Efficient separations of particles with micron and submicron dimensions are extremely useful in preparation and analysis of materials for nanotechnological and biological applications. Here, we demonstrate a nonintuitive, yet efficient, separation mechanism for μm and subμm colloidal particles and organelles, taking advantage of particle transport in a nonlinear post array in a microfluidic device under the periodic action of electrokinetic and dielectrophoretic forces. We reveal regimes in which deterministic particle migration opposite to the average applied force occurs for a larger particle, a typical signature of deterministic absolute negative mobility (dANM), whereas normal response is obtained for smaller particles. The coexistence of dANM and normal migration was characterized and optimized in numerical modeling and subsequently implemented in a microfluidic device demonstrating at least 2 orders of magnitude higher migration speeds as compared to previous ANM systems. We also induce dANM for mouse liver mitochondria and envision that the separation mechanisms described here provide size selectivity required in future separations of organelles, nanoparticles, and protein nanocrystals.
Bibliographical noteFunding Information:
We thank Dr. F. Camacho-Alanis from the School of Molecular Sciences at Arizona State University for her help with photolithography. We thank M. Kyba from the Department of Pediatrics at the University of Minnesota for providing mice for the isolation of mitochondria. E.A. and K.A.M. thank the National Institutes of Health (Grants ROI-AG020866 and T32- AG029796) for support to participate in this collaborative effort.