Fabrication of lead-free perovskite MASnBrI₂ nanocrystals-embedded polymer composites for flexible strain sensors

In this work, the flexible piezoresistive films were synthesized through in-situ dispersing perovskite MASnBrI(2) nanocrystals (NCs) into the elastic thermoplastic polyurethanes (TPU) substrate. Then, the flexible piezoresistive sensors were fabricated by sandwiching the NCs/TPU nanocomposite layer between interdigitated Ag electrodes. The piezoresistive behavior was attributed to the perovskite NCs which were distributed uniformly inside the TPU film. Specifically, it manifests as the change in electron cloud density of perovskite NCs under a pressure. The sensor made with a NCs/TPU composite membrane shows a pressure sensitivity of 0.796 kPa(-1) over a wide linear range of 0 similar to 0.7 kPa, an ultralow detect limitation of 0.2 Pa, a rapid response/recover time of 400 ms/370 ms and a good bending ability (90 degrees). Additionally, the strain sensor also shows excellent performance in detecting the respiratory airflow, wrist pulse and finger joint curvature. We believe that this work might open up new opportunities for flexible strain sensors in the areas such as health monitoring, human-computer interaction, and smart electronic wearables.