Biopolymer-based capillary suspensions: Influence of particle properties on network formation

Capillary suspensions are unique materials, in which the rheological properties can be tuned by controlling the particle network through capillary interactions. To gain insights into the influence of particle properties on the network formation and accompanying gel strength for water-absorbing, biopolymeric particles, protein particles of two different sizes and water absorption capacities (WACs) were prepared. Utilizing SESANS, we describe a novel approach towards detecting changes in water distribution between and within particles. While effects of WAC seemed to be overpowered by concurrent variations in surface roughness, a larger particle size or lower roughness led to a lower initial gel strength and a subsequent much larger relative increase in gel strength upon water addition. Even though similar maximum gel strengths were obtained, indicating that particle properties had a comparably small influence once capillary forces dominated the systems, particle size played a critical role for network collapse with increasing particle clustering at larger water volumes. The results pinpoint subsequent knowledge gaps in the existing literature and demonstrate the tunability of biopolymer-based capillary suspensions over a wide gel strength range by adjustment of particle properties. These insights offer exciting opportunities for application of capillary-force controlled systems in the food, pharmaceutical and cosmetic industries.