Affiliation:
1. Department of Chemical and Biomolecular Engineering North Carolina State University Raleigh NC 27695 USA
2. Department of Nano Convergence Engineering Jeonbuk National University Jeonju 54896 South Korea
3. School for Engineering of Matter Transport and Energy Arizona State University Tempe AZ 85287 USA
4. School of Chemical Engineering Sungkyunkwan University Suwon 16419 South Korea
Abstract
AbstractPastes and “foams” containing liquid metal (LM) as the continuous phase (liquid metal foams, LMFs) exhibit metallic properties while displaying paste or putty‐like rheological behavior. These properties enable LMFs to be patterned into soft and stretchable electrical and thermal conductors through processes conducted at room temperature, such as printing. The simplest LMFs, featured in this work, are made by stirring LM in air, thereby entraining oxide‐lined air “pockets” into the LM. Here, it is reported that mixing small amounts of water (as low as 1 wt%) into such LMFs gives rise to significant foaming by harnessing known reactions that evolve hydrogen and produce oxides. The resulting structures can be ≈4–5× their original volume and possess a fascinating combination of attributes: porosity, electrical conductivity, and responsiveness to environmental conditions. This expansion can be utilized for a type of 4D printing in which patterned conductors “grow,” fill cavities, and change shape and density with respect to time. Excessive exposure to water in the long term ultimately consumes the metal in the LMF. However, when exposure to water is controlled, the metallic properties of porous LMFs can be preserved.
Funder
Division of Civil, Mechanical and Manufacturing Innovation
North Carolina State University
State of North Carolina
National Science Foundation
Subject
Mechanical Engineering,Mechanics of Materials,General Materials Science