Direct‐Write Formation and Dissolution of Silver Nanofilaments in Ionic Liquid‐Polymer Electrolyte Composites

Abstract

Materials with reconfigurable optical properties are candidates for applications such as optical cloaking and wearable sensors. One approach to fabricate these materials is to use external fields to form and dissolve nanoscale conductive channels in well-defined locations within a polymer. In this study, conductive atomic force microscopy is used to electrochemically form and dissolve nanoscale conductive filaments at spatially distinct points in a polyethylene glycol diacrylate (PEGDA)-based electrolyte blended with varying amounts of ionic liquid (IL) and silver salt. The fastest filament formation and dissolution times are detected in a PEGDA/IL composite that has the largest modulus (several GPa) and the highest polymer crystal fraction. This is unexpected because filament formation and dissolution events are controlled by ion transport, which is typically faster within amorphous regions where polymer mobility is high. Filament kinetics in primarily amorphous and crystalline regions are measured, and two different mechanisms are observed. The formation time distributions show a power-law dependence in the crystalline regions, attributable to hopping-based ion transport, while amorphous regions show a normal distribution. The results indicate that the timescale of filament formation/dissolution is determined by local structure, and suggest that structure could be used to tune the optical properties of the film.

Silver Nanofilament Formation Dynamics in a Polymer‐Ionic Liquid Thin Film by Direct Write

“…[17] The thickness of the 35 wt% IL was ≈40 nm by focused ion beam (FIB)-SEM (Figure 7), and the 30 and 40 wt% IL samples were expected to be of similar thickness as our previous report indicated no thickness variations in the range of 10 to 50 wt% IL. This IL concentration range was chosen because they have faster formation kinetics compared to 50 wt% IL, and a more homogeneous structure (i.e., less obvious crystal features) compared to a 10 wt% IL sample.…”

Nanopore-Templated Silver Nanoparticle Arrays Photopolymerized in Zero-Mode Waveguides

“…Encouraged by the subwavelength control of the radial and axial field distributions provided by the ZMWs, we extended the fabrication of recessed Ag ring electrode array to include AgNPs and Ag + embedded in the photopolymerized PEGDA. In principle, AgNPs arrayed in the dielectric PEGDA could form the basis of a metamaterial, and the presence of Ag + would enable the electrochemical formation of nanofilaments connecting the AgNPs (Crouch et al, 2017; Chao et al, 2018). To understand the fabrication of nanopore-templated AgNPs embedded in PEGDA nanopillars, photopolymerization experiments were undertaken to investigate the influence of PEDGA concentration, Ag + concentration, and the presence or absence of AgNPs on the formation of solid-polymer electrolytes within the nanopore templates.…”

“…Silver ions in the PEGDA are required for subsequent direct-write nanofilament formation and dissolution between AgNPs (Crouch et al, 2017; Chao et al, 2018), so we also investigated how Ag + concentration affects the photopolymerization of PEGDA in the presence of AgNPs. Figures 5A,B show cross-sections of photopolymerized 1.0 wt% PEGDA with 2 mM AgNO 3 and 1 mM AgNO 3 , respectively.…”

“…Further, active control of conductive filament formation and dissolution in solid electrolytes may provide the foundation for a new class of metamaterials with reconfigurable optical properties, especially when combined with arrays of metal nanoparticles embedded in the dielectric host. Previously, we demonstrated actively reconfigurable constructs based on solid-polymer electrolyte-based nanoelectrochemical systems for the formation and dissolution of metal conductive filaments in polyethylene oxide (PEO)-based (Wu et al, 2011; Crouch et al, 2017) and poly(ethylene glycol) diacrylate (PEGDA)-based (Chao et al, 2018) electrolytes. In addition, polymer electrolytes formed by photopolymerization of polyethylene glycol (PEG)-based electrolyte have been utilized for various biomaterials and biomedical applications (Mellott et al, 2001; Burdick and Anseth, 2002; Aimetti et al, 2009; Huebsch et al, 2014; DeForest and Tirrell, 2015).…”

Green Chemistry Approach for Fabrication of Polymer Composites

“…These biopolymer composites can be utilized for CO 2 capture while the fluorinated and amine groups of ionic liquids influence the selectivity of CO 2 /CH 4 . Recently, Chao et al described that a polyethylene glycol diacrylate (PEGDA)-based electrolyte along with an ionic liquid directs the electrodeposition of silver nanofilaments from silver salt and subsequent dissolution [24]. Kinetics of silver nanofilaments formation and dissolution is influenced by the addition of an ionic liquid, especially an ionic liquid of >10 wt.% which limits the process.…”