(510d) Magnetic Microstructuring of Non-Magnetic Colloids

Studying the response of colloids to changes in the energy landscape is challenging but essential to understanding phenomena such as phase transitions. One approach to dynamically control interparticle interactions is to apply external magnetic fields that are contactless and chemically inert. In this study, we leverage the unique dual nature of magnetic nanoparticle dispersions to program interactions between suspended non-magnetic microspheres. At the microscale, the magnetic dispersion behaves as a continuous magnetic medium, while at the nanoscale, it is a discrete medium composed of individual particles. This enables the introduction of a pre-programmable depletion attractive potential and an in situ tunable magnetic repulsive potential, facilitating reversible transition of colloidal structures within a rich phase diagram using an external magnetic field. By actively controlling competing interactions, we create a model system encompassing a range of states, from large fractal clusters to low-density Wigner glass states.