On the non-equilibrium coupling of colloidal particles with a critical bath

At the mesoscopic scale, energy exchanges are on the edge of thermal fluctuations, giving rise to stochastic thermodynamics. This framework reshapes traditional notions of energy and entropy by incorporating environmental noise. Among various thermal environments, critical baths—created by a binary liquid mixture near its critical point—offer a unique platform for exploration. These baths mimic properties relevant to biological systems, such as adaptability and resilience. Despite their potential, the behaviour of systems coupled to critical baths under non-equilibrium remains poorly understood. In this study, we investigate colloidal particles in a micellar solution tuned to criticality. Using optical traps and local laser-heating, we drive the system out of equilibrium in controlled ways. We observe how particle dragging and temperature quenches reshape critical fluctuations and influence colloidal interactions. Our results reveal stronger-than-expected interactions, critical slowing down and an effective fluctuations-field. These phenomena suggest an emergent dynamic capable of processing information through environmental energy. This positions critical colloidal systems as candidates for novel soft-matter computing devices.