Scientists 3D print a robotic hand with human-like bones and tendons (RUPENDRA BRAHAMBHATT, 11/18/2023, Ars Technica)

In a VCJ system, along with a 3D printer, there is a 3D laser scanner that visually inspects each layer for surface irregularities as it’s deposited. “This visual inspection makes the print process fully contactless, allowing for a wider range of possible polymers to be deposited. We, for example, printed with thiol-based polymers because it enabled us to create UV-light and humidity-resistant structures,” Katzschmann told Ars Technica.

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. (The researchers used MRI data from a real human hand to model its construction.)

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.