Origins of strain localization in a silver-based flexible ink under tensile load
Origins of strain localization in a silver-based flexible ink under tensile load
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DOI：
10.1088/2058-8585/ac414c
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发表时间：
2021-12
影响因子：
3.1
通讯作者：
Qiushi Li;O. Pierron;A. Antoniou
中科院分区：
文献类型：
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作者：
Qiushi Li;O. Pierron;A. Antoniou
柔性电子产品通常采用由嵌入聚合物基体中的导电薄片组成的复合油墨来传输电信号。最近，局部颈缩被认为是导致归一化电阻随着施加应变而大幅增加的原因，从而对电气性能产生不利影响。目前的研究探讨了形成这种局部化的两个可能的影响因素——油墨表面粗糙度和银片体积分数的局部变化。杜邦 5025 型油墨的单轴张力实验用于为在不同基材上使用有限元方法实现的本构模型提供信息。表面粗糙度通过墨水高度的正弦变化进行建模，其幅度和波长由实验激光轮廓测量扫描数据得知。根据银片和丙烯酸粘合剂材料性能之间的混合物的逆规则，在施加任何应变之前从实验测量获得的局部薄片分数变化被建模为弹性模量的局部变化。研究发现，油墨高度粗糙度对随后的应变定位影响最大。基材的弹性特性影响定位带的数量和大小，较硬的基材会产生离域应变，并避免在更柔顺的基材上出现灾难性裂纹的形成。该模型结合了表面粗糙度，与不同基材上局部应变的实验测量结果非常吻合。该研究可以让设计者了解油墨表面粗糙度对定位的不利影响以及随后的电阻的有害增加。
Flexible electronics often employ composite inks consisting of conductive flakes embedded in a polymer matrix to transmit electrical signal. Recently, localized necking was identified as a cause of a substantial increase in normalized resistance with applied strain thereby adversely impacting electrical performance. The current study explores two possible contributing factors for the formation of such localization—ink surface roughness and local variations in silver flake volume fraction. Uniaxial tension experiments of a DuPont 5025 type ink are used to inform a constitutive model implemented using finite element method on different substrates. Surface roughness was modeled by sinusoidal variation in ink height, whose amplitude and wavelength are informed by experimental laser profilometry scan data. Local flake fraction variations obtained from experimental measurements before applying any strain, were modeled as local variations in the elastic modulus according to an inverse rule of mixtures between the silver flake and acrylic binder material properties. The study identified that the ink height roughness is the most impactful contributor to the subsequent strain localization. The substrate elastic properties impact the number and magnitude of localization bands, with the stiffer substrate delocalizing strain and averting catastrophic crack formation seen with a more compliant substrate. The model incorporating surface roughness closely matches experimental measurements of local strain across different substrates. The study can inform designers of the adverse impact of ink surface roughness on localization and subsequent detrimental increase of the resistance.