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2. Multi-material 3D printing of bioinspired mechanical structures

Author

Curto, Marco and Tozzi, Gianluca

Subjects
620.1
Abstract

Change has long assisted nature to build strong creatures. Species adapt every day obeying to the rule of withstanding loads. Inputs are gathered to grow hard and soft tissues where needed, saving life and preventing waste. Mimicking the same stunning mechanical performances is a hard challenge for man-made products obtained with top down processes. The aim of this project was to develop digital workflows for the generation of biologically inspired composites. The fabrication of hybrid composites inspired by tough biological materials such as nacre and compact bone were provided by the assembly of hard and soft phases through a multi-material 3D Printing (MM3DP) technique known as Multijet printing technology (MJP). To start, a systematic experimentation was conducted to quantify the mechanical properties of MJP base materials as well as the mechanical interplay between such multiple materials in a composites design. A workflow based on high contrast x-ray tomography (XCT) imaging data was then proposed to provide virtual models of less and more remodelled cortical bone. Mechanical properties of the cortical bone samples as well as the 3D printed replica were evaluated using acoustic measurements. Physical output show an elastic modulus almost ten times smaller (approximately 4 GPa) than the native bone (approximately 32 GPa), with the potential to tune the elastic modulus of the 3D printed replica depending on the employed manufacturing materials. The realization of controllable bioinspired 3D designs, represented the second goal of this project, in alternative to the extraction of key features from imaging data. Two workflows based on Generative Design (GD) were proposed to fluently draw and fabricate bioinspired compact bone and nacre. A parameterized version of the typical lamellar organization was presented for the first time to mimic compact bone and to supply a tool for the generation of a 3D crack blunting model. A further interactive workflow was proposed to produce a two-phase material inspired by nacre providing for a mechano-mimetic structure that dissipate energy via cracks delocalization, thus avoiding catastrophic failures. Results from tensile testing show increasing stress transfer from matrix to reinforcement by varying the diameter of the platelets from 2 to 9 mm. The resulting structures presented a volume fraction of the reinforcement that ranged from 54% to 69%, enough to absorb 20% energy than the stiffer base materials when subjected to dynamic loading. Finally, a semi-automated XCT based workflow was proposed to cover the absence of a volumetric metrology tool destined to multi-material AM when photo curable materials similar in density coexist.

Published
2019

3. Multi-material 3D printed composites inspired by nacre: a hard/soft mechanical interplay.

Author

Curto, Marco, Dowsett, Jack, Kao, Alexander P., Tozzi, Gianluca, and Barber, Asa H.

Subjects
*BIONICS, *HARD materials, *MECHANICAL behavior of materials, *STRUCTURAL engineering, *BIOMATERIALS
Abstract

Structural materials are used extensively in nature where mechanical function is required. These structures are composites consisting of soft and, in some cases, hard phases precisely distributed over different length scales. Bio-inspiration aims at producing materials with structure, design and/or mechanical properties adopted from biological tissues. To reproduce complex structures found in nature, additive manufacturing (AM) using three-dimensional printing (3DP) is an attractive method to assemble complex topologies with resolutions approaching the micro and nano-composition. Specifically, high-resolution MultiJetPrinting (MJP) 3D printing allows the simultaneous deposition of soft and hard photo curable plastic resins. Nacre is a prevalent example of a complex biological composite material organization that can test the ability of MJP to manufacture a bio-inspired engineering structure, where the organization of materials in nacre is optimized to avoid catastrophic failure. The ability to generate complex 3D organizations required to mimic the structure of nacre by controlled organization of soft and hard materials is achieved here using a generative design approach. Such a generative design is further enhanced by incorporating two differing MJP directions that provide relatively strong and weak interfaces between the soft and hard material phases. Consideration of classical stress transfer theory between at a hard material reinforcement interface was shown to correlate with experimental observations of mechanical performance and failure in 3D printed nacre inspired composites. Thus, the ability to distribute materials with a range of mechanical properties and incorporate further interfacial design is demonstrated. The approach presented is flexible and allows complex bio-inspired composites to be 3D printed that incorporate different interfacial quality through changing printing direction. [ABSTRACT FROM AUTHOR]

Published
2025
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4. Influence of Cooling Rate on the Flexural and Impact Properties of Compression Molded Non-Woven Flax/PLA Biocomposites.

