Electrochemistry on Stretchable Nanocomposite Electrodes: Dependence on Strain

Abstract

Stretchable nanocomposite conductors are essential for engineering of bio-inspired deformable electronics, human−machine interfaces, and energy storage devices. While the effect of strain on conductivity for stretchable conductors has been thoroughly investigated, the strain dependence of multiple other electrical-transport processes and parameters that determine the functionalities and biocompatibility of deformable electrodes has received virtually no attention. The constancy of electrochemical parameters at electrode−fluid interfaces such as redox potentials, impedances, and charge-transfer rate constants on strain is often tacitly assumed. However, it remains unknown whether these foundational assumptions actually hold true for deformable electrodes. Furthermore, it is also unknown whether the previously used charge-transport circuits describing electrochemical processes on rigid electrodes are applicable to deformable electrodes. Here, we investigate the validity of the strain invariability assumptions for an elastic composite electrode based on gold nanoparticles (AuNPs). A comprehensive model of electrode reactions that accurately describes electrochemical processes taking place on nanocomposite electrodes for ferro-/ferricyanide electrochemicals pair at different strains is developed. Unlike rigid gold electrodes, the model circuit for stretchable electrodes is comprised of two parallel impedance segments describing (a) diffusion and redox processes taking place on the open surface of the composite electrode and (b) redox processes that occur in nanopores. AuNPs forming the open-surface circuit support the redox process, whereas those forming the nanopores only increase the double-layer capacitance. The redox potential was found to be strain-independent for tensile deformations as high as 40%. Other parameters, however, display strong strain dependence, exemplified by the 2−2.5 and 27 times increases of active area of the open and nanopore surface area, respectively, after application of 40% strain. Gaining better understanding of the strain-dependent and-independent electrochemical parameters enables both fundamental and practical advances in technologies based on deformable electrodes.

Cryopolymerization enables anisotropic polyaniline hybrid hydrogels with superelasticity and highly deformation-tolerant electrochemical energy storage

“…tretchable supercapacitors, enabling desirable portable and wearable electronics applications incapable of using conventional rigid electronics, are highly desirable [1][2][3][4][5][6][7][8][9][10] . Although conventional electrodes for supercapacitors are usually not stretchable or superelastic, the engineering of conventional electrodes with geometrically engineered structures provides notable breakthroughs for the achievements of stretchable and foldable devices [11][12][13][14][15] .…”

Delayed Capillary Flow of Elastomers: An Efficient Method for Fabrication and Nanofunctionalization of Flexible, Foldable, Twistable, and Stretchable Electrodes from Pyrolyzed Paper

“…To the best of our knowledge, this device presented the highest electrochemical performance for a fully-integrated stretchable carbon-based device (Table S4, Supporting Information). The influence of the scan rate (10-200 mV s −1 ) in the presence of Fe(CN) 6 3−/4− ions is shown in Figure 2h,i. Well-defined cyclic voltammograms were observed in all scan rates, as shown in Figure 2h, indicating that peak current of the voltammograms has a linear behavior as a function of square root of scan rate (ν 1/2 ), indicating that the redox process is diffusion controlled, [33] as confirmed in Figure 2i and discussed in Figure S12, Supporting Information.…”

“…d) Cyclic voltammograms for (i) control and before (-) and after (-) stretching levels. Cyclic voltammograms were obtained in the presence of 5 × 10 −3 m Fe(CN) 6 3−/4− ions in KCl 0.5 m, scan rate for d(i-iv) was 30 mV s −1 .…”

“…Mater. 2020, 6,1900826 The nanofilm was prepared using MB and PDA by a co-deposition process and showed NADH electrooxidation at low potentials. Remarkably, the wettability of the surface can be tuned from hydrophobic to hydrophilic by changing the thickness of the nanofilms.…”

Structural Innovations in Printed, Flexible, and Stretchable Electronics

“…While some studies reported similar electrochemical behavior during stretching, due to the expansion of the printed composite material, most of the 2D tortuous structure still experience a significant drop in conductivity, hence impeding the overall device stability during deformations. [ 28,86 ] Depending on the quality of the stretchable ink and the substrate used, hysteresis effect has also been reported, where the conductivity of the printed inks changes temporally due to the viscoelastic behavior of the polymers and polymer composites. [ 87 ]…”