High-performance fiber-optic hot-wire flowmeter based on surface plasmon resonance and PDMS

In this work, a novel and simple fiber-optic hot-wire flowmeter based on a polydimethylsiloxane (PDMS)-coated gold-plated multimode-no-core fiber (MNF) tip is proposed and demonstrated. The gold coating not only excites the surface plasmon resonance (SPR) effect but also absorbs the laser energy to generate heat. Additionally, the sensor probe is coated with a temperature-sensitive layer of PDMS. The flow of fluids dissipates heat, causing the PDMS to reach different thermal equilibrium temperatures corresponding to certain flow rates. The experimental results prove that the real-time response of PDMS to external microfluidics can be used to sense flow rate and temperature via monitoring the dip wavelength of SPR. The sensor achieves a maximum flow rate sensitivity of 7.27 nm/(μL/s), with a detection limit of 27.5 nL/s. The response time of the sensor to flow rate change is 1.31 s. Furthermore, the PDMS coating enhances the stability and durability of the sensor. The sensor offers high sensitivity, simple fabrication, low cost, and other advantages, thereby promoting the industrial application of all-fiber-optic flow rate sensing devices.