China3D printingNet September 30, a group of researchers from the San Diego campus in San Diego developed a3D printingThe new method of liquid crystal elastomer (LCE), the method only needs to change the printing parameters to achieve the characteristics of functional gradual change.
The potential application is as a driving material for soft robots and artificial muscles, which can be used to tightly control the stiffness and contractility of the LCE through heating during and after printing.
Zizi Wang, the lead author of the study, explained: ” 3D printingIt’s a great tool for making many different things-in this case, we can print structures that can shrink and harden on demand under the stimulus needed. “
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LCE petal structure” alt=” turning on
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The petal structure of the LCE” width=”620″ height=”242″ />
turning on3D printingThe LCE petal structure. The picture is from the University of California, San Diego.
How does liquid crystal elastomer work?
The LCE can be actuated highly reversibly while producing a greater working density.In theory, this makes it very suitable for novel soft robots and wearable devices, but previous attempts have been made on materials with gradual or changing characteristics.3D printingThe attempt is very difficult. For example, you might want the joints of the robot to be more flexible, but the load-bearing beams should be stiffer.
Take a closer look, the driving effect of the LCE depends on the change in the direction of its liquid crystal cell (the basic unit of liquid crystal). When trying to rearrange the mesogens, many methods have been used before, including mechanical stretching and magnetic fields-each method has its own unique limitations.
For now, the most effective method for printing LCE structures is direct ink writing technology, through which a controlled volume of liquid ink can be dispensed from the micro nozzles and cured under UV light. It has been previously observed that the mesogens spontaneously align along the printing path due to the shear stress caused by extrusion. Researchers at the University of San Diego adopted this direct ink writing technique and put it into operation, making their own attempts at the process and experimenting with changes in printing temperature.
LCE extrusion process. The picture is from the University of California, San Diego.
3D printingFunctionally graded LCE structure
By first checking the properties of the material, the team can determine that the extruded LCE has a core-shell structure. The outer shell cools faster and becomes harder, suspending well-aligned mesogens in a high-viscosity matrix. On the other hand, the core stays heated longer and remains malleable, which means that its mesogen is relatively free to return to its chaotic, unaligned state.
To test the seemingly basic relationship between heat and stiffness, the researchers printed many geometric shapes with different temperature distributions. First print the disk at 40°C, and then heat it to 90°C in a water bath to deform it into a more conical shape. However, when the same disc is printed at constantly changing temperatures (intervals of 40°C, 80°C, and then 120°C), it will become a completely different shape after being placed in a water bath.
When printing the tubular structure, the same dynamics are observed. When printing at a regulated temperature, the LCE tube may stick for a longer time when starting up than a glass tube printed at a constant temperature. With this, the team basically produced a very basic robotic gripper. The next step of research involves the development of new inks that can be reprogrammed or even recycled.
Active lattice structure composed of functionally graded LCE. The picture is from the University of California, San Diego.
China3D printingOnline reviews:The field of soft robotics is an in-depth research field with new developments every year.A group of researchers from Linköping University in Sweden recently used a custom extrusion-based3D printingThe machine developed a set of micro actuators suitable for soft micro robots. The actuator contains an electroactive polymer, which can change its geometry in the presence of an electric charge, thereby giving the actuator a 4D function.
Elsewhere in Asia, researchers have recently3D printingWith soft robot fingers. The device is powered by an embedded single-electrode triboelectric curvature sensor (S-TECS), which can sense bending curvature at ultra-low operating frequencies without any external power supply.
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