Electromechanical characterization for wearable electronics
Puutio, Juuso (2025)
2025
Sähkötekniikan DI-ohjelma - Master's Programme in Electrical Engineering
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
Hyväksymispäivämäärä
2025-01-07
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202501061100
https://urn.fi/URN:NBN:fi:tuni-202501061100
Tiivistelmä
The modernization of electronics production demands intensive research to create environmentally friendly and sustainable electronics. In addition to reducing the environmental burden, electronics manufactured using printing technologies pave the way for flexible electronics. Unlike traditional electronics, which rely on rigid fiberglass substrates that cannot adapt to mechanical stress, flexible electronics use substrates and inks that are bendable and stretchable, allowing them to conform to new shapes. This flexibility opens up a range of applications that were previously impossible with rigid bodies.
This work investigates the electromechanical behavior of screen-printed tracks made from silver and carbon inks on various substrates, including PET, PLA, and paper substrates. Bending tests were conducted under various conditions to assess the electromechanical durability of each material combination.
Two different bending setups were utilized. The primary device featured two plates: a stationary bottom plate and a top plate that moved horizontally, bending the sample positioned between them. Resistance was continuously measured across each of the seven tracks on the sample, providing valuable information about the increase in resistance as a function of the bending cycles. To complement these findings, the secondary setup was employed to subject samples to varying bending radii. Furthermore, tests were conducted under both compressive and tensile stresses to assess durability more comprehensively.
A threshold of 1.7 times the initial resistance was used to define failure, and with at least eight replicates, the most durable material combinations were identified. The results showed that within all tested combinations, the print was consistently more durable under tensile stress compared to compressive stress. The effect of bending radius was as expected: larger radii resulted in less stress and longer lifespans. Notably, none of the combinations printed with carbon inks exhibited any signs of degradation, even under the most extreme bending condition, where the radius was reduced from 9 mm to 3 mm. Thus, the carbon-based samples were ranked as the most durable under bending. Additionally, substrates such as smooth, thin paper and cellulose based alternatives to plastic films demonstrated high durability, withstanding thousands of cycles,
whereas thicker, rougher substrates failed within tens or hundreds of cycles. Several factors influencing the bending reliability of screen-printed tracks were analyzed. The findings revealed how specific substrate-ink combinations behaved under mechanical stress, providing valuable insights into their potential usage in sustainable electronics.
This work investigates the electromechanical behavior of screen-printed tracks made from silver and carbon inks on various substrates, including PET, PLA, and paper substrates. Bending tests were conducted under various conditions to assess the electromechanical durability of each material combination.
Two different bending setups were utilized. The primary device featured two plates: a stationary bottom plate and a top plate that moved horizontally, bending the sample positioned between them. Resistance was continuously measured across each of the seven tracks on the sample, providing valuable information about the increase in resistance as a function of the bending cycles. To complement these findings, the secondary setup was employed to subject samples to varying bending radii. Furthermore, tests were conducted under both compressive and tensile stresses to assess durability more comprehensively.
A threshold of 1.7 times the initial resistance was used to define failure, and with at least eight replicates, the most durable material combinations were identified. The results showed that within all tested combinations, the print was consistently more durable under tensile stress compared to compressive stress. The effect of bending radius was as expected: larger radii resulted in less stress and longer lifespans. Notably, none of the combinations printed with carbon inks exhibited any signs of degradation, even under the most extreme bending condition, where the radius was reduced from 9 mm to 3 mm. Thus, the carbon-based samples were ranked as the most durable under bending. Additionally, substrates such as smooth, thin paper and cellulose based alternatives to plastic films demonstrated high durability, withstanding thousands of cycles,
whereas thicker, rougher substrates failed within tens or hundreds of cycles. Several factors influencing the bending reliability of screen-printed tracks were analyzed. The findings revealed how specific substrate-ink combinations behaved under mechanical stress, providing valuable insights into their potential usage in sustainable electronics.