School of Mechanical Engineering Seminar
Wednesday 1.11.2023 at 14:00

ZOOM SEMINAR

Electrokinetics, Dynamics & Stability of Single and Two Interacting Janus Particles Under Gravity

Yarin Vaknin

M.Sc. student of Prof. Touvia Miloh

School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel

Prof. Gottlieb Oded

Technion Israel

One of the simplest inhomogeneous geometries in electrokinetics is that of a Janus sphere, which comprises two hemispheres with differing properties. In our research, we explore the non-linear dipolophoretic motion (dielectrophoresis combined with induced-charge electrophoresis) of a nano/micro Janus particle when exposed to a spatially uniform ambient AC electric field, both in the presence and absence of a gravity field. In our case, we consider the special case of a "metallodielectric"  Janus sphere, comprises of two half-spheres - one metallic and the other dielectric.

Both the electrostatic and hydrodynamic problems are solved for the unbounded case (no walls) under the conventional Poisson-Nernst-Planck (PNP) model by assuming a “weak-field” and a “thin” Debye layer. Furthermore, we analyze the resulting dipolophoretic motion of two adjacent interacting Janus particles which are exposed to a spatially uniform ambient AC electric field (again with or without gravity). In addition to the electrostatic and hydrodynamic forces applied on a single sphere, we also calculate the induced velocity at the center of one sphere due to the Stokes motion of the other sphere by means of Faxen. In order to analyze the dynamics and stability of these complex phenomena, we employ a combination of analytical and numerical methods.

The implications of our findings are vast, with potential applications ranging from drug delivery systems to the design of probes based on Janus nanoparticles, which can provide directional data about cell-particle interactions.

https://tau-ac-il.zoom.us/j/86497933118

סמינר זה יחשב כסמינר שמיעה לתלמידי תואר שני

15:00 vited to attend a lecture on Thursday, July 20^th, 2023

Room 011, Kitot Building

Reconstruction of electric field in an M-S-M device, based on Transient current technique measurements

By:

Odelya Amzallag

M.Sc. student under the supervision of Prof. Arie Ruzin

Abstract

The profile of the electric field in the active volume of a detector affects its performance. In many practical devices this information is missing or not well established (e.g., the ohmic contacts may be not ideal, or the material can sustain radiation-induced damage and change its electrical properties). Thus, the ability to deduce the electric field distribution inside a detector, from experimental results is essential.  Such ability allows for exploration of the nature of the crystal, traps and their properties, the nature of the contacts, the effect of traditional treatments etc. This is the main goal of the TCT characterization. In TCT characterization the system injects short laser pulses into the semiconductor detector, to produce free charge carriers in a known location. The applied external voltage separates the holes and the electrons and drifts them in opposite directions. The resulting current pulses at the contacts of the device are amplified, measured, and recorded.  The moving carriers induce displacement currents in the contacts. Reconstruction of the electric field from the current pulses is not straightforward and requires certain simplifications. To address this issue, we present a few approximations that were designed to improve accuracy of the calculations. These approximations were developed based on TCAD high accuracy simulations. The method was then implemented on experimental current pulses, as part of different experiments.