OpenNIRScap: An Open-Source, Low-Cost Wearable Near-Infrared Spectroscopy-based Brain Interfacing Cap

TL;DR

OpenNIRScap is an affordable, open-source wearable fNIRS device designed to enable real-time brain activity monitoring outside clinical settings, supporting broader accessibility and portable neurotechnology applications.

Contribution

This work introduces a low-cost, open-source wearable fNIRS system with custom hardware and software, validated through bench tests and pilot studies, expanding accessibility for brain monitoring.

Findings

Successfully captured cognitively evoked hemodynamic responses

Validated system performance through bench and pilot tests

Open-sourced hardware and software for community use

Abstract

Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive, real-time method for monitoring brain activity by measuring hemodynamic responses in the cerebral cortex. However, existing systems are expensive, bulky, and limited to clinical or research environments. This paper introduces OpenNIRScap, an open-source, low-cost, and wearable fNIRS system designed to make real-time brain monitoring more accessible in everyday environments. The device features 24 custom-designed sensor boards with dual-wavelength light emitters and photodiode detectors, a central electrical control unit (ECU) with analog multiplexing, and a real-time data processing pipeline. Bench validation and pilot tests on volunteers have confirmed the ability of the system to capture cognitively evoked hemodynamic responses, supporting its potential as an affordable tool for cognitive monitoring and portable neurotechnology applications. The hardware, software, and graphical user interface have all been open-sourced and made publicly available at the following link: https://github.com/tonykim07/fNIRS.