A comparative study of Polarimetric sensing with freestanding n-type porous silicon and porous alumina membrane

Abstract

Sensors are everywhere in the modern world, and every aspect of our lives, including security, domestic, and environmental factors, is being monitored. Improving the precision and quality of such analysis are highly valued if more sophisticated, intelligent, and capable systems are available. This paper discusses the practical use of polarimetric sensing on n-type porous silicon and porous alumina freestanding membranes (Whatman-anodic membranes with pore widths of 200 nm and thicknesses of 60 μm). “In-plane and out-of-plane birefringence” is investigated for both types of free-standing membranes. With NaCl solution and a constant flow rate in flow-through mode, the sensing capability of these freestanding membranes, namely porous silicon freestanding membranes (15.54 μm thick) and porous alumina freestanding membranes (60 μm thick), was investigated. These two sensor systems have a sensitivity of 0.25°/ %NaCl and 0.30°/ %NaCl, respectively. Freestanding membranes have 8.32°/RIU-μm and 3.01°/RIU-μm sensitivity, respectively. Porous silicon and porous alumina freestanding membranes are used in conjunction with flow-through bovine serum albumin (BSA) sensor as the principal model system for LOC devices. The results support the increased sensitivity achieved in porous silicon membranes over porous alumina membranes.