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Sun D, Gao Y, Zhou Y, Yang M, Hu J, Lu T, Wang T. Enhance Fracture Toughness and Fatigue Resistance of Hydrogels by Reversible Alignment of Nanofibers. ACS APPLIED MATERIALS & INTERFACES 2022; 14:49389-49397. [PMID: 36273343 DOI: 10.1021/acsami.2c16273] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Biological tissues, such as heart valve, tendon, etc., possess excellent mechanical properties, which arises from their inherent anisotropic arrangement of soft and hard phases. Inspired by the anisotropic structures, many methods have been developed to synthesize hydrogels that can achieve mechanical properties comparable to biological tissues. Here, we describe a new method to enhance fracture toughness and fatigue resistance of hydrogels by introducing nanofibers which can reversibly align with elastic deformation to form an anisotropic structure. As a demonstration, we introduce stiff, rod-like cellulose nanocrystals (CNCs) into a polyacrylamide (PAAm) network. CNCs aggregate into clusters to form hard phases and entangle with the PAAm network. The CNC/PAAm composite hydrogel is initially isotropic, becomes anisotropic upon loading, and recovers to be isotropic upon unloading. During the deformation, the aligned CNC clusters at the crack tip can transmit the stress over the size of the cluster, effectively resisting crack growth. We use photoelasticity and small-angle X-ray scattering (SAXS) tests to observe the change of microstructures associated with deformation. The fracture toughness of CNC/PAAm hydrogels with different sizes of CNCs can reach 1000 J/m2. The fatigue threshold is about 100 J/m2, an order of magnitude higher than that of PAAm hydrogel. This work provides a simple and general method to strengthen hydrogels under both monotonic and cyclic loads.
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Affiliation(s)
- Danqi Sun
- State Key Lab for Strength and Vibration of Mechanical Structures, Soft Machines Lab, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Yang Gao
- State Key Lab for Strength and Vibration of Mechanical Structures, Soft Machines Lab, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Yifan Zhou
- State Key Lab for Strength and Vibration of Mechanical Structures, Soft Machines Lab, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Meng Yang
- State Key Lab for Strength and Vibration of Mechanical Structures, Soft Machines Lab, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Jian Hu
- State Key Lab for Strength and Vibration of Mechanical Structures, Soft Machines Lab, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Tongqing Lu
- State Key Lab for Strength and Vibration of Mechanical Structures, Soft Machines Lab, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Tiejun Wang
- State Key Lab for Strength and Vibration of Mechanical Structures, Soft Machines Lab, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, China
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Gao Y, Wang P, Zhao F, Liu X, Wu J, Hu J. A facile approach for anisotropic hydrogel with light-regulated stiffness and its application to achieve mechanical toughening. Macromol Rapid Commun 2022; 43:e2200077. [PMID: 35298857 DOI: 10.1002/marc.202200077] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Revised: 03/07/2022] [Indexed: 11/10/2022]
Abstract
Many load-bearing tissues in nature obtain high toughness by fabricating anisotropic structures with spatially regulated composition and modulus at macroscale. This reality inspires a toughening strategy for hydrogel based on the controlling of modulus heterogeneity. Herein, a facile approach to realize light-regulated spatial modulus heterogeneity with large contrast in hydrogel is proposed. Ferric citric acid complex is used as a light-responsive ionic crosslinker, which can first stiffen an alginate/polyacrylamide hydrogel by coordinating with the alginate to form another network, then realize light-triggered softening through photoreduction of ferric ions. Based on this, a stripe-patterned hydrogel with alternating stiff and soft segments can be fabricated through photopatterning. The modulus contrast between the stiff and soft phases can be adjusted by control of several influence factors and the maximum modulus contrast reach up to 87 times. As a result, the toughness of the stripe-patterned hydrogel is enhanced by 3.5 times comparing to that hydrogel without pattern. This approach shows great potential in synthesis of smart hydrogel with light-programmable mechanical performances, and may be widely applicable for the hydrogels with functional groups that can coordinate with metal ions. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Yang Gao
- State Key Laboratory of Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China
| | - Peiyao Wang
- State Key Laboratory of Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China
| | - Fei Zhao
- State Key Laboratory of Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China
| | - Xiao Liu
- State Key Laboratory of Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China
| | - Jingping Wu
- State Key Laboratory of Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China
| | - Jian Hu
- State Key Laboratory of Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China
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