Understanding resistance increase in composite inks under monotonic and cyclic stretching
Understanding resistance increase in composite inks under monotonic and cyclic stretching
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DOI：
10.1088/2058-8585/aca98a
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发表时间：
2022-12
影响因子：
3.1
通讯作者：
Qiushi Li;Antonia Antoniou;Olivier N Pierron
中科院分区：
文献类型：
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作者：
Qiushi Li;Antonia Antoniou;Olivier N Pierron
柔性电子墨水的循环降解仍然是一个关键挑战，而它们在生命关键应用中的部署仍在进行中。利用原位共聚焦显微镜和扫描电子显微镜实验，研究了丝网印刷可伸缩导电油墨在聚氨酯粘结剂中嵌入银片的单轴和循环拉伸的电降解来源，改变油墨厚度(1、2和3层，每层约8-10μm)和痕迹宽度(0.5、1和2 mm)。裂纹在单调拉伸下形成，裂纹图案(密度、长度和宽度)随施加应变的演变受油墨厚度的影响，因此三层油墨具有更大的归一化阻力，但略低于一层油墨的阻力，最高可达125%的应变。对于循环拉伸，裂纹密度和长度不随循环而变化。然而，裂缝变宽和加深，导致自行车阻力增加。疲劳寿命(即达到100的归一化阻力之前的循环次数)与应变幅度之间存在很强的相关性。与循环相关的归一化阻力增加率也随着应变幅度的增大而增大。电阻随循环的变化率随着油墨厚度和痕迹宽度的增加而减小。对于实际应用，应使用较厚(⩾25μm)和较宽(⩾2 mm)的油墨，以降低因重复变形而增加的阻力。
Cyclic degradation in flexible electronic inks remains a key challenge while their deployment in life critical applications is ongoing. The origin of electrical degradation of a screen-printed stretchable conductive ink with silver flakes embedded in a polyurethane binder is investigated under uniaxial monotonic and cyclic stretching, using in-situ confocal microscopy and scanning electron microscopy experiments, for varying ink thickness (1, 2, and 3 layers, each layer around 8–10 μm) and trace width (0.5, 1, and 2 mm). Cracks form under monotonic stretching, and the evolution of crack pattern (density, length and width) with applied strain is affected by ink thickness such that the 3-layer ink exhibits larger normalized resistance but slightly lower resistance than the 1-layer ink up to strains of 125%. For cyclic stretching, the crack density and length do not evolve with cycling. However, the cracks widen and deepen, leading to an increase in resistance with cycling. There exists a strong correlation between fatigue life, i.e. the number of cycles until a normalized resistance of 100 is reached, and the strain amplitude. The normalized resistance increase rate with respect to cycling is also found to scale with strain amplitude. The rate of change in resistance with cycling decreases with ink thickness and trace width. For practical applications, thicker ( ⩾ 25 μm) and wider (⩾2 mm) inks should be used to lower resistance increases with repeated deformation.