Contributors: He Pei, He Jianjian
Contributed by: State Key Laboratory of Mechanical Manufacturing System Engineering
Degradable bioelastomers are a type of biopolymer materials with high flexibility and elasticity. They have mechanical properties similar to those of soft tissues in the human body. They can guarantee structural stability and integrity in dynamic environments. The biomedical field has great application potential. However, their harsh processing conditions (such as high temperature, etc.) make it difficult to adapt to advanced manufacturing techniques to construct complex structures required in tissue engineering, limiting their application in the biomedical field. The development of bioelastic materials with excellent mechanical properties and adaptable to advanced manufacturing technologies is of great significance for the construction of complex structures in tissue engineering.
Polyglycerol sebacate (PGSA, poly (glycerol-co-sebacate) acrylate) is a new type of synthetic biocompatible elastic biomaterial with adjustable mechanical properties, which can achieve rapid polymerization at room temperature using ultraviolet light . 3D printing technology based on Digital Light Processing (DLP) can crosslink photopolymerizable polymers into arbitrary complex shapes. Due to the lack of scanning and continuous properties in the DLP printing process, the manufactured structures do not exist The artificial interface thus enhances the mechanical integrity of the entire structure. Chen et al. Of the University of California, San Diego used DLP-based 3D printing technology for the first time to construct a complex PGSA double network (DN, Double Network) structure composed of network segments (hard and soft segments) that use the same materials and have different mechanical properties (See Figure 1B), through finite element analysis (FEA) to explore the potential failure mechanism of the dual network structure, and optimize 3D printing parameters (such as network aspect ratio and stiffness ratio), while maintaining low mass density while improving the network structure toughness.
The DN system is composed of two structures, a hard segment and a soft segment. When the DN structure is stretched, the softer segment is used as a sacrificial material to consume energy, while the harder segment maintains the shape of the structure. Therefore, the overall toughness of the structure can be increased without increasing the material or increasing the density of the material. The researchers used a finite element analysis (FEA) model to predict the failure process of the DN structure under uniaxial tension. By using the soft segment as a sacrificial element, the structural integrity of the hard segment is preserved. Tensile testing of the single network (SN) and dual network structures after FEA optimized design confirmed that the toughness of the DN structure is twice that of SN. Some soft beams break before any failure of the rigid beam consumes energy to avoid the destruction of the rigid structure of the entire network. Therefore, the uninterrupted rigid beam can maintain the overall shape and function of the network structure, and the overall toughness of the network structure can be increased by 100%.
In the study, DLP-based 3D printing was used to rapidly manufacture DN structures from a single polymer solution. By controlling different concentrations of crosslinking agents and exposure time, digital control of the mechanical properties of the 3D printing network was realized. The elastic modulus of the printed elastomer network is 150 to 800 kPa, and the ultimate tensile strength is 100 to 300 kPa, which can withstand more than 50% strain before failure, and some combination of crosslinker concentration and exposure time It can withstand more than 100% strain before breaking, far exceeding other 3D printed polymer materials in biomedical applications. The DN structure is printed by assigning hard and soft segments to specific locations using different exposure times in a single location, by introducing soft segments to enhance toughness, a sacrificial beam is used to absorb energy during stretching, and hard segments Maintain the overall shape of the structure.
The research and design of an elastomeric network scaffold with adjustable mechanical strength, good biocompatibility and biodegradability. The developed FEA analysis method can be used for the design optimization of the mechanical properties of other biomaterials, combined with 3D printing technology for tissue engineering Domain integration builds a complex organizational structure.
references:
Wang, P., Berry, DB, Song, Z., Kiratitanaporn, W., Schimelman, J., Moran, A., He, F., Xi, B., Cai, S., Chen, S., 3D Printing of a Biocompatible Double Network Elastomer with Digital Control of Mechanical Properties. Adv. Funct. Mater. 2020, 1910391.
https://doi.org/10.1002/adfm.201910391
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