Combined Magneto- and Optofluidic Assembly of Colloidal Chains of Controllable Length

Combined magneto- and optofluidic assembly of colloidal chains of controllable length

Because of their unique characteristics, colloids have been used to investigate the fundamental physics of soft materials including both equilibrium phase behavior and kinetic processes. Unlike atoms, colloidal sizes can be conveniently tailored and are typically large enough to be probed individually with interaction strengths and effective ranges that can be modulated over several orders of magnitude. Despite these significant advantages, mostly relatively simple colloidal models such as spheres have been created; such systems in turn assemble into crystals of fairly limited symmetry, precluding the study of problems associated with complex structure. To push towards the synthesis of more complicated colloidal molecules, we use combined applied magnetic and anisotropic optical fields to fabricate colloidal chains. In these experiments, thiol-functionalized magnetic beads were linked via maleimide-functionalized polyethylene glycol crosslinker. Properties of assembled chains including flexibility and stability were tuned by varying the linker length and system temperature during synthesis. With integration of an optofluidic field, chain length and sequence could also be modified by balancing hydrodynamic shear stress, applied magnetic field, and applied optical forces.