In Situ Investigation of Swelling Dynamics of Acrylamide-Acrylic Acid Superabsorbent Microparticles at a Single Particle Level.

Abstract

Investigating the swelling behavior of superabsorbent polymer microparticles (SAP-MPs) at a single-particle level using traditional methods is constrained by low resolution and insufficient real-time data, especially for particles smaller than 300 µm. To address these challenges, a novel microfluidic device capable is developed of real-time, high-precision single-particle analysis. This platform hydrodynamically traps individual SAP-MPs, enabling continuous monitoring of their swelling dynamics under controlled conditions. SAP-MPs with varying sizes (90-270 µm), crosslinker concentrations (0.25%2>0.98) and minimal equilibrium volumetric swelling ratio deviations (ΔVSR_eq<4%), confirming diffusion as the primary swelling mechanism, particularly for smaller particles. Smaller SAP-MPs exhibited enhanced performance, with VSR_eq of ≈140 m³/m³-40% higher than their larger counterparts-and swelling rates (SR) up to 10 m³ m^{- 3}·s. This study establishes microfluidics as a transformative tool for single-particle characterization and provides insights into engineering hydrogels tailored for advanced applications in drug delivery, tissue engineering, and environmental sensing.