*1.3. Computational Skin*

If we can design artificial limbs controlled by thought and if we can implant technology into the body, can we enhance the skin, the largest sense organ, with computational capabilities? If so, this would be a major step in our cyborg future. Based on recent advances in technology, the answer is yes, but first a digression into popular culture. Enhancing the body's surface such that it is transformed into a "computational device" represents a change in our very self-identity as our skin is perceived as the barrier between our internal self and the external world—the *surface* of a person's identity, if you will. We theorize that any change to that visual biological-self model has the potential to increase our capabilities and interactiveness with the world, but also to potentially shift the normal of human "appearance".

On the point of popular culture and our cyborg future, a recent study showed that nearly forty percent of Americans under the age of forty have at least one tattoo (see generally [54,55]); however, like any trade, the tattoo industry must innovate to expand and gain new clients. In an analog world, one way to innovate is to make the switch to digital technology. Rather than being passive as are current tattoos, digital tattoos are active, they *do* things, and they are getting smart [17]. Digital tattoos have the potential to do more than serve the function of art or self-expression, even though these are laudable goals, they will indeed become digital devices as useful as smartphones—and may even monitor our health.

It is possible now to use a type of ink in a tattoo that responds to electromagnetic fields, which raises a host of new opportunities for cyborgs. In fact, Nokia patented a ferromagnetic ink technology that can interact with a device through magnetism. The basic idea is to enrich tattoo ink with metallic compounds that are first demagnetized (by exposing the metal to high temperatures) before the ink is embedded in a person's skin. Once the tattoo has healed, the ink is re-magnetized with permanent magnets. The resulting tattoo is then sensitive to magnetic pulses, which can be emitted by a device such as a cellular phone. Interestingly, a digital tattoo would allow a person's ringing phone to result in a haptic sensation experienced by the body; that is, the person would experience the phone ringing literally through the tattoo; an interesting computational capability for cyborgs and an interesting change in our use of technology and of our body.

If the tattoo consists of putting electronics on the surface of the skin, many more possibilities for body hacking exist. For computational skin, materials scientist and University of Illinois Professor John Rogers is developing flexible electronics that stick to the skin to operate as a temporary tattoo [18]. These so-called "epidural electronics" (or Biostamp) are a thin electronic mesh that stretches with the skin and monitors temperature, hydration and strain, as well as monitoring a person's body's vital signs [17,18]. The latest prototype of the Biostamp is applied directly to the skin using a rubber stamp. The stamp lasts up to two weeks before the skin's natural exfoliation causes it to come away. Rogers is currently working on ways to ge<sup>t</sup> the electronics to communicate with other devices like smartphones so that they can start building apps (eventually such devices will communicate with devices that are implanted within the body). Developing sensors worn by or implanted within the body that communicate with and controls external devices is a new capability for humans, essentially extending the "reach of the body" beyond that of the body's physical boundaries. Google, isn't far behind in developing digital tattoos, as the company's Advanced Technology and Projects Group patented the idea of a digital tattoo consisting of various sensors and gages, such as strain gauges for tracking strain in multiple directions (how the user is flexing), EEG and EMG (electrical impulses in the skeletal structure or nerves), ECG (heart activity), and temperature.

Considering another digital tattoo designed for a medical monitoring purpose, University of Pennsylvania's Brian Litt, a neurologist and bioengineer, is implanting LED displays under the skin for medical and bio-computation purposes [55]. These tattoos consist of silicon electronics less than 250 nanometers thick, built onto water soluble, biocompatible silk substrates. When injected with saline, the silk substrates conform to fit the surrounding tissue and eventually dissolve completely, leaving only the silicon circuitry. The electronics can be used to power LEDs that act as photonic tattoos. Litt is perfecting a form of this technology that could be used to build wearable medical devices—say, a tattoo that gives diabetics information about their blood sugar level. These examples highlight the use of cyborg devices to compute data, monitor the body, and eventually form closed-loop feedback systems with the body. Additionally, they demonstrate our increasing tendency to electively distance ourselves from our natural biology and technologically modify our very human form.

### *1.4. Body Hackers and Implantable Sensors*

The body hacking movement, especially about implantable sensors within the body, gained momentum from the work of Professor Kevin Warwick starting in 1998 at the University of Reading [30]. Professor Warwick was one of the first people to hack his body when he participated in a series of proof-of-concept studies which first involved implanting a sensor into his shoulder (see his paper, this special edition). Warwick's "cyborg application" consisted of the use of an RFID implant which allowed Professor Warwick to switch on lights and open doors as he entered rooms (thus Warwick was-able-to link his body directly to external devices). Later, others extended Warwick's seminal work using RFID devices and other implantable sensors. For example, in an extension of Professor Warwick's early work, Dr. John Halakha of Harvard Medical School, chose to be implanted with an RFID chip used to access medical information [56]. His implant stores information which can direct anyone with the appropriate reader to a website containing his individual medical data. He believes that implantable chips such as these can be valuable in situations where patients arrive at the hospital unconscious or unresponsive.

Another person with an RFID implant, Meghan Trainor has a less pragmatic but highly creative application for her implant [57]. Trainor received the implant as part of her master's thesis for NYU's Interactive Telecommunications Program. Her implant serves as part of an interactive art exhibit; RFID tags are embedded in sculptures which can be manipulated to play sounds stored in an audio database. Trainor can use the implant in her arm to further manipulate these sounds. Additionally, body hacker Anthony Antonellis implanted an RFID chip into his hand which can be wirelessly accessed by a smartphone [21]. While the chip holds only about 1 KB to 2 KB of data, it allows Antonellis to access and display an animated GIF on his phone that is stored on the implant. Since the RFID chip can transfer and receive data, Antonellis can swap out 1KB files as he pleases. Antonellis views the implant as a "net art tattoo", something for which quick response codes (QR, or matrix barcode), are commonly used. Similarly, Karl Marc, a tattoo artist from Paris designed an animated tattoo that makes use of a QR code and a smartphone [58]. The code basically activates software on the phone that makes the tattoo move when seen through the phone's camera. The use of cyborg technology to transform the body into electronic art is surely a new mode of interacting with the world and a hint of what is to come in the future.
