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Flip Fluvs


physical PROTOTYPING / health

Flip-Fluvs are wearables designed to help wearers enjoy sunny weather safely. A UV sensor on the Flip-Fluv detects UV rays and triggers a haptic motor on the shoe to vibrate and an LED on the wristband to light up and notify the wearer that they should apply sunscreen. The wearer then uses the wristband to input the SPF they used, which then resets the notification cycle. This triggers the Peltier in the shoe to cool down and provide the user with the reward of a soothing cold sensation. The design was inspired by the fact that sunscreen is a simple but often elided method of protecting one’s skin and body from the various health detriments of UV rays. Since sunlight is usually considered to be positive, people are often unaware of how vigilantly they should protect themselves from its negative effects. Flip-Fluv is intended to increase their awareness and proactiveness against sun damage.

Final Video of Flip-Fluvs. By Alyssa Li, Carolyn Chen, Christina Pappas, Michelle Kim, Yang Liu

Our Team

Alyssa Li, Carolyn Chen, Christina Pappas, Michelle Kim, Yang Liu

My Role

Interaction Designer, Prototyping Engineer


2 Months

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Background Research

One out of every 5 Americans will develop a form of skin cancer in their lifetime, and each year, nearly 5 million Americans are treated for skin cancer at a cost of about $8.1 billion. Yet the majority of skin cancer can be prevented by avoiding too much exposure to ultraviolet (UV) rays from the sun.

In order to better understand the link between UV rays and sun damage, and to develop our algorithmic formula determining how long a given individual can safely be exposed to the sun while wearing sunscreen of a certain SPF level, we conducted extensive background research, the results of which we have summarized below.

To figure out how long an individual can stay in the sun while wearing sunscreen with a given SPF, the theoretical equation would be: Minutes to burn without sunscreen * SPF number = maximum sun exposure time. However, experts recommend using sunscreen with SPF of no higher than 50, because its minimally incremental effectiveness is not worth it and is misleading to consumers; for example, an SPF of 50 absorbs 98 percent of UVB rays, but an SPF of 100 absorbs 98.7 percent. The SPF has doubled, but the absorption rate has increased by only 0.7 percent.

Minutes to burn without sunscreen * SPF up to 50 = max sun exposure time

However, people tend to use only half the amount of sunscreen recommended, dramatically decreasing its efficacy

Minutes to burn without sunscreen * (0.5)SPF up to 50= max sun exposure time

Also, despite water-proof or sweat-proof labels, all sunscreens decrease substantially in effectiveness when exposed to water or sweat.

Minutes to burn without sunscreen * (0.25)SPF up to 50= max sun exposure time

Finally, we needed to factor in UV levels, which we built into “minutes to burn without sunscreen”. To do so, we took the averages from chart below and other relevant sources:

Final Equation:

Minutes to burn without sunscreen x (0.25)SPF up to 50= max sun exposure where minutes to burn without sunscreen is a factor of UV level recorded. For example, on a sunny day with a UV level of 8, a person who applies SPF 35 sunscreen at 11am should need to reapply at 1:10pm, [(13) x (0.25)(40)] = 130 minutes. Note that in the future, we would like to make “minutes to burn without sunscreen” a dynamic input based on user’s melanin levels.

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Ethnographic User Research

For our ethnographic user research, we decided to focus on individuals who care about their skin and regularly wear sunscreen. The rationale for this is that our product is not designed to convince people who do not care about sun protection to start caring, but rather to enable the roughly 70 percent of Americans who already care about sun protection - but who, like most of us, execute the complexities of sun protection irregularly or imperfectly - to offload the burden of tracking when they have last applied sunscreen and calculating when they need to reapply.

One team member spoke with 11 individuals chosen via convenience sample as she waited (slathered in sunscreen!) outside of Haas School of Business over the course of three hours one afternoon. Of the 11 people she spoke with, 10 had what we termed a readily available “sunburn story,” validating the secondary research asserting sunburns and sun damage are a virtually universal phenomenon. For example, Corin, a 33-year-old MBA student, found herself outside all day for her sister’s college graduation; even though she thought she was putting on enough sunscreen, her resulting sunburn was so bad that she “felt like [she] should be in freaking a burn unit.” Twenty-eight-year-old Zach’s vacation to Thailand took a turn for the worse when his sunburn turned into sun poisoning, which he recalls “felt like fire ants were attacking [his] skin from the inside of [his] body.” Twenty-nine-year-old Chelsea described how a recent sunburn she’d gotten from studying outside for too long caused heat to radiate from her body and her skin to stiffen in “a pretty horrific way.” And after a game of beach volleyball gone awry, 24-year-old Melissa, who was new to Los Angeles and the famous Southern California sun, recalled that she “eventually shed all [her] skin like a damn snake.”

This research helped us to validate our product idea, as everyone we spoke with said they would be interested in flip-flops that alerted them when they needed to apply or reapply sunscreen. It also helped us better understand and address some nuances of our product. For example, we had initially planned to link the flip-flop to a smartphone app, where the user could record the time and SPF level of each sunscreen application. However, after hearing from several people that they’d prefer to avoid touching their phone with greasy post-application fingers, we decided to pivot to creating a wrist band where the user could easily input this information.

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Design Process

Our initial sketch consisted of a contact sensor at the heel of the foot to ensure that the user was currently standing on the flip-flop, a UV sensor in the center of the shoe logo, a haptic motor underneath, and (suggested by Christine), a peltier under the first layer of the flip-flop. This design closely matches the final iteration of Flip-Fluv. The exception was that we decided to design a wearable wrist device to peripherally connect to the flip-flop instead of using a phone app, due to reasons discussed above.

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Feature Selection

We used an FSR as the contact sensor, placed under the ball of the foot, a UV sensor that transmits analog UV indices, placed inside the logo, a haptic motor, placed underneath the logo, and a peltier, placed directly under the foot for maximal contact. The wristband consists of a soft potentiometer so that the user could record the level of SPF applied, a switch button used to record exactly when sunscreen was applied, and an LED that would notify the user of their sunscreen status (green if safe, red if sunscreen application was needed).

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We began by creating low fidelity prototype using foam and trying to find a way to house all electronics. We found it is necessary to design it such that it is detachable for ease of removing or testing electronics. All the dimensions of the electronics were measured and modeled them in Rhino for perfect fit. The diagram above shows how different parts come together. The final piece is a custom-designed puzzle joint so that the case is detachable.

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User Flow


The final user flow is described below:

  1. The first time sun is detected by the UV sensor, the haptic motor will buzz and the LED will flash RED to notify the user to apply sunscreen.

  2. The user applies sunscreen

  3. The user uses the potentiometer to indicate the level of SPF of the sunscreen and pushes the button to record an application of sunscreen.

  4. Peltier unit cools and LED turns to green

  5. The formula loaded onto the feather then estimates the duration that the sunscreen would last given the SPF and UV intensity

  6. The haptic motor on the flip-flop would buzz again once the amount of time is up, and the cycle repeats itself