A UV-sensing patch that technically worked wasn't enough. A field study in Florida with 20 participants revealed a behavioral barrier the engineering team never saw coming — and that finding changed everything.
20
Participants in Florida field study
200
UV sensor patches deployed across body locations
10
Patch placements per participant to test optimal position
Wired
Coverage for the product that came out of this research
While working in L'Oréal's Connected Beauty Incubator, part of the job was evaluating emerging technologies to see whether they could be meaningfully applied to beauty and skincare. The incubator was an early-stage function — identifying what was technically possible before the product teams knew what to ask for.
MC10, a Boston-based company, had developed flexible electronic patches capable of bending and conforming to skin. They claimed their material could degrade at roughly the same rate as sunscreen on skin — meaning it could theoretically tell you when your protection was wearing off, not just when a fixed timer expired.
La Roche-Posay, L'Oréal's dermatological skincare brand, was the natural home for this technology. The brief was to evaluate whether MC10's patch could power a consumer sun protection product. My job was to design and run the research that would answer that question honestly — not just technically, but behaviorally.
The research had two core problems to solve. The first was technical: where on the body does a UV patch capture the most consistent, reliable data? Body placement affects how much direct sun a sensor receives — a patch on the shoulder versus the wrist versus the chest produces meaningfully different readings depending on how a person moves and positions themselves throughout a day.
The second was behavioral: even if the technology worked, would people actually wear it?
I designed a field study in Florida — chosen specifically for guaranteed sun exposure — with 20 participants. Each participant wore 10 patches simultaneously across different body locations. I built a custom iPhone app to connect all 10 patches per person and record UV readings in real time, giving me synchronized data across all placement sites throughout the study period.
Phase 1
Baseline movement study
Participants walked a controlled route 10 times — a standardized protocol to simulate real-world movement and capture how each body location performed under consistent activity. The app logged all 10 patch readings simultaneously throughout.
Phase 2
Sunscreen degradation test
Sunscreen was applied directly to the patches to test whether the sensors would register degradation at the same rate as skin — the core product claim. Data was recorded before, during, and after application across all placement sites.
Phase 3
Waterproofing stress test
MC10 had certified the patches as waterproof. With everyone in the pool, this became a live durability test under real conditions — combined with qualitative observation of how participants interacted with the technology in an unscripted, social environment.
Phase 4
Qualitative debrief interviews
After the physical study, I conducted structured conversations with participants about their experience wearing the patches — what they noticed, what they felt, what they would and wouldn't do in their real lives. This is where the most important data emerged.
The study was deliberately designed to capture both dimensions simultaneously — quantitative sensor performance and qualitative human response — because a technology that works technically but fails behaviorally is not a product.
The quantitative results were mixed in the way that matters most for product decisions. The patches registered UV data accurately across most body locations, and the sunscreen degradation signal functioned as claimed. But consistency varied significantly by placement site — some locations produced reliable readings across different movement patterns, while others were too dependent on body positioning to be actionable for a consumer product.
No single body location was clearly dominant enough to prescribe as the standard placement. This was the first signal that the fixed-patch model had a product problem independent of the technology's performance.
10
Placement sites tested per participant — no single location clearly outperformed all others
2 barriers
Technical inconsistency and behavioral resistance — both had to be solved for a market-ready product
But the qualitative data was the real finding. When I asked participants about wearing the patches in their actual lives, two themes emerged with striking consistency: embarrassment and doubt about their own compliance.
"I wouldn't wear this to the beach with my friends. It would look weird and people would ask questions."
Participant debrief interview — representative of a theme that appeared across multiple participants unprompted
Participants weren't just self-conscious about the patches — they were also uncertain whether they'd keep them placed accurately enough to trust the data. The product's value proposition depended on consistent placement. But users were already telling us they wouldn't reliably maintain that consistency, even when they wanted the benefit.
This was a fundamentally different kind of finding from the sensor data. The technology's limitations were engineering problems. The behavioral barriers were human problems — and human problems don't get solved by better electronics.
The combined reading was clear: a prescribed fixed-patch model would struggle at market. Not because the technology was wrong, but because the form factor was asking users to behave in ways they had already told us they wouldn't.
The research findings reframed the product entirely. If no single body location was clearly dominant, and users were resistant to a prescribed placement they'd have to maintain, then the answer was to remove the prescription. Give users control over where they wear the sensor, and build the algorithm to account for variability.
That pivot — from fixed patch to user-controlled wearable — became the design direction. The sensor became something a person could place where it made sense for their life: clipped to a bag, worn on the wrist, attached to clothing. The experience shifted from "wear this correctly" to "wear this however works for you."
Fixed patch
Prescribed placement, user responsible for consistency, high behavioral friction
User-controlled wearable
Flexible placement, algorithm adapts to variability, behavioral friction removed
My Skin Track UV
Launched at CES. Covered in Wired. One of the first consumer UV wearables to market.
The product that shipped — L'Oréal's My Skin Track UV — is a direct descendant of the research decision made in that Florida study. The behavioral insight didn't kill the project. It saved it from launching in the wrong form.
This case study matters to me beyond the outcome because it illustrates something fundamental about what research is actually for. The engineering team had already validated the technology. What they didn't have was a clear picture of how real people would interact with it in their actual lives. That gap — between what works in a lab and what works in the world — is exactly where UX research lives.
Read the Wired coverage