In this thesis, the bi-phase coplanar substrate including hydrophilic SiO2 and hydrophobic F13-TCS self-assembled monolayer was manufactured by lithography and chemical vapor deposition processes, and the meaning of “coplanar” was also defined. Cassie & Baxter's model was investigated through the bi-phase coplanar and micro-structured SiO2 substrate. The average contact angle of the bi-phase coplanar substrate was raised with the increasing of the hydrophobic surface area, and the average contact angle of the bi-phase coplanar substrate with 75% hydrophobic surface area fraction was almost equaled to 100% hydrophobic surface substrate. The average contact angles of bi-phase coplanar substrates were all higher than those calculated through Cassie & Baxter's model. The average contact angle of the micro-structured substrate was raised by closed air cushion due to the air trapped in the microstructure. Because of the interaction between hydrophilic and hydrophobic phase on the bi-phase coplanar substrate surface, the air was trapped at the solid-liquid interface and formed dynamic air cushion instead of closed one. The wetting surface of the liquid wasn't a flat surface and transformed due to dynamic air cushion, and the wetting mechanism of the bi-phase coplanar substrate was assumed like liquid-air wetting behavior instead of original ideal solid-liquid wetting behavior. The average contact angle was also raised by air cushion effect.