DNA-induced changes in traveling wave dielectrophoresis velocity of microparticles

Electrokinetic motion of dielectric microparticles is used in various applications, as the dielectrophoresis (DEP) of the microparticles depends on their polarization in an electric field. This polarization, given by the Clausius-Mossotti (CM) factor, depends on a particle's surface conductance. This study demonstrates that DNA can induce changes to the nature of the traveling-wave DEP (twDEP) force on a microparticle. As DNA molecules have electric charges on their phosphate backbones, attaching these molecules to the surface of a microparticle increases its surface conductance, resulting in a change in the imaginary part of the CM factor. We conducted image-based analysis of the twDEP velocity of ensembles of microparticles labeled with DNA in the range of 100-10 000 molecules per microparticle. Our experiments revealed that, in addition to being proportional to the number of DNA molecules on a particle, the twDEP velocity of sparsely labeled microparticles (∼100 DNA molecules per microparticle) can be distinguished from that of a bare one, suggesting that the twDEP velocity measurement can be utilized as a DNA detection method.