5: Forces in Microfluidics Check Access

This chapter discusses different forces and their applications in microfluidic systems. It starts with the magnetic force used in diagnostic systems to extract DNA, RNA or proteins. This force can be controlled with permanent magnets or electromagnets to drag magnetic particles inside microfluidic systems or to keep magnetic particles stationary while moving the system around it. Dielectrophoresis, a technique used for sample purification with alternating current-based (ac) electromagnetic fields, is then discussed. Optical tweezers and the use of weak yet simple optical forces are explored. Acoustic forces are typically created at the piezoelectric substrate level and are used to move samples from place to place. Utilization of inertial forces is also popular, using either stationary substrates or mobile (centrifugal) methods for sample separation, processing or performing an entire micro total analysis system (µTAS).