title: Scaling law and microstructure of alginate hydrogel.
abstract: The gelation of alginate in aqueous solution was studied as a function of Ca(2+) concentration. At each given concentration of alginate, a critical gel concentration [Formula: see text] , was successfully determined for the first time using the Winter-Chambon criterion. The critical gel concentration [Formula: see text] was found to increase linearly with alginate concentration. At the same time, the critical relaxation exponent n decreased and the critical gel strength Sg increased linearly with alginate concentration. An improved egg-box model was proposed to describe the change in gel junction and gel network. In the stable gel state, the plateau modulus Ge of alginate gel depended on Ca(2+) concentration according to a power-law scaling, Ge=kɛ(1.5), where ɛ is the relative distance of a gelling variable (Ca(2+) concentration in this case) from the gel point ( [Formula: see text] ). The FESEM images verified the microstructure of alginate gel in which alginate chains associated into fibrils in the presence of Ca(2+) ions. The fibrillar diameter and network density increased with increasing Ca(2+) ion concentration while alginate concentration had a weak influence on fibrillar diameter.
authors.affiliation: School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Sijun
authors.initials: S
authors.lastname: Liu
authors.affiliation: School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Huijun
authors.initials: H
authors.lastname: Li
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Bijun
authors.initials: B
authors.lastname: Tang
authors.affiliation: School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Shuguang
authors.initials: S
authors.lastname: Bi
authors.affiliation: School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. Electronic address: mlli@ntu.edu.sg.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
keywords: Alginate; Egg-box model; Rheology; Scaling law; Viscoelasticity