Detection waveguide

The reduction of dimensions also reduces volumes which are accessible to the detector. Thus, detection principles related to geometric dimensions of the detector cell ai e not ideally suited for coupling to microsystems, whereas surface sensitive principles, such as electrochemical methods or optical methods utilizing the evanescent field of a waveguide, or methods which can be focussed on a small amount of liquid, such as electrochemiluminescence (ECE), ai e better suited. This is why electrochemiluminescence detectors ai e combined to microsystems. Moreover ECE has found wide applications in biochemistry because of its high sensitivity, relatively simplicity and feasibility under mild conditions. 

Dasgupta PK, Genfa Z, Poruthoor SK, et al. 1998. High sensitivity gas sensors based on gas permeable liquid core waveguides and long-path absorbance detection. Submitted to Analytical Chemistry. 

A novel fiber optic sensor concept using antibody-antigen reactions at a glass-liquid interface was reported by Daehne146. The reaction of antibodies immobilized onto the surface of fused silica fiber optic or planar waveguides with antigens in solution was detected by interaction with the evanescent wave. By detecting in-line fluorescence, the measurement of human IgG is described. 

Murthy Ch.S., Pustogov V.V., Mizaikoff B., Inberg A., Croitoru N., Trace level gas detection using mid infrared hollow waveguides, Proc. 5th Europtrode (2000), Lyon, p.275. 

In recent years, the evolution of the technological components required for IR sensor systems has been denoted by a significant miniaturisation of light sources, optics and detectors. Essentially, an IR sensor consists of (i) a polychromatic or monochromatic radiation source, (ii) a sensor head and (iii) a spectral analyser with a detector. As sensors where all optical elements can be included in the sensor head are the exception rather than the rule, also various optics, waveguides and filters may form essential parts of IR-optical chemical sensors. Another important building block, in particular when aiming at sensors capable of detecting trace levels, are modifications of the sensor element itself. 

Worrell C. and Gallen N., Trace-level detection of gases and vapours with mid-infra-red hollow waveguides,./. Phys. D Appl. Phys., 1997 30 1984-1995. 

Rowe-Taitt C.A., Hazzard J.W., Hoffman K.E., Cras J.J., Golden J.P., Ligler F.S., Simultaneous detection of six biohazardous agents using a planar waveguide array biosensor, Biosensors and Bioelectronics 2000 15 579-589. 

Demarco D.R., Lim D.V., Detection of Escherichia coli 0157 H7 in 10-and 25-gram ground beef samples with an evanescent-wave biosensor with silica and polystyrene waveguides, J. Food Protect. 2002 65 596-602. 

A. Szekacs, N. Trummerb, N. Adanyi, M. Varadi, and I. Szendro, Development of a non-labeled immu-nosensor for die herbicide trifluralin via optical waveguide lightmode spectroscopic detection. Anal. Chim. Acta 487, 31-42 (2003). 

Conventional evanescent sensing works exceedingly well for relatively small biomolecules such as proteins and DNA molecules whose size is much smaller than the decay length. However, it becomes less sensitive when detecting biospecies, such as cells, with dimensions over 1 pm. In Chap. 15, deep-probe waveguide sensors are developed to overcome this limitation, which have a decay length comparable to the size of the biospecies of interest. 

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