Particle Micromanipulation Using Single Magnetic Sources

Abstract

During the last few decades, a myriad of artificially built small-scale agents became able to emulate the movement of their natural counterparts, thanks to the complex machinery dedicated to inducing precise movement from the millimeter to nanometer scale. Manipulation of individual particles using single sources of a magnetic field, such as a permanent magnet or electromagnetic needles, has been studied in microfluidics and biophysics. These previous studies mostly focused on applications in biological characterization by pulling a single particle or separation of magnetic from non-magnetic particles. Little attention has been dedicated to particle manipulation techniques such as pick-and-place or trajectory control. The objective of this dissertation is to study these particle manipulation techniques using single magnetic sources. The work resulted in three new techniques, two new biological relevant applications, discovered two new motion modes and constructed a new theoretical model in particle manipulation by single magnetic sources. Firstly, a new pick-and-place technique for the manipulation of individual magnetic microparticles using an electromagnetic needle mounted on a nanopositioner is reported. This technique demonstrates the manipulation of the smallest magnetic particles (~5 µm in diameter) in a pick-and-place manner. The technique shows that individual microparticles surrounded by other particles can be selectively manipulated. This work contributes to the knowledge in the manipulation of magnetic microparticles in terms of individual addressability. Secondly, the applicability of the electromagnetic needle-superparamagnetic particle system utilized in a non-contact manner has been extended in the microrheological characterization of liquid-like coacervates. This application broadens the state-of-the-art in microrheology to types of materials to which magnetic-based microrheological technique has not been previously applied. Additionally, the non-contact manipulation of superparamagnetic particles by electromagnetic needle has been automated. This automatic technique addresses individual particles in a population resulting in automated selective extraction of magnetic particles from a population of particles and its application in targeted load delivery to single cells. This application has contributed to broadening the application domain of selectively manipulated magnetic microparticles in a non-contact manner. Lastly, two new motion modes have been discovered and a new theoretical model proposed. These novel contributions describe the underlying motion mechanism of non-magnetic milli- and micrometer spheroid particles on an air-magnetic liquid interface when subjected to a magnetic field from a permanent magnet. The new motion modes lead to new manipulation techniques on moving particles by robotic guiding and directed self-assembly on an air-magnetic liquid interface.