Dynamic evidence of the mechanism for surfactant adsorption to surfaces of like charge has been observed. Additionally, removal and retention of surfactant molecules on the surface were observed as a function of time. A decrease in surface charge is observed when metal counterions are introduced and is dependent on charge density as well as valency of the metal ion. When surfactant species are also present with the metals, a dramatic increase in surface charge arises. We observed that the rate and quantity of surfactant adsorption can be controlled by the presence of divalent Ca²⁺. Under isotonic conditions the introduction of Ca²⁺ is also easily distinguishable from that of monovalent Na⁺ and provides dynamic evidence of the divalent “cation bridging” phenomenon. Dynamic changes to surface charge are experimentally determined by utilizing current monitoring to quantify the zeta potential in a microfluidic device.

中文翻译：

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二价阳离子桥联促进动态表面活性剂吸附的观察

已经观察到表面活性剂吸附到类似电荷表面的机理的动态证据。另外，观察到表面活性剂分子在表面上的去除和保留是时间的函数。当引入金属抗衡离子时，观察到表面电荷的减少，这取决于电荷密度以及金属离子的化合价。当金属中还存在表面活性剂时，表面电荷会急剧增加。我们观察到，表面活性剂吸附的速率和数量可以通过二价Ca ²⁺的存在来控制。在等渗条件下，Ca ²⁺的引入也很容易与一价Na ⁺区别开来。并为二价“阳离子桥联”现象提供了动态证据。通过利用电流监测来量化微流体设备中的zeta电位，实验确定了表面电荷的动态变化。