Adhesion and Resistance Stability in Screen-Printed Graphite ECG Patches

Sammanfattning

Wireless electrocardiogram (ECG) patches are widely used in clinical care, but are often discarded after defibrillation regardless of actual damage. This leads to increased medical waste and unnecessary cost. A possible solution is to replace silver-based electrodes with graphite-based screen-printed electrodes on polyethylene terephthalate (PET), which are cheaper and more environmentally sustainable. However, their performance depends on reliable adhesion and stable electrical resistance under clinical stress. This study aims to evaluate how curing temperature and ink composition influence adhesion between the graphite layer and the PET substrate, and how this affects resistance stability. The study used a two-step method: first, calibration curves were generated for ink compositions with different graphite to binder ratios to identify compositions close to 3.3 kΩ ±20%. Second, the selected compositions were tested under mechanical loading and thermal cycling, using tape tests, pressure tests and heatmaps. The results show that increased curing temperature improves adhesion and reduces delamination. Stronger adhesion also results in more stable resistance, although thermal cycling still introduces some variation. Directional differences in resistance values confirm that screen printing pressure and direction influence layer formation. In conclusion, curing temperature and ink compositions with different graphite-to-binder ratios affect both adhesion and resistance stability in printed graphite electrodes. These findings support further development of cost-efficient and durable wireless ECG patches for sustainable clinical use.