Printed Conformal and Transparent Magnetoresistive Sensors for Seamless Integration and Environment-Resilient Touchless Interaction

Abstract

Combination of conformability and transparency is crucial for realizing the full capabilities of printed magnetoresistive sensors in cutting-edge technologies designed to blend into their surroundings and applications. However, achieving this poses a critical challenge due to conflicting requirements: magnetic nanowires optimized for deformability exhibit a tendency to cluster, thus compromising transparency. To balance this trade-off, we leverage magnetic fields to manipulate nanowires, simultaneously initiating alignment and pinning effects. These together ensure a uniform and anisotropic distribution across extensive areas, enhancing the sensor transparency (about 85%). Further, we harness the clustering tendency, repurposing it to create local entanglements that enhance mechanical durability against both bending (with a curvature radius of about 110 μm) and stretching (with 80% tensile strain) and result in stable performance during 10,000 magnetization cycles. With the anisotropic design, the printed sensors achieve high out-of-plane sensitivity, distinguishing them from traditional film-based counterparts with a predominant in-plane response. These sensors do not require physical contact during operation, fostering hygienic and safer interaction. Their robust performance under environmental interference (e.g., dust, liquid, and moisture) makes them versatile for real-world use. The above innovations position our sensor as an important driver across numerous emerging applications, e.g., touchless interactive transparent displays and integrated multifunctional windows.