Bubble‐Channeling Electrophoresis of Honeycomb‐Like Chitosan Composites

Abstract

A chitosan composite with a vertical array of pore channels is fabricated via an electrophoretic deposition (EPD) technique. The composite consists of chitosan and polyethylene glycol, as well as nanoparticles of silver oxide and silver. The formation of hydrogen bubbles during EPD renders a localized increase of hydroxyl ions that engenders the precipitation of chitosan. In addition, chemical interactions among the constituents facilitate the establishment of vertical channels occupied by hydrogen bubbles that leads to the unique honeycomb-like microstructure; a composite with a porosity of 84%, channel diameter of 488 μm, and channel length of 2 mm. The chitosan composite demonstrates an impressive water uptake of 2100% and a two-stage slow release of silver. In mass transport analysis, both Disperse Red 13 and ZnO powders show a much enhanced transport rate over that of commercial gauze. Due to its excellent structural integrity and channel independence, the chitosan composite is evaluated in a passive suction mode for an adhesive force of 9.8 N (0.56 N cm −2 ). The chitosan composite is flexible and is able to maintain sufficient adhesive force toward objects with different surface curvatures.

Continuous electro-growth of a hierarchically structured hydrogel on a non-conductive surface

“…A previous study on chitosan deposition on electrodes suggests that the in situ sol-gel transition of chitosan is caused by the electrophoresis of chitosan chains to the cathode under an electric field and the increased pH gradient near the electrodes. 39 However, the formation of the chitosan hydrogel film on the non-conductive surface was not caused by OH À generated at the cathode because the cation exchange membrane blocked the penetration of most OH À . In order to follow the migration of OH À or H + generated by the electrodes, a pH indicator was added to the phosphate buffer in the cathode and anode chambers.…”

“…The deposited hydrogels are formed directly on the electrodes, which suffer from harsh pH changes and structural damage caused by in situ generated air bubbles. 39 In this study, as an alternative to electrodeposition on conductive electrodes, we have developed an innovative method for the controlled preparation of polymeric hydrogel films on non-conductive surfaces. By programming electrical signal sequences, layered polymeric hydrogels with regulated ordered and disordered structures could be obtained continuously.…”