In biological systems, soft tissues can effectively adjust their mechanical strength to avoid damage through strain enhancement. These tissues, combined with the organism’s somatosensory system, can undergo a controlled sensory threshold shift from touch to pain, allowing the organism to actively perceive mechanical stimuli that may cause injury and further react quickly to prevent danger from occurring. Thus, the realization of the active protection function depends on a strong and rapid pain warning triggered by the sensory system before the strain is mechanically enhanced. Although traditional electronic skins can simulate human tactile or pain function through pre-set thresholds for resistance changes, there are still challenges in achieving active sensing through strain perception enhancement (SPS). In SPS material systems, the sensitivity coefficient (GF) and the applied strain have a typical positive correlation, and GF shows a significant improvement before and after the strain threshold, thus enabling the transition from touch to pain perception. More importantly, exploring SPS material systems that do not rely on physical size, shape and initial conductivity will facilitate the development of intelligent and friendly soft robots, which is of great significance for the early avoidance of dangers in human-computer interaction.
Recently, Researcher Chen Tao and Associate Researcher Xiao Peng of the Intelligent Polymer Materials Team of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, based on the research basis for the construction of carbon-based/polymer composite films and their flexible drive and sensing (ACS Nano, 2019, 13, 4368; Nano Energy, 2019, 59, 422; Nature Commun., 2020, 11, 4359; Nano Energy, 2021, 81, 105617; Adv. Funct. Mater., 2021, 31, 2105323; Adv. Funct. Mater. 2022, 32, 2107281; Nano-Micro Lett.,2022, 14, 32; Nano-Micro Lett., 2022, 14, 62 et al.), inspired by the mechanical enhancement of biological soft tissue strain, proposed a bionic skin based on the SPS effect to achieve a dynamic transition from touch to pain perception.
In this work, a two-dimensional graphene-based elastic ultra-film (ECF) with interface interlocking structure was constructed using interface self-assembly and in-situ functionalization strategies. Unlike ECFs based on one-dimensional carbon nanotubes, ECFs based on two-dimensional graphene sheets exhibit GF behavior that changes positively with strain, which has a similar perceptual trend to the neural sensory system of real vertebrates. In ECF, the dynamic network formed by stacking graphene sheet layers on top of each other can sensitively respond to external strain stimuli through different degrees of slip, thereby achieving normal tactile perception under low strain and pain perception above the strain threshold. Further, by regulating the thickness of the graphene sheet layer, it is possible to achieve a strain threshold change in the range of 7.2% to 95.3%. This excellent performance tunability will greatly facilitate the application of ECFs in SPS-based bionic skin to mimic the pain-sensing functions of human tissues, such as monitoring the over-stretching of tendons and the pain sensation caused by the pulling of the skin on the back of the hand. Inspired by the three-dimensional deformation of puffer fish skin, ecf is integrated into a self-supporting form of bionic skin that can be sensitive to contact or non-contact mechanical stimulation and real-time monitoring of three-dimensional aerodynamic deformation. Not only that, but it is also possible to effectively detect three-dimensional deformation in an over-expanding state through the SPS effect, and realize dynamic pain perception. In the future, ECFs based on sps effects are expected to be widely used in safe and friendly human-computer interaction, intelligent prosthetics and soft robots.
ECF-based bionic skin for tactile and pain management of strain perception enhancement (SPS).
The work was published in Adv. Funct. Mater., 2022, 32, 2201812。 This research was supported by the National Natural Science Foundation of China (52073295), the Zhejiang (Zhijiang) Laboratory Open Research Project (No.2022MG0AB01), the Sino-German Exchange Program of the National Natural Science Foundation of China (M-0424), the Frontier Science Key Research Project of the Chinese Academy of Sciences (QYZDB-SSW-SLH036), Funded by the Bureau of International Cooperation of the Chinese Academy of Sciences (174433KYSB20170061) and Wang Kuancheng’s International Crossover Team (GJTD-2019-13). (Source: Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences)
Related paper information:https://doi.org/10.1002/adfm.202201812
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