Considerable research has gone into electronic tattoos (or e-tattoos), as part of the emerging field of or epidermal electronics. These are a thin form of wearable electronics, designed to be fitted to the skin. The aim of these lightweight sensors is to collect physiological data through sensors.
The types of applications of the sensors, from Tsinghua University, include assessing exposure to ultraviolet light to the skin (where the e-tattoos function as dosimeters) and for the collection of ‘vital signs’ to assess overall health or reaction to a particular medication (biosensors).
The use of graphene aids the collection of electric signals and it also imparts material properties to the sensors, allowing them to be bent, pressed, and twisted without any loss to sensors functionality.
The new sensors, developed in China, have shown – via as series of tests – good sensitivity to external stimuli like strain, humidity, and temperature. The basis of the sensor is a material matrix composed of a graphene and silk fibroin combination.
The highly flexible e‐tattoos are manufactured by printing a suspension of graphene, calcium ions and silk fibroin. Through this process the graphene flakes distributed in the matrix form an electrically conductive path. The path is highly responsive to environmental changes and it can detect multi-stimuli.
The e‐tattoo is also capable of self-healing. The tests showed how the tattoo heals after damage by water. This occurs due to the reformation of hydrogen and coordination bonds at the point of any fracture. The healing efficiency was demonstrated to be 100 percent and it take place in less than one second.
The researchers are of the view that the e-tattoos can be used as electrocardiograms, for assessing breathing, and for monitoring temperature changes. This means that the e‐tattoo model could be the basis for a new generation of epidermal electronics.
Commenting on the research, chief scientist Yingying Zhang said: “Based on the superior capabilities of our e-tattoos, we believe that such skin-like devices hold great promise for manufacturing cost-effective artificial skins and wearable electronics.”
The development of the sensors has been published in the journal Advanced Functional Materials. The research paper is titled: “Self-Healable Multifunctional Electronic Tattoos Based on Silk and Graphene”.
