Saliva and blood plasma are non-Newtonian viscoelastic fluids that play essential roles in the transport of particulate matters (e.g., food and blood cells). However, whether the viscoelasticity of such biofluids alters the dynamics of suspended particles is still unknown. In this study, we report that under pressure-driven microflows of both human saliva and blood plasma, spherical particles laterally migrate and form a focused stream along the channel centerline by their viscoelastic properties. We observed that the particle focusing varied among samples on the basis of sampling times/donors, thereby demonstrating that the viscoelasticity of the human biofluids can be affected by their compositions. We showed that the particle focusing, observed in bovine submaxillary mucin solutions, intensified with the increase in mucin concentration. We expect that the findings from this study will contribute to the understanding of the physiological roles of viscoelasticity of human biofluids.

中文翻译：

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粘弹性粒子聚焦在人体生物体液中

唾液和血浆是非牛顿粘弹性流体，在颗粒物质（例如，食物和血细胞）的运输中起着重要作用。然而，这种生物流体的粘弹性是否会改变悬浮颗粒的动力学仍然未知。在这项研究中，我们报告说，在人类唾液和血浆的压力驱动微流下，球形颗粒通过其粘弹性特性横向迁移并沿通道中心线形成聚焦流。我们观察到根据采样时间/供体的不同，样品间的粒子聚焦会有所不同，从而证明人体生物流体的粘弹性会受到其组成的影响。我们表明，在牛颌下粘蛋白溶液中观察到的颗粒聚焦随着粘蛋白浓度的增加而增强。