Abstract

Chronic kidney disease (CKD) has been one of the most severe public health issues in recent decades. Patients affected by CKD require a complicated and expensive treatment such as hemodialysis. The management of hemodialysis patients have been a particular challenge for nephrologists during the COVID-19 pandemic [1]. The accepted measure of dialysis dose is based on the removal of urea from the blood pool. Urea concentration is usually evaluated with the aid of blood samples that are analyzed in a clinical laboratory, but there is still the need of continuous monitoring of the dialysis efficiency to optimize clinical treatments. Hence, we have investigated and demonstrated an optofluidic sensing platform to detect urea content in water solutions by comparing light transmittance across a flat microfluidic channel with and without fluid. We considered the effect of absorption in the wavelength bands around λ = 1.45 μm and λ = 2.15 μm, where water and urea exhibit characteristic peaks of absorbance [2]. In the instrumental configuration (Fig. 1(a)), radiation provided by two LEDs crosses the microfluidic device and is finally detected in time domain with an amplified InGaAs photodiode, connected to the oscilloscope for data visualization and acquisition. The microfluidic device is a rectangular section borosilicate glass capillary (Vitrocom, NJ, USA) with two extremities provided with heat shrink tubes to facilitate injection of the fluid into the channel. Nominal channel length and depth of the channel are 50 mm and 1 mm, respectively.

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