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Wearable Technology Insights
Posted on May 13, 2016 by  & 

Aesthetic and functional temporary tattoos

Microsoft Research and MIT's Media Lab have published details of Tattio, a fabrication process that draws from current body decoration processes (i.e., jewelry- like metallic temporary tattoos) for the creation of on- skin technology. The fabrication process generates functional components such as NFC tags, circuitry, to Thermochromic tattoos, while maintaining the aesthetics and user experience of existing metallic temporary tattoos. The fabrication process is low cost, accessible and customizable; aiming to enable individuals to design, make, and wear their own skin technology creations.
 
Introduction and Background
 
The near-ubiquity and miniaturization of electronics enables technology close to our bodies, redrawing the line between technology and ourselves. Human skin, the largest organ on the body, has been recognized as a promising surface for human-computer interactions. Skin has also been a canvas for decoration throughout human history from ancient tribal tattoos signaling identity, to recent fashion trends around jewelry-like metallic temporary tattoos. Tattio is a fabrication process that draws from current body decoration practices for the design of on-skin technology. The fabrication process generates functional components such as RFID NFC tags, circuitry, Thermochromic tattoos, while maintaining the aesthetics and user experience of existing metallic temporary tattoos.
 
 
For technology close to the body, there is a need for greater levels of customization, personal meaning, and intimacy, which could be achieved through a bottom-up approach that resembles this body decoration process, as compared to a top-down approach of purchasing a one-size-fits-all skin circuit. Tattio maintains this user experience; the process is accessible and extendable, leveraging off-the-shelf craft materials and enabling individuals to create their own designs. Tattio is inspired by advances in Epidermal Electronics, an active research field in material science.
 
Design Consideration
 
  • Accessible: The materials for Tattio are accessible and affordable; the cost of making a Tattio NFC tag is $1.5 USD. The process is also extendable, individuals can easily customize their circuitry designs.
  • Skin-Safe: For technology close to the human body, the team leverages fabrication materials that are commercially used and know to be safe for the human skin.
  • Removable: Tattio is a temporary tattoo and can be easily applied and removed by the wearer
  • Aesthetic: Inspired by body decoration, the team selects material (i.e., gold metal leaf) that emulates the aesthetics of metallic temporary tattoos while being conductive.
 
Fabrication Process
 
The process of gilding, applying fine gold or metal leaf onto solid surfaces to give a thin coating for decoration, has been in human history for over 5000 years. Gold leaf has also been used in foods and cosmetics, making it safer for applying to human skin. Current metal leaves are conductive and composed of a mixture of gold alloy, aluminum, and other materials. Based on experimentation with multiple materials, a process of applying gold imitation leaf onto tattoo paper with stencil traces cut out by a Silhouette Cameo Cutter, a tabletop cutter, was chosen.
 
 
NFC Tag
In their explorations, researchers started with the fabrication of a functional component that is passive and would not require power such as an NFC tag. Individuals can easily customize the antenna to different sizes. There are two points to consider for achieving sufficient radiation efficiency. First, radiation efficiency is limited by the conductivity of the traces; a lower resistance will increase the efficiency of the tag. This can be achieved by applying additional layers of gold leaf. Second, the size of the antenna dictates the relative aperture to harvest power from the reader. A smaller antenna, while able to blend more seamlessly into one's body, would harvest less power. Size and power harvested are design tradeoffs for individuals to consider when fabricating their own Tattio NFC Tags.
 
Circuitry
The researchers fabricated wire components to create basic circuitry. They could design wires that were curvy as well as geometric, and easily alter the shape and size. In fabricating the wires, they through-holed the tattoo paper at the wire ends, and connected small pieces of double-sided conductive fabric tape to the ends. When tattooed on skin, the conductive fabric would be exposed, which enabled them to place electronic components and make connections. Connected with a battery, researchers could light up LEDs and power vibration motors with the wires. By integrating other surface mount sensors and actuators on flex circuits, the team could see the capability for creating more complex circuitry on skin.
 
 
Thermochromic Tattoos
By fabricating gold leaf serpentine resistive heating traces and applying a layer of thermochromioc paint on top, the researchers created heat-activated color-changing tattoos.
 
Experiencing Tattio Components
To understand how participants experienced and interact with the fabricated components, the team conducted an initial study where 6 participants applied pre- fabricated NFC tags onto their skin. Temporary metallic jewelry tattoos were provided for participants to decorate their antennas to give it personal meaning.
 
A phone application was developed for participants to interact with each other though their tattoos. Participants could associate a "digital identity" (i.e., an image and text) to their NFC tag, and could change their identity throughout the day. By scanning each other's tattoos, participants would reveal each other's identities.
 
Conclusion
Inspired by metallic jewelry tattoos, Microsoft Research and MIT's Media Lab present an accessible fabrication process that generates on-skin circuitry that is aesthetic and functional. they hope their work inspires in bridging the emerging field of on-skin electronics to the everyday maker, while rethinking cultural and aesthetic perspectives for the design of on- skin technology.
 
 
Source and top image: Microsoft Research
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