Evaluating the effect of strong binding affinity ions on mechanical properties, electrical conductivity, and weldability of conductive alginate-based hydrogels

Abstract

Next-generation applications, such as actuators, sensors, soft robotics, and electronic devices, require flexible and wearable materials with robust mechanical properties, exceptional electrical conductivity, and complex designability. Additionally, using sustainable substances as alternatives to conventional ones is crucial for environmental preservation and minimizing fossil fuel usage. In this study, conductive hydrogels based on naturally derived materials, including alginate and activated charcoal (AC), have been successfully developed. They are created using an ion diffusion method, followed by drying and rehydration techniques, and an ion exchange process. The effect of strong binding affinity ions, such as Zn²⁺, Ba²⁺, Cu²⁺, and Al³⁺, on the mechanical performances, electrical conductivity, and weldability of the hydrogels is assessed transparently. The findings indicate that the hydrogel prepared with Ba²⁺ exhibits remarkable mechanical properties (Young’s modulus: ∼106.83 MPa, tensile strength: ∼10.31 MPa, and work of extension: ∼8.17 MJ·m⁻³). Meanwhile, Zn²⁺ imparts favorable electrical conductivity (∼0.537 mS·cm⁻¹) and excellent welding efficiency (adhesive strength: ∼1.14 MPa) to the gel. Monovalent ions, such as Li⁺, can be incorporated into the hydrogels to enhance conductivity (∼2.388 mS·cm⁻¹), yet their presence has a negligible effect on the gels’ mechanical properties. Furthermore, the gels are successfully utilized to fabricate flexible and wearable electrical components, such as electrical circuits. Considering these capabilities, the developed conductive hydrogels hold potential for applications in electronics and load-bearing systems.