Sliding Interconnection for Flexible Electronics with a Solution‐Processed Diffusion Barrier against a Corrosive Liquid Metal

Abstract

The epoch of flexible electronics demands new measures to interconnect electronic components and circuits under mechanical deformations such as bending, rolling, folding, and even stretching. Although liquid metal has been proposed as an alternative to solid‐state solder alloys and conductive adhesives, its corrosive nature rapidly deteriorates the electrical and structural integrity of metallic interconnects and has remained an arduous challenge. A facile solution‐processable method to construct a flexible and electrically conductive diffusion barrier on aluminum electrodes, which are vulnerable to liquid metal, is presented. The stacked layers of graphene oxide (GO) in conjunction with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) effectively block the diffusion of liquid metal, where PEDOT:PSS serves as an electrically conducting medium to complement the non‐conductive trait of GO, and as an impeding factor together with GO against the diffusion of liquid metal. A fluidic interconnect using liquid metal and aluminum electrodes with the solution‐processed diffusion barrier of the PEDOT:PSS/GO composite exhibits a better electrical contact property than a conventional interconnect. Finally, a novel proof of concept of sliding interconnection is demonstrated by rolling a carbon nanofiber‐coated liquid metal ball on aluminum electrodes coated with the PEDOT:PSS/GO composite, offering a new opportunity beyond flexibility and stretchability.

Liquid Metal Antennas: Materials, Fabrication and Applications

“…Although copper-based antennas are highly efficient and can withstand moderate bending, they underwent irreversible plastic deformation when stretched by more than 2% [4]. When interfacing with traditional metal interconnects like Cu, Ag, and Al etc., the Ga in the LM alloys is known to cause corrosion and reduces long-term stability of antenna performance [24,36,37]. However, these issues can be addressed by Ni-plating the LM/metal pin interface or by treating it with 1-decylphosphonic acid, by HCl-vapor [36], or with PEDOT:PSS/GO composite [37].…”

“…When interfacing with traditional metal interconnects like Cu, Ag, and Al etc., the Ga in the LM alloys is known to cause corrosion and reduces long-term stability of antenna performance [24,36,37]. However, these issues can be addressed by Ni-plating the LM/metal pin interface or by treating it with 1-decylphosphonic acid, by HCl-vapor [36], or with PEDOT:PSS/GO composite [37]. Furthermore, the development of LM-based nanocomposites has not only resulted in cheaper and reliable fabrication processes but also increases in their electrical properties.…”

“…In particular, Ga in LM alloys might come in contact with the surface of traditional metal interconnects like Cu, Ag, Au, and Al when interfacing with external biasing/output circuitry. The corrosive nature of Ga towards other metals might reduce long-term stability of antenna performance [24,36,37]. However, these issues can be Sensors 2020, 20, 177 5 of 26 addressed by Ni-plating the LM/metal pin interface or by treating it with 1-decylphosphonic acid or hydrochloric acid (HCl) vapor [36].…”

“…However, these issues can be Sensors 2020, 20, 177 5 of 26 addressed by Ni-plating the LM/metal pin interface or by treating it with 1-decylphosphonic acid or hydrochloric acid (HCl) vapor [36]. Additionally, modern composite materials like layers of graphene oxide (GO) together with poly 3,4-ethylenedioxythiophene: polystyrene sulfonate (PEDOT:PSS) can also be utilized [37]. In the composite material PEDOT:PSS/GO, GO blocks the Ga from coming in contact with metal surface while PEDOT:PSS overcomes the nominally insulative nature of GO and ensures good electrical contact between the metal interconnect pin and the LM alloy.…”

Recent Advances of Wearable Antennas in Materials, Fabrication Methods, Designs, and Their Applications: State-of-the-Art

“…It has opened new directions in the field of wearable applications [ 150 , 151 ]. In addition, new composite materials, such as a graphene oxide layer combined with poly 3,4-ethylenedioxythiophene: polystyrene sulfonate (PEDOT: PSS), can be utilized [ 152 ]. Therefore, the mixing of high-conductivity composites with low filler contents can increase the electrical and mechanical properties of the materials, like polymer, as shown in Figure 2 .…”