Surface Design of Nanocrystals for High-Performance Multifunctional Sensors in Wearable and Attachable Electronics

Multifunctional temperature–strain sensors that can simultaneously detect temperature and strain are fabricated through all-solution processes using colloidal Ag nanocrystals (NCs). Material and architecture design are introduced to efficiently distinguish signals, allowing accurate measurement from one sensor device. For material design, a ligand-exchange and reduction process is developed to increase the sensitivity. As a result, higher temperature coefficients of resistance, lower resistivity, and lower gauge factor values are observed. Furthermore, a partial oxidation process is used to widen the sensing range above 673 K, which overcomes the most challenging issue of nanomaterial-based sensors. For architecture design, three-dimensional mirror-stacked layer structures are fabricated at the top and bottom layers of the neutral mechanical plane for effective strain decoupling. Our twofold strategy provides a low-cost, simple, single-material-based method to achieve highly metallic thin films constructed on flexible substrates. Our sensor platforms can be fabricated on numerous substrates with a high pixel density for high spatial resolution, and we expect that they can be used for a variety of applications such as bioelectronics and robotics.