In-ear integrated sensor array for the continuous monitoring of brain activity and of lactate in sweat

Yuchen Xu; Ernesto De la Paz; Akshay Paul; Kuldeep Mahato; Juliane R Sempionatto; Nicholas Tostado; Min Lee; Gopabandhu Hota; Muyang Lin; Abhinav Uppal; William Chen; Srishty Dua; Lu Yin; Brian L Wuerstle; Stephen Deiss; Patrick Mercier; Sheng Xu; Joseph Wang; Gert Cauwenberghs

doi:10.1038/s41551-023-01095-1

In-ear integrated sensor array for the continuous monitoring of brain activity and of lactate in sweat

Nat Biomed Eng. 2023 Oct;7(10):1307-1320. doi: 10.1038/s41551-023-01095-1. Epub 2023 Sep 28.

Authors

Yuchen Xu^#¹, Ernesto De la Paz^#², Akshay Paul¹, Kuldeep Mahato², Juliane R Sempionatto², Nicholas Tostado², Min Lee¹, Gopabandhu Hota³, Muyang Lin², Abhinav Uppal¹, William Chen¹, Srishty Dua², Lu Yin², Brian L Wuerstle³, Stephen Deiss¹, Patrick Mercier⁴, Sheng Xu^{5

6}, Joseph Wang⁷, Gert Cauwenberghs⁸

Affiliations

¹ Shu Chien - Gene Lay Department of Bioengineering, University of California San Diego, La Jolla, CA, USA.
² Department of Nanoengineering, University of California San Diego, La Jolla, CA, USA.
³ Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA, USA.
⁴ Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA, USA. pmercier@ucsd.edu.
⁵ Shu Chien - Gene Lay Department of Bioengineering, University of California San Diego, La Jolla, CA, USA. shengxu@ucsd.edu.
⁶ Department of Nanoengineering, University of California San Diego, La Jolla, CA, USA. shengxu@ucsd.edu.
⁷ Department of Nanoengineering, University of California San Diego, La Jolla, CA, USA. josephwang@ucsd.edu.
⁸ Shu Chien - Gene Lay Department of Bioengineering, University of California San Diego, La Jolla, CA, USA. gcauwenberghs@ucsd.edu.

^# Contributed equally.

Abstract

Owing to the proximity of the ear canal to the central nervous system, in-ear electrophysiological systems can be used to unobtrusively monitor brain states. Here, by taking advantage of the ear's exocrine sweat glands, we describe an in-ear integrated array of electrochemical and electrophysiological sensors placed on a flexible substrate surrounding a user-generic earphone for the simultaneous monitoring of lactate concentration and brain states via electroencephalography, electrooculography and electrodermal activity. In volunteers performing an acute bout of exercise, the device detected elevated lactate levels in sweat concurrently with the modulation of brain activity across all electroencephalography frequency bands. Simultaneous and continuous unobtrusive in-ear monitoring of metabolic biomarkers and brain electrophysiology may allow for the discovery of dynamic and synergetic interactions between brain and body biomarkers in real-world settings for long-term health monitoring or for the detection or monitoring of neurodegenerative diseases.