Tunable Piezoresistivity from Magnetically Aligned Ni(Core)@Ag(Shell) Particles in an Elastomer Matrix.
Tunable Piezoresistivity from Magnetically Aligned Ni(Core)@Ag(Shell) Particles in an Elastomer Matrix.
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DOI：
10.1021/acsami.9b04287
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发表时间：
2019-05
影响因子：
9.5
通讯作者：
Fang Peng;Keke Chen;Armen Yildirim;Xuhui Xia;B. Vogt;M. Cakmak
中科院分区：
文献类型：
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作者：
Fang Peng;Keke Chen;Armen Yildirim;Xuhui Xia;B. Vogt;M. Cakmak
核壳（Ni@Ag）粒子在连续的卷对卷过程中利用磁场在聚二甲基硅氧烷（PDMS）薄膜的厚度上排列。在固化过程中，颗粒的排列显著降低了薄膜厚度的导电性渗透阈值，从无磁场时的28 vol %降低到有52 mT磁场时的约1 vol %，降低了近一个数量级。然而，对于中等Ni@Ag负载，磁力会导致粗糙的表面形貌，但是通过玻璃约束限制Ni@Ag/PDMS复合材料可以提供光滑的表面。这种几何上的差异改变了Ni@Ag颗粒垂直排列的“链”的形态，当薄膜不受约束时，这些链更聚集。当受约束薄膜的Ni@Ag浓度降至3.6%以下时，从x射线断层扫描中可以明显看出，排列颗粒中的断裂导致薄膜上的压敏阻力，阻力在阈值压力以上大幅下降。通过对PDMS中Ni@Ag的加载，阈值压力在≈15 ~≈290 kPa范围内可控，但在循环加载时该阈值压力减小。这些磁性排列复合材料代表了机械响应膜的简单途径，可用于不需要高于或低于阈值压力的循环载荷的各种应用，例如一次性压力传感器，用于确保产品通过运输的可靠性，以及用于识别关键位移的嵌入式结构健康监测。
Core-shell (Ni@Ag) particles are aligned through the thickness of a poly(dimethylsiloxane) (PDMS) film using a magnetic field in a continuous roll-to-roll process. The alignment of the particles dramatically decreases the percolation threshold for electrical conductivity through the thickness of the film by nearly an order of magnitude from 28 vol % without the field to ≈1 vol % with a 52 mT magnetic field during curing. However, the magnetic forces lead to rough surface topography for intermediate Ni@Ag loadings, but confining the Ni@Ag/PDMS composite by a glass constraint provides a smooth surface. This difference in geometry changes the morphology of the vertically aligned "chains" of Ni@Ag particles where the chains are more aggregated when the film is unconstrained. As the Ni@Ag concentration is decreased below 3.6% for the constrained film, breaks in the aligned particles evident from X-ray tomography lead to pressure sensitive resistance across that film with a large decrease in resistance above a threshold pressure. The threshold pressure is demonstrated to be controllable from ≈15 to ≈290 kPa through the loading of aligned Ni@Ag in the PDMS, but this threshold pressure decreases on cyclic loading. These magnetically aligned composites represent a facile route to mechanically responsive films that could be used in a variety of applications where cyclic loading above and below the threshold pressure is not required, such as disposable pressure sensors for ensuring reliability of products through transportation and embedded structural health monitoring for identifying critical displacements.