Nanostructured Photonic Hydrogels for Real-Time Alcohol Detection

Abstract

Rapid, reliable, and reusable sensors with a low limit of detection can play a vital role in alcohol detection, which is vital in a myriad of industries. Herein, hydrogel-based fiber optic probes were developed for alcohol sensing by a simple, rapid, and facile process. Aztec microstructures with a periodicity of 3 μm were imprinted onto alcohol-sensitive hydrogels for fabricating stand-alone and fiber optic sensors. The hydrogel matrix undergoes swelling in response to alcohol solutions, altering its diffraction efficiency. The real-time sensing capability of the developed sensors was demonstrated in response to various concentrations of ethanol, isopropanol, methanol, and dimethyl sulfoxide in the concentration range of 0 to 50 vol %. For the stand-alone sensors, sensitivities of 23, 21, and 15 μW/vol % were recorded for dimethyl sulfoxide (DMSO), isopropanol, and ethanol, respectively. For the optical fiber probes, sensitivities of 2.3, 2.2, 1.94, and 1.14 μW/vol % were recorded for DMSO, isopropanol, ethanol, and methanol, respectively. A fast response time of 20 s was recorded for both stand-alone and optical fiber sensors. Higher sensitivity toward DMSO was observed, with a low limit of detection of 0.5 vol %. The developed optical fiber sensors may have applications in remote and real-time alcohol sensing in forensics, medicine, food, and beverage manufacturing industries.

Hydrogel-integrated optical fiber sensors and their applications: a comprehensive review

“…269 To overcome the drawbacks of the existing fiber optic probe, an asymmetric microlens array-based glucose sensor has been developed where a light diffuser is imprinted on stimuli-responsive hydrogels for glucose, pH, and alcohol monitoring. 75,269,270 By crosslinking glucose-responsive PBA with acrylamide, a sensing probe containing an asymmetric microlens array was developed, which can reach equilibrium within 15 min. 271 The precursor solution for fiber tip functionalization was prepared from acrylamide, MBAm, and 3-APBA mixed with DMPA.…”

“…3 Their stimuli-responsive nature has led to extensive exploration of hydrogels for a broad range of applications, including biosensing, [4][5][6] environmental sensing, 7,8 bioelectronics, 9 tissue engineering, 10,11 artificial muscle development, 12 regenerative medicine, 13,14 cell separation, 15,16 brain function monitoring, 17,18 drug delivery, 19,20 photo-thermal therapy, 21 pharmaceuticals, 22 and diagnostics. 23,24 More recently, various hydrogel-based sensor platforms have been demonstrated to detect minuscule-level changes in glucose 28 and lactate concentrations 29 as well as in pH, 30 humidity, 31 and temperature levels. 32 By tailoring hydrogels' polymeric composition, physiochemistry, cross-linker density, and electrical charge of constituting polymer chains, 6 their viscoelasticity, molecular permeability, de/swelling kinetics, and responsiveness to various stimuli from light to mechanical forces 4 can be tuned further, and a new generation of hydrogel-based sensor systems can be constructed.…”

“…Stimuli-responsive hydrogel sensors can change phase and volume in response to exposure to a stimulus, while passive hydrogel sensors accommodate a responsive substrate in their matrices that can interact with input signals and produce output signals for detection. [24][25][26][27][28] The responsive components can be nanomaterials, biomolecules, and even living cells. 25 Because of their large solvent content, hydrogels are optically transparent to a wide range of the optical spectrum, from visible to near-infrared (NIR) frequencies.…”

“…For this reason, apart from the state-of-the-art applications mentioned above, hydrogels have been used to fabricate optical contact lenses that harvest the biocompatibility and gas-penetration capabilities of these polymeric networks. 1 More recently, beyond their conventional optical use in contact lenses, hydrogel-based optics 26,27 and photonics 28 have gained immense interest; hydrogel-based thin films, coatings, optical fibers, and waveguides have been explored as potential options for hydrogel photonics sensing, i.e., photonic bandgap, plasmonic, and reflection and refraction index modulation-based sensors. 29,30 An optical fiber generally consists of a core and cladding, where the refractive index (RI) difference between the core and the cladding confines light into the core and guides it through it.…”

“…Stimuli-responsive hydrogel sensors can change phase and volume in response to exposure to a stimulus, while passive hydrogel sensors accommodate a responsive substrate in their matrices that can interact with input signals and produce output signals for detection. 24–28 The responsive components can be nanomaterials, biomolecules, and even living cells. 25…”