Contact angle is measured between a solid and a liquid-vapor phase; a droplet of water on a table for example. I don't think you can measure or define contact angle between two immiscible fluids, it's always 180 degrees when they are still. Interfacial tension, however, is important in droplet microfluidics, for example in droplet production, the less the interfacial tension is, the easier it is to produce droplets. Hope that makes sense, maybe if you can be more specific, we can help more.
Muhsincan Sesen - Thank you for your comments. Let me know why it is easy to produce droplets when surfactant is added? Is it because of the reduction in surface energy due to molecular interactions as Mohammad Yaghoobi
mentioned? are there any other details which supports this theory?