The Physics of Microdroplets

Introduction

From Conventional Single-phase Microfluidics to Droplets and Digital Microfluidics

Starting in the year 1980, microfluidics was at first a mere downscaling of macrofluidics. Its development was triggered by the emergence of biotechnology and materials science, imagined by visionary pioneers like Feynman [1], deGennes [2], Whitesides [3] and others. In particular, biotechnology was as a new science at the boundary of physics and biology. The goal was to give biological, medical and pharmaceutical research new automation tools to boost the development of new drugs, fabricate new body implants and increase the potentialities of fundamental research. In reality, this plan imagined by these first researchers has been extremely effective and produced even more discoveries than what was first expected. In a way, biotechnology developments bloomed according to Feynman’s words: “The best way to predict the future is to invent it.” The foreseen goals have required the downscaling of fluidic systems to the “convenient” size to work at the proper scale characteristic of a population of biologic targets. At the same time, it was found that the downscaling brought economy in costly materials, fluids, and devices; that sensitivity was increased and operating times were greatly reduced by the integration of many functions on the same microchip. Gradually, as microsystems based on microflows become conventionally used, new approaches were investigated that required even less volume ...