Engineers optimize toolpaths to 3D print soft mechanical metamaterials

Elastomeric structures improve suction cup pull-off force by up to 85 percent.

Soft robotics is a challenging field from the perspectives of both materials science and mechanical engineering but its potential is enormous. From cilia to spiderwebs, leaves to lattices, the evidence that soft mechanical metamaterials are not only possible but functional abounds throughout the natural world.

Given these organic sources of inspiration, it’s only fitting that the technology enabling soft mechanical metamaterials would be 3D printing, with its capabilities to produce organic shapes and utilize advanced materials. However, the layer-by-layer approach in additive manufacturing (AM) processes is typically incompatible with materials such as silicone, epoxies and urethanes. These are essential for soft robotics applications, but they also often cure too slowly to be used in fused deposition modelling, for example.

Direct ink writing is a more promising AM process for such applications, but it tends to be held back by non-optimized toolpaths. “These issues lead to extended print times and are further exacerbated by the dynamic material behaviours in their uncured state,” explained associate professor Pablo Valdivia y Alvarado from the Singapore University of Technology and Design (SUTD) in a recent press release.


To address this problem, Valdivia y Alvarado and his team at SUTD proposed an architected design approach to optimize the toolpaths for 3D printing soft materials. The team used both segmented and continuous toolpath designs to generate toolpaths that contained fewer unnecessary starts and stops.

The team also tuned the properties of the printing materials to enhance their suitability for direct ink writing. Selecting three commercially available silicone materials, the team then added Thivex silicone thickener to create and characterise nine distinct material combinations that were more suitable for direct ink writing.

The researchers used these modified materials 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, while 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.

“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,” said Valdivia y Alvarado.

The research is published in the journal Advanced Intelligent Systems.

Written by

Ian Wright

Ian is a senior editor at engineering.com, covering additive manufacturing and 3D printing, artificial intelligence, and advanced manufacturing. Ian holds bachelors and masters degrees in philosophy from McMaster University and spent six years pursuing a doctoral degree at York University before withdrawing in good standing.