arXiv subjects

Jarrod Schiffbauer

Publications and source records attributed to Jarrod Schiffbauer.

9 recordsLinked to original sources

arXiv2026

Wall accumulation of confined active Janus colloids due to effective active diffusivity

Electrokinetically-driven Janus colloids, e.g., with one metallic and one dielectric hemisphere, confined between parallel walls exhibit a boundary-accumulation mechanism enabled by an effective cross-channel diffusivity which is distinct from wall accumulation of active Brownian or run-andtumble particles. Using density-matched suspensions and three-dimensional confocal imaging, we directly measure the full time-dependent redistribution of particles across the channel under an applied AC electric field. The wall population grows exponentially while the bulk depletes, and data obtained over multiple field strengths collapse onto a single curve when rescaled by the measured relaxation rate, revealing one dominant, confinement-controlled timescale. Propulsion follows the expected induced-charge electrophoretic scaling, with a mean orientation angle lying between 2 degrees and 10 degrees above horizontal, leading to a top-biased accumulation. Comparison with an overdamped Ornstein-Uhlenbeck turning model suggests that persistent stochastic turning about a small out-ofplane angle results in a cross-channel effective drift and diffusion. The drift governs the dominant timescale and the diffusion is strong enough to provide significant accumulation on the bottom wall despite a mean upward orientational bias.

cond-mat.soft↗

arXiv2025

Expanding Active Matter to the Third Dimension: Exploring Short and Long-Range Particle-Wall Interactions

Most active colloid experiments are quasi-2D. Here a 3D density-matched solution of active particles propelled and aligned with an AC electric field uniquely facilitates measurement of short and long-range particle-wall interactions. Near-wall mobility is reduced by Stokes drag and local electric-field distortion. Long-range attractions concentrate particles at upper and lower walls at a ratio dependent on particle orientation and rate proportional to speed and confinement. This approach may be extended to other active systems to understand particle-wall interactions and non-equilibrium phenomena.

cond-mat.soft↗

arXiv2022

Nanoparticle Photo-Ejection from Liquid via Excited Plasmonic Supercavitation

The ability to separate miniscule solid particles (e.g., nanoparticles, NPs) from liquid is important to a wide range of applications, such as water purification, material deposition, and biomedical engineering. Such separation is usually achieved by displacing liquid via filtration or distillation. However, directly moving small particles out of liquid is difficult, especially when their sizes approach the nanometer scale, as the capillary force on the NP at the liquid surface is too large for common body forces (e.g., optical or magnetic) to overcome. Here, we demonstrate the ability to eject metallic NPs out of liquid with a laser excitation at their surface plasmon resonance (SPR) wavelength. The laser applies an optical force on the NPs to drive them toward the liquid surface. In the meantime, the laser can also intensely heat the NP to form a nanobubble encapsulating the NP (i.e., supercavitation), which achieves the liquid-NP separation and thus eliminates the capillary force on the NP at the liquid free surface. We show that such a mechanism can expel NPs out of liquid as observed using a transient scattering experiment, which is further confirmed by molecular dynamics simulations. We also demonstrate depositing the NPs on a solid surface not in contact with the liquid. This study reveals an interesting mechanism to separate NPs from liquid and could potentially benefit separation, nanomaterials and biomedical applications.

physics.optics↗

arXiv2021

Transport Regimes of Underdamped Brownian Particles in a Tilted Washboard Potential

In this paper, a comprehensive examination of the temperature- and bias-dependent diffusion regimes of underdamped Brownian particles is presented. A temperature threshold for a transition between anomalous and normal diffusive behaviors is located, yielding a new phase diagram for the system. In the low-temperature regime, the system exhibits an apparent negative differential mobility due to persistent, long-time subdiffusion at low-bias; at high temperature (or critical bias,) the system rapidly approaches normal diffusion below an intermediate barrier height, $U_o \sim k_B T$. By consideration of numerical results, comparison to the overdamped case, and the related Kramers multistable escape problems, it is demonstrated that the low-bias non-monotonic temperature dependence of the diffusivity, persistent subdiffusion, and negative differential mobility can be traced to inertial effects, which are evident in the oscillatory modes of the velocity power spectra at low bias. In the giant diffusion regime, the velocity power spectra exhibit coupling between the ``locked" and ``running" states, with a characteristic frequency corresponding to the principal frequency of the limit cycles of a damped, driven plane pendulum near critical bias. Non-linear second harmonic generation, corresponding to oscillatory transient anomalous diffusivity, is observed with increasing bias and decreasing temperature, further emphasizing that the low-noise diffusion problem converges to noise-free dynamics, complementing analytic results for the average velocity [L. Cheng and N.K. Yip, Physica D, 2015].

