3D Printed Hydrogel-Based Sensors for Quantifying UV Exposure

Abstract

Exposure to excessive ultraviolet (UV) radiation can have detrimental effects on human health. Inexpensive easy-to-use sensors for monitoring UV radiation can allow broad-scale assessment of UV exposure, but their implementation requires technology that enables rapid and affordable manufacturing of these sensors on a large scale. Herein, we report a novel three-dimensional (3D) printing procedure and printable ink composition that produce robust, flexible, and wearable UV sensors. To fabricate the sensors, a color-changing hydrogel ink was first developed from which standalone constructs were 3D printed. The ink contains alginate, gelatin, photoactive titanium dioxide nanoparticles, and dyes (methyl orange, methylene blue, and malachite green) in which the nanoparticles are used to initiate photocatalytic degradation of dyes, leading to discoloration of the dye. The sensors resemble a color-changing tattoo that loses color upon exposure to UV. The viscosity and ink composition were optimized to achieve printability and tune the mechanical properties (e.g., modulus, hardness) of the sensors. The optimized procedure enabled the one-step fabrication of mechanically stable sensors that can effectively measure outdoor sun exposure by quantifying the decrease in color, visible to the naked eye. Apart from being used as wearable sensors, these sensors have the potential to be used along with UV-based workspace sterilizing devices to ensure that surfaces have been efficiently exposed to UV. The sensors are inexpensive, stable, extremely robust, biodegradable, and easy to use. The tunability, biocompatibility, and printability of the ink offer excellent potential for developing advanced 3D printing methods that, in addition to UV sensors, can be applied more broadly to fabricate other sensing technologies for a variety of other applications.

3D-Printable Nanocellulose-Based Functional Materials: Fundamentals and Applications

“…The indicator color was correlated with the CO2 and microbial growth and cha in volatile compounds as a freshness indicator in packaged chicken breast. Such s labels made of hydrogels can be easily fabricated by 3D printing using 3D extrusio oprinting [9], which enables printing of viscous inks of viscosity up to 6 × 107 mPa.s viscosity and ink composition can be easily tuned to achieve printability and mecha properties by varying the hydrogel components' composition, gelation conditions rheology characteristics. Using 3D printing, such sensors can be manufactured inex sively and in large quantities.…”

“…Using 3D printing techniques, mechanically stable constructs are fabricated through computer-controlled deposition of materials, layer by layer, until structures with precise macroscopic and microscopic control are created [8]. Increased usage of extrusion-based 3D printing has been seen, which involves the utilization of hydrogels or printable pastes constructed by incorporating viscous materials that can retain their shape after deposition through chemical, photo, or thermal crosslinking methods [9,10]. Nanocellulose can be introduced to these pastes to facilitate the deposition and realization of stable constructs for applications.…”

Slot‐Die Coated Organic UV Indicators and Filters Processed from Green Solvents

“…The 3D coated films showed discoloration over time under UV exposure and successfully function as UV indicators. [39] At this point we can claim that the D4 photochromic films SD coated from green solvents and function as reversible UV indicators is first to be reported here. Coating small molecules on large area using additive manufacturing approaches in air and from green solvents has proved challenging.…”

“…Although there are many studies reporting on UV indicators using photodegradable organic dyes/polymers as photoactive films, only two of them used printing approaches useful for large area fabrication. [18,39] One study used inkjet printing to coat titanium dioxide (TiO 2 ), PVP, and food dye (brilliant blue FCF) films on paper. TiO 2 acts as a photocatalyst to degrade the brilliant blue FC dye resulting in gradual discoloration of this film under UV exposure.…”

Smart and Biomimetic 3D and 4D Printed Composite Hydrogels: Opportunities for Different Biomedical Applications

“…UV exposure may have harmful effects. Finny et al produced the first portable, resilient, and economical 3D printed hydrogel sensors to detect UV exposure as colorimetrical indicators [ 323 ]. To construct them, independent structures were first printed using color-changing hydrogel ink.…”