Ion electrodiffusion governs silk electrogelation

Nikola Kojic, Matthew J. Panzer, Gary G. Leisk, Waseem K. Raja, Milos Kojic, David L. Kaplan

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


Silk electrogelation involves the transition of an aqueous silk fibroin solution to a gel state (E-gel) in the presence of an electric current. The process is based on local pH changes as a result of water electrolysis - generating H+ and OH- ions at the (+) and (-) electrodes, respectively. Silk fibroin has a pI = 4.2 and when local pH < pI, E-gel forms. An experimental system was constructed that allowed the measurement of E-gel growth and pH distribution for an applied current. To explain the observed rectangular pH profile of pHgel ≈ 4 surrounded by pH silk-solution ≈ 10, a finite-element ion electrodiffusion model was developed. The model relies on electrodiffusion of the generated H + and OH- ions. Initially, inputs into the model were the measured E-gel and voltage curves. The governing ion electrodiffusion equations were solved and the calculated pH matched the experimental pH profile, indicating that ion electrodiffusion dictates local pH changes and E-gel growth. Furthermore, the model predicted the constant currents (2 mA and 3 mA) necessary for two hypothetical E-gel growth curves and these results were then validated experimentally. The model thus shows how ion electrodiffusion governs the electrogelation process and also provides predictable outcomes for fundamental and practical E-gel applications.

Original languageEnglish (US)
Pages (from-to)6897-6905
Number of pages9
JournalSoft Matter
Issue number26
StatePublished - Jul 14 2012

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics


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