Textile Technique

Textile techniques have been developed to fabricate the complex tissue-like constructs with the structure and properties similar to native tissues. Conventional textile techniques, including weaving, knitting, and braiding (Fig. 2.8), have been used to making porous structures with good mechanical properties as tissue scaffolds or reinforcements [1, 73].

Weaving, as one of the widely used textile techniques, is totally based upon two distinct sets of warps or wefts, which interlace at right angles to form fabric with controlled strength, porosity, morphology, and geometry [67, 156]. The weaving structures are lightweight, strong, and flexible and have been used to prepare 3D scaffolds. However, the disadvantage of this technique is the poor resistance towards forces applied in the through-plane direction, because the structure is usually two dimensions. Recently, different layers have been connected by interlocking all the layers to overcome this problem and create a structure with a low shear resistance in the in-plane direction.

Overview of the instruments and techniques used for fabricating fibrous structures and scaffolds and representative microstructures

Fig. 2.8 Overview of the instruments and techniques used for fabricating fibrous structures and scaffolds and representative microstructures. (a) weaving of scaffolds by interlacing warp and weft fibers in perpendicular directions; (b) knitting of yarns in a series of connected loops; (c) braiding of fibers achieved by intertwining three or more fiber strands [73] (Adapted with permission from Ref. [73]. Copyright 2013 Elsevier Ltd)

Knitting is formed by intertwining yarns or threads in a series of symmetric loops as compared to weaving or other textile technique with straight threads. The knitted textile substrate includes fibers in the through-plane directions to offer higher through-plane mechanical properties [157, 158]. In addition, the knitted structure generally has a higher porosity but a lower thickness than that made by weaving. However, the disadvantage of the knitting structure is the weak mechanical properties in the in-plane direction. For their suitable mechanical properties and easy manufacture of 3D geometries, the knitted structure has been combined with other materials to provide sufficient and adjustable mechanical properties for various tissue engineering applications.

Braiding is good at forming complex structures or patterns by intertwining three or more fiber strands [159], which can make cylinder and rod structures suitable for engineering tissues with the similar shapes, like blood vessels etc. The multi-step braiding structure is the only textile construct that is resistant to bending, shear, inplane and through-plane loads, and they can also withstand twisting and internal pressure and offer the highest axial strength [160]. But the porosity of this technology is lower than that of knitting. The braid has the potential for the preparation of scaffolds with high mechanical strength and has also been developed to combine with other manufacturing techniques.

Textile technique is a conditional tissue engineering fabrication system that has been employed to fabricate the matrix or reinforcements in composite scaffolds and plays an important role among the fabrication techniques [161]. There are many studies on these techniques used for preparing reinforced scaffolds. For example, McCullen et al. [1] stated the use of traditional textile techniques to prepare fiber- reinforced scaffolds for tissue engineering and regenerative medicine. Huang [162] et al. investigated the mechanical properties of composites reinforced with woven and braided fabrics. Xu et al. [163] reinforced small-diameter PU vascular grafts by weft-knitted tubular fabric to improve the mechanical properties of the grafts. Ananta et al. [164] fabricated a 3D hybrid scaffold for cartilage regeneration by incorporating a type I collagen within a PLGA knitted mesh to improve cell adhesion. In another study, the knitted structure was used to enhance PU blood vessel grafts. The results were shown that the strength and elasticity of the graft made from the composite material were higher than that of the implant made from pure PU. Over the next few years, this technology will continue to be one of the main processing methods used to prepare reinforced scaffolds, especially fiber-based composites, and attract extensive research and attention in the field of tissue engineering.

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