Liquid Crystals for Chemical and Biological Sensing: Emerging Transduction Strategies beyond Polarized Optical...

Liquid crystal (LC) sensors exploit the ability of these anisotropic soft materials to amplify molecular-scale interfacial events into macroscopic optical responses. Although classical LC sensing platforms have demonstrated high sensitivity toward chemical and biological analytes, their practical implementation remains limited by the predominance of polarized-light optical microscopy (POM), which is often qualitative, instrument-intensive, and difficult to standardize. This Spotlight examines emerging transduction strategies that move LC-based sensing beyond conventional birefringent texture analysis toward quantitative and application-relevant readouts. We first discuss classical nematic and cholesteric sensing architectures, emphasizing how interfacial anchoring, topological defects, and helical pitch modulation translate molecular interactions into optical signals. We then highlight recent approaches-including photonic and resonant optical readouts, flow cytometry, machine learning-assisted analysis, dye-doped LC systems, and dynamically reconfigurable complex LC emulsions-that convert LC ordering transitions into measurable spectral, scattering, fluorescence, absorbance, or electrical outputs. By integrating interfacial molecular recognition, LC reconfiguration, and quantitative signal generation, these advances are expanding the capabilities of LC-based sensing toward more quantitative transduction and broader compatibility with portable and automated analytical formats. Finally, we discuss remaining challenges related to reproducibility, selectivity, device integration, and scalability, and outline future opportunities for translating LC-based sensors into robust platforms for biosensing, environmental monitoring, and point-of-care diagnostics.