Bioinspired Heat-Induced Viscoelasticity-Switchable Electrodes for Conformal Brain-Computer Interfaces

Area of Science:

• Bioelectronic Interfaces
• Neurotechnology
• Materials Science

Background:

• Electroencephalography (EEG) is crucial for brain-computer interfaces (BCIs).
• Current EEG electrodes (dry and wet) face limitations like signal instability or complex setup.
• These limitations hinder the adoption of wearable BCI systems, especially on hairy scalps.

Purpose of the Study:

• To develop a novel electrode for stable EEG signal acquisition on hairy scalps.
• To create a user-friendly, conformal electrode suitable for wearable BCI devices.
• To overcome the limitations of existing dry and wet EEG electrodes.

Main Methods:

• Introduction of a heat-induced viscoelasticity-switchable electrode (HIVE) inspired by honeybee behavior.
• HIVE utilizes a thermoresponsive gelatin gel within a sponge matrix and an on-electrode microheater.
• Temperature modulation enables switching between gel (conformal) and sol (permeating) states, with closed-loop impedance control.

Main Results:

• HIVE achieves conformal contact on hairy scalps by permeating hair in its sol state.
• The electrode demonstrates strong adhesion at body temperature due to its viscoelastic state.
• EEG recordings using HIVE in a visual evoked potential paradigm show high classification accuracy, comparable to wet electrodes.

Conclusions:

• HIVE provides a practical solution for stable, wearable BCI systems, particularly on challenging scalp conditions.
• The technology translates a honeybee's strategy for adaptable material properties to bioelectronic interfaces.
• This work presents a new paradigm for designing conformal biointerfaces on piliferous surfaces.