Micro-Drops and Digital Microfluidics

2

Theory of Wetting

2.1 Introduction

The understanding, development, and design of fluidic microsystems require dealing with forces that are usually overlooked and neglected at the macroscopic scale. In the case of digital microfluidics, interfaces are omnipresent and capillary and surface tension forces have a tremendous influence. These forces are of utmost importance at the microscopic level, whereas at a macroscopic scale, they are usually neglected in front of forces like pressure or gravity. Typical ranges of pressure in macroscopic applications are 1–100 bars, i.e., 10⁵ to 10⁷ Pa, whereas pressure levels seldom reaches 0.1 bar (10⁴ Pa) ...