Electronic Devices Made from Chitin: NAND Gates Made from Chitin Sorbates and Unsaturated Bridging Ligands—Possible Integration Levels and Kinetics of Operation

Chitin (usually derived from aq. arthropods like shrimp Pandalus borealis) acts as a potent metal sorbent in both environmental monitoring and retention applications such as wastewater purification or nuclear fuel reprocessing. Given this established (starting in the 1970s) use of chitin and the fact that adsorption of metal ions/complexes to chitin does increase the currents observed in metal-centered redox couples by a factor of about 10, it is straightforward to conceive self-organized (by adsorption modified by adding certain ligands bridging M and chitin) surface films which exert electrical information processing by means of inner-sphere redox processes. Preliminary work is shown concerning the influence of ligands—including some possibly acting as inner-sphere-transfer agents, like caffeic acid—on metal ion retention by chitin. Another ligand is reported to enhance current flow into electrodes (i.e., electron injection from some reducing cation). These inner-sphere redox processes, in turn, can be controlled by creating or removing a chain of conjugated double bonds, e.g., by Diels–Alder reactions. Devices admitting corresponding reagents in a controlled manner and appropriate array then act as NAND gates, thus being components capable of performing each kind of classical computation. Applications in environmental analysis and “green” computing for simple purposes like electronic keys are suggested. The empirical basis for these conclusions includes studies on the influences of ligand additions on M adsorption (Mn, Ni, several REEs…) on chitin; some of these bridging ligands, like caffeinate and ferulate, can reversibly react with appropriate dienes. At the employed concentrations, distances among adsorbed metal ions are 1–3 nm, meaning that the charge-flow control takes spacer ligands like carotenoids. Practical setups are pointed to, using evidence from ligand-augmented metal ion–chitin interactions, which might combine oxidizing (Ce) and optically address reducing (Eu) metal ions into a framework for coligand-controlled charge flow.