self healing magnetic ink

Magnetic ink used to create self-healing electronics

A magnetic ink that can be used to make self-healing batteries, electrochemical sensors and wearable, textile-based electrical circuits has been developed by a team of engineers at the University of California, San Diego.

The ink is composed of micro particles oriented in a certain configuration by a magnetic field.

Because of the way they’re oriented, particles on both sides of a tear are magnetically attracted to one another, causing a device printed with the ink to heal itself. The devices repair tears as wide as 3mm, which the developers say is larger than other self-healing systems.

“Our work holds considerable promise for widespread practical applications for long-lasting printed electronic devices,” said Joseph Wang who worked on the project.

Existing self-healing materials require an external trigger to kick start the healing process. They also take anywhere between a few minutes to several days to work.

By contrast, this system doesn’t require any outside catalyst to work. Damage is repaired within about 50 milliseconds (0.05 seconds).

Engineers used the ink to print batteries, electrochemical sensors and wearable, textile-based electrical circuits. They then set about damaging these devices by cutting them and pulling them apart to create increasingly wide gaps.

They repeatedly damaged the devices nine times at the same location and also inflicted damage in four different places on the same device. Despite the rigorous treatment, the devices still healed themselves and recovered their function while losing a minimum amount of conductivity.

“We wanted to develop a smart system with impressive self-healing abilities with easy-to-find, inexpensive materials,” said Amay Bandodkar who also worked on the ink.

Engineers loaded the ink with microparticles made of a type of magnet commonly used in research and made of neodymium, a soft, silvery metal.

The particles’ magnetic field is much larger than their individual size. This is the key to the ink’s self-healing properties because the attraction between the particles leads to closing tears that are millimetres wide.

The particles also conduct electricity and are inexpensive. But they have poor electrochemical properties, making them difficult to use in electrochemical devices, such as sensors, on their own. To remedy this problem, carbon black was added to the ink, a material commonly used to make batteries and sensors.

But researchers realised that the microparticles’ magnetic fields, when in their natural configuration, cancelled each other out, which robbed them of their healing properties. Engineers solved this by printing the ink in the presence of an external magnetic field, which ensured that the particles oriented themselves to behave as a permanent magnet with two opposite poles at the end of each printed device. When the device is cut in two, the two damaged pieces act as different magnets that attract each other and self-heal.

Self-healing clothing was demonstrated in July that is designed to protect soldiers and workers who could be exposed to hazardous materials. 

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