Tattoos of the New Generation

Epidermal Electronics/UCSD

Gone are the days of being attached to bulky monitors and machines if you have a weak heart. Researchers have developed a much more trendy method for doctors to diagnose and monitor the likes of heart arrhythmia and sleep disorders – say hello to the tattoos of the new generation.

Scientists in the USA, Singapore and China have blurred the boundaries between electronics and biology by developing thin electrochemical sensors that integrate with human skin and monitor temperature, strain and electric signals from the body to warn the wearer of any health or security risks. The device is flexible and small enough to require only infinitesimal amounts of power, which it can harvest from tiny solar cells.

Joseph Wang and his colleagues at the University of California, San Diego (UCSD) have incorporated these sensors into a temporary transfer tattoo (T3) as a non-invasive method of monitoring bodily functions. As well as being inconspicuous, the T3 material optimises skin contact due to its elasticity, which deforms to account for all epidermal irregularities. This allows the tattoos to be worn for extensive periods of time without the usual irritation of adhesive tapes and rigid electronics.

Serpentine Circuitry/University of Wisconsoin

The sensor must also be able to endure everyday conditions imposed on human skin, such as twisting, poking and pulling, without breaking. To combat this issue, Wang and his team have integrated carbon fibre segments into the tattoo ink, which enhances the sensor’s electrochemical behaviour via an interlinked, conductive backbone. This provides the sensor with sufficient mechanical reinforcement to prevent it from deteriorating from routine wear-and-tear. Last year, John A Rogers, Professor of Materials Science at the University of Illinois, Urbana-Champaign, developed incredibly thin components made of high-performance materials like silicon in a serpentine structure, which also helps increase tolerance towards deformation.

Needless to say, such devices have much potential as a human-computer interface in the areas of medical sensing and even computer gaming. Professor Rogers demonstrated this by mounting the tattoo onto a person’s throat, where it could measure electrical activity in the muscles; signals received from the device contained sufficient data for the software to recognise commands such as “left”, “right”, “up” and “down” to control a cursor on a computer screen. Todd Coleman, professor of bioengineering at UCSD, received a grant from the Gates Foundation to further develop epidermal electronics for unobstrusive preganancy monitoring. It is hoped that the sensor will have the ability to continuously measure and monitor fetal and maternal heart rate and body temperature and uterine contractions.