One-Step Generation of Alginate-Based Hydrogel Foams Using CO₂ for Simultaneous Foaming and Gelation

Area of Science:

• Materials Science
• Chemical Engineering
• Biomaterials

Background:

• Hydrogel foams are crucial in food, cosmetic, agricultural, and medical fields.
• Reliable and scalable generation of hydrogel foams remains a significant challenge.
• Existing methods often lack efficiency or versatility.

Purpose of the Study:

• To introduce a novel, one-step method for generating calcium alginate foams using carbon dioxide (CO2).
• To demonstrate the simultaneous foaming and gelation triggered by CO2-induced pH reduction.
• To characterize the foam properties and the gelation process.

Main Methods:

• Utilized carbon dioxide (CO2) for simultaneous foaming and pH reduction of alginate solutions.
• Employed a pH-responsive indicator for macroscopic monitoring of acidification.
• Conducted foam stability measurements to investigate CO2's role in foam aging.
• Applied interfacial rheology to confirm CO2-initiated gelation.

Main Results:

• Successfully generated calcium alginate foams with varying gas fractions in a single step.
• Demonstrated that CO2 dissolution triggers the gelation of alginate solutions.
• Confirmed the effectiveness of interfacial rheology in characterizing the gas-initiated gelation process.
• Showcased the potential for foam stability and controlled aging.

Conclusions:

• The novel CO2-based method provides a simple and effective way to produce hydrogel foams.
• Gas-initiated gelation and interfacial rheology are transferable techniques applicable to diverse gases and formulations.
• This approach offers a promising advancement for hydrogel foam production across multiple industries.