About Microfluidics
The field of microfluidics evolved as engineers and scientists explored new avenues to make use of the fabrication technologies developed by the microelectronics industry. These technologies enabled complex micron and submicron structures to be integrated with electronic systems and batch fabricated at low cost. Mechanical devices fabricated using these technologies have become known as microelectromechanical systems (MEMS), whilst fluidic devices are commonly referred to as microfluidic systems or “lab-on-a-chip” devices. A proper description of these microsystems usually requires multiple physical effects to be incorporated.
At the microscale different physical effects become important to those dominant at macroscopic scales. Properties that scale with the volume of the system (such as inertia) become comparatively less important than those that scale with the surface area of the system (such as viscosity and surface tension). Fluid flow is therefore usually laminar and chemical migration is often limited by diffusion. Electrokinetic effects become important as the electric double layers present at interfaces in the system interact with external applied fields. As systems are further miniaturized, the mean free path of the fluid can become comparable to the size of the system and rarefaction effects become important. At moderate Knudsen numbers (the Knudsen number is the ratio of the mean free path to the system size), it is still possible to use the Navier–Stokes equations to solve the flow; however, special slip boundary conditions are required.
Research activity in microfluidics is changing medical-diagnostic processes such as DNA analysis, and it is spurring the development of successful commercial products.
Tools to address the flow of fluids within porous media are also included as well as a physics interface to model moderately rarefied gas flows (the Slip Flow interface).