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4D printing of water and alcohol reversible control born

Source:未知Author:admin Addtime:2020-01-21 14:14:17 Click:
Humidity-responsive deformations are widespread in nature. For example, pods and wheat mangs can achieve autonomous opening and closing based on changes in external humidity. Based on these inspirations, researchers have created a large number of stimulus-responsive hydrogels, elastomers, and ceramic materials, and applied them in various fields such as software robots, biological equipment and tissue engineering. Among these materials, the double-layer hydrogel system has attracted extensive attention and research due to its convenient and adjustable characteristics. However, due to the slow diffusion rate of water in the hydrogel (10−10 to 10−9 m2 s−1) and the generally low modulus of the hydrogel (10 ~ 1000 KPa), the deformable hydrogel is caused The response and recovery time of the glue are very long, and it is difficult to obtain complex and stable deformation, which limits the application of the deformable hydrogel in practical engineering. Therefore, there is a need for a convenient and fast method for manufacturing stimulus-responsive hydrogels with fast response / recovery and stable complex deformation.
 
 
4D printing of water and alcohol reversible control born
 
 
Achievements
 
 
Recently, Professor Lu Jian's group at City University of Hong Kong, after pre-strain driving 4D printed ceramic precursors (G. Liu, Y. Zhao, G. Wu, J. Lu, Sci. Adv. 2018, 4, eaat0641), and Professor Kannie WY Chan and the team of Professor Hu Jinlian of the Hong Kong Polytechnic University have used 4D printing technology to prepare polymer strip-membrane structures that can achieve fast, stable, complex and reversible deformation in water / alcohol solutions. The researchers used a high-modulus chitin membrane as the driving layer to achieve stable deformation; designed a strip-membrane structure to increase the contact area of ​​water exchange, while using hydrophobic low-modulus PDMS as the limiting layer, to achieve the purpose of rapid response. Utilize the strong customization and design of 3D printing to make a series of complex deformed structures such as leaves, windmills, lotus and goldfish. The work was published on Advanced materials technologies under the title "Direct-Ink Written Shape-Morphing Film with Rapid and Programmable Multimotion".
 
 
Graphic guide
 
 
Figure 1. Basic performance parameters of the manufacturing process and materials.
 
 
 
 
Figure 2. Effect of different printing parameters on sample curvature.
 
 
 
 
Figure 3. Printing deformation of complex structures compared with finite element simulation.
 
 
 
 
Figure 4. Fast response and sequential response.
 
 
 
 
Figure 5. Designed and printed goldfish structure.
 
 
 
 
to sum up
 
 
In this work, a new method for fabricating a flexible actuator with a strip-membrane structure was designed. Compared with other actuators that require external energy to drive, our actuators can respond quickly and do not require external thermal or electrical stimulation. By adjusting the response time, you can achieve a sequential response. Stable and complex deformation can also be achieved and accurately predicted by finite element simulation. At the same time, by printing the complex self-assembled goldfish structure, the design, convenience and diversity of the method were proved. This method offers more possibilities for manufacturing complex and responsive software actuators.