Shahriar Sadi, Somayajula Kavya, Winkeljohn Conner, Mason Jeremy K, Seker Erkin
Department of Materials Science and Engineering, University of California-Davis, Davis, CA 95616, USA.
Department of Mechanical and Aerospace Engineering, University of California-Davis, Davis, CA 95616, USA.
Nanomaterials (Basel). 2024 Apr 25;14(9):758. doi: 10.3390/nano14090758.
Nanoporous gold (np-Au) has found its use in applications ranging from catalysis to biosensing, where pore morphology plays a critical role in performance. While the morphology evolution of bulk np-Au has been widely studied, knowledge about its thin-film form is limited. This work hypothesizes that the mechanical compliance of the thin film substrate can play a critical role in the morphology evolution. Via experimental and finite-element-analysis approaches, we investigate the morphological variation in np-Au thin films deposited on compliant silicone (PDMS) substrates of a range of thicknesses anchored on rigid glass supports and compare those to the morphology of np-Au deposited on glass. More macroscopic (10 s to 100 s of microns) cracks and discrete islands form in the np-Au films on PDMS compared to on glass. Conversely, uniformly distributed microscopic (100 s of nanometers) cracks form in greater numbers in the np-Au films on glass than those on PDMS, with the cracks located within the discrete islands. The np-Au films on glass also show larger ligament and pore sizes, possibly due to higher residual stresses compared to the np-Au/PDMS films. The effective elastic modulus of the substrate layers decreases with increasing PDMS thickness, resulting in secondary np-Au morphology effects, including a reduction in macroscopic crack-to-crack distance, an increase in microscopic crack coverage, and a widening of the microscopic cracks. However, changes in the ligament/pore widths with PDMS thickness are negligible, allowing for independent optimization for cracking. We expect these results to inform the integration of functional np-Au films on compliant substrates into emerging applications, including flexible electronics.
纳米多孔金（np-Au）已在从催化到生物传感等一系列应用中得到应用，其中孔形态对性能起着关键作用。虽然块状np-Au的形态演变已得到广泛研究，但关于其薄膜形式的知识却很有限。这项工作假设薄膜基底的机械柔顺性在形态演变中可能起关键作用。通过实验和有限元分析方法，我们研究了沉积在固定于刚性玻璃支架上的一系列厚度的柔顺硅酮（PDMS）基底上的np-Au薄膜的形态变化，并将其与沉积在玻璃上的np-Au的形态进行比较。与玻璃上的情况相比，PDMS上的np-Au薄膜中形成了更多宏观（10到100微米）裂纹和离散岛状物。相反，玻璃上的np-Au薄膜中形成的均匀分布的微观（100纳米）裂纹比PDMS上的更多，这些裂纹位于离散岛内。玻璃上的np-Au薄膜还显示出更大的韧带和孔径，这可能是因为与np-Au/PDMS薄膜相比，其残余应力更高。基底层的有效弹性模量随着PDMS厚度的增加而降低，从而导致np-Au的二次形态效应，包括宏观裂纹间距减小、微观裂纹覆盖率增加以及微观裂纹变宽。然而，韧带/孔径随PDMS厚度的变化可以忽略不计，这使得可以独立优化裂纹情况。我们期望这些结果能为将功能性np-Au薄膜集成到柔顺基底上应用于包括柔性电子器件在内的新兴应用提供参考。
