Photonic liquid crystals on a single substrate for label-free protein assays

Label-free qualitative and quantitative protein assays were established with a single-substrate biosensing platform based on cholesteric liquid crystal (CLC) films with different ratios of the thickness d to the helical pitch P. By adjusting the amount of chiral dopant incorporated in CLC, the d/P ratio or the center wavelength of Bragg’s reflection band can be fine-tuned to achieve signal amplification or to improve detection sensitivity. The single-substrate platform eliminates the need for LC cell assembly, which requires a pair of glass substrates, and can be conveniently integrated with the format of most clinical assays performed on a single solid surface.