Author

Pisupati, Anurag, Curto, Marco, Laurent, Thomas, Cosson, Benoit, Park, Chung Hae, and Dhakal, Hom Nath

Subjects
*FLEXURAL modulus, *FLAX, *THERMOCYCLING, *CRYSTALLINITY, *BRITTLENESS, *POLYLACTIC acid
Abstract

This work investigates the influence of crystallinity on the mechanical properties of needle-punched non-woven flax/polylactic acid (PLA) biocomposites with different flax fiber contents. Biocomposites were fabricated by a compression molding adopting different cooling rates to understand the mechanism of crystallinity and their contribution to the mechanical properties. Image-based analysis of the fiber distribution in non-woven preform indicates the probable origins of the residual porosities and the potential nucleation sites for crystal formation within the composites. The improvement of 25% and 100% in flexural modulus is observed for the composites with 40% and 50% of flax fiber mass fractions, respectively, when subjected to a lower cooling rate, which implies the significant influence of the void content on the brittleness of composites. The impact properties of the composites decrease from 11% to 18% according to the flax fiber mass fraction when the cooling rate decreases to 1 °C/min, and the composites become more brittle. The induced impact and flexural properties of the composites are compared with those of other composites in the literature to emphasize their applicability to semi-structural applications. [ABSTRACT FROM AUTHOR]

Published
2025
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7. Combined effects of global warming and plastic leachates from conventional and bio-based polymers on a harpacticoid copepod

Author

Niu, Zhiyue, Le Gall, Maelenn, Curto, Marco, Demeyer, Elke, Catarino, Ana I, Asselman, Jana, Janssen, Colin R., Dhakal, Hom, Davies, Peter, and Everaert, Gert

Subjects
Nitokra spinipes, SeaBioComp, plastic leachate, Biobased polymer, global warming
Abstract

Global warming and plastic pollution are two human-induced environmental stressors of rising concern due to their potential impact on ocean health. To tackle sustainability concerns on the production of conventional petroleum-based polymers, bio-based polymers, i.e. polymers originated from natural feedstocks, are seen as a potential alternative. However, just as conventional polymers, plastic items from bio-based polymers can leach additives and other associated substances into the (marine) environment. To date, the ecotoxicological effects of leachates from bio-based polymers are still unclear, but previous reports have demonstrated that leachates from petroleum-based polymers can induce adverse effects in marine invertebrates. Also, in the environment, organisms are subjected to a myriad of environmental stressors, among which global warming, and the combination of stressors is often not considered in environmental risk assessments. To increase our understanding of the combined effects of plastic leachates from either bio-based or petroleum-based polymers and elevated temperature (global warming), in this work we used the case study of polylactic acid (PLA) and polypropylene (PP), at control (22°C) and elevated water temperatures (25°C). To do so, we exposed newly hatched larvae of a harpacticoid copepod Nitokra spinipes to plastic leachates (80 g/L) as well as selected additives of both polymers as positive controls, at each temperature. Our preliminary results indicate that after 6 days exposure, lower larval development ratio (%) was found in 60% v/v of PP leachate (P Also see: https://micro2022.sciencesconf.org/427296/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

Published
2022
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9. Long-term durability and ecotoxicity of biocomposites in marine environments: a review

Author

Curto, Marco, Le Gall, Maelenn, Catarino, Ana Isabel, Niu, Zhiyue, Davies, Peter, Everaert, Gert, Dhakal, Hom N., Curto, Marco, Le Gall, Maelenn, Catarino, Ana Isabel, Niu, Zhiyue, Davies, Peter, Everaert, Gert, and Dhakal, Hom N.

Abstract

There is a growing interest in replacing fossil-based polymers and composites with more sustainable and renewable fully biobased composite materials in automotive, aerospace and marine applications. There is an effort to develop components with a reduced carbon footprint and environmental impact, and materials based on biocomposites could provide such solutions. Structural components can be subjected to different marine conditions, therefore assessment of their long-term durability according to their marine applications is necessary, highlighting related degradation mechanisms. Through an up-to-date review, this work critically discusses relevant literature on the long-term durability of biocomposites specific for marine environments. Importantly, in this review we report the effects of abiotic parameters, such as the influence of hygrothermal exposures (temperatures and UV radiation) on physical, mechanical and thermal characteristics of biocomposites. Furthermore, we identify and discuss the potential ecotoxicological effects of leaching substances and microplastics derived from biocomposites, as well as the change in mechanical, physical and thermal behaviours correlated to degradation in the fibre matrix interface, surface defects and overall deterioration of the composite's properties. Finally, the combined effects of various environmental exposures on the long-term durability of the biocomposites are critically reviewed.

