Microcantilevers, biosensors

M. Sepaniak, P. Datskos, N. Lavrik, and C. Tipple, Microcantilever Transducers A New Approach in Sensor Technology, Anal. Chem. 2002, 74, 568A C. Ziegler, Cantilever-Based Biosensors. Anal. Bioanal. Chem. 2004, 379, 946. 

New boxed applications include an arsenic biosensor (Chapter 0). microcantilevers to measure attograms of mass (Chapter 2), molecular wire (Chapter 14), a fluorescence resonance energy transfer biosensor (Chapter 19), cavity ring-down spectroscopy for ulcer diagnosis (Chapter 20), and environmental mercury analysis by atomic fluorescence (Chapter 21). 

Key words Microcantilever, Nanomechanical biosensors, MEMs, Immunoassay, Pesticide detection,... 

The working principle of the family of biosensors based on nanomechanical transducers, and specifically on microcantilevers, involves the translation of biochemical reactions into a mechanical movement in the nanometer range. In microcantilever sensors, the biochemical receptor layer is directly in contact with one of the cantilever surface. The biomolecular recognition process between the receptor layer and its corresponding analyte induce... 

The next step is the application of the microcantilever as biosensor in the environmental control field, by following an immunological detection scheme. For this purpose, we present the inhibition immunoassay performed to detect the highly toxic organochlorine insecticide compound dichlorodiphenyltrichloroethane (DDT). 

Campbell, G. A., Mutharasan, R Detection of pathogen Escherichia coli 0157 H7 using self-excited PZT-glass microcantilevers. Biosensors and Bioelectronics 2005, 21 (3), 462 73... 

Another compelling feature of microcantilever sensors is that they can be operated in air, vacuum, or liquid (P). The danq>ing effect in a liquid medium, however, reduces the resonance response of a microcantilever. In most liquids, the observed resonance response is approximately an order of magnitude smaller than that in air. The bending response, however, remains unaffected by the presence of a liquid medium (10-14). Iberefore, the feasibility of operating a microcantilever in a solution with hi sensitivity makes the microcantilever an ideal choice for biosensors. In addition, highly selective biochemical interactions can be used to regulate molecular adsorption and tune microcantilever response. 

Several popular laser-based biosensors, SPR, optic fibers, waveguides, and microcantilever biosensors, will be summarized below. 

Biosensors Using Lasers, Fig. 7 Scheme of the optical readout method for a microcantilever bending evaluation. The displacement of the free end of the cantilever is measured by monitoring the optical deflection of an incident laser beam on a position-sensitive detector... 

Biosensors Using Lasers, Fig. 8 Working principle of the microcantilever atomic force biosensor... 

Zhang XR, Xu XF (2004) Development of a biosensor based on laser-fabricated polymer microcantilevers. Appl Phys Lett 85 2423-2425... 

Among voltammetric MEMS biosensors, a piezoresistive microcantilever is a good example. The general configuration of a piezoresistive microcantDever sensor is shown in Fig. 4. The stress caused by biochemical reactions is concentrated on the surface of the microcantUever. Piezoresistors are usually placed on the microcantilever to the rim, where the stress is maximal. When the microcantilever is bent due to biochemical reaction, the resistivity of the microcantilever is changed. And by measuring the change, the concentration of the biochemical is detected [7]. 

MEMS-Based Biosensor, Fig. 4 Schematic and cross-sectional view of a piezoresistive microcantilever [7]... 

Microcantilever biosensor pSi is fabricated on the surface of crystalline Si microcantilevers by vapor phase stain etch Improved sensitivity of sensor Stolyarova et al. 2008... 

The resistive-type sensors measure strain-related mechanical properties such as strain, force, acceleration, and pressure-utilizing piezoresistive properties of sensitive film resistors [2,14,38,39]. These sensors are also incorporated as biosensors for detecting biomolecules. The electrode configuration is the same as in electrochemical transducers, but it measures the change of resistance when biomolecules interact with the biologically sensitive elements [2]. The piezoresistive microcantilever sensors are also extensively studied for biosensing. The piezoresistive sensors. 

The representative techniques currently applied for an efficient, specific, rapid detection of viruses are described by Cay gill et al. Among them, electrochemical biosensors based on amperometric, potentiometric, and impedance measurements, optical biosensors that use surface plasmon resonance, optical fibers and piezoelectric biosensors based on microcantilevers, and recently the use of nanoparticles and novel nanomaterials as alternate recognition surfaces have been widely applied. 

Fu L, Li S, Zhang K, Cheng ZY, Barbaree J (2007) Detection of Bacillus anthracis spores in water using biosensors based on magnetorestrictive microcantilever coated with phage. Proc SPIE 6556 655619... 

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