Multi-Material 3D Printed Conductive/ Neat TPU Dry Electrodes for ECG Monitoring Wearable Applications

Area of Science:

• Biomedical Engineering
• Materials Science

Background:

• Traditional gel-based Ag/AgCl electrodes present limitations like skin irritation and unsuitability for extended use.
• Development of next-generation dry electrodes is crucial for advanced bioelectricity monitoring.

Purpose of the Study:

• To fabricate high-performance, low-cost, 3D printed dry electrodes from thermoplastic elastomer.
• To optimize electrode design for skin conformity and mechanical properties using TPMS geometries.

Main Methods:

• Utilized Fused Filament Fabrication (FFF) for multi-material 3D printing of neat and conductive thermoplastic polyurethane (cTPU).
• Incorporated nature-inspired triply periodic minimal surface (TPMS) geometries (gyroid and square honeycomb) for enhanced skin conformity.
• Characterized electrodes via thermogravimetric analyses, tensile testing, cyclic bending, and electrode-skin impedance measurements.

Main Results:

• The multi-material gyroid electrode demonstrated the lowest electrode-skin impedance (298 kΩ at 20 Hz).
• Achieved high electrocardiogram (ECG) signal quality across various monitoring scenarios (stationary, 24h, standing, walking).
• Demonstrated tuneable compliance, stretchability, and flexibility matching human skin stiffness.

Conclusions:

• The proposed multi-material structure and TPMS design offer a scalable method for creating comfortable, reusable, high-performance dry electrodes.
• These electrodes support continuous bioelectricity monitoring in wearable applications by combining conductivity and skin-compliant mechanics.
• The gyroid TPMS design shows significant promise for next-generation wearable bio-monitoring devices.