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Liquid Metal-Elastomer Soft Composites with Independently Controllable and Highly Tunable Droplet Size and Volume Loading
ACS Applied Materials & Interfaces
  • Ravi Tutika, Iowa State University
  • Steven Kmiec, Iowa State University
  • A. B. M. Tahidul Haque, Iowa State University
  • Steve W. Martin, Iowa State University
  • Michael D. Bartlett, Iowa State University
Document Type
Article
Publication Version
Submitted Manuscript
Publication Date
1-1-2019
DOI
10.1021/acsami.9b04569
Abstract

Soft composites are critical for soft and flexible materials in energy harvesting, actuators, and multifunctional devices. One emerging approach to create multifunctional composites is through the incorporation of liquid metal (LM) droplets such as eutectic gallium indium (EGaIn) in highly deformable elastomers. The microstructure of such systems is critical to their performance, however, current materials lack control of particle size at diverse volume loadings. Here, we present a fabrication approach to create liquid metal-elastomer composites with independently controllable and highly tunable droplet size (100 nm ≦ D ≦ 80 μm) and volume loading (0 ≦ φ ≦ 80%). This is achieved through a combination of shear mixing and sonication of concentrated LM/elastomer emulsions to control droplet size and subsequent dilution and homogenization to tune LM volume loading. These materials are characterized utilizing dielectric spectroscopy supported by analytical modeling which shows a high relative permittivity of 60 (16x the unfilled elastomer) in a composite with φ = 80%, a low tan δ of 0.02, and a significant dependence on φ and minor dependence on droplet size. Temperature response and stability are determined using dielectric spectroscopy through temperature and frequency sweeps and with DSC. These results demonstrate a wide temperature stability of the liquid metal phase (crystallizing < -85 °C for D < 20 μm). Additionally, all composites are electrically insulating across a wide frequency (0.1 Hz - 10 MHz) and temperature (-70°C to 100°C) range even up to φ = 80%. We highlight the benefit of LM microstructure control by creating all soft matter stretchable capacitive sensors with tunable sensitivity. These sensors are further integrated into a wearable sensing glove where we identify different objects during grasping motions. This work enables programmable LM composites for soft robotics and stretchable electronics where flexibility and tunable functional response are critical.

Comments

This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Applied Materials & Interfaces, copyright © American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/acsami.9b04569. Posted with permission.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
Ravi Tutika, Steven Kmiec, A. B. M. Tahidul Haque, Steve W. Martin, et al.. "Liquid Metal-Elastomer Soft Composites with Independently Controllable and Highly Tunable Droplet Size and Volume Loading" ACS Applied Materials & Interfaces (2019)
Available at: http://0-works.bepress.com.library.simmons.edu/michael-bartlett/26/