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ABSTRACT Dielectrophoresis (DEP) has been extensively researched over the years for filtration, separation, detection, and collection of micro/nano/bioparticles. Numerical models have historically been employed to predict particle trajectories in three‐dimensional (3D) DEP systems, but a common issue arises due to inherent noise near the edges of electrodes due to electric potential discontinuity, specifically when calculating electric field and gradient of electric field‐squared, . This noise can be reduced to a certain extent with a finer mesh density but results near the electrode edge still have significant error. Realizing the importance of particle‐electrode edge interactions prevalent in positive DEP systems, analytical solutions given by Sun et al. was incorporated to demonstrate an improved 3D model of interdigitated electrodes. The results of electric field and gradient of electric field‐squared of the numerical model and the improved analytical 3D model were compared, within a simulation space of 50 µm height, 10 µm width, and 50 µm length with interdigitated electrodes of the same width and gap of 10 µm. The DEP particle trajectory error due to the noise was quantified for different particle sizes at various heights above the electrode edge. For example, at 5 Vrms, a trapped 500 nm particles exhibited a velocity error of 104µm/s (it should have been zero).
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This content will become publicly available on October 1, 2026
High-resolution mapping of the radial electric field in RF plasma sheath using a single optically trapped particle
Abstract Mapping individual components of the electric field,E, with high spatial resolution around the plasma sheath remains challenging, as mostin situplasma probes are generally too intrusive for reliable plasma potential measurements. An optically trapped micron-sized particle in a plasma environment represents the smallest, nonintrusive, or minimally intrusive diagnostic tool because it causes minimal disturbance to the plasma environment in which it is suspended. These microparticles can be used to map the electric fieldin situwith high spatial resolution in a radio frequency (RF) plasma sheath region. In this study, we optically trapped micron-sized single particles and precisely transported a single trapped particle within the cylindrically symmetric capacitively coupled plasma (CCP), over a radial distance of ∼ 0–15 mm, a 2400-fold displacement relative to the particle size, corresponding to a spatial resolution of tens of micrometers. We measured |E| and its spatial distributions in the examined range by analyzing the particle’s trajectory in the plasma after the optical forces were turned off. The radial component of the electric field, |Er|, was measured at multiple locations parallel to the electrode at 6.7 Pa. The |Er| was strongest near the circular electrode edges, reaching 0.478 ± 0.005 V mm−1, and decreased to 0.458 ± 0.001 V mm−1toward the center of the electrode. We reconstructed the radial plasma potential, yielding a center-to-edge potential decrease of 4.6 V over one centimeter. This ΔVis consistent with reported CCP trends of small mid-plane radial potential gradients and serves as the confining potential for dust crystal and dust cluster studies. These results highlight the use of optical trapping of a single particle as anin situ, nonintrusive microprobe for quantitative mapping ofEr(r) andV(r) in RF plasmas.
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- PAR ID:
- 10681428
- Publisher / Repository:
- IOP
- Date Published:
- Journal Name:
- Plasma Sources Science and Technology
- Volume:
- 34
- Issue:
- 10
- ISSN:
- 0963-0252
- Page Range / eLocation ID:
- 105023
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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