Soft materials for stretchable and self-healing electronic devices

The world needs flexible, stretchy and soft electronics. They are needed in soft robotics, wearable electronics, and bioelectronics that can self-adhere to human skin and tissues. A new and exciting step forward is addition of self-healing functionality to electronic devices so that they can heal themselves if they get damaged. The idea is simple: instead of devices breaking permanently when they are scratched, torn or otherwise damaged, they are built from special polymer materials that can repair themselves and keep working. This means electronics could become more durable, require less maintenance, and be better suited for everyday use, even in demanding conditions.

In the dissertation, soft and stretchable materials were used to fabricate soft temperature sensors that are not affected by humidity. These sensors can still measure temperature even when they are stretched. Another key is the development of a spontaneously self-healing, strain-insensitive, electrically conductive liquid metal elastomer (ECLME) which presents an important step forward in multifunctional material for printed electronics. This material enables the realization of electrical wiring and electronic components for communication, sensing, and signal transmission, while greatly simplifying device fabrication and assembly.

Building completely self-healing electronic devices is more challenging than just combining different materials together, as all the layers in a device need to align and reconnect properly after damage. In this dissertation, several working prototypes of self-healing electronic devices were fabricated using the developed materials. These included an LED display, a battery-integrated LED-device, RF transmission lines, and UHF RFID tag antennas. An important feature of the material is that it can stick to other materials on its own, without the need for extra adhesives. This self-adhesive behavior simplifies how devices are assembled and used.

The devices were tested under different conditions, such as being stretched repeatedly and being mechanically damaged and healed again. The results show that the materials are very promising for future electronics. At the same time, there is still more to be understood about the underlying physics and how the materials, structures, and functionalities interact. With further research, this material technology could lead to more reliable, more sustainable and longer-lasting electronics for wearables, soft robots, and devices that interact closely with the human body.