The creation of new, smart materials requires the ability to control properties indirectly, using an external stimulus. Lyotropic liquid crystals are the perfect candidates to form functional materials, due to their ordered nanostructures that are sensitive to their external environment. This has led to their implementation in applications as diverse as drug delivery vectors, ion conduction pathways for fuel cells and DNA templating. If we can manipulate this liquid crystal nanostructure using light, for example, we could create a stimulus-responsive analogue to these to unlock new levels of control for improved functionality. 

In this collaborative project between the Photoactive Materials group, Imperial College, London and the Diamond Light Source, we demonstrate the first example of a light-induced one-dimensional (hexagonal) to three-dimensional (cubic) phase transition in a lyotropic liquid crystal at room temperature. We show that irradiation with UV light triggers the phase transition, which creates a structural continuity in the material. We harness this change to create a gas membrane whose permeability can be controlled on-demand using light. This paves the way for the creation of switchable membranes for added control in microfluidic reactions, healthcare, or water treatment in the future. 

Figure caption: Irradiation with UV light drives a hexagonal (left) to cubic (right) phase transition in the liquid crystal, allowing the diffusion of carbon dioxide gas.