A team of international scientists has developed a groundbreaking flexible electrode that has the potential to revolutionize the field of biomedical devices. Inspired by the unique properties of spider silk, the electrode is able to wrap around muscles, nerves, and hearts, delivering electrical stimulation to tissues or recording electrical activity. Unlike conventional stretchable electrodes, this new technology is non-toxic and offers superior performance.
Published in the journal Nature in December, the study was led by Prof. Chen Xiaodong of NTU’s School of Materials Science and Engineering, Prof. Gao Huajian of NTU’s School of Mechanical and Aerospace Engineering, Prof. Liu Zhiyuan from the Chinese Academy of Sciences, and Prof. Hu Benhui from Nanjing Medical University. The electrode is made from a flexible material that contracts when wet, allowing it to securely conform to biological tissues and organs.
Taking inspiration from the structure of spider silk, which contracts when wet, the scientists created the material by combining a compound called semicrystalline poly(ethylene oxide) (PEO) with another compound known as poly(ethylene glycol)-α-cyclodextrin inclusion complex (IC). The IC connects the semicrystalline PEO structures and holds them together.
To create the electrode, the material was stretched repeatedly to form a thin film. This stretching process causes the semicrystalline PEO to create bridges and pores, while simultaneously re-forming into crystals, stabilizing the material in a stretched state when dry. When the dry film comes into contact with water, the PEO structures dissolve, causing the material to instantly contract and fit seamlessly around tissues, similar to shrink wrap.
Experiments conducted with cell cultures demonstrated that the material was not toxic to cells. The researchers then deposited gold, a highly conductive material, onto the dry and stiff film to create the flexible electrode. In tests on rats, the team showed that the electrode was able to effectively deliver electrical impulses to nerves. Furthermore, the electrode demonstrated a higher sensitivity than conventional stretchable gold electrodes when recording electrical signals from muscles, nerves, and the heart, thanks to the seal between the electrode and the tissue.
The scientists also conducted experiments to determine the electrode’s ability to detect electrical activity triggered by the stimulation of a muscle graft by a nerve. This is a procedure commonly used to control prosthetic limbs or treat phantom pain after limb amputation.
Dr. Yi Junqi, a research fellow from NTU’s School of Materials Science and Engineering and NTU’s Institute for Digital Molecular Analytics and Science, and the first author of the study, stated, “Our water-responsive material may play an important role in shaping the next generation of biomedical applications at the interface between electronics and the human body.”
The team also showcased the electrode’s ability to be wrapped around a rat heart to detect electrical signals resulting from abnormal heart rhythms without the need for customized sizing or shaping. To install the electrode, a small incision is made in the chest and guided by a camera before being delivered. Once inside the chest cavity, the electrode unfolds to surround the heart, and upon contact with water, it contracts to wrap around the heart.
The development of this spider-silk inspired electrode could have far-reaching implications in the biomedical field. It opens up possibilities for the creation of advanced biomedical devices that can monitor irregular heartbeats, aid in nerve repair, promote wound closure, and reduce scarring. With its versatility and superior performance, this innovative technology is poised to shape the future of biomedical applications at the intersection of electronics and the human body.
1. Source: Coherent Market Insights, Public sources, Desk research
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