Effect of porous structure and pore size on mechanical strength of 3D-printed comby scaffolds

Zhao, Hongxia; Li, Lihua; Ding, Shan; Liu, Chenxing; Ai, Jiaoyan

doi:10.1016/j.matlet.2018.03.205

Cited by 104 publications

(63 citation statements)

References 7 publications

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“…However, in the future the methodology can be applied to other objectives, for example, the strength of the structure and/or nutrient transport. As a general trend, the lower the porosity, the higher the mechanical strength of a structure [ 39 ]. In case nutrient transport is considered as a goal, then a certain value for the variance of the pore size is recommended.…”

Section: Discussionmentioning

confidence: 99%

3D Printing of Porous Scaffolds with Controlled Porosity and Pore Size Values

2018

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3D printed scaffolds can be used, for example, in medical applications for simulating body tissues or for manufacturing prostheses. However, it is difficult to print porous structures of specific porosity and pore size values with fused deposition modelling (FDM) technology. The present paper provides a methodology to design porous structures to be printed. First, a model is defined with some theoretical parallel planes, which are bounded within a geometrical figure, for example a disk. Each plane has randomly distributed points on it. Then, the points are joined with lines. Finally, the lines are given a certain volume and the structure is obtained. The porosity of the structure depends on three geometrical variables: the distance between parallel layers, the number of columns on each layer and the radius of the columns. In order to obtain mathematical models to relate the variables with three responses, the porosity, the mean of pore diameter and the variance of pore diameter of the structures, design of experiments with three-level factorial analysis was used. Finally, multiobjective optimization was carried out by means of the desirability function method. In order to favour fixation of the structures by osseointegration, porosity range between 0.5 and 0.75, mean of pore size between 0.1 and 0.3 mm, and variance of pore size between 0.000 and 0.010 mm2 were selected. Results showed that the optimal solution consists of a structure with a height between layers of 0.72 mm, 3.65 points per mm2 and a radius of 0.15 mm. It was observed that, given fixed height and radius values, the three responses decrease with the number of points per surface unit. The increase of the radius of the columns implies the decrease of the porosity and of the mean of pore size. The decrease of the height between layers leads to a sharper decrease of both the porosity and the mean of pore size. In order to compare calculated and experimental values, scaffolds were printed in polylactic acid (PLA) with FDM technology. Porosity and pore size were measured with X-ray tomography. Average value of measured porosity was 0.594, while calculated porosity was 0.537. Average value of measured mean of pore size was 0.372 mm, while calculated value was 0.434 mm. Average value of variance of pore size was 0.048 mm2, higher than the calculated one of 0.008 mm2. In addition, both round and elongated pores were observed in the printed structures. The current methodology allows designing structures with different requirements for porosity and pore size. In addition, it can be applied to other responses. It will be very useful in medical applications such as the simulation of body tissues or the manufacture of prostheses.

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Section: Discussionmentioning

confidence: 99%

3D Printing of Porous Scaffolds with Controlled Porosity and Pore Size Values

2018

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“…The relationship between the mechanical properties and honeycomb structure was studied in FEA. By adjusting the porosity of the honeycomb structure, Young's modulus can be controlled between cortical bone and cancellous bone (Golodnov et al, 2018;Zhao et al, 2018). By comparing the failure mechanism of the simple cube and honeycomb structure, and it can be seen that the failure of honeycomb structure was different in two directions under two kinds of vertical pressure (Choy et al, 2017).…”

Section: Honeycombmentioning

confidence: 99%

“…The honeycomb structure had low weight and high stiffness. However, as the mechanical properties of honeycomb structure vary significantly in different inclinations (directions), the honeycomb structure needs to be improved in the future Zhao et al, 2018).…”

Section: Honeycombmentioning

confidence: 99%

Porous Scaffold Design for Additive Manufacturing in Orthopedics: A Review

Chen

Han

Wang

et al. 2020

Front. Bioeng. Biotechnol.

141

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With the increasing application of orthopedic scaffolds, a dramatically increasing number of requirements for scaffolds are precise. The porous structure has been a fundamental design in the bone tissue engineering or orthopedic clinics because of its low Young's modulus, high compressive strength, and abundant cell accommodation space. The porous structure manufactured by additive manufacturing (AM) technology has controllable pore size, pore shape, and porosity. The single unit can be designed and arrayed with AM, which brings controllable pore characteristics and mechanical properties. This paper presents the current status of porous designs in AM technology. The porous structures are stated from the cellular structure and the whole structure. In the aspect of the cellular structure, non-parametric design and parametric design are discussed here according to whether the algorithm generates the structure or not. The non-parametric design comprises the diamond, the body-centered cubic, and the polyhedral structure, etc. The Voronoi, the Triply Periodic Minimal Surface, and other parametric designs are mainly discussed in parametric design. In the discussion of cellular structures, we emphasize the design, and the resulting biomechanical and biological effects caused by designs. In the aspect of the whole structure, the recent experimental researches are reviewed on uniform design, layered gradient design, and layered gradient design based on topological optimization, etc. These parts are summarized because of the development of technology and the demand for mechanics or bone growth. Finally, the challenges faced by the porous designs and prospects of porous structure in orthopedics are proposed in this paper.

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“…Porous scaffold with honeycomb structure, which exhibits excellent mechanical properties, has great application potential in tissue engineering [9] . And honeycomb sandwich is a structure that consists of two relatively thin face sheets bonded to a relatively thick lightweight honeycomb core [10] .…”

Section: Introductionmentioning

confidence: 99%

Finite Element Analysis of the Size Effect of Vertebral Implant with Honeycomb Sandwich Structure

Guo

Liu

Zhang

et al. 2020

Preprint

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Background: Because of osteoporosis, traffic accidents, falling from high places and other reasons, the vertebral body could be compressed injury, even collapse. Vertebral implant can be used for clinical treatment. Because of the advantages of honeycomb sandwich structure, such as low cost, less material, light weight, high strength, and good cushioning performance, honeycomb sandwich structure was used as the basic structure of vertebral implant.Methods: In this paper, we applied the orthogonal experiment method to analyze the size effect of honeycomb sandwich structure by finite element method. Based on the minimum requirements of three indexes of peak stress, axial displacement, and anterior-posterior displacement, the optimal structure size was determined. Further, through local optimization of the overall structure of the implant, we designed better honeycomb sandwich structure vertebral implant.Results: The optimal structure size combination is determined as the face sheets thickness 1mm, wall thickness 0.49mm, cell side length 1mm, height 6mm. Than through local optimization, the peak stress is further reduced, the overall stress distribution is uniform, and the deformation is reduced. The optimized peak stress decreases to 1.041MPa, the axial deformation is 0.111%, and the anterior-posterior deformation is 0.014%. The honeycomb sandwich structure vertebral implant with stable structure and good mechanical performance was designed.Conclusions: The research result provides a method for the optimal design of vertebral body implant structures, as well as provides a new idea and biomechanical basis for clinical treatment after vertebral body injury.

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Effect of porous structure and pore size on mechanical strength of 3D-printed comby scaffolds

Cited by 104 publications

References 7 publications

3D Printing of Porous Scaffolds with Controlled Porosity and Pore Size Values

3D Printing of Porous Scaffolds with Controlled Porosity and Pore Size Values

Porous Scaffold Design for Additive Manufacturing in Orthopedics: A Review

Finite Element Analysis of the Size Effect of Vertebral Implant with Honeycomb Sandwich Structure

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