Flexible Electrode Based on MWCNT Embedded in a Cross-Linked Acrylamide/Alginate Blend: Conductivity vs. Stretching

Abstract

A polyacrylamide-alginate hydrogel electrolyte, blended with Multi-Walled Carbon Nanotubes (MWCNT) as an electronically conductive fraction, allows for the creation of a flexible, durable, and resilient electrode. The MWCNT content is correlated with mechanical characteristics such as stretch modulus, tensile resistance, and electrical conductivity. The mechanical analysis demonstrates tensile strength that is comparable to similar hydrogels reported in the literature, with increasing strength for MWCNT-embedded hydrogels. The impedance spectroscopy reveals that the total resistance of electrodes decreases with increasing MWCNT content upon elongation and that bending and twisting do not obstruct their conductivity. The MWCNT-inserted hydrogels show mixed ionic and electronic conductivities, both within a range of 1-4 × 10 −2 S cm −1 in a steady state. In addition, the thermal stability of these materials increases with incrementing MWCNT content. This observation agrees with long-term charge-discharge cycling that shows enhanced electrochemical durability of the MWCNT-hydrogel hybrid when compared to pure hydrogel electrolyte. The hydrogel-carbon films demonstrate an increased interfacial double-layer current at a high MWCNT content (giving an area-specific capacitance of~30 mF cm −2 at 2.79 wt.% of MWCNT), which makes them promising candidates as printable and flexible electrodes for lightweight energy storage applications. The maximum content of MWCNT within the polymer electrolyte was estimated at 2.79 wt.%, giving a very elastic polymer electrode with good electrical characteristics.

Carbon-Based Polymer Nanocomposites for High-Performance Applications

“…Further, the thermal stability of the electrode improved upon raising the nanotube content. These nanocomposite films exhibited an interfacial double-layer capacitance at the highest nanotube content, corroborating their suitability for lightweight flexible energy storage applications [26].…”

A Flexible Ionic Polymer for “Soft Machines” – Where is the Low Temperature Limit?

“…This problem can be resolved by using ionic liquids or organic solvents as the internal medium. For example, by combining water-miscible alcohols with ionically conducting aqueous solutions, or with electronically conducting nanomaterials, [13] conjugated polymers [14] or metal nanoparticles. [15] Alternative to hydrogels are ionomers, [16] as they demonstrate promising temperature resistance.…”

Biodegradable Elastomers and Gels for Elastic Electronics

“…Beyond the mentioned conductive nanomaterials, other homogenous dispersed conductive nanomaterials or conjugated polymers including graphene oxide (GO), MWCNTs, PEDOT:PSS, and liquid metals were also used as fillers to composite with alginate hydrogels to develop the biodegradable, biocompatible, and elastic conductive composites for electronics. [146][147][148][149] The water-soluble properties and ion-induced fast gelation of alginate make the excellent ionic conductivity of hydrogels available. Various formats of alginate hydrogels conductors have been developed based on the ionic conductivity.…”

“…Beyond the mentioned conductive nanomaterials, other homogenous dispersed conductive nanomaterials or conjugated polymers including graphene oxide (GO), MWCNTs, PEDOT:PSS, and liquid metals were also used as fillers to composite with alginate hydrogels to develop the biodegradable, biocompatible, and elastic conductive composites for electronics. [ 146 , 147 , 148 , 149 ]…”