The goal of this study was to prepare an optical sensory film in the channel of the microreactor. The microreactor and the little plates were manufactured with 3D-printing technology. The sensory film was preliminary tested on the little plates to determine which coating will yield the best result. The film which yielded best results is then later tested in the microreactor channel. The utmost goal is to obtain functional film on the microreactor channel surface. Two methods of preparing the coating cocktail were studied. The first studied method was a sol-gel method in which we use acidly catalysed hydrolysis and condensation of precursors: tetraethoxysilane and trimethoxyphenylsilane to make six films. Three of the six films are made with single indicator and other three were mixtures of previous indicators. Those indicators are: methyl red, bromothymol blue, bromocresol green (BCG) and their mixtures methyl red with bromothymol blue, methyl red with bromocresol green and bromotyhmol blue with bromocresol green. The second set containing six little plates was made with the same single indicator and indicator mixtures as previously. The solution is made by dissolving cyclic olefin copolymer (COC) in toluene with heating and mixing and addition of bis(2-ethylhexyl) sebacate as a plasticizer. Third set of plates was made with same indicators as previous twelve with the only difference that the solution was made by dissolving polyvinyl chloride (PVC) in tetrahydro furane (THF) with the same plasticizer as before. The films made with PVC and THF yielded worst results because they did not pass any of the preliminary tests: scratch test or retention of the sensory properties test. All films were scratched easily with the pincers and none of them had the sensory properties, instead only leaching of indicator in solution was observed. The sol-gel method proved to be best of two methods used in this study. The most films that are scratch resistant come from this group of the little plates and the greatest number of the films kept sensory properties. The biggest problem of these films was the method of coating used which is drop coating in which we are unable to control the thickness of film and response time of the film is more than 20 minutes. The microreactor coated with the TEOSFTMS-BCG film changed the colour in 90 seconds. That shows us that it is possible to successfully coat the channel of the microreactor. One problem still lingers, the process is still irreversible because when bromocresol green goes into the deprotonated state, it is impossible to conduct the analysis in acidic solutions because the indicator does not go back to the protonated state.