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Strain Stiffening and Negative Normal Force of Agarose Hydrogels
Macromolecules ( IF 5.5 ) Pub Date : 2020-09-14 , DOI: 10.1021/acs.macromol.0c00601
Lahja Martikainen 1 , Kia Bertula 1 , Matti Turunen 1 , Olli Ikkala 1, 2
Affiliation  

Inspired by the specific strain stiffening and negative normal force phenomena in several biological networks, herein, we show strain stiffening and negative normal force in agarose hydrogels. We use both pre-strain and strain amplitude sweep protocols in dynamic rheological measurements where the gel slip was suppressed by the in situ gelation in the cross-hatched parallel plate rheometer geometry. Within the stiffening region, we show the scaling relation for the differential modulus K ∝ σ1, where σ is stress. The strain at the onset of stiffening is almost constant throughout the concentration range. The gels show negative apparent normal stress difference when sheared as a result of the gel contraction. The pore size of the hydrogel is large enough to allow water to move with respect to the network to balance the pressure difference caused by the hoop stress. The rheological analysis together with scanning electron microscopy suggests that the agarose gels can be described using subisostatic athermal network models where the connectivity dictates the stiffening behavior. Therefore, the simple agarose gels appear to capture several of the viscoelastic properties, which were previously thought to be characteristic to biological protein macromolecules.

中文翻译:

琼脂糖水凝胶的应变刚度和负法向力

受几种生物网络中特定的应变变硬和负法向力现象启发,在本文中,我们显示了琼脂糖水凝胶中的应变变硬和负法向力。我们在动态流变学测量中同时使用了预应变和应变幅度扫描方案,其中在交叉影线平行板流变仪几何形状中通过原位凝胶化抑制了凝胶滑移。内的加强区域,我们示出了用于差分模数的标度关系ķ ασ 1,其中σ是应力。在整个浓度范围内,刚开始时的应变几乎恒定。当凝胶收缩时,凝胶显示出负的表观法向应力差。水凝胶的孔径足够大,以允许水相对于网络移动,以平衡由环向应力引起的压差。流变学分析和扫描电子显微镜表明,可以使用亚等静热网络模型描述琼脂糖凝胶,其中连通性决定了硬化行为。因此,简单的琼脂糖凝胶似乎捕获了一些粘弹性质,这以前被认为是生物蛋白大分子的特征。
更新日期:2020-09-14
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