A Flexible Thermal Flow Sensor with Quadruple Heaters and Suspended Structure for Performance Enhancement

For the first time, we report a novel flexible flow sensor with quadruple heaters and a suspended structure with excellent performance. The device was fabricated using platinum thermal resistors and ultra-thin Parylene C film (20 µm) integrated with a flexible silicone substrate with a cavity. Instead of using traditional hot wire or calorimetric design, the high-performance flow sensor was designed with a quadruple heaters (QH) structure, which benefits the circuit's simplicity and performance enhancement. Compared with the sensitivity of the hot wire mode (32.3 mV/m/s) and sensor with a non-suspended structure (13.7 mV/m/s), the proposed novel flow sensor achieved around one order magnitude higher sensitivity of 181.6 mV/m/s. Furthermore, the sensor also owns the characteristics of better symmetrically bidirectional sensing function, high repeatability, and stability. Additionally, with its excellent performance and flexible characteristic, the sensor is a promising candidate as a wearable respiration monitoring device for human health monitoring.