Micro-arraying of nanostructured diatom microshells on glass substrate using ethylene-vinyl acetate copolymer and photolithography technology for fluorescence spectroscopy application

Diatoms, which have delicate nanoscale three-dimensional porous SiO2 structures, have potential applications in the fields of biosensors and other microsystems. To prepare a diatom-based substrate for biosensor applications, a fabrication technique for patterning nanostructured diatom microshells and bonding them to the substrate is developed. The patterning process is based on the photolithography technique. Hot-melt ethylene-vinyl acetate copolymer (EVA) is used as the bonding material. The patterning and bonding conditions are optimized by varying the reheating time and temperature of EVA. An array of diatom shells is formed on the substrate with high positioning accuracy and bonding quality when EVA is reheated at 60 °C for 2 min. The surface quality of the diatom shells and the bonding strength are analyzed. Standard proteins conjugated with fluorescein isothiocyanate are orderly dropped on blank EVA substrate, EVA substrate with dispersed diatom shells, and EVA substrate with a diatom shell array. The EVA substrate with diatom shells array provides the highest fluorescence intensity. Given the improved fluorescence detecting sensitivity, the patterned nanostructured diatom shells array can be used as a new compound substrate for biophotonics and biosensing devices.