Magneto-electrical orientation of lipid-coated graphitic micro-particles in solution

TL;DR

This study demonstrates the first confinement and orientation control of lipid-coated graphitic micro-particles in solution using combined magnetic and electric fields, enabling precise manipulation and measurement of their properties.

Contribution

It introduces a novel method for orienting and trapping micron-sized graphitic flakes in solution through magnetic and electric fields, with quantitative analysis of their rotational dynamics.

Findings

Successfully oriented and trapped micro-flakes in a defined plane

Quantified rotational trap stiffness and torque

Analyzed particle-surface interactions

Abstract

We demonstrate, for the first time, confinement of the orientation of micron-sized graphitic flakes to a well-defined plane. We orient and rotationally trap lipid-coated highly ordered pyrolytic graphite (HOPG) micro-flakes in aqueous solution using a combination of uniform magnetic and AC electric fields and exploiting the anisotropic diamagnetic and electrical properties of HOPG. Measuring the rotational Brownian fluctuations of individual oriented particles in rotational traps, we quantitatively determine the rotational trap stiffness, maximum applied torque and polarization anisotropy of the micro-flakes, as well as their dependency on the electric field frequency. Additionally, we quantify interactions of the micro-particles with adjacent glass surfaces with various surface treatments. We outline the various applications of this work, including torque sensing in biological systems.