Highly Sensitive Flow Sensor Based on Flexible Dual-Layer Heating Structures

Abstract

Hot film sensors detect the flow shear stress based on the forced convection heat transfer to the fluid. Current hot film sensors have been significantly hindered by the relatively low sensitivity due to the massive heat conduction to the substrate. This paper describes the design, fabrication, simulation, and testing of a novel flow sensor with dual-layer hot film structures. More specifically, the heat conduction was insulated from the sensing heater to the substrate by controlling both sensing and guarding heaters working at the same temperature, resulting in a higher sensitivity. The experiment and simulation results showed that the sensitivity of the dual-layer hot film sensor was significantly improved in comparison to the single-layer sensor. Additionally, the dual-layer sensor was designed and fabricated in an integrated, flexible, and miniaturized manner. Its small size makes it an excellent candidate for flow detection.

Recrystallization‐Induced Laser Lift‐Off Strategy for Flexible Thermal Sensors with Near‐Limit Sensitivity

“…The TCR of bulk nickel [ 28 ] is ≈6.4–6.9‰°C −1 , while the TCR of the thin film is generally lower than that of the block due to the electron scattering effect. In this work, the TCR of the thermal sensor can reach 6.2‰°C −1 , which is closer to the limit of bulk nickel and higher than other works [ 17–19,21,22,28,37–60 ] as shown in Figure 1e.…”

“…[9][10][11] Physical vapor deposition technology enables the deposition of temperature-sensitive metals in the form of DOI: 10.1002/admt.202301444 thin films on flexible organic substrates, such as polyimide (PI), [12] polyethylene terephthalate (PET), [13] polyvinyl alcohol (PVA), [14] polyurethane (PU). [15] Commonly used temperature-sensitive metals include nickel, [16,17] platinum, [18][19][20] gold, [21,22] and copper, [23] etc. However, many of the properties or characteristics of those metal films are entirely different from what they display in bulk form when materials shrink to dimensions on the nanoscale.…”

An Indirect Method for Determining the Local Heat Transfer Coefficient of Gas Flows in Pipelines

“…A large number of sensors (technical devices) and special techniques for conducting thermophysical experiments have been developed to implement these methods practically. One of the most common types of sensors are film sensors [3][4][5][6]. These sensors have a conductive film that is heated to a specific temperature to create a temperature difference between the flow and the surface.…”

“…Thermocouples under the film record the temperature change over time. Yan Y.-C. et al [3] developed a new film sensor based on a two-layer substrate structure. This made it possible to increase the sensitivity and accuracy of the measurement.…”