Polymer adsorption onto a micro-sphere from optical tweezers electrophoresis.
Polymer adsorption onto a micro-sphere from optical tweezers electrophoresis.
复制标题
通过光镊电泳将聚合物吸附到微球上。
作者：
Jan A van Heiningen;R. Hill
我们探索了一种光学镊子电泳仪的设计和操作，以解决在微流体环境中聚合物在单个微球上的吸附动力学。我们的模型系统代表了用于生物传感、基础胶体和表面科学诊断的更广泛类别的微流控电泳实验。我们跟踪了100 kDa聚氧乙烷均聚物在胶体二氧化硅球上的吸附，该胶体二氧化硅球被光学捕获在交叉平行板微通道中。在∼1μm粒长尺度上，用∼1 S时间分辨率对吸附动力学进行了探讨。由于颗粒的电泳迁移率和通道电渗流对聚合物层流体力学厚度非常敏感，聚合物吸附到微通道壁上可能会使颗粒动力学变得复杂。然而，通过实验和具有非均匀壁面ζ势的通道中的电渗流的理论模型，我们证明采用对称的流型可以减轻这种影响。当聚合物浓度∼10ppm(重量百分比)时，100 kDa聚氧乙烷在胶体二氧化硅上的平衡流体动力学层厚度为≳10 nm，其动力学反映了聚合物溶液浓度、流速和多分散性。
We explore the design and operation of an optical-tweezers electrophoresis apparatus to resolve polymer adsorption dynamics onto a single micro-sphere in a micro-fluidic environment. Our model system represents a broader class of micro-fluidic electrophoresis experiments for biosensing and fundamental colloid and surface science diagnostics. We track the adsorption of 100 kDa poly(ethylene oxide) homopolymer onto a colloidal silica sphere that is optically trapped in a crossed parallel-plate micro-channel. The adsorption dynamics are probed on the ∼1 μm particle length scale with ∼1 s temporal resolution. Because the particle electrophoretic mobility and channel electro-osmotic flow are exquisitely sensitive to the polymer layer hydrodynamic thickness, particle dynamics can be complicated by polymer adsorption onto the micro-channel walls. Nevertheless, using experiments and a theoretical model of electro-osmotic flow in channels with non-uniform wall ζ-potentials, we show that such influences can be mitigated by adopting a symmetrical flow configuration. The equilibrium hydrodynamic layer thickness of 100 kDa poly(ethylene oxide) on colloidal silica is ∼10 nm at polymer concentrations ≳10 ppm (weight percent), with the dynamics reflecting polymer solution concentration, flow rate, and polydispersity.