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.
Normalized Phase shift as a function of sample rotation relative to its surface, a PSi sample with 60 mA/cm2b Porous alumina sample. c Real time sensing with PSi FSM, and d sensing with Porous alumina FSM at a wavelength of 1350 nm. [Display omitted]
•Optical anisotropy of n-type PSi membranes with pore morphologies and porous alumina was studied in-plane and out-of-plane.•Real-time sensing with n-type PSi FSM and porous alumina membranes revealed that n-type PSi FSM had greater sensitivity.•For the respective FSM, sensitivity of 8.32°/RIU μm and 3.01°/RIU μm was recorded.•Sensor required a little quantity of analyte solution and had a rapid sensing time due to the simplicity of the FT design.•The results open new avenues for the development of n-type PSi-based LOC devices that are both fast and highly sensitive.