Synthesis of SiO₂ nanoparticles using the Stöber method and their self-assembly into liquid photonic crystals for surface stress sensing applications

This study investigates the synthesis of SiO₂ nanoparticles using the Stöber method and their self-assembly into liquid photonic crystals. Silica nanoparticles with diameters of 180 and 250 nm were centrifuged to induce precipitation, leading to their self-arrangement into a face-centered cubic (FCC) structure. The resulting self-assembled photonic crystal was sandwiched between two cover glasses and sealed with photocuring resin. Reflectance spectra, measured at varying incidence angles using UV–Vis spectrophotometry, demonstrated an angle-dependent reflection peak, which shifted toward shorter wavelengths with increasing incident angles. Scanning electron microscopy (SEM) confirmed the ordered nanoparticle arrangement. Additionally, color changes observed under applied mechanical forces revealed a correlation between force and the dominant wavelength of the reflected color, suggesting that the material’s mechano-chromic properties could be used for surface stress sensing. This work highlights the potential of SiO₂-based photonic crystals in sensor applications, offering a cost-effective, self-assembled solution for novel stress sensors.