Lanzhou Institute of Chemical Technology has made new progress in the research of bionic friction materials

Designing smart materials with reversible adhesion and friction control properties in wet environments has always been a major challenge in the fields of bionic science and materials engineering
.
Most organisms in nature can achieve rapid and reversible adhesion and detachment by relying only on the dynamic mechanical deformation of the adhesion organs without changing the physical and chemical interactions of the interface.
The most typical case is the gecko
.
The mechanical deformation of the gecko’s toe in motion will cause the state of the contact between the micro-nano structure of the gecko’s surface and the substrate to change, and the good bonding state (strong van der Waals force, high adhesion) through the crack propagation mechanism of peeling will be changed to the detached state (weak van der Waals Power, low adhesion)
.
This gives the gecko fast, reversible and switchable friction adhesion ability
.
At present, it is urgent to develop a bionic smart friction adhesion material with the characteristics of the mechanical peeling mechanism of gecko feet for complex operating environments such as dry and wet alternating
.
? The material table interface research group of the State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences has been committed to the design and construction of bionic wet-slippery intelligent interfaces for many years
.
Recently, the research group successfully prepared a smart gecko foot adhesion material with mechanical response and self-peeling characteristics
.
Researchers have developed a temperature sensitivity by coupling surface microstructure (mushroom-like silicone elastomer), interface adhesion chemistry (catechol-based wet adhesion copolymer glue) and material mechanical deformation (responsive hydrogel) The Bionic Multilayer Smart Adhesive Device (SPSA), dynamic mechanical deformation induces the change of the interface contact state, and then realizes the reversible regulation of underwater adhesion
.
Figure 1.
Demonstration of the operation of the bionic gecko foot wet-adhesion smart device based on the mechanical response peeling mechanism.
The researchers used the interface soft-contact adhesion meter measurement system to characterize the dynamic contact process between the SPSA device and the substrate surface in situ, and successfully captured The crack propagation and peeling boundary evolution process at the contact interface (Figure 2)
.
Through adhesion test and contact mechanics analysis, it is found that SPSA can achieve reversible control of adhesion through the peeling mechanism caused by the mechanical deformation of the body material in dry and wet environments
.
In addition, the relationship between the adhesion force and the deformation radius of curvature is 0.
5 scale law, and SPSA can be used continuously and reversibly for more than 20 times under dry and wet conditions..
The researchers integrated nanoparticles with photothermal response characteristics into the device.
The designed device can successfully achieve the process of contact bonding, deformation peeling, and desorption similar to the gecko toe under the irradiation of the near-infrared laser, and is used for Grabbing and transfer of underwater objects
.
? Figure 2.
The evolution of crack growth and peeling boundaries of SPSA smart adhesive devices under dry and wet conditions during dynamic loading, equilibrium, and unloading
.
The research work takes the real motion form of the gecko as the starting point of bionics.
By coupling the surface microstructure, interface chemistry and mechanical deformation, a new type of bionic gecko foot device with mechanical response and self-peeling characteristics under external field stimulation has been developed, which is a bionic smart adhesion and The engineering application of friction materials provides new design ideas
.
The work was published on Chemistry of Materials (2021, 33, 2785-2795) under the title "Gecko's Feet-inspired Self-peeling Switchable Dry/Wet Adhesive".
The first author is Zhang Yunlei, a PhD student at Lanzhou Institute of Physics and the corresponding author is Zhou Researcher Feng and associate researcher Ma Shuanhong
.
? The research work was supported by the National Natural Science Foundation of China, the Youth Innovation Promotion Association of the Chinese Academy of Sciences, and the International Cooperation Bureau of the Chinese Academy of Sciences.
It also received the help of Dr.
Xiaosong Li from Tsinghua University
.