System Integration - A Major Step toward Lab on a Chip

Microfluidics is a multidisciplinary field investigating the behavior and the manipulation of small amounts of fluids with characteristic length scales from nanometers to hundreds of micrometers [1,2]. The field has been under intensive development for over 20 years as a result of the emergence of microelectromechanical systems. The dramatic change in the length scale offer many new techniques due to the unique importance of phenomena at the microscale such as the domination of surface forces over inertial forces, the laminar nature of fluid flow, fast thermal relaxation and length scale matching with the electric double layer [3]. From a technological point of view, microfluidics offers many advantages including low fluid volumes (less reagents and lower cost), short assay time, low power consumption, rapid generation of small liquid compartments and high degree of parallelization [4-11]. Despite the fact that the inherent advantages of microfluidics are highly promising for realizing the concept of lab-on-a-chip, microfluidics has not been widely adopted in biological engineering and medical applications. By now, the most successful portable bioanalytical platforms with the largest market share are test stripes, which were introduced in the middle of 1980s [12-14].In the past decades, microfluidics has undergone rapid development with numerous new fabrication techniques and device designs. There are a large number of publications and patents of microfluidic devices functioning as pumps [12,13], mixers [14-16], concentrators [17], and valves [18-20], which are the building blocks for creating functional bioreactors and lab-on-a-chip systems. Nevertheless, a major hurdle for transforming microfluidics into practical applications is the integration of these components into a fully automated platform that can be conveniently accessed by the end users [21]. This is primarily due to the complexity of combining various components including bulky supporting equipments (e.