Plasmon resonances in gold-coated tilted fiber Bragg gratings

The transmission spectrum of fiber Bragg gratings with gratings planes tilted at a small angle (2°-10°) relative to the fiber axis shows a large number of narrowband cladding mode resonances within a 100 nm wide spectrum. When a gold coating with a thickness between 10 and 30 nm is deposited on the fiber, the transmission spectrum shows anomalous features for values of the outside medium refractive index between 1.4211 and 1.4499. These features are shown to correspond to the excitation of surface plasmon resonances at the external surface of the gold film

High resolution interrogation of tilted fiber grating SPR sensors from polarization properties measurement

The generation of surface plasmon resonances (SPRs) in gold-coated weakly tilted fiber Bragg gratings (TFBGs) strongly depends on the state of polarization of the core guided light. Recently, it was demonstrated that rotating the linear state of polarization of the guided light by 90° with respect to the grating tilt allows to turn the SPR on and off. In this work, we measure the Jones matrix associated to the TFBG transmission properties in order to be able to analyze different polarization-related parameters (i.e. dependency on wavelength of polarization dependent loss and first Stokes parameter). As they contain the information about the SPR, they can be used as a robust and accurate demodulation technique for refractometry purposes. Unlike other methods reported so far, a tight control of the input state of polarization is not required. The maximum error on refractive index measurement has been determined to be ~1 10(-5) refractive index unit (RIU), 5 times better than intensity-based measurements on the same sensors

Arthrobots

This paper describes a class of robots—“arthrobots”— inspired, in part, by the musculoskeletal system of arthropods (spiders and insects, inter alia). An exoskeleton, constructed from thin organic polymeric tubes, provides lightweight structural support. Pneumatic joints modeled after the hydrostatic joints of spiders provide actuation and inherent mechanical compliance to external forces. An inflatable elastomeric tube (a “balloon”) enables active extension of a limb; an opposing elastic tendon enables passive retraction. A variety of robots constructed from these structural elements demonstrate i) crawling with one or two limbs, ii) walking with four or six limbs (including an insect-like triangular gait), iii) walking with eight limbs, or iv) floating and rowing on the surface of water. Arthrobots are simple to fabricate, inexpensive, light-weight, and able to operate safely in contact with humans.Chemistry and Chemical Biolog

Surface plasmon resonance fiber sensor for real-time and label-free monitoring of cellular behavior

This paper reports on the application of an optical fiber biosensor for real-time analysis of cellular behavior. Our findings illustrate that a fiber sensor fabricated from a traditional telecommunication fiber can be integrated into conventional cell culture equipment and used for real-time and label-free monitoring of cellular responses to chemical stimuli. The sensing mechanism used for the measurement of cellular responses is based on the excitation of surface plasmon resonance (SPR) on the surface of the optical fiber. In this proof of concept study, the sensor was utilized to investigate the influence of a number of different stimuli on cells-we tested the effects of trypsin, serum and sodium azide. These stimuli induced detachment of cells from the sensor surface, uptake of serum and inhibition of cellular metabolism, accordingly. The effects of different stimuli were confirmed with alamar blue assay, phase contrast and fluorescence microscopy. The results indicated that the fiber biosensor can be successfully utilized for real-time and label-free monitoring of cellular response in the first 30. min following the introduction of a stimulus. Furthermore, we demonstrated that the optical fiber biosensors can be easily regenerated for repeated use, proving this platform as a versatile and cost-effective sensing tool

Plasmonic Optical Structures: Tilted FBGs excite optical-fiber plasmons

A plasmon-based sensor created from a standard single-mode optical fiber uses tilted Bragg gratings and gold coatings to form a biological sensor useful under a wide range of conditions

Intrinsic temperature sensitivity of tilted fiber Bragg grating based surface plasmon resonance sensors

A miniature surface plasmon resonance sensor is fabricated from a gold-coated standard optical fiber with an in-core tilted fiber Bragg grating fabricated by UV exposure. The sensor has a measured refractive index sensitivity of 571.5 nm/RIU (refractive index unit) at constant temperature. We show here that the intrinsic temperature sensitivity of this device is reduced to less than 6.3 pm/°C (between 23 °C and 59 °C) when measurements are referenced to a core mode reflection resonance of the grating. This residual sensitivity is essentially that of the 50 nm thick deposited gold layer but it is bigger by one order of magnitude than the expected value (0.51 pm/°C) for a gold-water interface

Surface plasmon resonance optical fiber biosensor for label-free characterization of biomolecular interactions

A fiber sensor was applied to monitor the interaction of biomolecules. Results indicate that the biosensor can be successfully applied for a wide range of biomolecular characterizations including identification of the biomolecules' binding constants