Researchers at the Italian Institute of Technology (IIT), using 3D printing technology, have developed a new kind of robotic hand, the team claims, using an SLA 3D process to create artificial muscles with more bionic capabilities.
The printed lifelike limb consists of a series of contractable and elongable actuators, or "GRACES" as they can be called. These actuators are 3D printed from a resin film that can stretch and contract like a muscle. Weighing only 8 grams, these tiny actuators can lift up to 1,000 times their own weight, and when integrated into a robotic hand, they have human finger-like functions such as the ability to bend and twist the palm of the hand and turn the wrist.
3D printing-based biomimetic technology
The natural world is full of examples of bionic research on animals and plants, which continues to inspire materials scientists and engineers. To reproduce these properties in artificial structures and robots, researchers often turn to 3D printing and, in doing so, have accomplished some impressive biomimicry.
At Zhejiang University, scientists used 3D printing technology inspired by cuttlefish to mimic the unique energy absorption capabilities of marine organisms. In fact, the team's early models had superb pressure tolerance, so much so that they were able to withstand pressures up to 20,000 times their own weight. Similarly, engineers at the National Taiwan University of Science and Technology in Taiwan, China, have 3D printed sea urchin shell-like lattices using FDM without the need for any support materials.
Elsewhere, in attempts at biomimicry of soft-bodied robots, researchers have deployed, actuators capable of converting energy and electrical signals into motion to create robots with realistic movements. And scientists in China have moved toward limb production by 3D printing soft robotic fingers.
By effectively combining these approaches, the IIT team says it is possible to 3D print, in the future, soft actuators that are robust and flexible enough to be effectively "integrated with natural and social environments," with applications ranging from biodiversity conservation to everyday care for the elderly. The team therefore sees their prototype robotic hand as a first step toward making such devices easier to create.
Developing a robotic hand with GRACE capabilities
According to the IIT researchers, artificial actuators have now reached an important stage in their development, where they are capable of achieving the same contractile properties as biological muscles. However, in their paper, the team added that the problem faced by previous techniques made it difficult to reproduce the "diversity and elegance of motion" brought about by the complex arrangement of muscles inside the human body.
To solve this problem, the team designed, instead, GRACE artificial muscles composed of a single material pleated membrane, which, from beginning to end, contract and extend using mathematical models. As a result, the actuators are able to perform as expected without the need to integrate strain limiting elements.
The Formlabs Form 3D printing device enabled the researchers, to integrate folds into the membrane of the device, which have the ability to fold and unfold, while, at the same time, giving them, the flexibility and strength needed to withstand repeated deformations. In practice, the team claims that these 3D printed phones have been tested and can lift increasingly heavy objects, both individually and in groups.
They have proven to be able to lift objects several orders of magnitude heavier than themselves, depending on the parameters of the materials used to make the devices. In one case, the 8-gram GRACE prototype model, was even able to lift 8 kilograms, which led scientists to relearn that they could be used as a potential 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 operate the hand with human-like movements, and efficiency. After successfully testing their method, the team said it demonstrated the possibility of 3D printing functional muscles in a single production step.
"GRACE can be manufactured by low-cost 3D printing, or even directly in a functional device, for example, a 3D printed pneumatic prosthesis in just one step." "This makes prototyping and manufacturing based on pneumatic artificial muscles much faster and more straightforward."