Thu, 07 Dec 2023

(CN) - To create humanoid robots less like C-3PO of the "Star Wars" universe and more like Data of the "Star Trek" franchise, scientists have recently adapted 3D printing techniques to accommodate slow-curing polymers that can produce soft, pliable plastics rather than rigid materials that are widely used.

An article released Wednesday in the journal Nature details how the new process allowed researchers - for the first time - to fabricate artificial body parts combining soft, elastic materials alongside more rigid polymers, all in one process.

In the months since, they have used the process to create tendon-driven hands, pneumatically actuated walking manipulators, pumps that mimic a heart and metamaterial structures, all made from multiple materials simultaneously. 

"We wouldn't have been able to make [the] hand with the fast-curing polyacrylates we've been using in 3D printing so far," explained Thomas Buchner, a doctoral student in the group of ETH Zurich robotics professor Robert Katzschmann and first author of the study. "We're now using slow-curing thiolene polymers. These have very good elastic properties and return to their original state much faster after bending than polyacrylates." 

Katzschmann added that the stiffness of thiolene polymers can be fine-tuned to meet the requirements to create soft robots, "which would present less risk of injury if working with humans, and they are better suited to handling fragile goods."

Robotics have come a long way since they were first widely adapted to complete automated industrial processes in the middle of the 20th century. Through the ensuing decades, as programming and manufacturing processes improved, robots have been introduced in hospitals, battlefields, farms and homes, among other places.

But for the most part, robots are still largely constructed with metal alloys, and more recently, 3D printed hard plastics. 

Most commercially available 3D printers on the market today use a process called fused filament fabrication, which feeds a roll of plastic material through a heated nozzle, then builds a rigid 3D model in tens or hundreds or thousands of layers, each just millimeters wide.

Traditional 3D inkjet printing uses thousands of individually addressable nozzles to deposit low-viscosity resins that are mechanically planarized, or smoothed, and then cured by an ultraviolet light. The latter method involves a device that scrapes off surface irregularities after each curing step, which limits its use of materials to fast-curing polyacrylates.

But according to the article, robotics researchers have long been interested in using 3D printing to recreate "complex structures and functions of natural organisms in a synthetic form."

A team from ETH Zurich and an American startup affiliated with MIT adapted the technology to propose an inkjet deposition process called "vision-controlled jetting." The new method combines 3D printing with a laser scanner and a feedback mechanism to allow the creation of "complex, more durable robots from a variety of high-quality materials in one go."

The process uses a scanning system to capture a model's geometry as it is being printed and then enables a digital feedback loop, eliminating the need for mechanical planarizers. Unlike fused filament fabrication and traditional inkjet printing, it's a contactless process that allows the use of "continuously curing chemistries" and can "print a broader range of material families and elastic moduli."

Rather than mechanically scraping off irregularities, the scanner "immediately checks each printed layer for any surface irregularities." Then, "the new technology simply takes the unevenness into account when printing the next 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," explained Wojciech Matusik, a professor at the Massachusetts Institute of Technology MIT and co-author of the study. 

Inkbit, the MIT spinoff, was responsible for developing the new printing technology while ETH Zurich researchers developed several related applications and helped optimize the technology for use with slow-curing polymers. 

According to the report, the printers themselves consist of a build plate that moves underneath the stationary inkjet, cure and scanner units. The multi-material objects are printed layer by layer, with the inkjet units depositing droplets of ink. The UV curing unit induces the polymerization of the jetted material while the scanner unit records a height map of the deposited layers on the build plate.

At ETH Zurich, Katzschmann's group aims to use the technology to explore additional designs and application. Inkbit is planning to use the new technology to offer a 3D printing service to its customers and to sell the new printers.

Source: Courthouse News Service

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