Exploring the Future: 3D Printed Robotic Hand Mimics Human Bones and Tendons



– Nov 18, 2023 1:00 pm UTC

Have you ever wondered why robots are unable to walk and move their bodies as fluidly as we do? Some robots can run, jump, or dance with greater efficiency than humans, but their body movements also seem mechanical. The reason for this lies in the bones they lack.

Unlike humans and animals, robots do not have real bones or the flexible tissues that connect them; they have artificial links and joints made of materials like carbon fiber and metal tubes. According to Robert Katzschmann, a professor of robotics at ETH Zurich, these internal structures allow a robot to make movements, grab objects, and maintain different postures. However, since links and joints are made up of hard materials, robot bodies are not as flexible, agile, and soft as human bodies. This is what makes their body movements so stiff.

But they may not need to stay stiff for long. A team of researchers from the Swiss Federal Institute of Technology (ETH) Zurich and US-based startup Inkbit have figured out a way to 3D print the world’s first robotic hand with an internal structure composed of human-like bones, ligaments, and tendons. What makes the hand even more special is that it was printed using an entirely new 3D inkjet deposition method called vision-controlled jetting (VCJ).

Fast-curing polyacrylates are typically used in the production of 3D printed robots. These solid and robust polymers solidify rapidly during deposition. But, to circumvent any inconsistencies, the layers of printing need mechanical planarization, a process of creating an even surface through the use of mechanical force, as pointed out by scientists. Consequently, conventional 3D printed robots lack elasticity and are restriction with respect to forms and materials.

The materials’ speedy solidification doesn’t allow for adjustments in separate layers. As a result, scientists have touse different manufacturing steps and structure assembly for various components of a single robot. The process of printing each part, assembling the different components, and testing them extensively is time-consuming and laborious.

The suggested VCJ method can bring about a significant improvement. It involves the usage of soft, slow-curing thiolene polymers in 3D printing. These have excellent elastic properties and restore to their original condition faster post bending than polyacrylates, explained Katzschmann, one of the authors of a paper describing the new technique.

In the VCJ method, a 3D laser scanner accompanies a3D printer to visually inspect the surface inconsistencies of every layer as it’s being deposited. Katzschmann remarked that this visual examination enables a contactless print process, allowing a wider selection of potential polymers to be deposited. For example, they used thiol-based polymers, enabling them to construct structures resistant to UV light and humidity.

After the scanning, there is no mechanical planarization of the deposited layer. Instead, the next layer is printed in such a way that it makes up for all the irregularities in the previous layer. “A feedback mechanism compensates for these irregularities when printing the next layer by calculating any necessary adjustments to the amount of material to be printed in real-time and with pinpoint accuracy,” said Wojciech Matusik, one of the study authors and a professor of computer science at MIT.

Moreover, the researchers claim that this closed-loop controlled system allows them to print the complete structure of a robot at once. “Our robotic hand can be printed in one go, no assembly is needed. This speeds up the engineering design process immensely—one can go directly from an idea to a functional and lasting prototype. You avoid expensive intermediate tooling and assembly,” Katzschmann added.

Using the VCJ technique, the researchers successfully printed a robotic hand that has internal structures similar to those of a human hand. Equipped with touch pads and pressure sensors, the robotic hand has 19 tendon-like structures (in humans, tendons are the fibrous connective tissues that connect bones and muscles) that allow it to move the wrist and fingers. The hand can sense touch, grab things, and stop fingers when they touch something.

In addition to the hand, they also printed a robotic heart, a six-legged robot, and a metamaterial capable of absorbing vibrations in its surroundings. The researchers suggest that all these robots work like hybrid soft-rigid systems (robots that are made of both soft and hard materials) that can outperform hard robots in terms of flexibility and overcome the design- and scale-related issues faced by soft robots.

Soft robots, crafted from flexible materials such as fluids or elastomers, present a unique challenge for scientists. Ensuring these robots retain their geometry and strength at larger scales can be difficult, as their materials might not maintain their physical properties and structural integrity. This is why soft robots are typically created on a smaller scale, such as in centimeters or millimeters. However, VCJ holds the promise of creating scalable hybrid soft-rigid robots.

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VCJ could potentially outmode all contact-based inkjet printing methods in the future. It promises the creation of functional parts for various industries, including robotics and medical implants. The high resolution, appropriate material properties, and long lifespan of VCJ system prints make them extremely useful for both research and commercial applications, according to Katzschmann’s discussion with Ars Technica.

Published in Nature, 2023. DOI: 10.1038/s41586-023-06684-3. About DOIs

Rupendra Brahambhatt, an experienced journalist and filmmaker, is known for his comprehensive coverage of science and culture news. Over the past five years, he has been actively collaborating with several innovative news agencies, magazines, and media brands globally.

Original source


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