Two dissimilar hydrogel layers bonded together become unstable when the compressive stresses due to diffusion-driven swelling of the layers reach a critical point and creases form at the interface. Although creasing instabilities observed on surfaces of soft solids subjected to large compressions are well studied, the transient nature and critical conditions for the emergence of interface creases as a result of swelling behavior of hydrogels remain elusive. Here, we investigate the formation and transient growth of interface creases in bilayer hydrogels through experimental and computational approaches. Equipped with a mixed isogeometric analysis that accounts for large swelling deformations along with dissipative fluid transport phenomena, we show that both the equilibrium and the transient characteristics of interface creases can be tuned by controlling the material properties, in contrast to the reported material-independent behavior of creases in elastomers. The effects of material parameters on the onset and growth of interface creases are quantified in terms of the critical swelling ratio and critical chemical potential, and these values are compared to the critical conditions for the emergence of wrinkling instabilities. In agreement with our experimental observations of swelling bilayer hydrogels, our computational results demonstrate that the formation of creases is energetically more favorable than wrinkle formation at the interface.

当由于扩散驱动的膨胀引起的压缩应力达到临界点并在界面处形成折痕时，粘合在一起的两个不同的水凝胶层变得不稳定。尽管已经对软质固体经受大压缩的表面上的折皱不稳定性进行了很好的研究，但由于水凝胶溶胀行为而导致界面折痕出现的瞬态性质和临界条件仍然难以捉摸。在这里，我们通过实验和计算方法研究双层水凝胶中界面折痕的形成和瞬时生长。配备了混合等几何分析，可以解释大的溶胀变形以及耗散的流体传输现象，我们表明，可以通过控制材料的性能来调整界面折痕的平衡和瞬态特征，这与弹性体中折痕的材料无关行为有关。根据临界溶胀率和临界化学势，可以量化材料参数对界面折痕的开始和生长的影响，并将这些值与产生皱纹不稳定性的临界条件进行比较。与我们对膨胀的双层水凝胶的实验观察结果一致，我们的计算结果表明，在界面上，折痕的形成在能量上比皱纹的形成更有利。根据临界溶胀率和临界化学势，可以量化材料参数对界面折痕的开始和生长的影响，并将这些值与产生皱纹不稳定性的临界条件进行比较。与我们对膨胀的双层水凝胶的实验观察结果一致，我们的计算结果表明，在界面上，折痕的形成在能量上比皱纹的形成更有利。根据临界溶胀率和临界化学势，可以量化材料参数对界面折痕开始和生长的影响，并将这些值与产生皱纹不稳定性的临界条件进行比较。与我们对膨胀的双层水凝胶的实验观察结果一致，我们的计算结果表明，在界面上，折痕的形成在能量上比皱纹的形成更有利。