Performance of nanoimprinted and nanocoated optical label-free biosensor-nanocoating properties perspective

In recent years, nanoimprinted structures have gained attention due to development of lithographic techniques and molds that enable mass fabrication of a large variety of devices, including optical sensors and biosensors. In this work, one-dimensional photonic crystals (PhC) were nanoimprinted in UV-curable polymer. To enhance interactions between light and medium at PhC surface, optically transparent, high-refractive-index titanium oxide nanocoating with well-defined thickness was deposited on the structure using magnetron sputtering. Since spectral response of PhC varies with optical properties and thickness of layers formed at their surface, they can be used for biosensing applications. In this work we focus on the impact of the nanocoating properties on performance of the optical label-free biosensor. First, the effect of the bound biological material thickness has been studied numerically and experimentally using an incremental atomic layer deposition of aluminum oxide with refractive index reaching 1.6 in the visible spectral range as a reference layer to a biological film. It was shown that there is an optimal thickness of the coating for which the sensing properties (including capability to detect biomolecules of various sizes) are the greatest. Next, using biotin as a receptor and peridinin-chlorophyll-protein conjugated with streptavidin as a target, we have proven that when the nanocoating properties are not optimized for the biomaterial at the sensor surface, sensing capabilities are highly limited.