Chemical signal-responsive fibers

Fiber-optic chemical sensors are composed of a sensing material and a transducer. The transducer converts the recognition and sensing events obtained by the sensing materials into a response such as an optical signal. Optical measurements can provide rapid, sensitive, and nondestructive analysis of many important compounds. In fiberoptic chemical sensors, optical fibers are used to transmit the optical signal to the measurement device, enabling a remote detection of the analyte in the sample. The use... 

In general, optical-based pH measurement techniques require relatively expensive and cumbersome instruments, and their sophisticated method cannot be easily carried out for routine assay. Interfering contact and reactions of the dye molecules, particularly considering in-vivo measurements, cannot be excluded [34], Some other possible factors, such as a weaker signal at shorter response times, complications in microfabrication, and difficulties in attaching the chemical or biological agents to the small fiber tip, are potential limitations for the application of these optical sensors to in-vivo measurements in micro environments [35]. 

Optical fiber detectors (OFD) are devices that measure electromagnetic radiation transmitted through optical fibers to produce a quantitative signal in response to the chemical or biochemical recognition of a specific analyte. Ideally, an OFD should produce a specific and accurate measurement, continuously and reversibly, of the presence of a particular molecular species in a given sample medium. Additionally, OFD should pro vide maximum sensitivity and minimal interferences fromsuperfluous ions or molecules to obtain low detection limits. Other attractive features include the miniaturization of the fiber s tip to accommodate single-cell analysis and portable instrumentation to allow in situ analysis. 

Advantages cited for fiber sensors include their small size and low cost. In contrast to electrical measurements, where the difference of two absolute potentials must be measured, fiber optics are self-contained and do not require an external reference signal. Because the signal is optical, there is no electrical risk to the patient, and there is no direct interference from surrounding electric or magnetic fields. Chemical analysis can be performed in real-time with almost an instantaneous response. Furthermore, versatile sensors can be developed that respond to multiple analytes by utilizing multiwavelength measurements. 

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