A study on the weldability of tough alginate–poly(acrylic acid) hydrogels

Abstract

Hydrogels have emerged as a promising class of next-generation materials for numerous applications in biomedical and engineering fields. Recently, there has been significant focus on developing effective techniques for shaping these materials into complex patterns for practical uses. In this research, we successfully develop a novel welding technique for effectively constructing hierarchical and complex structures of tough hydrogels prepared using alginate (Alg) and poly(acrylic acid) (PAAc) polymers via ion diffusion and thermo-polymerization steps. In this technique, the hydrogels are efficiently welded via a straightforward process that includes three main steps: immersing in a highly concentrated NaCl aqueous solution, washing in water, and submerging in an Alg solution. As demonstrated, the synthesized hydrogels exhibit excellent mechanical properties with the highest Young’s modulus, tensile strength, and work of extension of ~ 3.15 MPa, ~ 1.37 MPa, and ~ 2.85 MJ·m⁻³, respectively. The gel layers are adequately bonded via the developed technique, as confirmed by field-emission scanning electron microscopy (FE-SEM) images and energy dispersive X-ray (EDX) analysis. Remarkably, Taguchi and Analysis of Variance (ANOVA) methods are employed to optimize the welding process, aiming to achieve the maximum adhesive strength. The welded hydrogels, fabricated using the optimal process with immersion durations of 210 min, 20 min, and 210 min for each main step, respectively, exhibit remarkable adhesive performance with shear strength, tensile strength, and peel strength of ~ 221.84 kPa, ~ 295.05 kPa, and ~ 109.89 N·m⁻¹, respectively. Additionally, a complex gel mesh structure is successfully created via the developed welding process. With these obtained characteristics, the present developed technique is expected to strengthen the real-world applications of Alg/PAAc-based hydrogels significantly.