Optical Properties of Liquid Crystals in Biosensing Applications

Introduction: Liquid crystals (LCs) combine fluidity with long-range molecular order, giving rise to strong optical anisotropy (birefringence), polarization-dependent transmission, and (in cholesterics) selective reflection. These features make LC interfaces exquisitely sensitive to biomolecular binding events that perturb anchoring and director fields, enabling label-free biosensing. Materials and Methods: A structured literature review (2016–Jan 2026) was designed around optical LC biosensors (nematic, cholesteric, blue phase, chromonic; planar films, droplets, elastomers, microcavities). Studies were screened using predefined inclusion/exclusion criteria and extracted for platform geometry, surface chemistry, optical readout, target class, and analytical performance. Results: Across included studies, dominant readouts were polarized optical microscopy (POM) texture change, quantitative birefringence/retardation, and wavelength shifts from cholesteric reflection bands. Sensitivity improvements were commonly achieved via nucleic-acid amplification strategies and signal-amplifying interfacial chemistries. Six synthesis tables summarize optical properties, device architectures, functionalization routes, readout metrics, representative targets, and translation considerations. Conclusion: LC optical biosensors are maturing from qualitative “dark-to-bright” assays toward quantitative, portable formats using smartphone optics, elastomeric photonic films, and robust surface chemistries. Key remaining challenges include standardization of alignment layers, suppression of matrix effects in biofluids, and reproducible quantification across lighting/imaging conditions.