Fluence-Dependent Morphological Transitions in Laser-Induced Graphene Electrodes on Polyimide Substrates for Flexible Devices
Fluence-Dependent Morphological Transitions in Laser-Induced Graphene Electrodes on Polyimide Substrates for Flexible Devices
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DOI：
10.1021/acsanm.1c00101
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发表时间：
2021-03-11
影响因子：
5.9
通讯作者：
Bedewy, Mostafa
中科院分区：
文献类型：
--
作者：
Abdulhafez, Moataz;Tomaraei, Golnaz N.;Bedewy, Mostafa
聚合物的激光碳化是一种新兴技术，可以直接为多种柔性设备（包括超级电容器和传感器）的导电碳电极进行图案化。虽然这些激光诱导纳米碳 (LINC) 图案先前已被证明具有各种分层多孔和纤维状石墨烯形态，但形成特定 LINC 形态的基本机制仍然很大程度上缺失。在这里，我们提出了一种利用空间控制的光能通量梯度来激光聚酰亚胺薄膜的方法。与高斯光束建模相结合，我们的方法独特地能够连续扫描不同的激光注量值，作为沿激光路径的空间图。我们发现，在注量值高于 5 J/cm(2) 时，多孔 LINC 会逐渐碳化和膨胀。我们还确定了与形态转变相对应的两个附加阈值：首先，在 12 J/cm(2) 下从各向同性多孔形态到各向异性网络；其次，从各向异性网络到 17 J/cm(2) 下的排列纳米纤维。我们的结果表明，各向异性蜂窝网络的导电性最强，并且具有最高质量的 sp(2) 碳。然而，排列整齐的羊毛纳米纤维形态沿着激光线的长度是电绝缘的，尽管它们表现出最高的碳化程度和最少的杂原子含量。因此，我们的结果提供了对 LINC 形成背后的物理化学过程的注量依赖性的见解。此外，我们的方法能够生成 LINC 的形态图，这有助于基于易于控制的加工参数（例如激光功率和光束散焦程度）精确调节 LINC 图案的形态和属性。
Laser carbonization of polymers is an emerging technique that enables directly patterning conductive carbon electrodes for a plethora of flexible devices, including supercapacitors and sensors. While these laser-induced nanocarbon (LINC) patterns were previously shown to have various hierarchical porous and fibrous graphene-based morphologies, the fundamental mechanisms underlying the formation of specific LINC morphologies is still largely missing. Here, we present a method for lasing polyimide films with spatially controlled gradients of optical energy flux. Combined with Gaussian beam modeling, our approach uniquely enables continuously sweeping different laser fluence values as a spatial map along the laser path. We find that above the fluence value of 5 J/cm(2), progressive carbonization and swelling results in porous LINC. We also identify two additional thresholds that correspond to morphological transitions: first, from isotropic porous morphology to anisotropic networks at 12 J/cm(2); second, from anisotropic networks to aligned nanofibers at 17 J/cm(2). Our results show that anisotropic cellular networks are the most electrically conducting and have the highest quality sp(2) carbon. However, the aligned woolly nanofiber morphology is electrically insulating along the length of the lased lines, although they exhibit the highest degree of carbonization with the least heteroatom content. Hence, our results provide insights into the fluence-dependence of the physicochemical processes underlying LINC formation. Moreover, our approach enables generating a morphology diagram for LINC, which facilitates precise tunability of both the morphology and properties of LINC patterns, based on easy-to-control processing parameters, such as laser power and degree of beam defocusing.