It hurts! Your central nervous system sends a warning to your brain: protect yourself through stress reaction!
Researchers have always hoped that bionic skin, like the skin of organisms, can have the ability to feel pain, and then stimulate the self-protection response of individuals with “skin”.
Inspired by the mechanical strain enhancement of biological soft tissues, the intelligent polymer materials team of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (hereinafter referred to as Ningbo Institute of Materials) proposed a bionic skin based on strain sensing enhancement (SPS) effect, based on the research accumulation in the construction of carbon-based/polymer composite films and their flexible driving and sensing, and realized the dynamic transformation from tactile sensation to pain perception. Related results were published online in Advanced Functional Materials recently.
Active perception is more sensitive.
In biological system, the mechanical strength of soft tissue can be effectively adjusted by strain enhancement to avoid injury. Traditional electronic skin can simulate human tactile or pain function through a preset resistance change threshold, but there are still some challenges in realizing active sensing through strain sensing enhancement (SPS).
“At present, the research on pain bionic skin mostly focuses on pressure sensing. When the pressure reaches a set threshold, the control system will be activated to make necessary early warning or behavioral response to cope with greater pressure.” Xiao Peng, the first author of the paper and an associate researcher at Ningbo Institute of Materials, told China Science Journal.
The soft tissue combined with the somatosensory system of the organism can undergo a controllable threshold transition from tactile sensation to pain sensation when the tissue or skin is stretched, so that the organism can actively perceive the mechanical stimulus that may cause harm and respond quickly to prevent the danger from happening.
Therefore, the realization of active protection function depends on the strong and rapid pain warning triggered by the sensory system before strain mechanical enhancement.
Xiao Peng said that in SPS material system, the sensitivity coefficient (GF) has a typical positive correlation with the applied strain, and GF shows obvious improvement after reaching the strain threshold, thus realizing the transition from tactile sensation to pain sensation.
Research on “pandering”
In this published achievement, the author uses “pulling” action to carry out research.
They adopted the strategy of interface self-assembly and in-situ functionalization to construct a two-dimensional graphene-based elastic ultrathin film (ECF) with an interface interlocking structure. Different from ECF based on one-dimensional carbon nanotubes, ECF based on two-dimensional graphene sheets shows GF behavior that changes positively with strain, which is similar to the sensory system of real vertebrates.
In ECF, the dynamic network formed by stacking graphene sheets can respond to external strain stimuli sensitively through different degrees of sliding, thus achieving normal tactile perception at low strain and above the strain threshold..Pain perception of value.
Furthermore, by adjusting the thickness of graphene sheet, the strain threshold can be made at 7..2% to 95%.Change within 3%.
“That is to say, bionic skin made by ECF will be more sensitive, and slight pulling and pulling can stimulate pain perception, thus informing the processing system to take the initiative to respond before a greater degree of pulling stimulation occurs and avoid risks.” Xiao Peng explained, “Moreover, the strain threshold for stimulating pain perception can be adjusted according to demand, which will help more complex functional management.”
This excellent performance adjustability will greatly promote the application of ECFs in bionic skin based on SPS effect, imitating the pain perception function of human tissues, such as monitoring the overstretching of tendons and the pain caused by pulling the skin on the back of the hand.
“transform” like a puffer fish
When threatened, puffer fish will “transform” and grow spikes all over. Inspired by the three-dimensional deformation of puffer fish skin, researchers integrated ECF into a self-supporting bionic skin, which can sensitively sense contact or non-contact mechanical stimulation and monitor three-dimensional aerodynamic deformation in real time, and then effectively detect three-dimensional deformation in an over-expanded state through SPS effect to realize dynamic pain perception.
Researchers believe that exploring SPS material system independent of physical size, shape and initial conductivity will be beneficial to the development of intelligent and friendly soft robot, and it is of great significance to avoid danger in human-computer interaction. In the future, ECFs based on SPS effect is expected to be widely used in safe and friendly human-computer interaction, intelligent prosthesis and soft robot.
Of course, the current technological achievements are still far from applying bionic skin to organisms. Xiao Peng said: “We will make ECF into ultra-thin film, which is close to the structure of human skin, and it is sure to realize more real skin functions in the future.”
(Source: Ningbo Science and Technology Bureau)