Progress has been made in the field of self-healing ionic skin

Human skin is an important body organ that can sense mechanical external forces such as pressure, strain, and torsion through ion transport mechanisms
.
At the same time, it is also self-healing and is able to restore initial function
after external injury.
Inspired by the perceptual structure of human skin, individual research teams have reported several ionic skin
with ion transport mechanisms.
They are highly immune to interference, excellent spatial resolution, and excellent response to
static and dynamic stimuli.
However, these ionic skins are vulnerable to accidental mechanical damage caused by continued wear and tear, resulting in disruption of function or reduced
equipment life.
Therefore, the ability to self-repair similar to human skin is an important inherent attribute
necessary to restore impaired function to ensure stability and increase the lifespan of the device.

Zhu Jin's team, a researcher at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, based on years of experience in the research and development of self-healing materials and electronic skin (Advanced Functional Materials, 2022, 32, 2106341; Advanced Functional Materials, 2021, 31, 2009869; Chemical Engineering Journal, 2021, 420, 127691; Chemical Engineering Journal, 2021, 410, 128363; ACS Applied Materials & Interfaces, 2020, 12, 11072; Materials Today Physics, 2020, 14, 100219.
), and the team of Professor Do Hwan Kim of Hanyang University in South Korea.
Kyung Jin Lee, a professor at Chungnam University in South Korea, teamed up to develop an ultra-sensitive and self-repairing ionic skin
.
It has elasticity like human skin and has self-healing ability, and its sensitive tactile function can be restored
as wounds heal.

According to the mechanical stimulus response principle of tactile cells, the research team designed and synthesized a new thermoplastic polyurethane material
containing dynamic disulfide bond functional groups and chlorine substituents by simulating the self-healing function and bioion signaling mechanism of real human skin.
Dynamic disulfide bonds are constantly undergoing reversible dynamic bonding, allowing wounds to heal
quickly and autonomously at room temperature without additional energy.
They used ionic liquids as signal transmission media, filled with the above-mentioned thermoplastic polyurethane materials, and developed a new type of ionic conductor; Silver nanowires are used as flexible electrodes and polyurethane as packaging materials to assemble into target ionic skin
.
Due to the large electronegativity of the chlorine substituents introduced in polyurethane, there is a reversible ionic dipole interaction
with ionic liquids.
Mechanical stimulation to change the reversible ionic dipole interaction between the chlorine substituent and the ionic liquid can effectively increase the difference between the immediate capacitance and the initial capacitance, thereby improving sensitivity
.
Not only that, the research work also systematically elaborated the mechanism of piezo-ionic dynamics to explain the initiation principle
of high sensitivity.
The results of this study simulate an ion signaling system similar to biological tactile cells, controlling the ion distribution inside the ion conductor according to changes in force, maximizing tactile perception
.
The study proposes a new concept of ionic skin technology that simultaneously restores wound and tactile function, which is expected to be applied to human-machine interfaces
in the field of wearable medicine.

The results were published online in
Nature Communications under the title Ultrafast, autonomous self-healable iontronic skin exhibiting piezo-ionic dynamics.

Design concept design of ionic skin: action potential stimulation generated by ion dynamics and bond exchange effect of dynamic disulfide bonds simulate the external force perception and self-healing function of human skin