Influence of lay-down angles on mechanical properties of three-dimensional printed polycaprolactone scaffolds

doi:10.12307/2022.246

Abstract

Abstract: BACKGROUND: Three-dimensional (3D) printed polycaprolactone scaffold is one of the hotspots in recent years. It is difficult to prepare porous scaffolds with appropriate materials and excellent mechanical properties in current studies.
OBJECTIVE: To manufacture 3D porous polycaprolactone scaffolds with different lay-down angles and study their mechanical properties.

METHODS: 3D porous polycaprolactone scaffolds with different lay-down angles (0°/90°, 0°/60°, 0°/60°/120°, 0°/45° and 0°/45°/90°/135°) were designed and prepared using 3D printer. The porosity, compression and tensile properties of the scaffold were measured.

RESULTS AND CONCLUSION: (1) There was no significant difference in the porosity of the five scaffolds (P > 0.05). (2) In Z direction compression, there was little difference for polycaprolactone scaffolds with different lay-down angles. (3) In Y direction, the compression of the 0°/45°, 0°/60°, and 0°/90° scaffolds increased with the increase of the filling angle. The compressive modulus and strength of 0°/45°/90°/135° were higher than those of 0°/45°. The compressive modulus and strength of 0°/60°/120° scaffolds were stronger than those of 0°/60°. (4) When the three scaffolds were compressed in X direction, the law of the compression modulus and strength of the scaffold was opposite to those of the compression in the Y direction. Among the five types of scaffolds, the tensile modulus and strength of the 0°/45°/90°/135° scaffolds were the largest, and the tensile modulus and strength of the 0°/90° scaffold were the smallest; the tensile strength and modulus of the 0°/45°, 0°/60°, and 0°/90° scaffolds decreased with the increase of the angle. (5) The results show that the 0°/90° and 0°/60°/120° scaffolds can meet the requirements of the physiological environment with isotropic mechanical properties, and the other three structures can meet the requirements of the anisotropic growth environment of human tissues.

Key words: 3D printing, tissue engineering, polycaprolactone, scaffold, lay-down angles, anisotropic, mechanical properties, tensile, compression

CLC Number:

Liu Jiali, Suo Hairui, Yang Han, Wang Ling, Xu Mingen. Influence of lay-down angles on mechanical properties of three-dimensional printed polycaprolactone scaffolds[J]. Chinese Journal of Tissue Engineering Research, 2022, 26(16): 2492-2497.

Figures/Tables 6

0°/45°组、0°/60°组、0/90°组支架的压缩模量和压缩强度随填充角度增加，力学性能增强，这是因为填充角度越大细丝越接近力的方向，当填充角度为90°时细丝方向与力方向一致，此时可以看作力施加在了圆柱结构上，不易变形，当填充角度逐渐减小，此时可看作力施加在了弹簧结构上，容易变形[18]，其中0°/45°组支架变形最为明显；0°/60°/120°组支架的压缩模量是0°/60°组的1.71倍(P < 0.05)，压缩强度是0°/60°组的2.25倍(P < 0.05)，这是因为0°/60°/120°组形成的三角形结构具有更高的稳定性；0°/45°/90°/135°组支架的压缩模量和压缩强度较0/45°组更强(P < 0.05)，这是因为0°/45°/90°/135°组在4次旋转中会形成沿力方向的细丝。从X方向压缩时，0°/45°组、0°/60°组、0°/90°组支架的压缩模量随填充角度增加，力学性能较弱，这是因为X方向与Y方向呈现相反的关系，即在Y方向填充角度越大，那么在X方向填充角度越小，0°/45°组、0°/60°组支架的压缩强度比较差异无显著性意义(P > 0.05)，变化较为平稳，0°/60°组支架的压缩强度比0°/90°组大2.51 MPa(P < 0.05)；0°/60°/120°组支架的压缩模量和压缩强度较0°/60°组弱 (P < 0.05)，原因是0°/60°组支架沿力的方向的细丝有10层，而0°/60°/120°组支架沿力的方向的细丝仅有7层(共20层)，这些沿力方向的细丝构成了阻止变形的柱形主体。由于分别受到柱形主体和三角形结构的支撑，0°/60°/120°组支架在X方向和Y方向上的压缩性能较接近；0°/45°组支架的压缩模量较0°/45°/90°/135°组更大(P < 0.05)，原因是0°/45°组支架沿力的方向的细丝有10层，而0°/45°/90°/135°组支架沿力的方向的细丝仅有5层，虽然0°/45°组支架的压缩强度较0°/45°/90°/135°组小，但差异无显著性意义(P > 0.05)。从X、Y、Z方向压缩，0°/45°组、0°/45°/90°/135°组、0°/60°组支架的压缩强度和压缩模量各不相同，而0°/90°组、0°/60°/120°组的压缩力学性能相近。值得指出的是，0°/90°组在Z方向上的压缩模量和压缩强度比X、Y方向上的略小，这是因为从不同方向压缩0°/90°组时受力载荷传递机制不同，当从Z方向压缩，受力主体为层与层之间的重叠区域，当从X、Y方向压缩时受力主体为沿力的方向的细丝，刚性更强、变形更小。图6为不同填充结构聚己内酯支架的拉伸性能。0°/45°组、0°/60°组、0°/90°组支架拉伸模量和拉伸强度随填充角度增加而降低，这是因为填充角度越小细丝的方向越接近于拉力的方向，当填充角度为0°时相邻两层细丝重合，相当于拉伸并行的圆柱。在5种填充结构的支架中，0°/45°/90°/135°组支架的拉伸模量(34.6±1.55) MPa和强度(4.16±0.37) MPa最大，而0°/90°组支架的拉伸模量(18.88±0.98) MPa和强度(2.56±0.23) MPa最小，0°/45°/90°/135°组支架拉伸模量是0°/90°组的1.83倍，拉伸强度是0°/90°组的1.37倍，这说明可以通过改变填充结构而改变支架的拉伸力学性能。"

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