High conductivity Sepia melanin ink films for environmentally benign printed electronics

Abstract

Melanins (from the Greek μέλας, mélas, black) are bio-pigments ubiquitous in flora and fauna. Eumelanin is an insoluble brown–black type of melanin, found in vertebrates and invertebrates alike, among which Sepia (cuttlefish) is noteworthy. Sepia melanin is a type of bio-sourced eumelanin that can readily be extracted from the ink sac of cuttlefish. Eumelanin features broadband optical absorption, metal-binding affinity and antioxidative and radical-scavenging properties. It is a prototype of benign material for sustainable organic electronics technologies. Here, we report on an electronic conductivity as high as 10 −3 S cm −1 in flexographically printed Sepia melanin films; such values for the conductivity are typical for well-established high-performance organic electronic polymers but quite uncommon for bio-sourced organic materials. Our studies show the potential of bio-sourced materials for emerging electronic technologies with low human- and eco-toxicity.

Controlling ions and electrons in aqueous solution: an alternative point of view of the charge-transport behavior of eumelanin-inspired material

“…However, in those studies, no attention was drawn to a possible increase in their charge transport electronic component. Also, a recent study has shown that a natural sepia -NF-eumelanin can support such an IS behavior in a dried environment, 45 ascribed to the electronic component.…”

“…Nonetheless, shreds of evidence for an electronic component cannot be ignored entirely. 30,[42][43][44][45] Herein, we investigate the electrical properties of eumelanin by systematically evaluating its electrical current response in a biomimetic aqueous suspension (phosphate buffer saline, PBS, solution) under different pH levels. Electrical DC and voltage-dependent impedance/dielectric spectroscopy measurements are carried out on high-quality thin films.…”

The influence of copper ions on the transport and relaxation properties of hydrated eumelanin

“…[12][13][14] Consequently, it was used as a gate material in a solid-state electrochemical transistor whose channel was made of PEDOT:PSS. 15,16 Other well-known areas of applied development exploit the properties of eumelanin as a photoacid, 17 use its ability to convert ionising radiation, 18 allow creating printed electronics using eumelanin-based conductive ink, 19 as well as various sensors and electrodes. 20 Many of these applications depend on the conductive properties of eumelanin, which are determined by the structure of the material.…”

A nanoscale study of the structure and electrical response of Sepia eumelanin

“…Sepia powder was extracted using a previously reported extraction protocol. 19,20 Briefly, 300 g of raw ink was suspended in 500 mL of HCl (2 M, Acros Organics). The suspension was stirred at room temperature for 24 hours, sequentially centrifuged (Allegra X-30R centrifuge, Beckman Coulter) and dispersed as follows: three times with HCl (0.5 M), once with de-ionized (DI) water, once with a buffer solution (0.02% v/v of monobasic sodium phosphate (200 mM, Sigma Aldrich), 32.49% v/v of dibasic sodium phosphate (200 mM, Sigma Aldrich) and 67.49% v/v of DI water), once with ethanol (Sigma Aldrich), once with DI water and finally once with ethyl acetate (Sigma Aldrich), for a total of 10 steps.…”