Directional Motion of Gallium-Based Liquid Metal Induced by Asymmetric Chemical Surrounding

Interfacial,or surface tension, is a significant topic in chemicaleducation. This paper describes the directional motion of gallium-basedliquid metal drops, resulting from a difference of interfacial tensionacross the drop. This demonstration can engage students in discoveringthe underlying chemical principles. A mechanism for the drop'sdirectional motion is proposed to provide insight into this intriguingphenomenon. It appears that unbalanced chemical environments causedifferent physical or chemical processes to occur on each hemisphereof the drop, such as a pH difference, redox reactions, galvanic replacement,or adsorption. As a result, a difference in the interfacial tensionacross the drop is generated, providing the driving force that actson the drop. This demonstration can be used to introduce the fundamentalprinciples in chemical reactions, such as redox activity, electricaldouble layer formation, and interfacial tension.