Digital tattoos come with different names: e-tattoos, electronic tattoos, or even e-skin but with a single purpose: Offering a discreet and efficient way to monitor health or interface with electronics for human-machine interactions.

Like implantable RFID-chips are the first step towards transhumanism and the cyborg transformation of society, electronic skins can expand the ways we interact with the world.

What are electronic tattoos made of?

Digital tattoos are the natural evolution of printed electronics. The key is for both the circuitry and the substrate to be bendable.

In 2003, the research group of Pr. Someya at the University of Tokyo engineered the first flexible e-skin. Electronic skin tattoos are temporary tattoos, including electronic circuits in a thin film.

Thin-fin Transistors (TFT) are an integral part of this revolution. They integrate into a printable elastic conductor. Flexible electronic conductors can serve numerous purposes such as recording muscle activities, act as heart monitors, feel minimal pressures or body temperature changes, or even light up a LED and communicate wirelessly with other devices.

Source: Takao Someya/University of Tokyo

During his twenty years of improvement, the latest nanomesh temporary tattoos developed by Pr. Someya are perfectly compatible with the human skin.

They can be worn for as long as one week without producing any irritation. The only drawback is that flexibility and comfort come at the cost of durability. A simple shower or hand wash will be enough to rub them off.

From fashion to the future of wearable

Chaotic Moon, an Austin based software design company, started developing digital tattoos made of electric paint in the mid-2010s. The project was at the intersection of fashion and biometric data collection.

Their approach was quite innovative and set the ground for integrating digital tattoos in our daily life without compromising fashion and design. Accenture ultimately acquired the company, and the project appears to be on the back burner.

Anyhow, such initiatives developed by think tanks and digital design companies have the potential to open new avenues about the future of connected wearables.

Applications of digital tattoos in healthcare

Electronic tattoos can open a whole new range of applications for health monitoring purposes, from electrocardiograms to blood glucose tracking.

Record brain and muscle activities

Conductive polymers printed using an inkjet printer on standard tattoo paper were develop by the group of Dr. Francesco Greco from École Nationale Supérieure des Mines de Saint-Étienne in France to record a basic electroencephalogram (EEG).

The devices are comfortable to wear long-term. They open doors to a new generation of conductive polymer electrodes for use in neuroregeneration, epilepsy monitoring, and even to control electronic devices with a simple thought.

This new generation of tattoos allows measuring signals reliably and comfortably. Hair can even grow through the polymer without interfering with the signal.

Improve clinical trial data collection

The Massachusetts-based company MC10 already uses its Food and Drug Administration (FDA) cleared monitoring device to change data collection during clinical trials. BioStamp is certainly bigger than a simple digital tattoo but shows the many potentials of such technology.

Source: MC10

The data sensors can be applied anywhere on the body and can record 44 standard metric vital signs. The wearable sensor transmits the data wirelessly to the company platform.

The raw data are processed to provide clinical insights relative to sleep, posture, activity, and vital signs.

Monitor blood glucose

A couple of years ago, researchers at Harvard and The Massachusetts Institute of Technology (MIT) developed a project called DermalAbyss to experiment with color-changing bio-interfaces.

It was a proof of concept that the ink used for the tattoo could provide actionable color-changing indications depending on the level of specific biochemical components present in the body fluids.

Depending on the pH, glucose, and Sodium levels in the interstitial compartments, the ink will react and change color, thus informing the user of a physiological variation.

More than a digital tattoo, DermalAbyss was the first time that the many possibilities of color-changing bio-ink sensors were explored. One ink changes from green to brown as glucose concentration increases. Used by diabetics, the tattoo color will change depending on the glucose level providing visual cues to the user in real-time.

In 2016, researchers from the University of Seoul partnered with MC10 to develop a graphene patch bringing one step further using smart-patch to control diabetes or other pathologies. The goal was to monitor specific physiological indicators such as glucose in the sweat and trigger micro-needles to release drugs.

Benefits and risks of digital tattoo

The field of skin wearable is still in its infancy, but the potential uses in healthcare and human-machine interactions are limitless. By connecting electronic-skin and transmitting data continuously to a smartphone or health monitoring platform, physiological data tracking will become basically invisible and convenient to use.

The team of Pr. Zhang in Beijing recently published an article about the development of a self-powered e-skin with applications in interactive wearable devices, military applications, artificial prosthetics, and intelligent robots.

Just imagine the many benefits of replaceable skin patches to track vital signs, control the environment, and even deliver the proper amount of medicine in real-time.

A digital tattoo constantly monitoring your health may be the future of healthcare, but it doesn’t come without limitations. In the age of biometrics, privacy is a major concern to ensure that the data is used appropriately and not shared with employers, insurers, or public organizations.

As tattoos are unique and can be used to identify individuals, digital inks are active devices with the potential to transmit personal information. Technology is also a two-sided coin, and the benefits should always be considered regarding potential online privacy risks.