MSc..Thesis Defense:Seba Nur Alhasan

FLEXIBLE MICROMACHINED TEXTILE-LIKE GRAPHENE BIOELECTRODES FOR ELECTROCARDIOGRAPHY MONITORING

Seba Nur Alhasan
ELECTRONIC ENGINEERING  MSc. THESIS, JULY 2024

Thesis Jury

Asst. Prof. Murat Kaya YAPICI (Thesis Advisor),

Prof. Fevzi Çakmak CEBECİ,

Asst. Prof. Seval KINDEN

Date & Time: 18th, July 2024 – 03:30 PM

Place: FENS L067

Keywords: Biosensor, ECG Electrode, Flexible, Graphene Oxide, Vitamin C, Medical Garment, Nanomaterials, Personalized Medicine, Smart Fabric, Wearable Electronics

Abstract

Dry electrodes capable of accurately recording vital signals represent a promising future for wearable long-term health monitoring devices. This thesis introduces an ultrathin, flexible, textile-like, microstructured dry electrode that features self-adhesive capabilities for conformal attachment to skin facilitating wearable electrocardiography (ECG) monitoring applications. The electrode design employs Poly (methyl methacrylate) (PMMA), a material commonly used in the textile industry, onto which functional graphene layers are coated along with photo-patternable SU-8 epoxy as the backing layer. The textile-like structure of the micromachined electrodes includes 100 µm gap sizes with 100 µm spacing, achieved by patterning PMMA through oxygen plasma and hard-mask layer without requiring expensive e-beam lithography (EBL) processes. Graphene oxide is applied to the electrodes via drop casting as the active material for signal acquisition, followed by a simple reduction step using eco-friendly pure vitamin C (L-ascorbic acid). The electrode's functionality for ECG monitoring is demonstrated by reporting the skin-contact impedance and benchmarking the electrodes against clinical-grade pre-gelled, “wet” Ag/AgCl electrodes, achieving a correlation of up to 98.84%. Additionally, the electrodes' capability to record biopotentials during physical activities with the presence of motion is demonstrated both in dry and wet conditions to verify their performance for wearable applications. The results demonstrate the remarkable self-adhesiveness, flexibility, reusability, and water resistance of the electrodes, maintaining conformal skin-electrode contact and offering high-quality signal acquisition.