Ultrasonically Patterning Silver Nanowire–Acrylate Composite for Highly Sensitive and Transparent Strain Sensors Based on Parallel Cracks

It has long been a challenge to develop strain sensors with large gauge factor (GF) and high transparency for a broad strain range, to which field silver nanowires (AgNWs) have recently been applied. A dense nanowire (NW) network benefits achieving large stretchability, while a sparse NW network favors realizing high transparency and sensitive response to small strains. Herein, a patterned AgNW-acrylate composite-based strain sensor is developed to circumvent the above trade-off issue via a novel ultrasonication-based patterning technique, where a water-soluble, UV-curable acrylate composite was blended with AgNWs as both a tackifier and a photoresist for finely patterning dense AgNWs to achieve high transparency, while maintaining good stretchability. Moreover, the UV-cured AgNW-acrylate patterns are brittle and capable of forming parallel cracks which effectively evade the Poisson effect and thus increase the GF by more than 200-fold compared to that of the bulk AgNW film-based strain sensor. As a result, the AgNW-based strain sensor possesses a GF of ∼10,486 at a large strain (8%), a high transparency of 90.3%, and a maximum stretchability of 20% strain. The precise monitoring of human radial pulse and throat movements proves the great potential of this sensor as a measurement module for wearable healthcare systems.