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A new type of human immunoglobulin G (IgG) sensors based on the surface plasmon resonance (SPR) in the low refractive index (RI) plastic optical fiber (POF) and an antibody immobilization method is presented. A 50-nm-thick gold film was formed on the polished D-shaped fiber surface by magnetron sputtering. The RI response of the POF sensor is 30 049.61 nm/RIU, which is 26.5 times higher than that of single mode fiber (SMF) SPR sensors. The proposed SPR biosensor can be developed by simple and rapid modification of the gold film with 11-mercapto undecanoic acid (MUA). Upon immobilization of the goat anti-human IgG antibody, the resonance wavelength shifts by 11.2 nm. The sensor can be used to specifically detect and quantify the human IgG at concentrations down to 245.4 ng/mL with the sensitivity of 1.327 7 nm per µg/mL, which offers an enhancement of 12.5-fold compared to that of the conventional SMF based SPR sensors. The proposed device may find the potential applications in the case of use at the point of care. [ABSTRACT FROM AUTHOR]

Optical manipulation is a non-contact and non-destructive method to capture and manipulate micro/nano particles, biological macromolecules and cells with application of optical forces. With the rapid development of optical manipulation, various kinds of optical fiber tips have been presented and demonstrated in recent years. In this letter, a novel structure of optical fiber tip with an imbedded hollow cavity is presented. The electric field distribution of the fiber tip and the influence of cavity geometry are simulated with finite-difference time-domain method. The unique advantage is that the electric field intensity will be significantly enhanced when the fiber tip is filled with high refractive index medium in the cavity, which brings the potential to generate a three-dimensional optical trap for particles. Through experiments, we also demonstrate that the velocity of the particles driven by the optical force has a quadratic relationship with the laser power. The relationship can be used in microfluidic technology to measure the velocity of micro fluid. And the balance between the scattering force and the fluid force can be used to study non-invasive migration of particles. [ABSTRACT FROM AUTHOR]