Flexible electronics is a hot research topic for medical device development which promises advancements such as turning simple vascular balloons into smart sensing devices and making contact lenses with built-in displays. While flexibility is key for many applications, also being transparent would be a major advantage for contact lens electronics.
Researchers at South Korea’s Ulsan National Institute of Science and Technology (UNIST) have developed transparent and stretchable electrodes made of graphene and silver nanowires that are effective conductors while not being brittle. They were able to embed the new material as an inorganic light-emitting diode (ILDED) into a soft contact lens which was worn seemingly without irritation by a live rabbit for five hours.
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Graphene is also well known as good a candidate for transparent electrode because of their unique electrical properties and high mechanical flexibility. However, scalable graphene synthesis methods for commercialization produces lower quality graphene with individual segments called grains which increases the electrical resistance at boundaries between these grains.
Silver nanowires, on the other hand, have high resistance because they are randomly oriented like a jumble of toothpicks facing in different directions. In this random orientation, there are many contact between nanowires, resulting in high resistance due to large junction resistance of nanowires. Due to these drawbacks, neither is good for conducting electricity, but a hybrid structure, combined from two materials, is.
As a result, it presents a high electrical and optical performance with mechanical flexibility and stretchability for flexible electronics. The hybrid Transparent electrode reportedly has a low “sheet resistance” while preserving high transmittance. There’s almost no change in its resistance when bent and folded where ITO is bent, its resistance increases significantly. Additionally the hybrid material reportedly has a low “sheet resistance” while preserving electrical and optical properties reliable against thermal oxidation condition.
Press release: Stretchable, transparent graphene-metal nanowire electrode…