We describe the fabrication of physical chitosan hydrogels exhibiting a layered structure. This bilayered structure, as shown by SEM and confocal microscopy, is composed of a thin dense superficial zone (SZ), covering a deeper zone (DZ) containing microchannels orientated perpendicularly to the SZ. We show that such structure favors diffusion of macromolecules within the hydrogel matrix up to a critical pressure, σ_c, above which channels were constricted. Moreover, we found that the SZ provided a higher wear resistance than the DZ which was severely damaged at a pressure equal to the elastic modulus of the gel. The coefficient of friction (CoF) of the SZ remained independent of the applied load with μ_SZ = 0.38 ± 0.02, while CoF measured at DZ exhibited two regimes: an initial CoF close to the value found on the SZ, and a CoF that decreased to μ_DZ = 0.18 ± 0.01 at pressures higher than the critical pressure σ_c. Overall, our results show that internal structuring is a promising avenue in controlling and improving the wear resistance of soft materials such as hydrogels.

中文翻译：

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壳聚糖水凝胶的生物启发性微观结构提供了增强的磨损保护功能†

我们描述了物理壳聚糖水凝胶的制造，表现出层状结构。如SEM和共聚焦显微镜所示，这种双层结构由薄的致密表层区域（SZ）组成，覆盖了较深的区域（DZ），其中包含垂直于SZ定向的微通道。我们表明大分子的水凝胶基质内达到临界压力，即这种结构主张扩散σ _Ç，高于该信道被收缩。此外，我们发现SZ比DZ具有更高的耐磨性，而DZ在等于凝胶弹性模量的压力下受到严重破坏。摩擦（COF）的SZ的系数保持独立与施加负载的μ _SZ= 0.38±0.02，而在DZ测量失效后果表现出两个状态：初始失效后果地接近该值在SZ找到，一个失效后果即下降到μ _DZ更高= 0.18±0.01在压力比临界压力值σ _Ç。总体而言，我们的结果表明，内部结构化是控制和改善软质材料（如水凝胶）的耐磨性的有前途的途径。