ExpressInk : a UV Indicator
Engineering ExpressInk, a novel, color-changing pen that transforms sunscreen reapplication into an act of self-expression, through rigorous biomaterial testing and user-driven refinement.
Role:
Product & Visual Designer
Duration:
Jan. 2024 - Apr. 2024
Guided By:
Jiabao Li
Team:
Allison Chen, Carrie Wang
Our team of 3 multidisciplinary designers created ExpressInk, a pen-like applicator that lets users draw freely on their skin before applying sunscreen over it. As the sunscreen wears off, the active photochromic pigments in the drawing slowly reappear, signaling that it’s time to reapply. This project was undertaken during material exploration for Jiabao Li’s Biodesign course at UT Austin.
I introduced a speculative future, one where the UV index required constant and consistent sunscreen application, that created the concept of ExpressInk. Collectively, we ran multiple rounds of material experiments with biomaterials and inquiry into ink composition. This was followed by leading and documenting user testing sessions, with each change to the formula and applicator backed by real feedback from the people who tried it.
Opportunity
Sunscreen only protects people when they remember to reapply it, and most don’t.
Sunscreen loses its effectiveness after prolonged UV exposure, yet few people reapply throughout the day. The stakes are high: sunscreen use reduces the risk of melanoma by 50%, and with a depleting ozone layer, protecting skin from damage is more urgent than ever. Existing indicators, like UV dot stickers, attempt to close this gap, but in our testing we found they go unnoticed because of their small size and often fall off. We identified a gap in how reapplication is signaled: the reminder needs to be noticeable, durable, and something people actually want to wear.
Recognizing four important questions, how might we tell complex sustainability stories to increase visibility and action among park goers by addressing what these stories look like, how they’re told, how they’re interacted with and where they live.
Research
We didn’t want our solution to just be more visible; we wanted it to be meaningful.
Many cultures have long used art on the body, through tattoos, painting, and other forms, to express identity and tell stories. There is always a story to be told, and we saw an opportunity in a tool that allows flowing ink on skin.
This shaped our direction: rather than a sticker that sits passively on the body, ExpressInk would invite people to draw, and the drawing itself would become the reminder thus making it more visible.
Solution
Test the formula, vary the applicator, gather feedback from different users, and refine the formula & experience based on what we hear and document.
Formulate a skin-safe, UV-reactive ink from natural ingredients:
We built an ink-like consistency by combining propylene glycol, aloe vera gel, and rose water with photochromic pigment, balancing flow, drying time, and comfort on the skin.
Design an applicator that supports free-flowing expression:
To make drawing on skin feel natural, we housed the ink in a marker pen tube and tested a range of nibs, bottles, and applicators to find a form that gave users precision and control.
With guidance from our faculty and advisors, we ran multiple tests on the ink formula, adjusting the biomaterial combinations to balance drying time, comfort, and performance. Simultaneously, we tested the formula across a range of nibs, bottles, and applicators. These were tried on many occasions with different users and test groups, giving us a broad view of what worked and what didn’t. We paid close attention to what was instinctive to the users utilizing the applicators, how the ink felt on their skin, the drying time and whether they could apply sunscreen over the solution.
Prototype + Result
Documenting feedback across repeated test sessions, we recognized recurring observations about the ink and its application.
Users gave us insight into three areas in particular: the texture of the liquid, the flow of the ink, and instinct after application.
Texture of the liquid: The liquid felt sticky on skin with a lot of our initial solutions. We attributed this feeling to the amount of aloe vera gel, and realized it was also interfering with the drying time
Flow of the ink: Some of our initial explorations were imbalanced in composition, resulting in either very thick or thin ink that was difficult to draw on skin with. We workshopped the composition, such that the consistency of ink remained ‘ink-like’ while allowing for a working composition of the other materials
Instinct after application: Many users reported feeling the need to ‘rub’ the formula into their skin, like with sunscreen and other topical creams. In inquiring further into why they felt that way, we realized that the ink was not drying quick enough to allow any other assumption of the formula.
Our prototyping process was iterative. We focused on recurring feedback, taking patterns across users into consideration when making changes, and we checked those changes with our faculty and advisors before moving forward.
The final deliverable was ExpressInk, a pen-like applicator filled with a fluid ink that dries quickly enough to be coated over with sunscreen.
The name carries a two-fold meaning: “express” refers both to the quick-drying formula and to the self-expression the pen enables. Applied under effective sunscreen, ExpressInk stays dormant. As UV rays penetrate, the pigments awaken into color, signaling the need to reapply.
Our project received recognition by being awarded ‘Student Notable Project 2025’ for Core77 Design Awards!
![](data:image/svg+xml,<svg display="block" id="1141722559" role="presentation" viewBox="0 0 627 128" xmlns="http://www.w3.org/2000/svg"><g fill="transparent" height="128.00004309501043px" id="dymmJbIkO" width="626.9159027103601px"><path d="M 233 0 L 300 0 L 344 67 L 377.5 33.5 L 452.5 33.5 L 377.5 128 L 247.5 128 L 280 95.5 L 264.406 63.815 L 301.5 10.5 L 244.695 23.764 Z M 14 128 L 0 10.5 C 0 10.5 92.938 -7.9 144.5 33.5 C 159.581 45.608 169.946 58.718 177.064 71.207 L 138 128 L 192.5 128 C 192.5 128 192.5 128 192.5 128 Z M 192.5 128 C 192.502 127.963 194.271 101.398 177.064 71.207 L 203 33.5 L 244.695 23.764 L 264.406 63.815 L 219.75 128 Z M 395.5 128 L 469.5 33.5 L 578.5 10.5 L 626.916 128 L 626.916 128 L 551.127 97.863 C 549.691 89.959 547.095 82.418 542.5 78 C 530.312 66.281 504.06 76.536 500.828 77.863 L 464.708 63.5 L 463 128 Z M 626.916 128 L 626.916 128 L 463 128 L 463 128 L 464.708 128 L 500.5 78 C 500.5 78 500.613 77.951 500.828 77.863 L 551.127 97.863 C 553.754 112.323 552.5 128 552.5 128 L 558 128 C 558 128 558 128 558 128 L 612.5 128 L 612.5 128 Z M 491.5 80 L 468 113.5 L 469.5 72 Z M 290.5 17 L 264.5 54 L 250.5 26 Z M 612.5 128 L 558 128 C 558.001 127.99 558.375 121.121 558 115.5 C 557.625 109.875 556.5 105.5 556.5 105.5 Z M 144.5 128 L 176.5 81.5 C 176.5 81.5 182.875 96.375 185.5 108 C 188.125 119.625 187 128 187 128 Z" fill="rgba(0, 170, 255, 0.5)" height="128.00004309501043px" id="Zg9ikXZGV" width="626.9159027103601px"/></g></svg>)