Question

Problem 4: It is possible control electronically the internal pressure within a liquid droplet, thereby affecting the contact angle of the droplet. This method is used in camera phones to create liquid lenses. Changing the pressure creates a variable focal length. Let's consider a spherical cap that has a base diameter of 3 mm. The pressure in the droplet is set to 205 Pa and the contact angle at the surface is 30°. What is the surface tension that holds the droplet in place? (5 points)

Answer 1

droplet Patm Pin 2oSKP R130 Dbase = 3mm Patm = lookipa Pin = 205 Pascal .. AP=(Paton Pin) = (10o - 0.205) APF 99.795 kPa Applying force balance Ap xo] 2 = S & D x cose 99.7954103 0.003 – s & col 30² surface tension ass = 86.4 25 cm