Particles larger than ordinary molecules or atoms but still invisible to the naked eye can create useful structures like tiny propellers, cellular probes, and microwheels for drug delivery. A team of Rice University chemical engineers led by Lisa Biswal discovered that exposing micron-sized beads with magnetic sensitivity to a rapidly alternating magnetic field causes them to organize into anisotropic structures that can be manipulated to create new material structures and properties. The finding is significant for advanced materials design and provides a way to control particles with precision.
The research focused on superparamagnetic colloids, which are responsive to magnetic fields and commonly used as building blocks for high-performance materials. By considering the magnetic relaxation time of the beads, the researchers were able to influence the interactions between particles, leading to the formation of crystal lattices and elongated clusters. By combining experiments, simulations, and theoretical predictions, the team analyzed concentrated and dilute bead suspensions under different magnetic field conditions, to observe how various parameters influenced the formation of elongated clusters and alignments.
Experimental insights from dimers helped explain the alignment and elongation in larger clusters, with the results matching simulations once the magnetic relaxation time measurements were taken into account. The Pac-Man shape described in the data represented the distribution of a bead’s magnetization, showing the weakest interactions at the mouth and the strongest interactions at the head, leading to the alignment of dimers and clusters. This unique phenomenon would not have been understood without deviating from traditional assumptions used to study these beads, showcasing the significance of the study.
The team’s research combines experiments, simulations, and theoretical predictions to understand the behavior of superparamagnetic colloids under magnetic fields. By analyzing the response of the beads to changes in field direction, they were able to control the particles with precision, creating anisotropic structures with tunable properties. The findings highlight the importance of considering magnetic relaxation time in the design of advanced materials, and the potential for creating novel structures with unique functionalities.
The study’s findings have implications for bottom-up advanced materials design, enabling precise control over particles to create tailored material structures with specific properties. By manipulating the interactions between the colloids and magnetic fields, the researchers were able to form crystal lattices in two dimensions and elongated, aligned clusters in three dimensions. The research opens up new possibilities for creating advanced materials with enhanced functionality and provides insights into the behavior of superparamagnetic colloids under varying magnetic field conditions.
The research, led by Lisa Biswal and her team of chemical engineers at Rice University, sheds light on the potential of manipulating superparamagnetic colloids to create anisotropic structures with unique properties. Through a combination of experiments, simulations, and theoretical predictions, the team identified the influence of magnetic relaxation time on the interactions between particles, leading to the formation of novel material structures. The study provides valuable insights for the design of advanced materials and highlights the importance of considering the magnetic properties of particles in material engineering.
