The effect of the spacing and angle arrangement of the droplet on the spreading area in simultaneous multiple droplets deposition

Simultaneous multiple droplet deposition involves dispensing of multiple droplets at the same instant on the substrate. A newly defined parameter, arrangement angle is considered as one of the factor that influencing the coalescence of the multiple droplets. However, the effect of such factor on the coalescence is largely neglected in the past. The paper aims to investigate the effect of droplet centre-to-centre distance and arrangement angle on the spreading area of four droplet deposited simultaneously using simulation method. The project starts with single droplet deposition and following by simultaneous multiple droplet deposition. For single droplet deposition, the spreading area of 80% wt aqueous glycerin droplet on the glass substrate were obtained using simulation and experimental methods. A correlation function was introduced to match the simulation result with the experiment result. For simulations of multiple droplet deposition, three droplet centre-to-centre distances as 2.22 mm, 3 mm and 4 mm and three droplet arrangement angles as 90°, 110° and 120° were studied. The larger the droplet spacing, the larger the spreading area for arrangement angle of 90°. The spreading area are largest for spacing of 4 mm, followed by 2.22 mm and 3 mm for arrangement angle of 110° and 120°. The arrangement angle is proven as a factor that affect the spreading area.