| Recently,various intelligent devices that perform programmable deformation and motion under external stimulation have received extensive scientific attention.Under external stimulation,oriented liquid crystal elastomers(LCEs)can undergo reversible deformation at the macroscopic scale upon an order–disorder phase transition of the mesogens.This property is widely explored for developing those intelligent devices.Among all kinds of stimulus responsive LCE materials,light responsive LCE was selected as the primary choice material for intelligent devices due to have remote controllability and high selectivity toward wavelength.Combined with the excellent stimulus responsive property of LCE,a kind of soft actuator with controllable morphology and a light-driving soft snake robot are developed.The specific research contents and results are listed as follows:1.The morphology has a great influence on the properties of materials,so controlling morphology has become a simple and feasible strategy for preparing intelligent devices.The precious actuator with controllable morphology was prepared by photo-alignment technology to built three-dimensional topology in the multi-domain LCE,which has the defects of complicated preparation process,the expensive equipment,and absence of remote light-driving mode.Thus limiting its application in practice.The Y1709-YHD796C LCE film obtained by acyclic diene metathesis polymerizationd will adhere to the side wall of the mould closely during the film formation process.According to this phenomenon,the spatially structure can be built in the multi-domain LCE using a mold with spatially structure bottomas as long as the thickness of the film and the height of the spatially structure are limited.Inspired by this,two actuators(W-LCE and M-LCE)with controllable morphology and potential to support items are obtained.Ultraviolet-visible absorption spectrum(Uv-Vis)shows that LCE film have strong and sharp absorption peaks at 796 nm wavelength.The thermal stimulus response test showed that both W-LCE and M-LCE contracted rapidly at 125?hot stage,and gradually deformed into spatially structure at 145?.After cooling to room temperature,the two films can quickly return to original flat state.Through heating/cooling cycle stimulation,this reversible deformation from flate to spatially structure can be repeated.2.Snake robots have received extensive scientific attention due to their flexible serpentine locomotion mode.So far,those snake robots that mimic this mode are based on hardware integration which have the defects of large size,high power consumption,and poor adaptation.However,soft robots just to make up for these defects.In a locomotion mode,snake contracts its muscles,thrusts its body from side to side,and creates a series of S-shaped curves.The key challenge in the fabrication of snake soft robot is how to achieve a reversible transformation from one S-shaped motion to the reverse S-shaped motion.Based on this basic design logic,two strategies were adopted to fabricate snake soft robots.The first strategy was very straightforward,we built an S-shaped structure(State 1)in the polydomain LCE sample obtained from the pre-crosslinking stage,performed mechanical programming to reverse the S-shaped structure,and solidified this permanent state 2 during the second crosslinking stage.Under NIR light irradiation,this S-shaped LCE0 ribbon exhibited a reversible deformation from the wavy structure(state 2)to a nearly flat state instead of the desired reverse wavy structure(state 1).We further optimized the strategy 1,by adopting one extra LCE supporting layer LCE2 which had larger contraction strain than the main layer LCE1 and would contribute to reverse the S-shaped structure beyond the LC-to-isotropic phase transition.Here,we designed and prepared two LCE ribbon LCE1 and LCE02 by two-step crosslinking process,and composited them to obtain a two-component bilayered LCE ribbon.Ultimately,a near infrared(NIR)light-driven snake-mimic robot was obtained by install serrated feett at both ends of the abdomen of the bilayered LCE1-LCE2 ribbon to provide asymmetric friction.Uv-Vis absorption spectrum and photothermal conversion test results show that both ribbon LCE1 and ribbon LCE2 have strong and sharp absorption peaks at 796 nm wavelength,and have a strong photothermal conversion ability for 808 nm near infrared(NIR)light.Furtherly,the stimulus responsive behavior of the ribbon LCE1,the bilayered LCE1-LCE2 ribbon and the soft snake robot were studied.The result shows that the ribbon LCE1 can realize the reversible deformation from wavy structure to flate state under the repeating on/off illumination cycles of808 nm NIR light.The bilayered LCE1-LCE2 ribbon undergoes reversible deformation from S-shape to reverse S-shape under heating/coolng cycles.Thus indicated that the bilayered LCE1-LCE2 ribbon have the ability to mimic the S-curve during serpentine locomotion.The snake-mimic robot based on bilayered LCE1-LCE2 ribbon constantly deformed between an S-shaped motion and a reverse S-shaped motion,and moved forward with a crawling velocity of ca.0.13 mm/s under the repeating on/off illumination cycles of 808 nm light(15 s per cycle,including 9 s light on and 6 s light off).Meanwhile,the real-time position coordinate of the point A,the included angle?and curvature(1/r)of the snake-mimic robot were recorded during motion.Dates show that the location distribution of the point A presented a regular wave-like motion trajectory.The bending angle varies from 72°to-45°and the curvature varies from 3.14cm-1 to-2.00 cm-1 cyclically.All date indicated that the robot could keep moving forward through a regular morphing between the S-shaped motion and the reverse S-shaped motion.This soft snake-mimic robot has potential application prospects in the field of miniature detectors. |
PDF Full Text Request