Researchers from Canada and Germany walk that fine line from the 3D into the 4D, sharing their findings in ‘4D pine scale: biomimetic 4D printed autonomous scale and flap structures capable of multi-phase movement,’ recently published in Philosophical Transactions of the Royal Society A.
Because much of the 4D movement is centered around objects that can deform and then revert back to their initial shape, scientists involved in such research are usually focused on the study of a wide variety of materials, from reinforced composites to biopolymers, metamaterials, and more. Here, the authors are concerned with a complex ‘biomimetic hygro-responsive composite.’
It is not uncommon to find that scientists are inspired by nature and in fascinating ways. Not to disappoint here, either, the scientists were motivated to create biomimetic materials due to the reversibility in the shape of Bhutan pine (Pinus wallichiana) cone seed scales. In studying the complexity of the pine cone seed scales, the researchers hoped to create ‘versatile and self-sufficient scale and flap systems.’
In relation to 4D deformability, the researchers studied how pinecones are affected by moisture in their environment, remaining closed while they are wet, keeping their seeds protected, and then opening when it is dry, allowing the seeds to be released on the wind.
“Such passive waterdriven motion responses are nastic and, therefore, structurally ‘programmed’ into the individual seed scales,” explained the researchers. “Each scale forms a functional bilayer structure through a gradation in its tissue structure, from the sclereid cells at the bottom of the scale to a region of sclerenchymatous strands at the top.”
The sclereid layer serves as the actuating layer, while the sclerenchymatous layer serves as the resistant layer. Together, the layers either bend upward due to moisture levels or bend downward after drying—with the cone opening.
“Furthermore, the structural integrity of the cone scales can be conserved for millions of years, highlighting extraordinary functional resilience and robustness,” said the researchers. “The stratification of the pinecone scale’s functional bilayer set-up is not homogeneous and the dimensions of sclereid and sclerenchymatous tissues vary over the length of the individual scale.”
For this study, the researchers used an FFF 3D printer with ‘high-performance lightweight composites,’ along with reinforced polymers, and wood composites too, mixed with a co-polyester polymer matrix and able to imitate the swellable lower sclereid layer. They also used ABS as it is still vulnerable to moisture but it ‘undergoes negligible dimensional changes compared to WPC.’ For that reason, the researchers used ABS material to imitate the stiffer upper layer as they created a functional sample.
The research team created 54 movement sequences of the pinecone scale, imitating a natural environment by submitting the material alternately to a drying oven and an aquarium. They also noted that after all the experimentation, the scale was still undamaged and with no signs of delamination.
The researchers were able to transfer a motion sequence they observed via the pinecone scales into a 4D printed artificial scale, offering potential in the future for other studies delving into robotics and methods for triggering motion like steps.
“For architectural applications, these novel multi-stage actuation movements can lead the way to develop advanced and passively actuated façade systems, with highly tailored shape-change capacity,” concluded the researchers. “It is a very promising prospect for future biological studies to investigate the interrelation of scale architecture (cellular characteristics at different regions) in combination with the scale biomechanics (e.g. by AFM measurements) and the locally successive evaporation of water (probably via MRI), altogether leading to the observed multi-phase motion.
“Our analyses show the potential of full-field 3D displacement and deformation analyses for evaluation and validation of movement principles in plants and technical structures.”
What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.[Source / Images: ‘4D pine scale: biomimetic 4D printed autonomous scale and flap structures capable of multi-phase movement’]
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