What you need to know about the inkjet printed tattoo that is bringing us closer to electronic skin

By Elton Gomes

Scientists have created a fast and inexpensive new method to develop an electronic skin that can help robots and prosthetic devices to have tactile abilities. With the help of the skin, such devices will be able to detect pressure, temperature, and other sensations that allow tactile interactions with the environment.

The new method was developed by researchers from the Carnegie Mellon University in the US, and the University of Coimbra in Portugal. The work has been published in ACS Applied Materials & Interfaces.

Through the method, the scientists can create an ultra-thin, stretchable electronic skin, which can be used for several human-machine interactions, by producing thin-film circuits with integrated microelectronics.

The method comes as a breakthrough, especially in the field of printed electronics. For the first time, the researchers proved that inkjet-printed patterns can be sintered at room temperature with the help of an alloy.

“We showed for the first time that inkjet-printed patterns of silver nano particles can be sintered at room temperature using the gallium indium alloy. Removing the need for high temperature sintering makes our technique compatible with thin-film and heat sensitive substrates,” Mahmoud Tavakoli, core member and project manager at Institute of Systems and Robotics, University of Coimbra, Portugal, said in a statement.

How did the scientists develop the skin?

The researchers first printed circuits made of silver nano particles. They then patterned this circuit template onto a sheet of transfer tattoo paper. Then, they coated the tattoo paper with a silver paste, which adhered only to the printed toner ink.

Credit: Institute of Systems and Robotics of the University of Coimbra, Portugal and College of Engineering, Carnegie Mellon University.

Thereafter, the team deposited a gallium-indium liquid metal alloy. This alloy increased the electrical conductivity and flexibility of the circuit. Finally, the researchers added external electronics, such as microchips, with a conductive glue that was made up of vertically aligned magnetic particles embedded in a polyvinyl alcohol gel.

The researchers transferred the electronic tattoo to various objects and demonstrated several applications of the new method. The scientists tested movements such as controlling a robot prosthetic arm, monitoring human skeletal muscle activity, and incorporating proximity sensors into a 3D model of a hand.

How will electronic skin be helpful?

Electronic skin could be used in a number of applications, including prosthetic devices, wearable health monitors, robotics, and even virtual reality.

A major challenge is transferring ultrathin electrical circuits onto complex 3D surfaces, and then having electronics that are bendable and stretchable enough so that movement can occur.

Some scientists have developed flexible “electronic tattoos” for this purpose. However, their production is typically slow, expensive, and requires clean-room fabrication methods such as photolithography.

Electronic skin in the future

Scientists around the world have developed artificial organs such as bionic eyes. Such artificial devices have the potential to restore sensory feelings to the disabled or provide sensory capabilities to machines.

Keeping in mind that robots could play a crucial role in the future, enabling tactile sensing could help in ensuring that robots function safely. If robots are going to be around, they will have to detect when a surface is slippery as well as sense the shape, texture, and temperature of the objects it grasps.

This is where electronic skin plays an important role. Electronic skins will help robots in accurately identifying the properties of an object, thus it can decide how much force to apply while holding it.

A significant breakthrough for electronic skin was when it can be made soft and bendable – the current researchers have come with a method to do just that. Such breakthroughs would also mark a significant step in wearable technology.

Elton Gomes is a staff writer at Qrius

Carnegie MellonElectronic SKin