Flexible and Implantable Capacitive Microelectrode for Bio-potential Acquisition

Electrodes should be adhered onto the body steadily under motion, and implanted stably into the tissue without any damages while maintaining conformal contact. Although most electrodes are fabricated with biocompatible materials, they should be shielded from tissues to prevent mechanical delamination from the device itself and to avoid adverse effects such as irritation, allergic reactions, or inflammation. Herein, we demonstrate a simple process for the development of a flexible and implantable capacitive electrode based on a minimal incision accessible design with polyimide (PI) and Gold/Titanium (Au/Ti) layers and completely encapsulated in a polydimethylsiloxane (PDMS) substrate. Electrodes of three different sizes (recording site diameters of 1.8 mm, 2.8 mm, and 3.8 mm, respectively) were fabricated and examined in this work. Electrocardiography (ECG) was recorded in the dorsal area of the rat for 4 weeks for biological signal checkup. We obtained stable and robust ECG signals owing-to the intrinsic property of capacitive coupling, with almost no leakage current compared to the direct contact electrode for the applied current over the range of 0 to 10 mA. These results indicate that our electrode can be used to detect bio-signals effectively in the long term, and can play a role in electroceuticals in the near future.