New Methods to Transport Fluids in Micro-Sized Devices

Microfluidics encompasses the science and technology of systems that process or manipulate extremely small volumes of fluids, generally ranging from nanoliters to attoliters (10 –9 to 10 –18 liters). Applications span from physical-science-based applications such as inkjet printers and microfuel cells to biotechnology applications such as DNA analysis and drug discovery. The appeal of microfluidics, particularly in biotechnology, is the ability to separate and detect cells, molecules, and other entities and to perform analyses more quickly and with increased sensitivity, automation, and parallelization. Moreover, the reduction in reagent and sample volumes means less cost per analysis [1]. Such miniaturization also opens up the possibility of developing portable devices for medical diagnostic tools or environmental monitors. However, the miniaturization of fluid systems poses significant challenges. For example, the fundamental task of integrating fluid into a micro-sized device can be difficult because fluid-handling tools required to go from the macro-world to the micro-world are not yet well established. In addition, the ability to precisely control and transport fluid in micro-sized structures presents its own unique set of challenges. At the root of these challenges is fundamental fluid physics. For devices in which feature dimensions are on the scale of micrometers and fluid volumes on the order of nanoliters, surface tension, viscosity, and electrical charges become dominant forces over inertial forces. As a consequence, performing the basic fluidic operations that are essential to the functionality of the system— such as fluid transport, mixing, and filtering—requires Applications of microfluidics require a self-contained, active pumping system in which the package size is comparable to the volume of fluid being transported. Over the past decade, several systems have been developed to address this issue, but either these systems have high power requirements or the microfabrication is too complex to be cost efficient. A recent effort at Lincoln Laboratory using an emerging technology called electrowetting has led to the development of several novel micropump concepts for pumping liquids continuously, as well as for pumping discrete volumes.