Chemical Modulation of Optical Forces for Dynamic Light-Driven Materials.

Controlling colloidal assembly with high spatial and temporal precision is essential for next-generation photonic and functional materials. Optical forces offer unique advantages, yet remain largely decoupled from chemical stimuli. Here, we introduce a simple strategy to chemically gate absorption-driven optical forces using pH-responsive polyaniline-doped polystyrene microparticles. Under basic conditions, enhanced absorption at 561 nm amplifies axial optical forces, producing superdiffusive motion and promoting the formation of large, ordered interfacial assemblies. Instead, acidic conditions suppress absorption, yielding only small, disordered clusters. This reversible chemical control establishes a general framework for coupling light-matter interactions with chromogenic chemistry, enabling chemo-adaptive, light-driven materials for dynamic sensing and programmable matter.