Surface effects of liquid metal amoeba

• Published in: Science bulletin Vol. 62; no. 10; pp. 700 - 706
• Main Authors: Hu, Liang, Li, Jing, Tang, Jianbo, Liu, Jing
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30.05.2017
• Subjects: Liquid metal amoeba; Substrate materials; Surface effect; Surface tension; 机器人设计; 液态金属; 石墨表面; 表面性质; 表面效应; 表面电荷密度; 表面粗糙度; 金属材料; Surface effect; Substrate materials; Surface tension; Liquid metal amoeba
• ISSN: 2095-9273; 2095-9281
• DOI: 10.1016/j.scib.2017.04.015

Liquid metals （LM） such as eutectic gallium-indium and gallium-indium-tin are important functional liquid-state metal materials with many unique properties, which have attracted wide attentions espe- cially from soft robot area. Recently the amoeba-like transformations of LM on the graphite surface are discovered, which present a promising future for the design and assemble of self-fueled actuators with dendritically deformable body. It appears that the surface tension of the LM can be significantly reduced when it contacts graphite surface in alkaline solution. Clearly, the specific surface should play a vital role in inducing these intriguing behaviors, which is valuable and inspiring in soft robot design. However, the information regarding varied materials functions underlying these behaviors remains unknown. To explore the generalized effects of surface materials in those intriguing behavior, several materials includ- ing glass, graphite, nickel and copper oxides （CuO） were comparatively investigated as substrate surfaces. Important results were obtained that only LM amoeba transformations were observed on graphite and CuO surfaces. In order to identify the proper surface condition for LM transformation, the intrinsic prop- erties of substrate surfaces, such as the surface charge and roughness, as well as the specific interaction with LM like wetting behavior and mutual locomotion etc., were characterized. The integrated results revealed that LM droplet appears more likely to deform on surfaces with higher positive surface charge density, higher roughness and less bubble generation on them. In addition, another surface material, CuOx, is identified to own similar ability to graphite, which is valuable in achieving amoeba-like transfor- mation. Moreover, this study offers a fundamental understanding of the surface properties in realizing LM amoeba transformations, which would shed light on packing and structure design of liquid metal-based soft device within multi-material system.