Abstract: Surprisingly, electric fields can induce a dramatic response in soft materials made from nonconducting biopolymers. Capsules made from Alginate, Chitosan, and Gellan gum, all of which are charged polysaccharides and are biocompatible and biodegradable. Each capsule is formed by crosslinking biopolymer chains via physical (ionic/electrostatic) interactions. Under a DC electric field, the capsules rupture and disintegrate in a span of less than five minutes. The mechanism for the electroresponse is attributed to electrophoretic rearrangement of ions and/or polyelectrolyte chains in the capsule. Alginate capsules first swell anisotropically on their side closer to the anode (+ electrode). Cations migrate away from the anode, thereby lowering the crosslink density on that side. As further crosslinks are lost from the anode side, the capsule eventually breaks. A valve design utilizes an orifice that is blocked by a capsule and the valve is opened when the capsule is dislodged by the field.

Abstract: A method of system of forming a biopolymer hydrogel structure includes a mold loaded with a cation. At least a portion of the surface of the mold is exposed to a solution comprising a gellable polymer such as alginate. An electric potential is applied to the mold so that the cation therein and the gellable polymer migrate via electrophoresis toward the surface portion, thereby interacting and forming a hydrogel structure adjacent to the surface portion.