Catch bond-inspired hydrogels with repeatable and loading rate-sensitive specific adhesion.

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Biophysics

Background:

• Mammalian cell adhesion involves mechanochemical processes, including catch bonds where bond lifetime increases with applied force.
• Designing synthetic materials that mimic these dynamic biological adhesion properties remains a challenge.

Purpose of the Study:

• To create a hydrogel adhesive inspired by biological catch bonds.
• To investigate the loading rate-dependent adhesion properties of the novel hydrogel.
• To explore the potential of this hydrogel in biomedical and soft robotics applications.

Main Methods:

• Synthesized a hydrogel using acrylic acid-N-acryloyl glycinamide (AA-NAGA) copolymers and tannic acids (TA) via hydrogen bonding.
• Evaluated adhesion to polar and nonpolar surfaces under varying external loading rates (5–500 mm min⁻¹).
• Developed a mechanochemical coupling model using Monte Carlo simulations to analyze adhesion behavior.

Main Results:

• The hydrogel exhibited rapid, robust, and repeatable adhesion to polar surfaces, with minimal adhesion to nonpolar materials.
• Shear adhesive strength and interfacial adhesive toughness increased up to five-fold with increasing loading rates.
• The mechanochemical model accurately predicted the nonlinear, rate-sensitive adhesion, aligning with experimental findings.

Conclusions:

• The developed hydrogen bonding hydrogel effectively mimics catch bond behavior, demonstrating tunable, rate-sensitive adhesion.
• The hydrogel possesses biocompatibility, antioxidant, antibacterial properties, and promotes wound healing.
• This work presents a novel strategy for bionic hydrogel design for applications in flexible electronics, soft robotics, and biomedicine.