Edible Cuttlefish Ink: Complex Chemistry, Structure, and Electrical Response

Cuttlefish ink (Sepia ink) has biological functions such as defense and camouflage. The use of this black‐brown ink in writing and drawing dates to ancient times. In this work, we found that edible cuttlefish ink is a naturally formulated conductive ink where the conductive component includes the biopigment eumelanin. There are no naturally formulated conductive inks reported in the literature. With the long‐term objective to develop a bio‐based printable electronic ink, we carried out an explorative study of edible cuttlefish ink through an integrated approach of chemistry‐structure‐electrical properties. We revealed the elemental and molecular composition of the ink by Instrumental Neutron Activation Analysis and Ultra High‐Pressure Liquid Chromatography coupled with High‐Resolution Mass Spectrometry. We probed the electrical response of spin‐coated ink samples through current–voltage and current–time characteristics and thoroughly characterized their structure and composition by scanning electron microscopy and energy dispersive X‐ray spectroscopy. In ambient conditions, we observed the presence of electronic transport, with a conductivity of about 3.4 ± 1.0 × 10 −4 S/cm at 1 V. Current–time characteristics indicate the simultaneous presence of ionic transport. Our work contributes to the development of bio‐based, biocompatible, and biodegradable printable electronics inks and advances the understanding of the biorole of cuttlefish ink.