High Dynamic Range Thin‐Film Resistive Flow Sensors for Monitoring Diverse Biofluids

Abstract Monitoring biofluid flow can serve as an important indicator for understanding physiological conditions, detecting diseases, and evaluating therapeutic responses. However, existing flow sensors suffer from rigid designs, large sizes, non‐biocompatible materials, poor integrability, and complex fabrication processes, which hinder their adaptation to biological environments. Furthermore, existing sensors have limited dynamic ranges, restricting their ability to capture the full spectrum of biofluid flow rates. This study addresses these challenges by introducing a library of thin‐film serpentine resistive flow sensors engineered for seamless biological integration. These sensors employ two distinct sensing mechanisms: 1) thermoresistive sensing and 2) piezoresistive sensing, which are implemented through innovative cavity and origami‐inspired architectures. They are fabricated with biocompatible platinum thin films and miniaturized to sub‐millimeter active areas via femtosecond laser micromachining. Their functionality is demonstrated across diverse biofluid analogs, saline, oil, and blood, covering nearly the full biofluid flow rate spectrum in humans, demonstrating potential adaptability for biological applications such as wearable sweat monitoring, implantable closed‐loop drug delivery and wound healing management.