CONTENTS 6.1 Introduction ................................................................................................ 144 6.2 Background................................................................................................. 145 6.3 Fabrication Processes ................................................................................ 148 6.4 Mechanical Micropumps .......................................................................... 150

6.4.1 Actuation Sources ......................................................................... 150 6.4.1.1 External Actuators .......................................................... 150 6.4.1.2 Electromagnetic Actuation ............................................ 150 6.4.1.3 Piezoelectric Actuation .................................................. 151 6.4.1.4 Pneumatic Actuation...................................................... 153 6.4.1.5 Shape Memory Alloy ..................................................... 153 6.4.1.6 Integrated Actuators....................................................... 153 6.4.1.7 Electrostatic Actuation ................................................... 153 6.4.1.8 Thermopneumatic Actuation........................................ 153 6.4.1.9 Bimetallic Thermal Actuation....................................... 154

6.4.2 Positive Displacement Pumps .................................................... 154 6.4.2.1 Positive Displacement Pumps with Integrated

Check Valves.................................................................... 155 6.4.3 Fixed-Geometry Rectification Micropumps.............................. 156 6.4.4 Peristaltic Pumps........................................................................... 162 6.4.5 Acoustic Streaming ....................................................................... 164

6.5 Nonmechanical Micropumps .................................................................. 166 6.5.1 Electroosmotic Flow Micropumps ............................................. 166 6.5.2 Electrowetting ................................................................................ 168 6.5.3 Marangoni Pumps......................................................................... 169 6.5.4 Buoyancy-Driven Flows............................................................... 171

6.6 Conclusions................................................................................................. 172 References ............................................................................................. 172

Batch-fabricated microfluidic platforms that can mimic conventional sample handling techniques performed in hospitals and laboratories hold great potential to enable both research and healthcare advances. Such miniaturized diagnostic devices have been termed micro total analysis systems (µTAS) or biochips, and combine sensing mechanisms (physical, optical, electrical, or chemical) with microfluidics. Such autonomous platforms have attracted considerable research interest due to the opportunity for fabricating a highly integrated system able to perform all necessary processing steps required for the specific application. While microfluidics promises to have an impact in many research fields, one of the more attractive applications of microfluidics has been in biomedical and life science diagnostics [1]. µTAS applications are attractive because of the potential of such systems to allow faster analysis of biological material, as well as reducing the amount of reagent required for processing steps. In addition, miniaturization of such systems can result in higher repeatability and precision of analysis, lower power consumption, and the potential to create portable diagnostic tools for on-site analysis. These advantages result not only in time and cost savings for diagnostic tests, but can also be life saving in time-critical environments such as critical medical diagnostics or biowarfare pathogen detection. A major research thrust in microfluidics has been the development of autonomous platforms for allowing controlled microscale fluid transport allowing fluid flow rates ranging from nl/hrs to µl/min within compact fluid-handling and delivery systems-micropumps [2,3].