A Study on Increasing Sensitivity of Rectangular Microcantilevers Used in Biosensors

Beyond biology: alternative uses of cantilever-based technologies

Micromechanical cantilever sensors are attracting a lot of attention because of the need for characterizing, detecting, and monitoring chemical and physical properties, as well as compounds at the nanoscale. The fields of application of micro-cantilever sensors span from biological and point-of-care, to military or industrial sectors. The purpose of this work focuses on thermal and mechanical characterization, environmental monitoring, and chemical detection, in order to provide a technical review of the most recent technical advances and applications, as well as the future prospective of micro-cantilever sensor research.

Modeling and analysis of nature-inspired branched micropillars for enhanced dynamic bio-sensing

Research evidence abounds on the effectiveness of micropillar-based microelectromechanical systems for the detection of a wide variety of ultrasmall biological objects for clinical and non-clinical applications. However, the standard micropillar-based sensing platforms rely on a single-column micropillar with a spot at the tip for binding of objects. Although this long-standing form has shown immense potential, performance improvement is hindered by the fundamental limits enforced by physical laws. Moreover, the single-column micropillar has a lower sensing area and is ill-suited for a simultaneous differential sensing of chemical/biological objects of different mass. Here, we report a new set of nature-inspired, branched micropillar-based sensing resonators to address the highlighted issues. The characteristics of the newly proposed branched micropillars are comprehensively examined with three payloads (Bartonella Bacilliformis, Escherichia coli, and Micro magnetic beads). Anchored on the capability of continuum theoretical framework, the mathematical model of the micropillar is formulated through the synthesis of the modified couple stress, the Rayleigh-Love, and the Timoshenko theories. The finite element method is employed to shed light on the variability of the structures' resonant response under performance reduction factors (payload's rotary inertia, damaged substrate, and density of a surrounding fluid). The results obtained indicate superior performance indicators for the triply-branched micropillar: enhanced response sensitivity for multiple payloads and less susceptibility to deterioration in resonant frequencies due to fluid immersion.

Atomic force microscopy as a tool applied to nano/biosensors

This review article discusses and documents the basic concepts and principles of nano/biosensors. More specifically, we comment on the use of Chemical Force Microscopy (CFM) to study various aspects of architectural and chemical design details of specific molecules and polymers and its influence on the control of chemical interactions between the Atomic Force Microscopy (AFM) tip and the sample. This technique is based on the fabrication of nanomechanical cantilever sensors (NCS) and microcantilever-based biosensors (MC-B), which can provide, depending on the application, rapid, sensitive, simple and low-cost in situ detection. Besides, it can provide high repeatability and reproducibility. Here, we review the applications of CFM through some application examples which should function as methodological questions to understand and transform this tool into a reliable source of data. This section is followed by a description of the theoretical principle and usage of the functionalized NCS and MC-B technique in several fields, such as agriculture, biotechnology and immunoassay. Finally, we hope this review will help the reader to appreciate how important the tools CFM, NCS and MC-B are for characterization and understanding of systems on the atomic scale.

Electrostatic excitation for the force amplification of microcantilever sensors

This paper describes an electrostatic excited microcantilever sensor operating in static mode that is more sensitive than traditional microcantilevers. The proposed sensor comprises a simple microcantilever with electrostatic excitation ability and an optical or piezoresistive detector. Initially the microcantilever is excited by electrostatic force to near pull-in voltage. The nonlinear behavior of the microcantilever in near pull-in voltage i.e., the inverse-square relation between displacement and electrostatic force provides a novel method for force amplification. In this situation, any external load applied to the sensor will be amplified by electrostatic force leading to more displacement. We prove that the proposed microcantilever sensor can be 2 to 100 orders more sensitive compared with traditional microcantilevers sensors of the same dimensions. The results for surface stress and the free-end point force load are discussed.

Design of a pressure sensor based on optical fiber Bragg grating lateral deformation

This paper describes steps involved in the design and realization of a new type of pressure sensor based on the optical fiber Bragg grating. A traditional pressure sensor has very limited usage in heavy industrial environments, particularly in explosive or electromagnetically noisy environments. Utilization of optics in these environments eliminates all surrounding influences. An initial motivation for our development was the research, experimental validation, and realization of a complex smart pressure sensor based on the optical principle. The main benefit of this solution consists of increasing sensitivity, resistance to electromagnetic interference, dimensions, and potential increased accuracy.

Comparison between Deflection and Vibration Characteristics of Rectangular and Trapezoidal profile Microcantilevers

Arrays of microcantilevers are increasingly being used as physical, biological, and chemical sensors in various applications. To improve the sensitivity of microcantilever sensors, this study analyses and compares the deflection and vibration characteristics of rectangular and trapezoidal profile microcantilevers. Three models of each profile are investigated. The cantilevers are analyzed for maximum deflection, fundamental resonant frequency and maximum stress. The surface stress is modelled as in-plane tensile force applied on the top edge of the microcantilevers. A commercial finite element analysis software ANSYS is used to analyze the designs. Results show paddled trapezoidal profile microcantilevers have better sensitivity.