Quantitative Volatile Organic Compound (VOC) Sensing with Liquid Crystal Core Fibers

We present a quantitative assessment of the ability of liquid crystal (LC)-filled polymer fibers to sense volatile organic compounds (VOCs). By correlating the birefringence ∆n of two LCs with different nematic-isotropic transition temperatures T_NI to the concentration c_tol of toluene vapor in the atmosphere, we show that T_NI is critical for the performance. The ∆n(c_tol) response is fully reversible and quantitatively repeatable over several cycles. The response time is reduced from minutes to seconds by priming the fibers with a toluene pre-exposure. We propose that broad operating temperature range can be realized by combining fibers with different LC mixtures, yielding autonomous VOC sensors with textile form factor suitable for integration in apparel or in furniture that can compete with existing consumer grade electronic VOC sensors in terms of sensitivity and response speed, and outperform them in terms of selectivity.