Refractometric Sensing of Protein in Urine by the Photonic Crystal Fiber Biosensor in THz Regime

The presence of albumin in human urine is one of the confirmed early symptoms of kidney dysfunction. A precise urine protein identification process is very important to monitor the kidney's proper functioning. To identify the presence of albumin in urine, a refractometric protein sensing approach in the photonic crystal fiber (PCF) environment has been introduced here. A PCF geometry with suspended cladding and a circular hollow core has been proposed and investigated in the terahertz (THz) spectrum for protein identification in the liquid samples. Three levels of albumin concentrations in urine (7-125 mg/dl, 250-500 mg/dl, and 1000 mg/dl) are considered to evaluate the sensing performances of the proposed PCF. The numerical investigations are performed on the COMSOL Multiphysics platform where the finite element method (FEM) figures out the numerical outcomes. The performances of the proposed PCF exhibit highly sensitive characteristics for albumin identification in the different albumin concentration levels of urine. The sensitivity shows more than 98.5% for all the tested concentration levels due to the strategic selection of geometrical parameters and proper optimization. Alongside, negligible confinement loss of 10-16 cm-1 is attained at the same operating point of 4.3 THz. Furthermore, dispersion profiles and practical implementation strategies are also investigated and discussed in detail.