Photocromic polymer brushes were synthesised on the interior of fused silica micro-capillaries using the “grafting from” approach [1]. This technique enables high surface loadings of the stimuli-responsive polymer in a limited area and enhances the switching effect compared to conventional films. Upon irradiation with UV light the passive spiropyran (SP) unit undergoes a heterocyclic ring cleavage that results in the merocyanine (MC) formation [2]. In contrast to the uncharged and colourless spiropyran form, the merocyanine is highly charged and can be utilised as ligand for other charged species. Based on the coordination-induced photochromism characteristic of the MC form, we focus our studies in the photo-controlled detection of target metal ions when flowing through the modified micro-capillaries. Using this approach we have created a photonically controlled self-indicating system for metal ion detection that will ensure real-time measurements and fast analysis protocols in systems and micro-systems that operate in continuous flow (e.g. analytical devices like HPLC, CE or micro-chips). Investigations into the metal-ion binding behaviour of the spiropyran-polymer brushes have shown that they are capable of binding different metals ions (Cu2+, Ni2+, Co2+) causing an appreciable colour and spectral change when exposed to UV light while a solution of these metals ions is passed through the capillary. Moreover, these ions can be released by photonic-conversion of the MC moiety into the inactive SP form using white light. This sequence can be successfully repeated, suggesting that this sensing behaviour can be switched on/off remotely using light, either along the entire length of the capillary, or at patterned locations using the appropriate mask. [1] B. Zhao, W. J. Brittain, Prog. Polym. Sci. 2000, 25, 677. [2] M.V. Alfimov, O.A. Fedorova, S.P. Gromov, J Photochem Photobiol A-Chem., 2003, 158.