Interactions of electrical fields with fluids: laboratory-on-a-chip applications

The area of 'laboratory-on-a-chip', miniaturised or microfluidic analysis systems, is a rapidly developing field. At the microscale, electrokinetic processes become enhanced, and the advent of AC electrokinetics (EK) in recent years further promotes the development of electrokinetic devices for microfluidics. ACEK has demonstrated to manipulate fluids and polarisable particles at low voltages without some of the disadvantages from DCEK, such as electrochemical reactions and the limitation of low ionic strength fluids. The three major mechanisms of ACEK, that is, dielectrophoresis, AC electro-osmosis and AC electrothermal effect, provide versatility and flexibility to interface with many current methods and technologies in multiple biological, chemical and physical disciplines. This paper gives an overview of ACEK and its applications, with an emphasis on fluid manipulation by electric fields.