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Biological tissues, such as cartilage, tendon, ligament, skin, and plant cell wall, simultaneously achieve high water content and high load-bearing capacity. The high water content enables the transport of nutrients and wastes, and the high load-bearing capacity provides structural support for the organisms. These functions are achieved through nanostructures. This biological fact has inspired synthetic mimics, but simultaneously achieving both functions has been challenging. The main difficulty is to construct nanostructures of high load-bearing capacity, characterized by multiple properties, including elastic modulus, strength, toughness, and fatigue threshold. Here we develop a process that self-assembles a nanocomposite using a hydrogel-forming polymer and a glass-forming polymer. The process separates the polymers into a hydrogel phase and a glass phase. The two phases arrest at the nanoscale and are bicontinuous. Submerged in water, the nanocomposite maintains the structure and resists further swelling. We demonstrate the process using commercial polymers, achieving high water content, as well as load-bearing capacity comparable to that of polyethylene. During the process, a rubbery stage exists, enabling us to fabricate objects of complex shapes and fine features. We conduct further experiments to discuss likely molecular origins of arrested phase separation, swell resistance, and ductility. Potential applications of the nanocomposites include artificial tissues, high-pressure filters, low-friction coatings, and solid electrolytes.
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Fabricating hydrogels to mimic biological tissues of complex shapes and high fatigue resistance
Biological tissues, such as heart valves and vocal cords, function through complex shapes and high fatigue resistance. Achieving both attributes with synthetic materials is hitherto an unmet challenge. Here we meet this challenge with hydrogels of heterogeneous structures. We fabricate a three-dimensional hydrogel skeleton by stereolithography and a hydrogel matrix by cast. Both the skeleton and matrix are elastic and stretchable, but the skeleton is much stiffer than the matrix, and their polymer networks entangle topologically. When such a hydrogel is stretched, the compliance of the matrix deconcentrates stress in the skeleton and amplifies fatigue resistance. We fabricate a homogeneous hydrogel and a heterogeneous hydrogel, each in the shape of a human heart valve. Subject to cyclic pressure, the former fractures in 560 cycles but the latter is intact after 50,000 cycles. Soft materials of complex shapes and high fatigue resistance open broad opportunities for applications.
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- Award ID(s):
- 2011754
- PAR ID:
- 10499989
- Publisher / Repository:
- Cell Press
- Date Published:
- Journal Name:
- Matter
- Volume:
- 4
- Issue:
- 6
- ISSN:
- 2590-2385
- Page Range / eLocation ID:
- 1935 to 1946
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.matt.2021.03.011
