Principles for measurement of chemical exposure based on recognition-driven anchoring transitions in liquid crystals

The competitive binding of a molecule forming a liquid crystal and a target ed anatyte to a common molecular receptor presented at a solid surface poss essing nanometer-scate topography is used to trigger an easily visualized s urface-driven change in the orientation of a micrometer-thick film of liqui d crystal. Diffusion of the targeted analyte from atmosphere to surface-imm obilized receptor across the micrometer-thick film of liquid crystal is fas t (on the order of seconds), and the competitive interaction of the targete d analyte and liquid crystal with the receptor provides a high level of tol erance to nontargeted species (water, ethanol, acetone, and hexanes). Syste ms that provide parts-per-billion (by volume) sensitivity to either organoa mine or organophosphorus compounds are demonstrated, and their use for imag ing of spatial gradients in concentration is reported. This approach does n ot require complex instrumentation and could provide the basis of wearable personalized sensors for measurement of real-time and cumulative exposure t o environmental agents.