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Introduction to Microfluidics
Microfludics is to study fluids in microscale. The field involves (1) microfabrication (to make devices containing microscale features), (2) microflows (to study fluids, e.g, pumping, valving, mixing, and simulation), and (3) applications.
Devices are fabricated using techniques similar to those used for fabricating computer chips. The techniques include film deposition, patterning (as in photolithography), etching, assembly, and others. The process of making a plastic device is illustrated in Figure 1.
Figure 1. The process to fabricate a plastic microfluidic device. (J. MEMS, 15, 2006, 1060)
Manipulation of fluids in a microfluidic device needs pumps. Electroosmosis (EO) is one of mechanisms suitable for pumping fluids in microdevices. EO is generated in a micro-channel filled with an appropriate solution when a voltage is applied across the channel. Figure 2 shows that a fluorescent dye is electroosmotically pumped through a vertical channel and then injected into multiple horizontal channels. Click the link (.avi) to watch the video.
Applications of microfludics and BioMEMS devices include cell culture and analysis, clinical diagnostics, environmental monitoring, DNA and protein analysis, and biological warfare agent detection. Examples of extensive reviews on the topic include: Special issue in Nature, Vol 442, July 27, 2006, 367-418; Manz, et al. Analytical Chemistry 2008, 80, 4403-4419.
Figure 2. EO pumping of a fluorescent dye into multiple horizontal channels.
Selected Research Projects in Dr. Fan's Lab
2D Chip. The goal is to design and fabricate a microfluidic device that provides an alternative approach to two-dimensional gel electrophoresis, which is extensively used in chemical and biological labs. The microfluidics-enabled method likely leads to rapid analysis, high separation resolution, improved protein identification accuracy, and enhanced reproducibility. The device could be used as a tool for biomarker discovery and screening. The project has been funded by USA Army.
Hydrogen Sensor. The goal is to develop a sensor for detecting possible leakage of hydrogenthe fuel of today's space vehicle and possibly tomorrow's automobiles. The sensor is based on an enzyme-catalyzed reaction, which can be carried out in a microfluidic device. Compared to the state-of-the-art, metal or alloy-based hydrogen gas sensors, the benefits include ambient temperature operation and enhanced selectivity over background gases. The project has been funded by National Science Foundation (NSF) and National Aeronautics and Space Administration (NASA).
Toxin Detection. The goal is to develop a multiplexed, in vitro protein expression system for detecting biological warfare agents or other hazards. The system consists of an array of microfluidic units and each unit functions as a sensor. When a toxic agent is present, the inhibition of protein expression in the array will be characterized, generating a signature of responses. The system may also be useful for high-throughput protein production. The project is currently funded by Defense Advanced Research Projects Agency (DARPA).
Microfluidic Valves. The goal is to develop thermally actuated and manufactuable microfluidic valves for a variety of applications. The valves can be integrated in a device; the actuation of valves will be controlled by a printed circuit board (PCB). The valves are expected to be useful in any system that needs flow controls and fluid metering. The project is currently funded by DARPA.
Examples of Corporations Using Microfluidics
Agilent Technologies Caliper Life Sciences Cepheid Eksigent
Fluidigm Gyros Micralyne Micronics Nanostream
Useful Links:
A scientific journal dedicated to the field, Lab on a chip, by Royal Society of Chemistry.
Many scientific conferences dedicated to the field, including µTAS, Transducers, Hilton Head, Microscale BioSeparation, MEMS, etc.