Department of Bioengineering, University of Washington, Seattle, Washington, United States of America.
PLoS One. 2022 May 27;17(5):e0268747. doi: 10.1371/journal.pone.0268747. eCollection 2022.
Hydrophilic materials immersed in aqueous solutions show near-surface zones that exclude suspended colloids and dissolved molecules. These exclusion zones (EZs) can extend for tens to hundreds of micrometers from hydrophilic surfaces and show physicochemical properties that differ from bulk water. Here we report that exposure of standard aqueous microsphere suspensions to static magnetic fields creates similar microsphere-free zones adjacent to magnetic poles. The EZs build next to both north and south poles; and they build whether the microspheres are of polystyrene or carboxylate composition. EZ formation is accompanied by ordered motions of microspheres, creating dense zones some distance from the magnetic poles and leaving microsphere-free zones adjacent to the magnet. EZ size was larger next to the north pole than the south pole. The difference was statistically significant when polystyrene microspheres were used, although not when carboxylate microspheres were used. In many ways, including both size and dynamics, these exclusion zones resemble those found earlier next to various hydrophilic surfaces. The ability to create EZs represents a feature of magnets not previously revealed.
亲水材料浸入水溶液中会在表面附近形成排斥悬浮胶体和溶解分子的区域。这些排斥区（EZs）可以从亲水表面延伸数十到数百微米，并表现出与体相水不同的物理化学性质。在这里，我们报告称，将标准的水性微球悬浮液暴露于静态磁场中会在磁极附近产生类似的无微球区。EZs 会在南北极两侧形成；而且无论微球是聚苯乙烯还是羧酸盐组成，EZs 都会形成。EZ 的形成伴随着微球的有序运动，在远离磁极的地方形成密集区，并在磁极附近留下无微球区。在靠近北极的地方，EZ 的尺寸比靠近南极的地方大。当使用聚苯乙烯微球时，这种差异具有统计学意义，尽管当使用羧酸盐微球时，这种差异没有统计学意义。在许多方面，包括尺寸和动力学，这些排斥区与早些时候在各种亲水表面附近发现的排斥区相似。这种创建 EZs 的能力代表了磁铁以前未被揭示的一个特征。
