Microparticle Manipulation with Low Frequency Alternating Current Electric Potential in Insulator-Based Dielectroforesis Microdevices

Many microfluidics applications require techniques that can effectively trap, sort, separate and concentrate particles, especially those of biological importance, such as proteins, DNA and cells.  Important research efforts are dedicated towards the development of microfluidic techniques. Dielectrophoresis (DEP) is a microscale technique with great potential for the manipulation of bio-microparticles in applications for food and water safety, environmental monitoring of pathogens and clinical analysis. DEP is the movement of particle due to polarization effects caused by exposing the particles to non-uniform electric fields. That is, for DEP to occur, it is necessary to generate a non-uniform electric field. One of the leading methods of applying DEP is the use of insulating structures to create the required non-uniform electric fields, the insulator act as “obstacles” that distort the electric field distribution, creating regions of higher and lower field intensity. Insulator based dielectrophoresis (iDEP) allows to produce highly controlled particle manipulation in microfluidic channels. Electrophoresis (EP) is the electrokinetic (EK) movement of charged particles through a conductive medium in a direct current (DC) electric field to an oppositely charged electrode. Electroosmotic flow (EOF) is the EK movement of a conductive bulk fluid by exploiting the electrical double layer in a microfluidic channel with the application of an electric field. Both of these EK phenomena correlate linearly with the electric field and pale in comparison to the second order effect of dielectrophoresis.  Previous experiments [1] have demonstrated the advantages of using low frequency (~ 1 Hz) alternating current (AC) potentials, in which microparticles can be precisely controlled to flow in a bidirectional manner, over DC, an omnidirectional flow field. By manipulating the frequency of the applied AC electric potential in the low frequency domain, the ability to trap particles, the speed in which bands of trapped homogeneous particles are formed, and the systematic release of desired particles, can be controlled. By increasing the complexity of the applied electric potential, utilizing offset values, resolution of the applied AC signal, frequency and amplitude, not only can trapping/concentration of particles be improved, but the ability to selectively release specific particles greatly increases. The results and potential capabilities of iDEP combined with AC electric potentials are presented and discussed.

 [1]        Baylon-Cardiel JL, Jesús-Pérez NM, Chávez-Santoscoy AV, Lapizco-Encinas BH (2010) Controlled microparticle manipulation employing low frequency alternating electric fields in an array of insulators. Lab Chip 10(23):3235-3242.