Study Of Multi-stimuli Responsive Soft Biomimetic Actuation Materials And Devices

Flexible smart materials can respond specifically to external stimuli such as heat,light,pressure,electricity or magnetic fields.Flexible actuator based on flexible smart materials can change its shape and size greatly,generate multi-degree of freedom deformation,realize continuous and complex motion.It can be used to imitate the wriggling,swimming,crawling and other forms of movement of natural organisms.Therefore,it has shown great application prospects in the fields of bionic technology and flexible robots.However,in the research of existing flexible driving materials,there are challenges such as single driving stimulus source,monotonous deformation mode and complicated preparation process.Choosing the right flexible smart material and combining its characteristics to design a flexible driver with multi-stimulus response and complex deformation function will be the key to apply it in bionic technology and flexible robotics.Inspired by the fact that pine cones produce bending deformation under low humidity conditions,we prepare multi-functional double-layer flexible actuators by using paper,silver nanoparticles(Ag NPs)and polydimethylsiloxane(PDMS).The paper is used as the active layer due to the property of expansion in high-humidity environment and shrinking in low-humidity environment.PDMS with a large thermal expansion coefficient is used as the other active layer.In the middle,the Ag NPs is printed on the paper and served as the electro-thermal energy conversion layer between the paper layer and PDMS layer.Due to the layers coupling,the double-layer paper-based composite can bend to the side of the PDMS layer when increasing environmental humidity or lowering temperature,and bend to the side of the paper layer when reducing humidity,increasing temperature,or applying electrical stimulation.The U-shaped driver is designed by the flexible driving material.Its various properties such as electrically induced deformation,mechanics output,electric heat,and humidity response are measured.The deformation could be increased by optimizing the thickness of PDMS,anisotropy structure of paper,preparation process and so on.When the shear angle is 90°,and the thickness ratio of PDMS and paper layer is 3:1,the actuator has the largest deformation angle.When the thickness of PDMS layer in the actuator is about 265 um,the deformation is up to 270° and the driving voltage is low(?4V).In addition,different shapes of actuators are designed by cutting and heat setting process,and multi-degree of freedom and controlled deformation(bending,stretching and folding)under the excitation of different stimulation sources are also achieved.The additional electrochromic function of the actuator is further achieved by adding temperature-sensitive color-changing microcapsules during the preparation process.The actuators added with the electrochromic microcapsules with different colors can change its color from brown to green,black to white,brown to red,separately when the temperature exceeds 35?.The color-change snake and discoloration painting is further prepared based on this function of the actuator.We design and prepare flexible biomimetic multifunctional intelligent materials and explore their applications in biomimetic actuation devices.The materials show controllable large deformation under the stimulation of low voltage,temperature,or humidity change.And the actuators exhibit multi-degree of freedom deformation including bending,stretching,folding,and electrochromic function.The results exhibit the considerable application prospects of this type of soft actuator with advantages of low cost,easy preparation,high-performance,and multi-stimuli-response in the field of soft robots,smart wearing,flexible sensing and other fields.