Electrolytic reduction of liquid metal oxides and its application to reconfigurable structured devices.

Jinqi Wang,Sivaraman Guruswamy,Kanagasundar Appusamy,Ajay Nahata

doi:10.1038/srep08637

Abstract

Structured metallic patterns are routinely used for a wide variety of applications, ranging from electronic circuits to plasmonics and metamaterials. Numerous techniques have been developed for the fabrication of these devices, in which the metal patterns are typically formed using conventional metals. While this approach has proven very successful, it does generally limit the ability to reconfigure the geometry of the overall device. Here, we demonstrate the ability to create artificially structured metallic devices using liquid metals, in which the configuration can be altered via the electrolysis of saline solutions or deionized water. We accomplish this using an elastomeric mold with two different sets of embedded microfluidic channels that are patterned and injected with EGaIn and water, respectively. The electrochemical reaction is then used to etch the thin oxide layer that forms on eutectic gallium indium (EGaIn) in a controlled reproducible manner. Once the oxide layer is dissolved locally, the underlying liquid metal retracts away from the original position to a position where a new stable oxide layer can reform, which is equivalent to erasing a section of the liquid metal. To allow for full reconfigurability, the entire device can be reset by refilling all of the microchannels with EGaIn.

Highlights

Structured metallic patterns are routinely used for a wide variety of applications, ranging from electronic circuits to plasmonics and metamaterials
We have recently shown that when metamaterials fabricated using eutectic gallium indium (EGaIn) inside a polydimethylsiloxane (PDMS) microfluidic structure are exposed to an acid environment, the oxide layer is dissolved and the resulting bare liquid metal retracts away from the exposed area, effectively erasing the affected area[13]
While the approach was successful in erasing components of the liquid metal geometry, it suffered from several limitations: (i) the size of the HCl drop on the PDMS surface limited the minimum dimensions of the erased area (ii) the HCl exposure time varied depending upon the thickness and porosity of the PDMS layer (iii) the erased area was dependent on the thickness of the PDMS layer and (iv) repeated exposure to HCl degraded the elastomer, thereby limiting the number of erase/refill cycles that could be performed

Summary

Introduction

Structured metallic patterns are routinely used for a wide variety of applications, ranging from electronic circuits to plasmonics and metamaterials. While the approach was successful in erasing components of the liquid metal geometry, it suffered from several limitations: (i) the size of the HCl drop on the PDMS surface limited the minimum dimensions of the erased area (ii) the HCl exposure time varied depending upon the thickness and porosity of the PDMS layer (iii) the erased area was dependent on the thickness of the PDMS layer and (iv) repeated exposure to HCl degraded the elastomer, thereby limiting the number of erase/refill cycles that could be performed In this submission, we demonstrate that an electrolytic process can be used to change the geometry of a liquid metal-based structured device in a more localized and controlled manner. The approach is sufficiently general that it can be applied to a wide variety of other geometries and applications, including reconfigurable antennas and electrical circuits

Methods

Results

Conclusion