Добірка наукової літератури з теми "MEMS Nanomechanical Platform"

Nanomechanical characterization of vertically aligned micro- and nanopillars plays an important role in quality control of pillar-based sensors and devices. A microelectromechanical system based scanning probe microscope (MEMS-SPM) has been developed for quantitative measurement of the bending stiffness of micro- and nanopillars with high aspect ratios. The MEMS-SPM exhibits large in-plane displacement with subnanometric resolution and medium probing force beyond 100 micro-Newtons. A proof-of-principle experimental setup using an MEMS-SPM prototype has been built to experimentally determine the in-plane bending stiffness of silicon nanopillars with an aspect ratio higher than 10. Comparison between the experimental results and the analytical and FEM evaluation has been demonstrated. Measurement uncertainty analysis indicates that this nano-bending system is able to determine the pillar bending stiffness with an uncertainty better than 5%, provided that the pillars’ stiffness is close to the suspending stiffness of the MEMS-SPM. The MEMS-SPM measurement setup is capable of on-chip quantitative nanomechanical characterization of pillar-like nano-objects fabricated out of different materials.

Detecting the concentration of Pb2+ ions is important for monitoring the quality of water due to it can become a health threat as being in certain level. In this study, we report a nanomechanical Pb2+ sensor by employing the complementary metal-oxide-semiconductor microelectromechanical system (CMOS MEMS)-based piezoresistive microcantilevers coated with PEDOT:PSS sensing layers. Upon reaction with Pb2+, the PEDOT:PSS layer was oxidized which induced the surface stress change resulted in a subsequent bending of the microcantilever with the signal response of relative resistance change. This sensing platform has the advantages of being mass-produced, miniaturized, and portable. The sensor exhibited its sensitivity to Pb2+ concentrations in a linear range of 0.01–1000 ppm, and the limit of detection was 5 ppb. Moreover, the sensor showed the specificity to Pb2+, required a small sample volume and was easy to operate. Therefore, the proposed analytical method described here may be a sensitive, cost-effective and portable sensing tool for on-site water quality measurement and pollution detection.

A compact piezoresistive microcantilever platform integrated by MEMS technique provides a convenient and reliable approach for biochemical detection. In contrast to the conventional double free-standing piezoresistive cantilever beams of heterogeneous sensing surfaces, a single free-standing piezoresistive microcantilever sensor was first proposed with the elimination of interference of chemical effect. The single beam piezoresistive sensor which is temperature-sensitive was well controlled within ±0.2°C by introducing the novel method of self elimination of thermal effect. This new approach maintains device compactness with no additional use of bulky temperature-controlled apparatus, and significantly reduces noises of temperature coefficient of resistance (TCR) and bimorph effect. The C-reactive protein (CRP) detection of the microcantilever biosensor with self elimination of thermal effect was verified with the concentration of 100 μg/mL in a room-temperature environment.

This paper presents the development and implementation of a robust nonlinear control framework for piezoresistive nanomechanical cantilever (NMC)-based force tracking with applications to high-resolution imaging and nanomanipulation. Among varieties of nanoscale force sensing platforms, NMC is an attractive approach to measure and apply forces at this scale when compared with other previously reported configurations utilizing complicated MEMS devices or inconvenient-to-handle nanowires and nanotubes. More specifically, a piezoresistive layer is utilized here to measure nanoscale forces at the NMC’s tip instead of bulky laser-based feedback which is commonly used in Atomic Force Microscopy (AFM). In order to track a predefined force trajectory at the NMC’s tip, there is a need to model the piezoresistive NMC and design appropriate controller to move its base to provide the desired force. In previous publications of the authors, a new distributed-parameters modeling framework has been proposed to precisely predict the force acting on the microcantilever’s tip. In contrast to this approach and in an effort to ease the follow-up controller development, the NMC-based force sensor is modeled here as a lumped-parameters system. However, replacing the NMC with a linear mass-spring-damper trio, creates a variety of uncertainties and unmodeled dynamics that need to be addressed for a precise force sensor’s read-out. Moreover, the very slow response of NMC’s piezoresistive layer to force variations at the NMC’s tip, makes the tracking problem even more challenging. For this, a new controller is proposed to overcome these roadblocks. Using extensive numerical simulations and experimental results it is shown that utilizing the proposed controller instead of the commonly used PID controller can significantly enhance the controller’s stability and performance characteristics, and ultimately the imaging resolution and manipulation accuracy needed at this scale.