Hybrid Sensors Fabricated by Inkjet Printing and Holographic Patterning

Inkjet printing and patterning strategies have been developed for fabrication of hybrid holographic sensors using zeolite nanocrystals on glass-supported photopolymers. The flexibility of the proposed techniques was demonstrated by fabrication and characterization of two types of holographic sensors. The first type, which is a reversible sensor, is based on a transmission hologram recorded in a hydrophobic MFI-type zeolite doped layer with high sensitivity toward alcohols. In this type of sensor the patterning of the zeolite nanocrystals in the volume of the polymer layer is achieved by holographic recording; the pattern periodicity is in the submicrometer range. The second type of sensor is based on a reflection hologram, and it is produced by inkjet printing of zeolite nanocrystals on photopolymer layer before holographic recording. The resulting localized presence of zeolite nanocrystals in the layer is key for the performance of the sensor. Irreversible humidity sensors based on photopolymer layers doped with hydrophilic EMT-type zeolite are fabricated using the second approach and characterized in a controlled humidity environment. We demonstrate that the inkjet printing approach enables fabrication of a variety of patterns with high precision and uniformity, using zeolite nanocrystals (10–50 nm sizes). Limitations and future directions of this fabrication technique are discussed.