Tactile Tattoos: The Ultimate in Wearables

by Ines Wynn

Imagine accessorising your outfit with a gold leaf sticker on your arm, leg -or any other body part for that matter– and using it as a touch pad much like the one on your smartphone in order to control your mobile devices, to display information or store data. How about a skin bracelet that acts as a music controller? A bit of body art that tells you when you are anxious, in the mood or running a fever? A skin-based antenna that lets you communicate with your mobile devices like a wearable Blue Tooth?

It sounds farfetched, futuristic and a tad techno-rad but it’s definitely coming to a tattoo parlour near you. A few years ago, the Los Angeles Times published an article entitled ‘Excuse me, my tattoo is ringing’. It reported that Nokia had filed a patent with the United States Patent and Trademark Office for a tattoo that would send a perceivable impulse to your skin whenever someone tried to contact you on the phone. As described in the patent application, the phone would communicate with the tattoo by emitting magnetic waves and the tattoo would act as a receiver, setting off a tactile response in the user’s skin. I’m not sure if Nokia ever marketed this tattoo and my curiosity was still peaked so a bit of googling quickly provided an update on those tactile tattoos. There has not exactly been a flurry of activities on that front but I did find a few promising developments.

A collaborative project called DuoSkin between MIT Media Labs and Microsoft is creating on-skin or epidermal electronics with three types of interfaces that can sense touch input, display information and perform wireless communications with other electronic devices. These on-skin tattoos are very different from the wearable electronic gadgets embedded in clothing or these ungainly strap-on fitness trackers that can measure your biomedical vital signals, monitor glucose levels or count walking or running distances. These devices limit themselves to health, medical and wellness hacks. With the advent of on-skin electronics, the range of applications is vastly expanded.

DuoSkin tattoos are non-invasive temporary tattoos that perform as interfaces, letting them act as input for smartphones or computers, display data via thermochromatic layers or initiate wireless communication by using a short-range antenna. They control smartphones, computers, and devices via touch. The process uses gold leaf, commonly found in craft stores, as a conductor in order to create adhesive decals emulating three different classes of ‘devices’. The input device turns your skin into a track pad or music player controller using traditional user interfaces such as buttons, sliders and 2D trackpads. The output device is a thermochromic skin patch that changes colour according to the wearer’s emotions or body temperature. The third is a communications device using a short range NFC (near field communications) component that includes small microchips to store data that can be read by phones or other NFC devices nearby.

In order to create these ultra-thin on-skin stencils, the process uses durable, skin-safe gold leaf decals which can be pressed on to the skin. Gold leaf acts as a conductor and is combined with a thin tattoo paper silicone as the flexible substrate that attaches to the skin. It is easy to attach, easy to remove and clean. The stencil acts like an electrical circuit.These decals are fabricated in a multiple-step process using computer based graphic design software to create an actual stencil of the circuitry, applying gold leaf as the conductive material and applying flexible surface-mount electronics on thin temporary tattoo paper. After completing the circuitry, the souped-up decal is applied to the user’s skin through water-transfer which is a process similar to a temporary tattoo.

The tattoos can be a DIY job. That is, you can create your own stencils and doll them up according to your artistic inclinations, your personal style and identity. You can design decals with geometric, tribal or your choice of patterns. The process of creating your own personal on-skin user interface is relatively easy and the costs are very modest. Alternatively you can elicit the assistance of a temporary tattoo parlour where someone else could custom-design the decal of your dreams. And there you have it.Your skin transformed into an interactive medium for interfacing with all your other electronic gadgets. You can wear it permanently or peel it off after a time when no longer needed. These patches definitely provide a simpler, less restrictive way to monitor your vital signs, or let you command a computer with simple movements. And they can even be embedded in another temporary tattoo.

Early prototypes of electronic tattoos were similar to traditional tattoos which are invasive interventions performed on the skin. These tattoos were etched directly into the skin with digital ink or electronic ink and contained encapsulated microspheres embedded in the skin. Philips Design did research on tattoo forms based in digital inks which respond not only to touch, but also to neural and endocrinal variations.

Several university research departments have developed medical applications for the touch tattoos such as applications for controlling Parkinson’s symptoms or prostheses. MIT researchers developed silk-silicon LEDs that act as photonic tattoos. These tattoos show blood-sugar readings, allowing a great range of mapping the physiological functions. All these tattoos still require that sensors are inserted under the skin. From embedded technology it was a logical step to the development of a new dynamic and interactive tattoo using technological adhesives without invasive procedures. These smart tattoos may look like body art or fashion statements but they cleverly disguise electrical components that make the tattoos interactive.

Future developments of this technology could veer in many different directions. There is simply no end to imagining possible applications. It could serve as a substitute for identification, enable you to buy subway cards or movie tickets, even function as a virtual wallet. Your arm could soon become your miniature keyboard on the go.