Microelectrode devices for manipulating and analysing bioparticles

Micro-fabrication techniques, such as photo- and electron beam lithography and etching processes, are currently being used to develop microelectrode structures and new devices for applications in biomedicine and biotechnology. With these devices various types of bioparticle can be subjected to strong inhomogeneous electric fields, rotating fields or travelling fields. These fields can be generated over a wide range of electrical frequencies, so that the characteristic dielectric properties of the bioparticles can be tharaughly diagnosed or exploited. This article describes how the AC electrokinetic techniques of dielectrophoresis (motion of particles in inhomogeneous fields) and electrorotation can be used to detect or selectively manipulate cells and micro-organisms. New results, employing travelling field dielectrophoresis, of the separation of red and white blood cells and of the selective separation and concentration of viable yeast cells, are also presented.