As a very pale person, the struggle against sunburn is real, and as Clarkson University researchers explain, about 1.7 million new skin cancer cases are diagnosed in the US each year that result from the sun’s ultraviolet (UV) radiation. However, that doesn’t mean we need to hide in the dark during the summer, because most UV radiation exposure is only intermittent. But we still need to take precautions against getting a sunburn, which normally means frequently applying copious amounts of sunscreen. But this research team may have a better solution, and it involves 3D printed wearable technology, which has been used in the past for healthcare monitoring applications.
Silvana Andreescu, Professor and Egon Matijevic Endowed Chair of Chemistry and Biomolecular Science at Clarkson, and two members of her lab, graduate student Abraham Finny and undergraduate student Cindy Jiang, published a paper about their work developing 3D printed, hydrogel-based, non-toxic sensors that can prevent sunburns by indicating unexpected exposure to damaging rays of UV light.
The abstract states, “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.”
The researchers, who are also affiliated with 3D bioprinting company Allevi, thought it would be great to have a small, inexpensive way to offer UV light detection, and developed a custom bioink that can be 3D printed into a UV sensor that’s biocompatible, so it’s safe to wear on the skin, as well as biodegradable.
Andreescu explained, “We decided to explore the capabilities of 3D bioprinting to manufacture these wearable UV-responsive sensors, as 3D printers have become inexpensive and accessible.”
They used 3D bioprinting to make the functional, mechanically stable, wearable sensors, which allowed for one-step, reproducible fabrication. To form a composite ink, the team combined 10% gelatin and 8% alginate, but the main photoactive component was common titanium oxide powder, which releases electrons and changes color when exposed to UV radiation…similar to a color-changing tattoo.
“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 team wrote.
“The viscosity and ink composition were optimized to achieve printability and tune the mechanical properties (e.g., modulus, hardness) of the sensors.”
The researchers used multiple colored dyes, such as malachite green and methyl orange, during testing, and said that their bioink has “excellent 3D printing properties,” as it exhibits shear-thinning behavior when it’s enclosing titanium oxide and dye particles, so it can extrude well and hold a patch shape after it’s printed. The gelatin forms a partial chemical crosslink with the alginate when it’s cold, and the alginate remains “partially cross-linkable by cations,” which makes the ink more adaptable.
Additionally, the team reports that the color changes in the 3D printed constructs were predictable. When the titanium oxide was excited, a chain of reduction-oxidation reactions within the hydrogel would start, which eventually degraded the contained organic molecules. Because the hydrogel held enough dye, titanium oxide, and water, these changes were visible, and allowed for enough UV penetration to complete the reaction “in a timely manner.” When the researchers tested their 3D printed wearable sensor outdoors, they observed a decrease in color intensity that matched the length of exposure.
Another potential application for these inexpensive 3D printed sensors could be in the UV sanitation field. Here, a sensor could determine whether or not a tool or piece of clothing has been exposed to enough UV light that it’s considered sanitized.
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