Abstract
Separation of (biological) particles (ll {10}~{upmu }text {m}) according to size or other properties is an ongoing challenge in a variety of technical relevant fields. Dielectrophoresis is one method to separate particles according to a diversity of properties, and within the last decades a pool of dielectrophoretic separation techniques has been developed. However, many of them either suffer selectivity or throughput. We use simulation and experiments to investigate retention mechanisms in a novel DEP scheme, namely, frequency-modulated DEP. Results from experiments and simulation show a good agreement for the separation of binary PS particles mixtures with respect to size and more importantly, for the challenging task of separating equally sized microparticles according to surface functionalization alone. The separation with respect to size was performed using 2 {upmu }m and 3 {upmu }m sized particles, whereas separation with respect to surface functionalization was performed with 2 {upmu }m particles. The results from this study can be used to solve challenging separation tasks, for example to separate particles with distributed properties.
Highlights
Separation of particles (≪ 10 μm ) according to size or other properties is an ongoing challenge in a variety of technical relevant fields
With ε = ε0εr − i ωσ, where σ is the conductivity, ε0 the vacuum permittivity and ω = 2π f represents the angular frequency of the applied electric field. This factor ranges between - 0.5 and 1 and determines the movement direction of the particle: When Re(CM) > 0, particles experience positive dielectrophoresis and move towards local field maxima, when Re(CM) < 0, particles experience negative dielectrophoresis and are repelled from field maxima
We have used simulation and experiments to demonstrate three different particle behaviors in frequency-modulated chromatography, i.e., retardation due to negative dielectrophoresis (nDEP) or positive dielectrophoresis (pDEP)-dominated behavior or a balanced behavior leading to no retardation
Summary
Separation of (biological) particles (≪ 10 μm ) according to size or other properties is an ongoing challenge in a variety of technical relevant fields. Results from experiments and simulation show a good agreement for the separation of binary PS particles mixtures with respect to size and more importantly, for the challenging task of separating sized microparticles according to surface functionalization alone. We like to note that many biological separation tasks[8,9,10,11] or valuable dust fractions[2] are within this size range For such particle sizes, (gel-)electrophoresis[12,13], field-flow-fractionation (FFF)[14], or size-exclusion c hromatography[15] are some common methods. Due to its dependency on field frequency and medium properties, Re(CM) can change its value or sign during an experiment, which can result in a movement direction change of target particles. The net conductivity of a microparticle of non-conducting bulk material in an electrolyte suspension can be calculated a s16,23 σp
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