Highly Stretchable and Strain‐Insensitive Liquid Metal based Elastic Kirigami Electrodes (LM‐eKE)

• Published in: Advanced functional materials Vol. 33; no. 30
• Main Authors: Choi, Hyesu, Luo, Yichi, Olson, Gina, Won, Phillip, Shin, Joo Hwan, Ok, Jehyung, Yang, Ye Ji, Kim, Tae‐il, Majidi, Carmel
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01-07-2023
• Subjects: Circuits; Elastic deformation; elastic kirigami; Elastomers; Electrical resistivity; Electrodes; Electroencephalography; Eutectic alloys; eutectic gallium‐indium; Gallium; liquid metal; Liquid metals; Materials science; soft electronics; Strain; strain‐insensitive conductors; Stretchability; stretchable electronics; Substrates; Tracking devices
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202301388

Kirigami, a traditional paper‐cutting art, is a promising method for creating mechanically robust circuitry for unconventional devices capable of extreme stretchability through structural deformation. In this study, this design approach is expanded upon by introducing Liquid Metal based Elastic Kirigami Electrodes (LM‐eKE) in which kirigami‐patterned soft elastomers are coated with eutectic gallium‐indium (EGaIn) alloy. Overcoming the mechanical and electrical limitations of previous efforts with paper‐like kirigami, the all soft LM‐eKE can be stretched to 820% strain while the electrical resistance only increases by 33%. This is enabled by the fluidic properties of the EGaIn coating, which maintains high electrical conductivity even as the elastic substrate undergoes extreme deformation. Applying the LM‐eKE to human knee joints and fingers, the resistance change during physical activities is under 1.7%, thereby allowing for stable electrical operation of wearable health monitoring devices for tracking electroencephalogram (EEG) signals and other physiological activity.
A Liquid Metal based Elastic Kirigami Electrode (LM‐eKE) is reported as a promising stretchable electrode which allows stable electrical operation of devices with strain‐insensitive properties. Coating a biphasic Au‐EGaIn thin film on kirigami‐patterned soft elastomers, the LM‐eKE has high electrical conductivity and deforms extremely through structural‐elastic transition.