| Abstract [eng] |
In this work fabrication of sensors using three-dimensional laser lithography (3DLL) is presented. This method is based on photopolymerization reaction induced by a laser beam in a polymer precursor volume. Usage of this technology enables formation of three-dimensional microstructures which can have high spatial resolution and various properties depending on the fabrication parameters and polymeric material used. Certain structures may also have the properties of smart materials. Structures fabricated out of such materials may change their shape or properties when exposed to certain external stimuli. Using polymeric substance SZ2080 photosensitized by adding 1% of photoinitiator Irgacure 369 microsensors based on the principle of Moiré patterns which result from overlap of two polymeric gratings were formed. Such structures can deform (swell or shrink) when exposed to different liquids. It is possible to assess the magnitude and type of these deformations by measuring the change of Moiré patterns and determine change of fluids or their concentrations. In order to functionalize these sensors they were fabricated in microfluidic fused silica channels. It was found that high roughness of the channels bottom surface has a negative effect on the fabrication and durability of such sensors. As expected, while reducing the laser power larger deformations can be seen due to increased porosity in the structure of the sensor resulting in a higher angle of the Moiré pattern. During this work a microsensor was formed which showed deformation amplitude of 19.9%. This particular example swelled by 5,7% in 4-methyl-2-pentanone and shrunk by 14,2% in distilled water corresponding to a 112° change in the Moiré pattern angle. A tendentious change of Moiré patterns in the same solvent was observed when the sensors were evaluated 7 days after the development process. When evaluating these sensors after 14 days, the angles did not change further and corresponded to the values recorded after 7 days. In conclusion, sensors based on the principle of Moiré patterns were successfully fabricated in fused silica microchannels and essential factors of such method were determined. These sensors could be used in biological, medical or similar applications which require fluid change monitoring. Since various materials can be processed by 3DLL, the functionality and longevity of such sensors could be improved by fabricating them from other polymeric precursors or their mixtures which would not show changes in deformations over time. |