Published
2021
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12. Potential solution for marine litter ? Assessment of the degradability and ecotoxicity of biobased composites

Author

Niu, Zhiyue, Catarino, Ana Isabel, Davies, Peter, Le Gall, Maelenn, Curto, Marco, Jiang, Chulin, Dotcheva, Mariana, Vancoillie, Gertjan, Dhakal, Hom, Vandegehuchte, Michiel, Everaert, Gert, Niu, Zhiyue, Catarino, Ana Isabel, Davies, Peter, Le Gall, Maelenn, Curto, Marco, Jiang, Chulin, Dotcheva, Mariana, Vancoillie, Gertjan, Dhakal, Hom, Vandegehuchte, Michiel, and Everaert, Gert

Published
2020

13. Design methods and geometric modelling of scaffolds for bone tissue engineering

Author

Curto, Marco, thesis supervisor: De Crescenzio, Francesca, Curto, Marco, and thesis supervisor: De Crescenzio, Francesca

Abstract

Every year, thousand of surgical treatments are performed in order to fix up or completely substitute, where possible, organs or tissues affected by degenerative diseases. Patients with these kind of illnesses stay long times waiting for a donor that could replace, in a short time, the damaged organ or the tissue. The lack of biological alternates, related to conventional surgical treatments as autografts, allografts, e xenografts, led the researchers belonging to different areas to collaborate to find out innovative solutions. This research brought to a new discipline able to merge molecular biology, biomaterial, engineering, biomechanics and, recently, design and architecture knowledges. This discipline is named Tissue Engineering (TE) and it represents a step forward towards the substitutive or regenerative medicine. One of the major challenge of the TE is to design and develop, using a biomimetic approach, an artificial 3D anatomy scaffold, suitable for cells adhesion that are able to proliferate and differentiate themselves as consequence of the biological and biophysical stimulus offered by the specific tissue to be replaced. Nowadays, powerful instruments allow to perform analysis day by day more accurateand defined on patients that need more precise diagnosis and treatments.Starting from patient specific information provided by TC (Computed Tomography) microCT and MRI(Magnetic Resonance Imaging), an image-based approach can be performed in order to reconstruct the site to be replaced. With the aid of the recent Additive Manufacturing techniques that allow to print tridimensional objects with sub millimetric precision, it is now possible to practice an almost complete control of the parametrical characteristics of the scaffold: this is the way to achieve a correct cellular regeneration. In this work, we focalize the attention on a branch of TE known as Bone TE, whose the bone is main subject. Bone TE combines osteoconductive and morphological aspects of the s

14. Design methods and geometric modelling of scaffolds for bone tissue engineering

Author

Curto, Marco and Curto, Marco

Abstract

Every year, thousand of surgical treatments are performed in order to fix up or completely substitute, where possible, organs or tissues affected by degenerative diseases. Patients with these kind of illnesses stay long times waiting for a donor that could replace, in a short time, the damaged organ or the tissue. The lack of biological alternates, related to conventional surgical treatments as autografts, allografts, e xenografts, led the researchers belonging to different areas to collaborate to find out innovative solutions. This research brought to a new discipline able to merge molecular biology, biomaterial, engineering, biomechanics and, recently, design and architecture knowledges. This discipline is named Tissue Engineering (TE) and it represents a step forward towards the substitutive or regenerative medicine. One of the major challenge of the TE is to design and develop, using a biomimetic approach, an artificial 3D anatomy scaffold, suitable for cells adhesion that are able to proliferate and differentiate themselves as consequence of the biological and biophysical stimulus offered by the specific tissue to be replaced. Nowadays, powerful instruments allow to perform analysis day by day more accurateand defined on patients that need more precise diagnosis and treatments.Starting from patient specific information provided by TC (Computed Tomography) microCT and MRI(Magnetic Resonance Imaging), an image-based approach can be performed in order to reconstruct the site to be replaced. With the aid of the recent Additive Manufacturing techniques that allow to print tridimensional objects with sub millimetric precision, it is now possible to practice an almost complete control of the parametrical characteristics of the scaffold: this is the way to achieve a correct cellular regeneration. In this work, we focalize the attention on a branch of TE known as Bone TE, whose the bone is main subject. Bone TE combines osteoconductive and morphological aspects of the s

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