**1. Introduction**

"Biological microelectromechanical systems" (BioMEMS) is a special class of Microelectromechanical systems (MEMS) where biological matter is manipulated for analyses and meas‐ ures of its activity, characterisations under any class of scientific study. The BioMEMS-based devices are an attractive area of development based on microtechnology. The techonolgy has more exciting developments in the application of MEMS technology in recent decades. For scientific analysis and measurement, various novel sensor and detection platforms in the BioMEMS and microfluidic fields are required and have been reported, in addition to basic components, such as microchannels, micropumps, microvalves, micromixers and microreac‐ tors for flow management at microscopic volumes [1]. Any of the most important applica‐ tions based on BioMEMS are: biomedical and biological analysis and measurements, micro total analysis systems (µTAS) and lab-on-a-chip systems [2-5], which will give new applica‐ tions in biomedicine and biology, especially the ability to perform point-of-care measure‐ ments. The advantages of such systems are that they can deliver and process the biological or biomedical samples in microvolumes for testing and analysis in an integrated way there‐ fore dramatically reducing the requirement to the manipulation steps and the samples, and improving data quality and quantitative capabilities. The BioMEMS technology also helps to reduce overall cost and time for the measurement. At the same time it improves the sensitiv‐ ity and specificity of the analysis.

To the BioMEMS technology and application, biosensors play a critical role in the process of information gathering with the technologically advanced development of our civilization, demand for information. With new applications in the areas – genetics, diagnostics, drug discovery, environment and industrial monitoring, quality control as well as security and threat evaluation [6], the need for high throughput label-free multiplexed sensors for biolog‐ ical sensing has increased in the last decade.

© 2013 Sang et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Sang et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A biosensor is a device for the detection of an analyte that combines a biological component with a physicochemical detector component [7]. In general, one concept of biological sensors encompasses two main features in addition to the associated signal processors used for the display of the results in a user-friendly way: the sensitive biological element which is a chemically receptive or selective layer, and the transducer or the detector element (it can work in a physico-chemical way, optical, piezoelectric, electro-chemical, etc.) that transforms the signal induced by the interaction between the analytes and the biological element into another more easily measured and quantified signal, Figure 1. The chemical layer provides specific binding sites for the target analyte of interest, such as molecules, proteins and cells. To most biological and chemical sensors, sensitivity has been increased tremendously in re‐ cent years, but it still has some deficiency and needs more improvement. The selectivity of the receptive layer can be designed employing principles of molecular and biomolecular rec‐ ognition; for example antigen-antibody binding (i.e. any chemicals, bacteria, viruses, or pol‐ len binding to a specific protein)[8]. Other surface functionalizations such as self-assembled monolayer [9, 10] and polymer coatings are also employed. The selectivity is then achieved by a specific chemical reaction on the functionalized sensor's surface. However, absolute se‐ lectivity remains a major challenge. In fact, most sensing technologies are faced with the is‐ sue of non-specific interactions which can complicate the sensor response, produce false positives, and affect the reproducibility and the suitability of the sensor system for a particu‐ lar application. Therefore, the chemical layer must be designed to maximize the sensor's sensitivity to the specific response.

**Figure 1.** Generalized schematic representation of a biological sensor [11]

Once the analyte is recognized by the chemical layer, the transducer converts the chemical stimulus into a measurable output signal, as shown in Figure 1. Both the chemical layer and the physical transducer impose limitations on the performance of a certain class of sensors. Nevertheless it is often the physical transducer which determines the limits of detection at‐ tainable. The search for new transduction principles is therefore constantly stimulated [8]. In fact, each step depicted in Figure 1 has an influence on the sensor's performance. From the mechanism that drives the analyte to the sensor (e.g. microfluidic, activated diffusion, etc.), to the instrument reading the output signal of the transducer; all stages are the subject of extensive research efforts.

Besides, microfluildic technology is a frequent technology which is used in biosensors. Mi‐ crofluidic devices or components have emerged in the beginning of the 1980s and were quickly used in the development of inkjet print heads, Deoxyribonucleic Acid (DNA) chips, lab-on-a-chip technology and micro-thermal devices. Microfluidics can precisely control and manipulate fluids and analytes that are geometrically constrained to a small size, typically sub-millimeter, and scale. One of the most attractive applications of microfluidics has been in biomedical and life science diagnostics [12]. µTAS applications are attractive because of the potential of such systems to allow faster analysis of biological material. Further they can reduce the requirement to the amount of reagent and the number of processing steps. In ad‐ dition, miniaturization of such systems can result in higher repeatability and precision of analysis, lower power consumption, and the potential to create portable diagnostic tools for on-site analysis. These advantages result not only in time and cost savings for diagnostic tests, but can also be life saving in time-critical environments such as critical medical diag‐ nostics or biowarfare pathogen detection.
