Non-contact reflectometric readout of disposable microfluidic devices by near infra-red low-coherence interferometry

Abstract

We are here demonstrating the functionality of infra-red low-coherence reflectometry for the spot optical readout of solution concentrations in commercially available microfluidic devices. Disposable polymeric microfluidic devices composed by 100-µm-deep channels were connected to an external fluidic path that allowed flow-through of water-glucose solutions at different concentrations. Measurements were performed with near-infrared low-power sources, namely a tungsten lamp and a Superluminescent Light Emitting Diode (SLED), allowing the read-out in a wavelength region of minimum invasiveness for biological fluids. The selected optical scheme based on an all-fiber Michelson configuration is well suited for non-contact, remote investigations of the fluids flowing in plastic microfluidic devices, with arbitrary layout and thickness. For the first time, using the SLED, we exploited the double round trip of light in the fluid channel for doubling the sensitivity with respect to the standard single pass set-up, previously demonstrated.

Keywords

• optical low-coherence reflectometry
• infrared radiation
• microfluidics
• concentration measurements
• disposable devices
• Michelson interferometer