Electrical Writing onto a Dynamically Responsive Polysaccharide Medium: Patterning Structure and Function into a Reconfigurable Medium

Abstract

AbstractHistorically, paper is the medium to write information. Here, the concept of writing is expanded from the addition of mass (i.e., ink) onto a static polysaccharide medium (i.e., paper), to the addition of electrical energy to a dynamically reconfigurable polysaccharide medium. Specifically, a dual‐responsive interpenetrating polysaccharide network is used as a dynamic medium. Electrical writing is achieved using an electrode pen to locally perform the cathodic electrolysis reactions that generate high‐pH regions that neutralize the interpenetrating chitosan chains and induce their self‐assembly into crystalline regions. Surprisingly, the gradients in structure induced by cathodic writing are stable even after the pH gradient has dissipated. Molecular modeling indicates that this stability results from structure‐induced changes in chitosan's pKa. Various experimental approaches demonstrate that the changes in structure generated by cathodic writing alter the medium's mechanical, chemical, and biological properties. Importantly, the structure and information imparted into the film is reversible allowing the medium to be erased and new information to be written. Broadly, this work demonstrates the use of top‐down electrical inputs to induce bottom‐up structural changes in a biopolymer‐based medium and these structural changes fundamentally alter how this medium interacts chemically and biologically with its environment.