Test-Paper-Like Photonic Crystal Viscometer

A test-paper-like photonic crystal viscometer was proposed for the first time to determine the viscosity of liquid sample by its infiltration time to soak the PC film. For practical sensing, the infiltration time of standard samples obtained from TRRS and their known viscosities are first adopted to plot a working curve for a specific viscous fluid, which is then used to determine the unknown viscosity of a tested sample according to its measured infiltration time. By optimizing the microstructure of PC film, the optimal measurement range can be flexibly tuned to achieve more accurate or efficient sensing in the low- or high-viscosity end. The reported sensor is universal to many viscous liquids including silicone oil, mixture of EG and glycerol, and mixture of mineral oils. Compared to the traditional glass capillary viscometer, the PC-based viscometer provides a low cost and portable solution for on-site monitoring with disposable sensing material and small amount of sample required. The viscosity sensing can be flexibly accomplished either by an optical spectrometer or by naked-eye observation based on the change in reflection and structural colors.