Classical dielectrophoresis (DEP) theories based on the Clausius–Mossotti (CM) factor can become inadequate at the nanoscale and for biomolecules, making experimental characterization of particle polarizability increasingly important. Existing characterization approaches often rely on single-particle tracking, which becomes challenging for small particles or particles with low fluorescence intensity. Here, we demonstrate a hybrid experimental–computational approach that enables nanoparticle polarizability quantification without the need for individual particle tracking.
The method is demonstrated using polystyrene nanoparticles suspended in low-conductivity media. Nanoparticles are captured by DEP using an array of interdigitated microelectrodes and imaged using confocal microscopy, from which image-based metrics sensitive to DEP strength are extracted. In parallel, a continuum transport model is used to calculate steady-state particle concentration profiles during DEP capture. The simulated concentration distributions are convolved with the experimentally measured point-spread function of the imaging system, enabling direct quantitative comparison between simulations and microscopy experiments.
By fitting the model to experimental measurements, effective particle polarizabilities are determined for polystyrene nanoparticles of different sizes and across media of different conductivities. This approach provides a route toward quantitative characterization of DEP response in systems for which conventional single-particle methods are impractical and where classical theories break down.
