The integration of light sensitive materials in biotargets can allow the use of light as precise tool to control their bioactivity. Azobenzenes is largely used for these tasks, as it undergoes large spatial rearrangement upon light stimulation and, therefore, can be used as light-fed molecular machine. We have designed an azobenzene molecule that shows a specific affinity for the cellular membrane. We took advantage of this to modify reversibly the cellular membrane potential upon light exposure and, in neurons, also trigger potent firing. These results hold great promise for possible applications in photopharmacology. Our calculations show that insertion of the molecule causes a thinning of the membrane already in the dark. For this, we propose to investigate by means of QENS whether this effect would lead to change in lipid dynamics and possibly to other effects, i.e. phase transition