Doubly Photopolymerized Holographic Sensors.


Jiang N(1)(2), Davies S(2), Jiao Y(2), Blyth J(2), Butt H(3), Montelongo Y(4)(5), Yetisen AK(2).
Author information:
(1)West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, China.
(2)Department of Chemical Engineering, Imperial College London, London SW7 2AZ, U.K.
(3)Department of Mechanical Engineering, Khalifa University, Abu Dhabi 127788, UAE.
(4)Centro de Investigaciones en Óptica, A.C., Colonia Lomas del campestre, PC, León 37150, Mexico.
(5)Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.


Holographic sensors are two-dimensional (2D) photonic crystals that diffract narrow-band light in the visible spectrum to quantify analytes in aqueous solutions. Here, a holographic fabrication setup was developed to produce holographic sensors through a doubly polymerization system of a poly-2-hydroxyethyl methacrylate hydrogel film using a pulsed Nd:YAG laser (λ = 355 nm, 5 ns, 100 mJ). Wavelength shifts of holographic Bragg peak in response to alcohol species (0-100 vol %) were characterized. Diffraction spectra showed that the holographic sensors could be used for short-chain alcohols at concentrations up to 60 vol %. The reversibility of the sensor was demonstrated, exhibiting a response time of 7.5 min for signal saturation. After 30 cycles, the Bragg peak and color remained the same in both 20 and 60 vol %. The fabrication parameters were simulated in MATLAB using a 2D finite-difference time-domain algorithm to model the interference pattern and energy flux profile of laser beam recording in the hydrogel medium. This work demonstrates a particle-free holographic sensor that offers continuous, reversible, and rapid colorimetric readouts for the real-time quantification of alcohols.