This lifelike limb is made up of a series of contractile and elongated actuators, or "GRACES." The actuators are 3D-printed from resin membranes that stretch and contract like muscles. Weighing just eight grams, these tiny actuators can lift 1,000 times their own weight and, when integrated into a robotic hand, have human finger-like functions, such as the ability to bend and twist the palm and rotate the wrist.
Biomimetic technology based on 3D printing
Nature is filled with examples of biomimetic studies of animals and plants that remain an inspiration to materials scientists and engineers. To reproduce these properties in artificial structures and robots, researchers often turn to 3D printing, and in doing so, have pulled off some impressive biological mimicacies.
At Zhejiang University, scientists have used 3D printing technology inspired by cuttlefish to mimic the unique energy-absorbing ability of Marine creatures. In fact, the team's early models were so resistant that they could withstand pressures up to 20,000 times their own weight. Similarly, engineers at Taiwan University of Science and Technology in China have 3D-printed sea urchin shell-like lattices using FDM, without the need for any supporting materials.
Elsewhere, in biological mimicry attempts with soft robots, researchers have deployed actuators capable of converting energy and electrical signals into motion to create robots with realistic actions. And scientists in China are moving closer to limb production by 3D-printing soft robotic fingers.
Develop a GRACE capable manipulator
According to IIT researchers, artificial actuators have now reached an important stage in their development where they are able to achieve the same contractile performance as biological muscles. However, in their paper, the team added that previous techniques faced problems in recapitulating the "variety and elegance of movement" brought about by the complex arrangement of muscles within the human body.
To solve this problem, the team designed GRACE artificial muscles, made of a single material fold membrane, that use mathematical modeling to contract and stretch from beginning to end. As a result, the actuator is able to perform as expected without the need to integrate strain limiting elements.
With the Formlabs Form 3D printing device, the researchers were able to integrate the folds into the membrane of the device, allowing them to fold and unfold, giving them the flexibility and strength needed to withstand repeated deformations. In practice, the team claims that the 3D-printed phones have been tested to lift heavier and heavier items, both individually and in groups.
It turns out that, depending on the parameters of the materials used to make these devices, they are able to lift objects several orders of magnitude heavier than themselves. In one case, an 8-gram prototype of GRACE was able to lift as much as 8 kilograms, leading scientists to rediscover their potential as a means of simulating muscles and body parts.
To test this theory, the researchers chose to connect 18 actuators of different sizes to create a robotic hand and wrist. By applying pressure to each 3D-printed membrane, they found that they could manipulate the hand with human-like motion and efficiency. After successfully testing their method, the team said it demonstrated the possibility of 3D printing functional muscle in a single production step.
"GRACE can be manufactured by low-cost 3D printing or even directly in a functional device, such as a pneumatic prosthesis that can be 3D-printed in one step." "This makes the prototyping and fabrication of pneumatic artificial muscles faster and more straightforward."