In a recent post about biohacking, I wrote about people who have implanted chips into their bodies to benefit their health, simplify their lives, or connect themselves to an external network. Though some have been quick to adopt it, biohacking is still a relatively new and bizarre trend that makes many people wary. The thought of burying chips in our arms is unsettling, and most of us would only do it if it was medically necessary. But for those who are curious yet not quite ready to take the chip-implantation plunge, there’s now another way to join the biohacking party: temporary tattoos.

Created by MIT PhD student Cindy Hsin-Liu Kao in conjunction with Microsoft Research, the Duoskin tattoos transfer onto your skin with water, and they can be customized for both aesthetic and functional purposes. Hsin-Liu Kao presented her paper about the tattoos at the International Symposium on Wearable Computers in Heidelberg, Germany last week.

The first step in creating a tattoo is to make a tiny circuit board using graphic design software. A stencil of the circuit is created by applying a layer of vinyl film onto tattoo paper, then gold leaf is layered over the stencil to act as conductive material. The last step is to surface-mount electronics. All tattoos except those with an NFC chip connect to a microcontroller that processes sensor data, supplies power, and links devices through Bluetooth. The total cost of creating a three by four centimeter squared NFC tag is less than $2.50.

In trials, the team tested conductive thread and copper tape as alternatives to gold leaf, but found gold leaf to be the most durable and the most skin-friendly.

Three Functions

Duoskin plans to offer the tattoos in three different user interface types:

Input: On-skin input elements resemble traditional user interfaces like buttons, sliders, and 2D trackpads. The 2D touchpad uses row-column scanning in a two-layer construction that isolates horizontal traces from vertical traces. These tattoos can turn your skin into a track pad or a controller. For example, instead of pressing the arrow on your phone to skip to the next song on your playlist, you could just tap a spot on your skin.

Output: Soft displays on skin are enabled through the ink-like qualities of thermochromic pigments. These displays have two different states, and a color change is triggered when body temperature rises. Displays can be separated into designated sections, and to activate color changes, resistive heating elements are fabricated underneath the thermochromic layer of the tattoo. Want everyone to know you’re angry or excited without having to say it? Your tattoo could send the message for you.

Communication: Tattoos provide wireless communication for exchanging data across on-skin interfaces using NFC (near-field communication) technology. NFC tags include a chip that connects to a coil, which Duoskin fabricates using gold leaf customized to various shapes and sizes. You can read data directly off your skin; have someone touch their phone to your arm to communicate a message of your choice, or touch your arm to a card reader to make a payment.

Control Your Devices in Style

Hsin-Liu Kao wants the tattoos to be as much a fashion statement as they are a biohack. In her native Taiwan, there’s a widespread culture of aesthetics and street fashion. It’s cheap to edit your appearance, and making changes to the way you look allows you to express your personality and identity to the outside world. Hsin-Liu Kao says, “There’s no fashion statement greater than being able to change the way your skin looks.” One option on her temporary tattoos is to add LED lights, which make the tattoo look more like jewelry.

If you wouldn’t implant a chip into your arm, would you wear a tattoo that can send and receive data? If you did, how important would the aesthetic aspect be to you?

Hsin-Liu Kao predicts that in the future the tattoos will become “extensions of ourselves.” Fashion has always been a mode of self-expression; now it’s just a matter of integrating technology into your personal style statement, if you choose to do so.

Image credit: MIT Media Lab