Interface Enhancement Method for Silver-Sintered Flexible Strain Sensors Toward Improved Reliability and Sensitivity

Abstract

Flexible strain sensors are key components in emerging fields such as soft robotics and wearable electronics, where robust interfacial adhesion, low electrical resistance, and mechanical stability under repeated deformation are essential. Conventional metal films on polymer substrates often exhibit poor reliability due to thermal expansion mismatch and weak interfacial bonding. Therefore, silver sintering has emerged as a promising low-temperature interconnect material with high conductivity and flexibility, yet controlling porosity during sintering and ensuring strong adhesion to polymers remain critical challenges. This work presents a strategy to expand sintered silver for flexible strain sensor applications. On the one hand, the silver (Ag) porosity was controlled from 20% to 40% through a pressureless sintering process; On the other hand, the Ag-polymer interface was reinforced via a nanoscale surface modulation method using a two-step etching treatments, while the 40 min etched sample demonstrated the most uniform performance, with the lowest electrical conductivity average degradation of 2.97%. The proposed approach effectively improves the microstructural integrity and interfacial reliability, paving the way for high-performance, durable, flexible sensors suitable for the next-generation soft electronic systems.