Department of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel.
Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA.
J Mech Behav Biomed Mater. 2021 Aug;120:104605. doi: 10.1016/j.jmbbm.2021.104605. Epub 2021 May 18.
Hydrogels are hydrophilic polymer networks that swell upon submersion in water. Thanks to their bio-compatibility, compliance, and ability to undergo large deformations, hydrogels can be used in a wide variety of applications such as in situ sensors for measuring cell-generated forces and drug delivery vehicles. In this work we investigate the equilibrium mechanical responses that can be achieved with hydrogel-based shells filled with a liquid core. Two types of gel shell geometries are considered - a cylinder and a spherical shell. Each shell is filled with either water or oil and subjected to compressive loading. We illustrate the influence of the shell geometry and the core composition on the mechanical response of the structure. We find that all core-shell structures stiffen under increasing compressive loading due to the load-induced expulsion of water molecules from the hydrogel shell. Furthermore, we show that cylindrical core-shell configurations are stiffer then their spherical equivalents. Interestingly, we demonstrate that the compression of a core-shell structure with an aqueous core leads to the transportation of water molecules from the core into the hydrogel. These results will guide the design of novel core-shell structures with tunable properties and mechanical responses.
水凝胶是亲水性聚合物网络，在浸入水中时会发生溶胀。由于其生物相容性、顺应性和能够发生大变形，水凝胶可用于各种应用，例如用于测量细胞产生的力的原位传感器和药物输送载体。在这项工作中，我们研究了填充有液体芯的水凝胶基壳可以达到的平衡力学响应。考虑了两种类型的凝胶壳几何形状-圆柱壳和球壳。每个壳均填充有水或油，并承受压缩载荷。我们说明了壳几何形状和芯组成对结构力学响应的影响。我们发现，由于水凝胶壳中水分子的负载诱导排斥，所有核壳结构在逐渐增加的压缩载荷下都会变硬。此外，我们表明，圆柱形核壳结构比其球形等效结构更硬。有趣的是，我们证明了具有水性核的核壳结构的压缩会导致水分子从核转移到水凝胶中。这些结果将指导具有可调特性和机械响应的新型核壳结构的设计。
