kit

The study of how surface tension gradients affect the mixing of liquids is beneficial in understanding applications that involve an air-liquid interface. Our work investigates the mixing of a yellow food color (tartrazine) droplet in an ethanol (EtOH) droplet. Though studies of droplet coalescence and mixing on a plane have been carried out, the effects of the air-liquid interface and the resulting nonuniform surface tension distribution were not well understood. To fill the knowledge gap, we study the impact of surface tension gradient, or Marangoni stress, on the mixing of two droplets. Using tartrazine as the mixing material in water, we first evaluate how the mixing rate obtained from our proposed two-droplet system differs from the mixing rate that would occur if molecular diffusion alone was present. Second, we assess the impact of surface tension gradient through studying the mixing of tartrazine in various EtOH concentrations. Through a mathematical model built using COMSOL, we confirmed that varying the EtOH concentration did not impact the mixing time. Our simulation also presented a qualitative understanding of mixing rate as a function of contact angle.