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3D printing bio-inspired structures for wearables and robotics

3D printing bio-inspired structures for wearables and robotics

Technology News |
By Jean-Pierre Joosting



Since its introduction in 1985, 3D printing has become cheaper than traditional manufacturing technologies, but more importantly offers the ability to customise designs and make prototypes on demand. Over the past decade, there has been an accelerating demand for 3D printing methods across sectors, ranging from aerospace and defence to medicine.

However, Associate Professor Pablo Valdivia y Alvarado from the Singapore University of Technology and Design (SUTD) believes that there are still ways to go before 3D printing can achieve its full potential.

Typically the printing process uses a nozzle to print the material layer by layer, and the path that the nozzle takes is known as the toolpath. However, layer-by-layer printing is incompatible for use with materials like silicone, epoxies, and urethanes that are slow-curing and take more time to harden. These types of materials are often used to create soft mechanical metamaterials which, in turn, are used for lightweight, nature-inspired structures, such as lattices and web structures. Deposition-based processes in 3D printing, such as direct ink writing, would be able to work with these materials to create such structures, but these suffer from non-optimised toolpaths.

“These issues lead to extended print times and are further exacerbated by the dynamic material behaviours in their uncured state,” explained Associate Professor Valdivia y Alvarado. It therefore remains challenging to 3D-print complex bioinspired structures.

To address this, Associate Professor Valdivia y Alvarado and his team at SUTD proposed an architected design approach. Looking specifically at how direct ink writing can be used to fabricate lightweight structures, the team first designed a method to optimise the toolpaths. By breaking down the object’s 3D design into points and simple shapes, the researchers could then make use of both segmented and continuous toolpath designs to improve the overall toolpath — enabling the generation of toolpaths that contained fewer unnecessary starts and stops.

The researchers printed several types of bioinspired structures using this method for generating optimised toolpaths. They first sought to tune the properties of the printing materials to further enhance their suitability for direct ink writing. By selecting three commercially available silicone materials, and then adding a modifier known as Thivex, the team created and characterised nine distinct material combinations that were more suitable for direct ink writing.

To test the functionalities of the structures in different settings, the researchers then proceeded to 3D-print cilia, webs, leaf-like structures, and lattices using their proposed approach. For the 3D-printed cilia, the team found that adding it to suction cups improved the suction cups’ pull-off force; meanwhile, the 3D-printed lattice proved to be an effective energy-absorbing structure, demonstrating a reduction of maximum impact peak forces by up to 85 percent.

Associate Professor Valdivia y Alvarado commented, “Although the approach is still in the research phase, its potential for customised, high-performance designs makes it highly relevant for industries focused on robotics, wearable technologies, and advanced metamaterials.”

He added that deposition-based additive manufacturing processes could find a niche in advanced applications, complementing traditional methods that would remain essential for producing high-volume and standardised structures.

The team is focused on improving the scaling efficiency of their method, reducing its costs, and expanding the versatility of the materials to industrial settings. To do this, the researchers plan to explore multi-material printing which would allow different materials to be printed, in turn creating “engineered metamaterials”. Machine learning techniques could also enable 3D printing users to specify performance metrics for the metamaterial designs that they wish to generate.

“These advancements will further unlock the potential of 3D-printed metamaterials for a wide range of applications, including soft robotics and wearable protective gear,” according to Associate Professor Valdivia y Alvarado.

Image: 3D printed cilia formations depicting the letter “S”. Credit SUTD.

Paper: https://doi.org/10.1002/aisy.202400514

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