Carnegie Mellon researchers find novel biological sources for battery materials



The marine cuttlefish may be the next best source of electrode materials

The squirmy marine cuttlefish may be the next best source of electrode materials for batteries to power edible medical devices.

Carnegie Mellon University's Chris Bettinger and Jay Whitacre have found that ink from the cuttlefish, a close relative of the squid, provides the perfect chemistry and nanostructure to power tiny electronic devices that can be either ingested or implanted into the body for applications ranging from biosensing to drug delivery.

"We found that the melanin pigments in cuttlefish ink make it a perfect fit for use in battery electrodes that would ultimately be used in devices that operate in close proximity to sensitive living tissue," said Bettinger, an assistant professor in the departments of Materials Science and Engineering (MSE) and Biomedical Engineering. Melanin is the pigment responsible for the dark color of skin, hair, scales, and is also found in animals.

In a paper appearing in the Dec. 9 online edition of the Proceedings of the National Academy of Sciences, CMU researchers show that naturally occurring melanins exhibit higher charge storage capacity compared to other synthetic melanin derivatives when used as anode materials. Pigment-based anodes are an important component in sodium-ion batteries, a battery technology that has been pioneered by Whitacre, an associate professor of materials science and engineering and engineering and public policy.

"Using natural materials in energy storage devices increases the likelihood for use in powering devices that operate in sensitive environments such as the human body," Bettinger said.

At present, high-performance energy storage systems for medical devices are designed to supply power to semi-permanent devices that are often encapsulated. These scenarios permit the use of potentially toxic electrode materials and electrolytes. Electronically active medical devices that are either biodegradable or ingestible require new energy storage materials that are benign and can operate in hydrated environments. Melanin-based electrodes represent a step closer to this goal.

"Our research shows that alternative systems that use biocompatible electrode materials with aqueous sodium-ion batteries could provide onboard energy sources for a variety of temporary medical devices including biodegradable electronic implants and ingestible systems," Bettinger said.

Earlier this year, Bettinger and Whitacre reported that they were creating edible power sources for medical devices using materials found in a daily diet. Their initial design involved a flexible polymer electrode and a sodium ion electrochemical cell, which allows them to fold the mechanism into an edible pill that temporarily encapsulates the device.

Bettinger has worked for more than a decade at the interface of materials science and biomedical engineering. Some of his innovative technologies include new synthetic materials that mimic the natural properties of soft tissue and biodegradable electronics that could usher in a new era of electronically active implants.

Whitacre studies the materials science of synthesizing and implementing promising materials and device architectures for energy storage and generation technologies.

Other researchers involved in the project from CMU's MSE Department include Young Jo Kim, a research associate; Wei Wu, a Ph.D. student; and Sang-Eun Chun, a former MSE graduate student now a post-doctoral fellow in the Department of Chemistry at the University of Oregon-Eugene.

Carnegie Mellon University