Fused silica micro-capillaries were functionalised with spiropyran-polymer brushes using surface-initiated ring-opening metathesis polymerisation. Based on the inherited spiropyran properties, the functionalised capillaries were successfully used to photo-identify solvents of different polarity when passing through the micro-capillary in continuous flow. In the present study, six different solvents (toluene, tetrahydrofuran, acetone, acetonitrile, ethanol and methanol) can be easily detected while passing through the modified micro-capillary by simply irradiating a portion of it with UV light (365 nm). This converts the closed spiropyran moiety to the open merocyanine form and as a consequence, the micro-capillary gains a distinct colour and spectral response depending on the polarity of the solvent. The rate of ring opening of the spiropyran-polymer brushes coatings has been determined in-situ in the presence of different solvents, showing that the coloration rate is also influenced by the solvent polarity and therefore can be used as an additional parameter for solvent sensing.