TY - JOUR
T1 - Interplay between Interfacial Energy, Contact Mechanics, and Capillary Forces in EGaIn Droplets
AU - Amini, Shahrouz
AU - Chen, Xiaoping
AU - Isaiah Chua, Jia Qing
AU - Tee, Jinq Shi
AU - Nijhuis, Christian A.
AU - Miserez, Ali
N1 - Funding Information:
This research was supported by the Singapore Ministry of Education (MOE) under award No. MOE2019-T2-1-137 and by the Strategic Initiative for Bioinspired and Biomimetic Materials (IBSM) at the Nanyang Technological University. The Prime Minister’s Office, Singapore, under its medium-sized center program is also acknowledged for supporting this research. The authors thank Peter Fratzl for his inputs into the formation mechanisms of the EGaIn capillary bridges.
Funding Information:
Open access funded by Max Planck Society.
Publisher Copyright:
© 2022 The Authors. Published by American Chemical Society.
PY - 2022/6/22
Y1 - 2022/6/22
N2 - Eutectic gallium-indium (EGaIn) is increasingly employed as an interfacial conductor material in molecular electronics and wearable healthcare devices owing to its ability to be shaped at room temperature, conductivity, and mechanical stability. Despite this emerging usage, the mechanical and physical mechanisms governing EGaIn interactions with surrounding objects─mainly regulated by surface tension and interfacial adhesion─remain poorly understood. Here, using depth-sensing nanoindentation (DSN) on pristine EGaIn/GaOx surfaces, we uncover how changes in EGaIn/substrate interfacial energies regulate the adhesive and contact mechanic behaviors, notably the evolution of EGaIn capillary bridges with distinct capillary geometries and pressures. Varying the interfacial energy by subjecting EGaIn to different chemical environments and by functionalizing the tip with chemically distinct self-assembled monolayers (SAMs), we show that the adhesion forces between EGaIn and the solid substrate can be increased by up to 2 orders of magnitude, resulting in about a 60-fold increase in the elongation of capillary bridges. Our data reveal that by deploying molecular junctions with SAMs of different terminal groups, the trends of charge transport rates, the resistance of monolayers, and the contact interactions between EGaIn and monolayers from electrical characterizations are governed by the interfacial energies as well. This study provides a key understanding into the role of interfacial energy on geometrical characteristics of EGaIn capillary bridges, offering insights toward the fabrication of EGaIn junctions in a controlled fashion.
AB - Eutectic gallium-indium (EGaIn) is increasingly employed as an interfacial conductor material in molecular electronics and wearable healthcare devices owing to its ability to be shaped at room temperature, conductivity, and mechanical stability. Despite this emerging usage, the mechanical and physical mechanisms governing EGaIn interactions with surrounding objects─mainly regulated by surface tension and interfacial adhesion─remain poorly understood. Here, using depth-sensing nanoindentation (DSN) on pristine EGaIn/GaOx surfaces, we uncover how changes in EGaIn/substrate interfacial energies regulate the adhesive and contact mechanic behaviors, notably the evolution of EGaIn capillary bridges with distinct capillary geometries and pressures. Varying the interfacial energy by subjecting EGaIn to different chemical environments and by functionalizing the tip with chemically distinct self-assembled monolayers (SAMs), we show that the adhesion forces between EGaIn and the solid substrate can be increased by up to 2 orders of magnitude, resulting in about a 60-fold increase in the elongation of capillary bridges. Our data reveal that by deploying molecular junctions with SAMs of different terminal groups, the trends of charge transport rates, the resistance of monolayers, and the contact interactions between EGaIn and monolayers from electrical characterizations are governed by the interfacial energies as well. This study provides a key understanding into the role of interfacial energy on geometrical characteristics of EGaIn capillary bridges, offering insights toward the fabrication of EGaIn junctions in a controlled fashion.
KW - capillary bridge
KW - depth-sensing nanoindentation
KW - EGaIn
KW - molecular junctions
KW - self-assembled monolayers
UR - http://www.scopus.com/inward/record.url?scp=85132105900&partnerID=8YFLogxK
U2 - 10.1021/acsami.2c04043
DO - 10.1021/acsami.2c04043
M3 - Article
C2 - 35649179
AN - SCOPUS:85132105900
SN - 1944-8244
VL - 14
SP - 28074
EP - 28084
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 24
ER -