Low-Cost and Scalable Flexible Infrared Detectors Based on VO ₂ (B) Nano-Ink: From Single-Device Sensing to Array Imaging

Vanadium oxide (VO x )-based uncooled infrared (IR) microbolometers have been commercially used in thermal sensing and imaging owing to their compact form factor, low power consumption, and high operational stability. However, the intrinsically low temperature coefficient of resistance (TCR) value of VO x compound, nonflexible devices, and costly fabrication processes remain critical bottlenecks for a wearable IR device or other specific applications. Here, we prepare a flexible IR thermal detector with VO 2 (B) nanosheet ink via a facile and scalable drop-casting strategy. Due to the achieved high TCR of VO 2 (B) up to 4.57% K –1 at room temperature, the IR device shows the responsivity of 9.84 A/W and a specific detectivity of 3.27 × 10 8 Jones at room temperature. This flexible IR sensor is utilized for respiratory rate monitoring, which demonstrates stable and sensitive performance. A prototype for noncontact digital IR imaging is realized through integration into a 5 × 5 flexible printed circuit array, showing the great potential for fabricating large-scale and high-pixel flexible IR detectors. Our work not only establishes a low-cost and scalable materials-to-device integration strategy for flexible IR thermal sensing but also paves the way for VO 2 (B)-based systems for next-generation wearable and large-area infrared imaging technologies.