Simulation study of dielectrophoretic assembly of nanowire between electrode pairs

Abstract

Dielectrophoresis (DEP) of rod-shaped nanostructures is attractive because of its exceptional capability to fabricate nanowire-based electronic devices. This efficient manipulation method, however, has a common side effect of assembling a certain number of nanowires at undesired positions. It is therefore essential to understand the underlying physics of DEP of nanowires in order to better guide the assembly. In this work, we propose theoretical methods to characterize the dielectrophoretic force and torque as well as the hydrodynamic drag force and torque on the nanowire (typical length: 10 lm). The trajectory of the nanowire is then simulated based on rigid body dynamics. The nanowire is predicted to either bridge the electrodes or attach on the surface of one electrode. A neighborhood in which the nanowire is more likely to bridge electrodes is found, which is conducive to successful assembly. The simulation study in this work provides us not only a better understanding of the underlying physics but also practical guidance on nanowire assembly by DEP.

A 3D nanoelectrokinetic model for predictive assembly of nanowire arrays using floating electrode dielectrophoresis

“…This report addresses this need and makes the following contributions: (i) it employs a 3D nanoelectrokinetic model to determine NW trajectories and localization sites on electrodes as a function of all relevant FE-DEP assembly parameters, (ii) this effort considers the impact of the entire electrode array design on the resultant assembly process through the choice of appropriate boundary conditions on simulation workspace. This is in contrast to past reports where the computational models have predominantly considered single electrode locations in isolation while neglecting the impact of neighboring electrodes [27,28], (iii) this report establishes a quantitative correlation between models and experimental data, and thereby, establishes a pathway for quantitative prediction of assembly performance metrics, and (iv) it reveals interesting insights into the asymmetry in NW localization at electrode sites and into the suspension volume from which NWs are drawn to assemble such that their center-of-mass is located either in the inter-electrode gap regions (desired) or on top of one of the assembly electrodes (undesired). This analysis is leveraged to outline a strategy, which involves a physical confinement of the NW suspension within lithographically patterned reservoirs during assembly, for single NW deposition across large arrays with estimated assembly yields on the order of 87%.…”

Photovoltaic Rotation and Transportation of a Fragile Fluorescent Microrod Toward Assembling a Tunable Light-Source System

“…It is important to note that the total electrostatic force on the microrod is obtained by integrating the force acting on each ellipsoid. The electrostatic torque on the microrod primarily comprises two components: the orientational torque ( T 1 , Note S3, Supporting Information), which represents the torque exerted on each ellipsoid to make it align with the local electrostatic field direction, and the rigid body rotational torque (T 2 , Figure S11 and Note S4, Supporting Information) formed by the electrostatic force acting on each ellipsoid relative to a fixed rotation axis of the microrod. − Since the rotation of our microrods in the experiment is two-dimensional, our analysis focuses on the electrostatic force and torque within the rotation plane. The electrostatic force and torque acting on the i-th segment can be described by using the following equations. ⟨ F normalD normalE normalP i ⟩ = 4 π a b c ( ε 2 − ε 1 ) 3 [ E i x 1 + true( ε 2 − ε 1 ε 1 true) L x ∂ ∂ x + E i y 1 + true( ε 2 − ε 1 ε 1 true) L y ∂ ∂ y ] E i F normalD normalE normalP x i = 4 π ...…”

“…In addition to the force and torque exerted by the electrostatic field, the microrod is also subjected to the drag force and torque caused by the viscosity of the oil medium. When the microrod moves in any direction within a two-dimensional plane, the drag force can be expressed as , F normalD normalR normalA normalG = prefix− 2 π η L ln ( L r ) − 0.5 ν x − 4 π η L ln ( L r ) + 0.5 ν y where η is the viscosity of the surrounding fluid, L is the length of the microrod, r is the radius of the microrod, v x and v y are the components of the velocity v along the x and y axes, respectively. In our experiment, the viscosity of the oil, η, is 0.0202 kg m –1 s –1 .…”

Parallel Manipulation and Flexible Assembly of Micro-Spiral via Optoelectronic Tweezers

“…The sphere or rod particles generally use the equivalent dipole moment method to analyze the force ( Tao et al, 2015 ). However, it is not easy to precisely calculate the force of the complex shape of micro-spiral particles.…”

“…Here, we built an equivalent single-shell spiral model for demonstrating the moving characteristics. In addition, because the spiral can be divided into many cylinders segments ( Dalir et al, 2009 ; Tao et al, 2015 ; Li et al, 2016 ), the depolarizing factor of three different axes is set to the same in any one cylinder segment for simplifying the calculation. Thus, the dielectric property parameters use the simplified sphere assumption model to analyze (For details, see Supplementary Theory ).…”