Polymeric optical fibre

Harlin, A., Myllymaki, H., Grahn, K., September 2002. Polymeric optical fibres and future prospects in textile integration. AUTEX Research Journal 2. 

Harlin, A., Makinen, M., Vuorivirta, A., 2003. Development of polymeric optical fibre fabrics as illumination elements and textile displays. Autex Research Journal 3 (1). 

Since ideally, a biosensor should be reagentless, that is, should be able to specifically measure the concentration of an analyte without a supply of reactants, attempts to develop such bioluminescence-based optical fibre biosensors were made for the measurements of NADH28 30. For this purpose, the coreactants, FMN and decanal, were entrapped either separately or together in a polymeric matrix placed between the optical fibre surface and the bacterial oxidoreductase-luciferase membrane. In the best configuration, the period of autonomy was 1.5 h during which about twenty reliable assays could be performed. 

The nonlinear optical and dielectric properties of polymers find increasing use in devices, such as cladding and coatings for optical fibres, piezoelectric and optical fibre sensors, frequency doublers, and thin films for integrated optics applications. It is therefore important to understand the dielectric, optical and mechanical response of polymeric materials to optimize their usage. The parameters that are important to evaluate these properties of polymers are their dipole moment polarizability a, hyperpolarizabilities 0... 

Optical fibres behave as wave guides for light. The original ones were made of glass but now polymeric materials are mostly used as they are cheaper than glass and metal wires. 

In one common method used with multimode fibres (Paik and Sung, 1994, Powell et al., 1995, 1998), the cladding is stripped from the optical fibre and the polymerizing network is sensed by the evanescent wave (Figure 3.43). 

For economic recycling of plastics, various types of polymeric materials have to be separated in a short period of time. The near-infrared spectral range allows the monitoring of structural or molecular properties of the plastic under investigation. The spectrometer system described is based on optical fibres for absorption and reflexion measurements, an acousto-optic tunable filter and a transputer system. It is able to detect 1,000 spectra/ s and to identify 20 pieces/second. 10 refs. 

More recently, hydroxy-substituted cobalt tetraphenylporphyrins, electro-polymerized onto an optically transparent electrode and adapted onto the tip of an optic fibre were used as sensing materials for the development of optic fibres as pH-sensors . The pH values by this chemically modified optic fibre were monitored by spectrophotometric measurement of the Soret band wavelength for the supported porphyrin. 

Many optical fibre chemical sensors employ optical fibre transducers that are interfaced with immobilized chemical reagent(s). At the chemical transducer end, active chemical/biochemical reagents are held on supporting polymeric matrices and covered by membrane materials in certain applications. The following sections review some developments in this field. 

Various techniques such as optical and electron microscopy, IR-ATR ESCA and SIMS have been used for failure mode analysis in polymeric adhesive joints. However, these techniques are not amenable for in situ, non-destructive examination of the failure surfaces as failure occurs. In order to develop in situ techniques, UV reflection and fluorescence methods are evaluated, as they can be applied via optical fibres to the actual failure surface. Failure surfaces of two types of adhesive joints are examined by UV reflection and fluorescence, complemented by FT-IR ATR studies. The first joint studied is PU on epoxy-coated steel. The second is PETP/PE/PETP. 8 refs. 

Raman is simple to use and require virtually no sample preparation. The vibrational spectra of polymer samples in their original forms can be measured and casting or hotpressing of the material into thin films (commonly used for FTIR measurements), a very time-consuming procedure that can affect the original structure of the material, are not required. It also offers remote analysis capabilities if combined with fibre optics [108, 109]. Accurate determination of contaminant content in recycled polymeric resins have been reported in the literature [110, 111, 112]. 

Hardware sensors for the on-line monitoring of polymerization such as in batch reactors have been reviewed (Kammona et al. 1999). In Section 3.4 the use of ruggedized conversion sensors for fibre-optic near-infrared (NIR) spectroscopy during extrusion was described. In many ways, the requirements are simpler than for control of a batch reaction (as in a polymer-synthesis autoclave) since... 

---