DMD-based optical printing of PHEMA hydrogel gratings for sensitive and rapid alcohol sensing

Abstract

A straightforward, controllable, and cost-effective system was developed for the optical printing of photosensitive polymers. By utilizing a digital micromirror device (DMD), the optical printing system enables the facile and rapid fabrication of photosensitive materials with any desired structures. As such, poly(2-hydroxyethyl methacrylate)(PHEMA)-based 1D and 2D diffraction gratings with high resolution and excellent optical performance were printed for use as alcohol sensors, where the diffraction efficiency would change due to the expansion of the hydrogel matrix upon exposure to alcohol solutions. During alcohol sensing measurements, both zero- and first-order optical powers of hydrogel gratings were recorded in response to various concentrations in the range of 0 to 50 vol% of ethanol, isopropanol, and methanol for the analysis of variations in diffraction efficiency. The sensing performance was explored across different crosslinking densities of PHEMA-based 2D gratings. Significant changes were observed, with a low detection limit of 1 vol% for methanol and ethanol in 2D gratings printed from a 98% HEMA solution. Moreover, sub-second response times were achieved in all the measurements, and the gratings demonstrated excellent recyclability. The proposed optical printing system offers advantages such as customization of microstructures, a wide choice of hydrogels, high efficiency, low cost and environmental friendliness. This versatile and powerful platform holds promise for developing highly sensitive and selective sensors for a wide array of applications in physical, chemical, and biological sensing.