cond-mat.stat-mech↗

arXiv2021

Plasmonic Nanobubbles: A Perspective

The field of plasmonic nanobubbles, referring to bubbles generated around nanoparticles due to plasmonic heating, is growing rapidly in recent years. Theoretical, simulation and experimental studies have been reported to reveal the fundamental physics related to this nanoscale multi-physics phenomenon. Using plasmonic nanobubbles for applications is in the early stage but progressing. In this article, we briefly review the current state of this research field and give our perspectives on the research needs in the theoretical, simulation and experimental fronts. We also give our perspectives on how the fundamental understanding can be applied to more practical applications.

physics.optics↗

arXiv2019

Light-Guided Surface Plasmonic Bubble Movement via Contact Line De-Pinning by In-Situ Deposited Plasmonic Nanoparticle Heating

Precise spatio-temporal control of surface bubble movement can benefit a wide range of applications like high-throughput drug screening, combinatorial material development, microfluidic logic, colloidal and molecular assembly, etc. In this work, we demonstrate that surface bubbles on a solid surface are directed by a laser to move at high speeds (> 1.8 mm/s), and we elucidate the mechanism to be the de-pinning of the three-phase contact line (TPCL) by rapid plasmonic heating of nanoparticles (NPs) deposited in-situ during bubble movement. Based on our observations, we deduce a stick-slip mechanism based on asymmetric fore-aft plasmonic heating: local evaporation at the front TPCL due to plasmonic heating de-pins and extends the front TPCL, followed by the advancement of the trailing TPCL to resume a spherical bubble shape to minimize surface energy. The continuous TPCL drying during bubble movement also enables well-defined contact line deposition of NP clusters along the moving path. Our finding is beneficial to various microfluidics and pattern writing applications.

physics.app-ph↗

arXiv2017

Liquid phase stabilization versus bubble formation at a nanoscale-curved interface

We investigate the nature of vapor bubble nucleation near a nanoscale-curved convex liquid-solid interface using two models; an equilibrium Gibbs model for homogenous formation, and a nonequilibrium dynamic van der Waals/diffuse interface model for phase change in an initially cool liquid. Vapor bubble formation is shown to occur for sufficiently large radius of curvature and is suppressed for smaller radii. Solid-fluid interactions are accounted for and it is shown that liquid-vapor interfacial energy, hence Laplace pressure, has limited influence over bubble formation. The dominant factor is the energetic cost of creating the solid-vapor interface from the existing solid-liquid interface, as demonstrated via both equilibrium and non-equilibrium arguments.

physics.flu-dyn↗

arXiv2015

Probing space charge and resolving overlimiting current mechanisms at the micro-nanochannel interface

We present results demonstrating the space charge-mediated transition between classical, diffusion-limited current and surface-conduction dominant over-limiting current in a shallow micro-nanochannel device. The extended space charge layer develops at the depleted micro-nanochannel entrance at high current and is correlated with a distinctive maximum in the dc resistance. Experimental results for a shallow surface-conduction dominated system are compared with theoretical models, allowing estimates of the effective surface charge at high voltage to be obtained. In comparison to an equilibrium estimate of the surface charge obtained from electrochemical impedance spectroscopy, it is further observed that the effective surface charge appears to change under applied voltage.

physics.flu-dyn↗

arXiv2015

Extended space charge near non-ideally selective membranes and nanochannels

We demonstrate the role of selectivity variation in the structure of the non-equilibrium extended space-charge using 1D analytic and 2D numerical Poisson-Nernst-Planck models for the electro- diffusive transport of a symmetric electrolyte. This provides a deeper understanding of the underly- ing mechanism behind a previously-observed maximum in the resistance-voltage curve for a shallow micro-nanochannel interface device [Schiffbauer, Liel, Leibowitz, Park, and Yossifon, submitted to Phys. Rev. E.]. The current study helps to establish a connection between parameters such as the geometry and nanochannel surface-charge and the control of selectivity and resistance in the over-limiting current regime.

cond-mat.soft↗