Abstract In contrast to the conventional passive reaction to analytes, here, we create a proof-of-concept nanochannel system capable of on-demand recognition of the target to achieve an unbiased response. Inspired by light-activatable biological channelrhodopsin-2, photochromic spiropyran/anodic aluminium oxide nanochannel sensors are constructed to realize a light-controlled inert/active-switchable response to SO 2 by ionic transport behaviour. We find that light can finely regulate the reactivity of the nanochannels for the on-demand detection of SO 2 . Pristine spiropyran/anodic aluminium oxide nanochannels are not reactive to SO 2 . After ultraviolet irradiation of the nanochannels, spiropyran isomerizes to merocyanine with a carbon‒carbon double bond nucleophilic site, which can react with SO 2 to generate a new hydrophilic adduct. Benefiting from increasing asymmetric wettability, the proposed device exhibits a robust photoactivated detection performance in SO 2 detection in the range from 10 nM to 1 mM achieved by monitoring the rectified current.