Polarizer-Free Dye-Doped Liquid Crystal Sensors with High Precision

Abstract

The surface-induced ordering of liquid crystals (LC) has been harnessed to detect a wide range of chemical and biological stimuli. In most sensor designs, the information-rich response of the LC is transduced from an analyte-triggered change in the out-of-plane orientation of the LC. Quantifying the out-of-plane LC orientation, however, is often complicated by simultaneous changes in the in-plane orientation of the LC when using polarized light for transduction. Here we introduce a sensing approach that combines a dichroic dye-doped LC (DDLC) with unpolarized light and a photodiode to achieve precise quantification of analyte-driven changes in the out-of-plane orientations of LCs. We benchmark the performance of the new methodology against polarizer-based approaches using a model amphiphilic analyte in aqueous solution and show that the DDLC provides a substantial reduction in the coefficient of variation (300% to less than 5%), an enhanced analytical sensitivity (0.16 to 3.73 μM^–1), and an expanded dynamic range. In addition, when used to sense concentration gradients of analytes, the new approach distinguishes differences as small as 0.03 μM/μm over a dynamic range of 2 μM/μm, significantly outperforming conventional polarizer-based approaches that detect differences of 0.3 μM/μm over a dynamic range of 0.6 μM/μm. Overall, we conclude that the improved sensing performance and simpler implementation (no polarizers) of the DDLC approach, as compared to conventional LC sensors based on crossed-polars, will facilitate the deployment of LC sensors in diverse contexts, including the development of high-throughput screens for chemical formulations.