Ma Jinwoo, Bharambe Vivek T, Persson Karl A, Bachmann Adam L, Joshipura Ishan D, Kim Jongbeom, Oh Kyu Hwan, Patrick Jason F, Adams Jacob J, Dickey Michael D
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh 27695, North Carolina, United States.
Department of Electrical and Computer Engineering, North Carolina State University, Raleigh 27695, North Carolina, United States.
ACS Appl Mater Interfaces. 2021 Mar 24;13(11):12709-12718. doi: 10.1021/acsami.0c17283. Epub 2020 Nov 25.
Liquid metals adhere to most surfaces despite their high surface tension due to the presence of a native gallium oxide layer. The ability to change the shape of functional fluids within a three-dimensional (3D) printed part with respect to time is a type of four-dimensional printing, yet surface adhesion limits the ability to pump liquid metals in and out of cavities and channels without leaving residue. Rough surfaces prevent adhesion, but most methods to roughen surfaces are difficult or impossible to apply on the interior of parts. Here, we show that silica particles suspended in an appropriate solvent can be injected inside cavities to coat the walls. This technique creates a transparent, nanoscopically rough (10-100 nm scale) coating that prevents adhesion of liquid metals on various 3D printed plastics and commercial polymers. Liquid metals roll and even bounce off treated surfaces (the latter occurs even when dropped from heights as high as 70 cm). Moreover, the coating can be removed locally by laser ablation to create selective wetting regions for metal patterning on the exterior of plastics. To demonstrate the utility of the coating, liquid metals were dynamically actuated inside a 3D printed channel or chamber without pinning the oxide, thereby demonstrating electrical circuits that can be reconfigured repeatably.
尽管液态金属具有较高的表面张力，但由于存在天然氧化镓层，它们能附着在大多数表面上。相对于时间改变三维（3D）打印部件内功能流体形状的能力是一种四维打印类型，然而表面附着力限制了将液态金属泵入和泵出腔体及通道而不留下残余物的能力。粗糙表面可防止附着力，但大多数使表面粗糙化的方法难以或无法应用于部件内部。在此，我们表明悬浮在适当溶剂中的二氧化硅颗粒可注入腔体内以包覆壁面。该技术形成一种透明的、纳米尺度粗糙（10 - 100纳米范围）的涂层，可防止液态金属附着在各种3D打印塑料和商用聚合物上。液态金属在经过处理的表面上滚动甚至弹起（后者即使从高达70厘米的高度掉落时也会发生）。此外，可通过激光烧蚀局部去除涂层，以在塑料外部创建用于金属图案化的选择性润湿区域。为证明该涂层的实用性，液态金属在3D打印通道或腔体内动态驱动，而不会固定氧化物，从而展示了可重复重新配置的电路。
