Novel Magnetic Actuation Strategies for Precise Ferrofluid Marble Manipulation in Magnetic Digital Microfluidics: Position Control and Applications

TL;DR

This paper introduces a novel magnetic actuation method using Helmholtz coils and permanent magnets for precise control of ferrofluid marbles in microfluidic systems, enabling advanced manipulation and application capabilities.

Contribution

It presents the first detailed control strategy for ferrofluid marbles in magnetic digital microfluidics, including governing equations, magnetic setup designs, and experimental validation.

Findings

Successful demonstration of precise FM positioning

Comparison of magnetic setups in energy efficiency and tracking

Applications in liquid transport and sample extraction

Abstract

Precise manipulation of liquid marbles has significant potential in various applications such as lab-on-a-chip systems, drug delivery, and biotechnology and has been a challenge for researchers. Ferrofluid marble (FM) is a marble with a ferrofluid core that can easily be manipulated by a magnetic field. Although FMs have great potential for accurate positioning and manipulation, these marbles have not been precisely controlled in magnetic digital microfluidics, so far. In this study for the first time, a novel method of magnetic actuation is proposed using a pair of Helmholtz coils and permanent magnets. The governing equations for controlling the FM position are investigated, and it is shown that there are three different strategies for adjusting the applied magnetic force. Then, experiments are conducted to demonstrate the capability of the proposed method. To this aim, different magnetic setups are proposed for manipulating FMs. These setups are compared in terms of energy consumption and tracking ability across various frequencies. The study showcases several applications of precise FM position control, including controllable reciprocal positioning, simultaneous position control of two FMs, the transport of non-magnetic liquid marbles using the FMs, and sample extraction method from the liquid core of the FM.