Fiber biosensor exploiting the microfiber light polarization modulation

An optical fiber biosensor is demonstrated exploiting the detection of microfiber light polarization modulation. Microfiber is immersed in the magnetic fluid (MF) which contains carboxylated magnetic nanoparticles (CMNPs), without needing the modification of the microfiber surface. While, only an external magnetic field is utilized. Self-assembly of CMNPs is induced after adding bovine serum albumin (BSA) into the MF. The microfiber light polarization modulation relaxation time is prolonged, when external magnetic field is applied or removed for a given period of time. The concentration of BSA solution can be detected by detecting the maximum light polarization degree, or detecting the difference between the maximum and minimum polarization degree. The signal processing system of the biosensor is not only simple but also cost effective. Moreover, biomasses, such as virus, biotin, DNA, and phosphate compounds can also be detected using our scheme.