Sensor platforms

Caspases. Figure 2 Caspase activating complexes. Schematic representation of all described long prodomain caspase activation complexes. Each complex contains essentially three functionally different building blocks a sensor/platform, an adaptor and an effector in the form of a particular caspase. Some instigating ligands, possible outcomes and regulatory proteins are indicated. 

Lichlyter D, Haidekker MA (2009) Immobilization techniques for molecular rotors -towards a solid-state viscosity sensor platform. Sens Actuators B Chem 139 648-656... 

Recent developments in microsystems technology have led to the widespread application of microfabrication techniques for the production of sensor platforms. These techniques have had a major impact on the development of so-called Lab-on-a-Chip devices. The major application areas for theses devices are biomedical diagnostics, industrial process monitoring, environmental monitoring, drug discovery, and defence. In the context of biomedical diagnostic applications, for example, such devices are intended to provide quantitative chemical or biochemical information on samples such as blood, sweat and saliva while using minimal sample volume. 

Sensitivity impacts upon the limit of detection and resolution of the device, making it a key performance parameter. Recently, several strategies have been developed in order to provide sensitivity enhancements for optical sensor platforms based on both optical absorption and fluorescence phenomena. These strategies are the result of rigorous theoretical analyses of the relevant systems and, combined with polymer processing technology and planar fabrication protocols, provide a viable route for the development of low-cost, efficient optical sensor platforms. 

The primary focus of this chapter is on the sensor platform and, in particular, on the specific advantages conferred by planar platforms. 

The options available for sensor platforms for optical chemical and biosensors are primarily optical fibres, and planar platforms. 

Figure 4. A planar, evanescent-wave absorption-based sensor platform.

The absorption-based platforms described previously employed evanescent wave interrogation of a thin sensing layer coated onto a planar waveguide. A sensitivity enhancement strategy for optical absorption-based sensors based on planar, multimode waveguides was developed recently by us18. The objective was to apply this theory to the development of low-cost, robust and potentially mass-producible sensor platforms and the following section outlines the assumptions and predictions of this theoretical model. 

Figure 6. Optical absorption-based sensor platform under consideration for enhancement strategy.

The demand for mass-producible, low-cost diagnostic chips has had a significant impact on the development trends for optical sensor platforms. Arguably the most important characteristics of recent systems are the integration of multiple functionalities onto a single platform, the ability to perform multianalyte detection and the production of low-cost sensor platforms. These strategies are intended to maximise the viability of a device for development as a commercial product. 

B. Grocholsky, A. Makarenko, and H. Durrant-Whyte, Information-theoretic coordinated control of multiple sensor platforms, in Proceedings of the IEEE International Conference on Robotics and Automation, Taipei, Taiwan, September 2003, pp. 1521-1526. 

The interferometric sensor platform is highly sensitive and is the only one that provides an internal reference for compensation of refractive-index fluctuations and unspecific adsorption. Interferometric sensors have a broader dynamic range than most other types of sensors and show higher sensitivity as compared to other integrated optical biosensors . Due to the high sensitivity of the interferometer sensor the direct detection of small... 

The underwater sensor platform is derived from the Fido explosives vapor sensor, originally developed under the Defense Advanced Research Projects Agency (DARPA) Dog s Nose Program. The vapor sensor, whose operation is discussed in Chapters 7 and 9 and in other publications [7-9], was developed for the task of landmine detection. The underwater adaptation of the sensor is very similar to the vapor sensor. In the underwater implementation of the sensor, thin films of polymers are deposited onto glass or sapphire substrates. The emission intensity of these films is monitored as water (rather than air) flows past the substrate. If the concentration of TNT in the water beings to rise, the polymer will exhibit a measurable reduction in fluorescence intensity. The reduction in emission intensity is proportional to the concentration of target analyte in the water. Because the sensor is small, lightweight, and consumes little power, it proved to be ideal for deployment on autonomous platforms. 

T. Wagner, T. Yoshinobu, C. Rao, R. Otto andM.J. Schoning, All-in-one solid-state device based on a light-addressable potentiometric sensor platform, Sens. Actuators B Chem., 117(2) (2006) 472—479. 

This chapter focuses on the approach we followed for developing a novel electrochemical sensor platform based on disposable polymer microchips with integrated microelectrodes for signal transduction. It presents the development of the so-called Immuspeed technology, which is dedicated to quantitative immunoassays with reduced time-to-results as well as sample and reagent volumes. Prior to presenting the specific characteristics of Immuspeed, the basic principles integrated in this platform are first presented and illustrated with reference to... 

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