Dou Xiaoqiang, Wang Haoran, Liu Zihan, Zheng Bowen, Zheng Zijian, Liu Xuqing, Guo Ruisheng
State Key Laboratory of Solidification Processing, Center of Advanced Lubrication and Seal Materials, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China.
Department of Applied Biology and Chemical Technology, Faculty of Science, Research Institute for Intelligent Wearable Systems, and Research Institute for Smart Energy, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR 99077, China.
ACS Appl Mater Interfaces. 2023 Oct 24. doi: 10.1021/acsami.3c11011.
Flexible copper conductors have been extensively utilized in flexible and wearable electronics. They can be fabricated by using a variety of patterning techniques such as vacuum deposition, photolithography, and various printing techniques. However, vacuum deposition and photolithography are costly and result in material wastage. Moreover, traditional printing inks require posttreatment, which can damage flexible substrates, or grafting polymers, which involve complex processes to adhere to flexible substrates. Therefore, this study proposes a facile method of fabricating flexible metal patterns with high electrical conductivities and remarkable bonding forces on a diverse range of flexible substrates. Catalytic ink was prepared by using a mixture of epoxy resin, copper nanopowder, and nanosilica. The ink was applied to a variety of flexible substrates, including a poly(ethylene terephthalate) (PET) film, polyimide film, and filter paper, using screen printing to establish a bridge layer for subsequent electroless deposition (ELD). The catalytic efficiency was significantly improved by treating the cured ink patterns with air plasma. The fabricated flexible metals exhibited excellent adhesion and desirable electrical conductivity. The sheet resistance of the copper layer on the PET substrate decreased to 9.2 mΩ/□ after 150 min of ELD. The resistance of the flexible metal on the PET substrate increased by only 3.125% after 5000 bending cycles. The flexible metals prepared in this study demonstrated good foldability, and the samples with filter paper and PET substrates failed after 40 and 70 folds, respectively. A pressure sensor with a bottom electrode consisting of a copper interdigital electrode on a PET substrate displayed favorable sensing performance.
柔性铜导体已广泛应用于柔性和可穿戴电子设备中。它们可以通过多种图案化技术制造，如真空沉积、光刻和各种印刷技术。然而，真空沉积和光刻成本高昂且会导致材料浪费。此外，传统印刷油墨需要后处理，这可能会损坏柔性基板，或者接枝聚合物，而这涉及到复杂的工艺来附着在柔性基板上。因此，本研究提出了一种简便的方法，可在多种柔性基板上制造具有高电导率和显著结合力的柔性金属图案。通过使用环氧树脂、铜纳米粉末和纳米二氧化硅的混合物制备催化油墨。使用丝网印刷将该油墨施加到包括聚对苯二甲酸乙二酯（PET）薄膜、聚酰亚胺薄膜和滤纸在内的各种柔性基板上，以建立用于后续化学镀（ELD）的桥接层。通过用空气等离子体处理固化后的油墨图案，催化效率得到显著提高。所制备的柔性金属表现出优异的附着力和理想的导电性。PET基板上铜层的方块电阻在化学镀150分钟后降至9.2 mΩ/□。PET基板上的柔性金属在5000次弯曲循环后电阻仅增加3.125%。本研究制备的柔性金属表现出良好的可折叠性，滤纸基板和PET基板的样品分别在折叠40次和70次后失效。一种底部电极由PET基板上的铜叉指电极组成的压力传感器显示出良好的传感性能。
