Wetting and Young s Equation

Why do droplets of different liquids deposited on identical solid substrates behave so differently Why do identical droplets — for example, aqueous droplets deposited on different substrates — behave so differently  

FIGURE 1.1 Nonwetting case contact angle is bigger than k/2. 

FIGURE 1.2 Partial wetting case the contact angle is in between 0 and tc/2. 

FIGURE 1.3 Complete wetting case the droplet spreads out completely, and only the dynamic contact angle can be measured, which tends to become zero over time. 

FIGURE 1.4 Interfacial tensions at the three-phase contact line. R is the radius of the droplet base, 9t is the radius of the droplet. The droplet is small enough, and the gravity action can be neglected. 

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