In recent years, a popular way of photo-modulating flow control in microfluidic channels has been through the use of acidified spiropyran (SP) hydrogels that needed to be externally protonated with HCl solutions.1,2 In the swollen protonated merocyanine (MCH+) form, the hydrogel blocks the channels and prevents flow. When exposed to white light, the positively charged MCH+ is converted to the uncharged SP form, triggering shrinking of the hydrogel, and the channel opens. The addition of acrylic acid copolymerised within the hydrogel provides an internal source of protons that allows repeatable photo- actuation in neutral pH environments. Here we report the effect of the polymerization solvent on the shrinking and swelling kinetics of the photo-responsive hydrogel. Using this approach, reversible fast photo-actuated hydrogels have been obtained and have been successfully used for micro-valves applications in micro-fluidic channels.