Journal Article

Soft, curved electrode systems capable of integration on the auricle as a persistent brain–computer interface

Lee, Woosik, Bretl, Timothy, Wang, Xiao-Qi, Lee, Dong Sup, Yeo, Woon-Hong, Huang, Yonggang, Won, Phillip, Paik, Ungyu, Jung, Sung-Young, Norton, James J. S., Liu, ZhuangJian, Jeong, Jae-Woong, Kwon, Yong Ho, Umunna, Stephen, Rogers, John A., Akce, Abdullah, Cheng, Huanyu, Lee, Jung Woo, Kwon, Ohjin, Na, Ilyoun

2015

Overview

Recent advances in electrodes for noninvasive recording of electroencephalograms expand opportunities collecting such data for diagnosis of neurological disorders and brain–computer interfaces. Existing technologies, however, cannot be used effectively in continuous, uninterrupted modes for more than a few days due to irritation and irreversible degradation in the electrical and mechanical properties of the skin interface. Here we introduce a soft, foldable collection of electrodes in open, fractal mesh geometries that can mount directly and chronically on the complex surface topology of the auricle and the mastoid, to provide high-fidelity and long-term capture of electroencephalograms in ways that avoid any significant thermal, electrical, or mechanical loading of the skin. Experimental and computational studies establish the fundamental aspects of the bending and stretching mechanics that enable this type of intimate integration on the highly irregular and textured surfaces of the auricle. Cell level tests and thermal imaging studies establish the biocompatibility and wearability of such systems, with examples of high-quality measurements over periods of 2 wk with devices that remain mounted throughout daily activities including vigorous exercise, swimming, sleeping, and bathing. Demonstrations include a text speller with a steady-state visually evoked potential-based brain–computer interface and elicitation of an event-related potential (P300 wave). Significance Conventional electroencephalogram (EEG) recording systems, particularly the hardware components that form the physical interfaces to the head, have inherent drawbacks that limit the widespread use of continuous EEG measurements for medical diagnostics, sleep monitoring, and cognitive control. Here we introduce soft electronic constructs designed to intimately conform to the complex surface topology of the auricle and the mastoid, to provide long-term, high-fidelity recording of EEG data. Systematic studies reveal key aspects of the extreme levels of bending and stretching that are involved in mounting on these surfaces. Examples in persistent brain–computer interfaces, including text spellers with steady-state visually evoked potentials and event-related potentials, with viable operation over periods of weeks demonstrate important advances over alternative brain–computer interface technologies.

• Publisher: National Academy of Sciences,National Academy of Sciences, Washington, DC (United States)
• Subject: 60 APPLIED LIFE SCIENCES / auricle integration / Bending / Brain-Computer Interfaces / brain–computer interface / Cognition / Computers / diagnostic techniques / Ear, External / Electrodes / electroencephalography / Electroencephalography - instrumentation / Electroencephalography - methods / Electronics / Engineering / Equipment Design / Event-Related Potentials, P300 / evoked potentials / Exercise / Fractals / head / Human-computer interaction / Humans / MATHEMATICS AND COMPUTING / Mechanical properties / monitoring / Physical Sciences / Signal Processing, Computer-Assisted / Signal-To-Noise Ratio / sleep / soft electronics / Swimming / text speller / Topology