title: Soft, curved electrode systems capable of integration on the auricle as a persistent brain-computer interface.
abstract: 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).
authors.affiliation: Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801;
authors.forename: James J S
authors.initials: JJ
authors.lastname: Norton
authors.affiliation: Department of Chemical and Life Science Engineering, Virginia Commonwealth University, Richmond, VA 23284; Department of Mechanical and Nuclear Engineering, Center for Rehabilitation Science and Engineering, Virginia Commonwealth University, Richmond, VA 23284;
authors.forename: Dong Sup
authors.initials: DS
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; Department of Materials Science and Engineering, Department of Energy Engineering, Hanyang University, Seoul 133-791, Republic of Korea;
authors.forename: Jung Woo
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Department of Mechanical and Nuclear Engineering, Center for Rehabilitation Science and Engineering, Virginia Commonwealth University, Richmond, VA 23284;
authors.forename: Woosik
authors.initials: W
authors.lastname: Lee
authors.affiliation: Department of Mechanical and Nuclear Engineering, Center for Rehabilitation Science and Engineering, Virginia Commonwealth University, Richmond, VA 23284;
authors.forename: Ohjin
authors.initials: O
authors.lastname: Kwon
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801;
authors.forename: Phillip
authors.initials: P
authors.lastname: Won
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea;
authors.forename: Sung-Young
authors.initials: SY
authors.lastname: Jung
authors.affiliation: Departments of Civil and Environmental Engineering and Mechanical Engineering, Center for Engineering and Health, Skin Disease Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Huanyu
authors.initials: H
authors.lastname: Cheng
authors.affiliation: Department of Electrical, Computer, and Energy Engineering, University of Colorado Boulder, Boulder, CO 80309;
authors.forename: Jae-Woong
authors.initials: JW
authors.lastname: Jeong
authors.affiliation: Google Inc., Mountain View, CA 94043;
authors.forename: Abdullah
authors.initials: A
authors.lastname: Akce
authors.affiliation: Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801;
authors.forename: Stephen
authors.initials: S
authors.lastname: Umunna
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; Department of Chemical Engineering, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea;
authors.forename: Ilyoun
authors.initials: I
authors.lastname: Na
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801;
authors.forename: Yong Ho
authors.initials: YH
authors.lastname: Kwon
authors.affiliation: Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611;
authors.forename: Xiao-Qi
authors.initials: XQ
authors.lastname: Wang
authors.affiliation: Institute of High Performance Computing, 138632, Singapore; and.
authors.forename: ZhuangJian
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, Department of Energy Engineering, Hanyang University, Seoul 133-791, Republic of Korea;
authors.forename: Ungyu
authors.initials: U
authors.lastname: Paik
authors.affiliation: Departments of Civil and Environmental Engineering and Mechanical Engineering, Center for Engineering and Health, Skin Disease Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
authors.forename: Timothy
authors.initials: T
authors.lastname: Bretl
authors.affiliation: Department of Mechanical and Nuclear Engineering, Center for Rehabilitation Science and Engineering, Virginia Commonwealth University, Richmond, VA 23284; jrogers@illinois.edu whyeo@vcu.edu.
authors.forename: Woon-Hong
authors.initials: WH
authors.lastname: Yeo
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; jrogers@illinois.edu whyeo@vcu.edu.
authors.forename: John A
authors.initials: JA
authors.lastname: Rogers
mesh_terms: D062207:Brain-Computer Interfaces; D003071:Cognition; D003201:Computers; D004431:Ear, External; D004566:Electrodes; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods*; D004581:Electronics; D004867:Equipment Design; D018913:Event-Related Potentials, P300; D017709:Fractals; D006801:Humans; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio
keywords: auricle integration; brain–computer interface; soft electronics; text speller