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Thomas Thundat - One of the best experts on this subject based on the ideXlab platform.
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standoff mechanical resonance spectroscopy based on infrared sensitive hydrogel Microcantilevers
Analytical Chemistry, 2016Co-Authors: Inseok Chae, Faheem M. Khan, Jungki Song, Taewook Kang, Thomas ThundatAbstract:This paper reports a highly sensitive and selective remote chemical sensing platform for surface-adsorbed trace chemicals by using infrared (IR)-sensitive hydrogel Microcantilevers. Poly(ethylene glycol) diacrylate (PEG-DA) hydrogel Microcantilevers are fabricated by ultraviolet (UV) curing of PEG-DA prepolymer introduced into a poly(dimethylsiloxane) mold. The resonance frequency of a PEG-DA microcantilever exhibits high thermal sensitivity due to IR irradiation/absorption. When a tunable IR laser beam is reflected off a surface coated with target chemical onto a PEG-DA microcantilever, the resonance frequency of the cantilever shifts in proportion to the chemical nature of the target molecules. Dynamic responses of the PEG-DA microcantilever can be obtained in a range of IR wavelengths using a tunable quantum cascade laser that can form the basis for the standoff mechanical resonance spectroscopy (SMRS). Using this SMRS technique, we have selectively detected three compounds, dimethyl methyl phosphonate...
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Standoff infrared spectroscopy on energetic materials using hydrogel Microcantilevers
2016 IEEE 29th International Conference on Micro Electro Mechanical Systems (MEMS), 2016Co-Authors: Inseok Chae, Faheem M. Khan, Jungki Song, Thomas ThundatAbstract:A standoff trace-chemical sensing system for the detection of highly energetic materials is developed by using infrared (IR) sensitive hydrogel microcantilever. Low cost, hydrogel Microcantilevers having rectangular cross-section are simply fabricated by ultraviolet curing of polyethyleneglycol diacrylate (PEGDA) introduced into a polydimethylsiloxane (PDMS) mold. For the first time, we are demonstrating that PEGDA Microcantilevers exhibit significant shifts of resonance frequency upon heating and IR. The IR absorption by target chemical weapons at specific IR wavelengths decreases the resonance frequency shift of the PEGDA microcantilever which provides a foundation for photothermal cantilever resonance spectroscopy (PCRS). Using this, we detect four different chemical weapons located four meters away from the PEGDA Microcantilevers with a limit of detection of 40 ng/cm2.
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photothermal spectroscopy of bacillus anthracis and bacillus cereus with Microcantilevers
Sensors and Actuators B-chemical, 2006Co-Authors: Edward T. Arakawa, Ali Passian, T L Ferrell, Thomas ThundatAbstract:Microcalorimetric optical and infrared spectroscopy is a method of determining the spectral absorption of small quantities of materials over a wide range of incident wavelengths. In this paper, the first spectroscopic results for Microcantilevers coated with Bacillus anthracis (BA) are presented. These results, for B. anthracis from 2.5 to 14.5 μm, are compared with results from Microcantilevers coated with Bacillus cereus (BC) and standard spectroscopic absorption data. The results demonstrate strong correlation between the deflection measurements and the reference spectroscopic absorption peaks. An advantage of this microcantilever-based method over traditional spectroscopy is that much smaller amounts of material (nanogram quantities) can be detected in comparison with the milligram amounts needed for standard methods. Another advantage is that the complete system can be relatively small without sacrificing spectral resolution.
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Influence of nanobubbles on the bending of Microcantilevers
Applied Physics Letters, 2006Co-Authors: Sangmin Jeon, Fang Tian, Ramya Desikan, Thomas ThundatAbstract:Young’s equation, which is commonly used for determining the contact angle of liquid drops on a solid surface, ignores the vertical component of the surface energy. Although this force is extremely small and its effect on the solid can be ignored, it plays a significant role for flexible surfaces such as Microcantilevers. A gold-coated silicon microcantilever and a dodecanethiol coated silicon microcantilever were used to detect real-time formation of nanobubbles on their surfaces when exposed to air-rich water. As air nanobubbles form on the surfaces of the cantilever, the cantilever undergoes bending, and we relate this to the vertical component of surface energy in Young’s equation. This implies that the vertical component of the surface tension should be considered for flexible solid surfaces, and the formation of nanobubbles should be avoided when cantilevers are used as sensors to avoid artifacts.
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Microcantilever biosensors.
Methods (San Diego Calif.), 2005Co-Authors: Karolyn M Hansen, Thomas ThundatAbstract:Biosensors are sensors in which biomolecular interactions are used as sensing reactions. Biomolecular interactions, when combined with a microcantilever platform, can produce an extremely powerful biosensing design. The resonance frequency of a microcantilever shifts sensitively due to mass loading from molecular interaction as in the case of any acoustic sensors. In addition, the Microcantilevers also undergo bending if the molecular adsorption is confined to a single surface of a microcantilever. This cantilever bending is due to a differential surface stress caused by the forces involved in the adsorption process and is amplified by making the cantilever surfaces chemically different. Lack of specificity, the main disadvantage of the cantilevers, can be overcome by using the extremely selective biochemical reactions such as receptor-ligand, antibody-antigen, or enzyme-substrate reactions. Here we review the microcantilever technology and discuss a number of highly sensitive biochemical sensor applications based on Microcantilevers.
Gregory P. Nordin - One of the best experts on this subject based on the ideXlab platform.
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Microcantilever Arrays with In-Plane Photonic Readout for Biosensing
2010Co-Authors: Gregory P. Nordin, Weisheng Hu, Ryan R. Anderson, Stan Ness, William Dahlquist, Daniel RichardsAbstract:Microcantilever sensors exhibit high sensitivity in both liquid and gaseous environments when operated in static deflection mode, in which adsorption of target molecules by a receptor coating on one side of a microcantilever results in microcantilever deflection due to a change in surface stress. However, traditional microcantilever transduction techniques have not lent themselves to high sensitivity readout of large scale arrays of Microcantilevers on a single chip. We have recently demonstrated a new in-plane photonic transduction method that is scalable to simultaneous readout of hundreds of Microcantilevers with a readout sensitivity comparable to the best achievable with the gold standard method of laser reflection such as used in atomic force microscopy [1-3]. Moreover, we are decreasing the thermal sensitivity issues of traditional microcantilever sensors by approximately two orders of magnitude through elimination of the commonly used Au adhesion layer for receptor molecule attachment. In addition, we have integrated multilayer PDMS microfluidics with microcantilever sensing arrays. Functionalization of individual Microcantilevers is performed with inkjet deposition.
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in plane photonic transduction of silicon on insulator Microcantilevers
Optics Express, 2008Co-Authors: Ryan R. Anderson, Jaime Cardenas, Gregory P. NordinAbstract:We demonstrate an in-plane photonic transduction method for Microcantilevers, which have been widely investigated for sensor applications. In our approach the microcantilever is etched to form a single mode rib waveguide. Light propagates down the microcantilever and crosses a small gap at the free end of the microcantilever, some of which is captured by an asymmetrical multimode waveguide that terminates in a Y-branch. The Y-branch outputs are used to form a differential signal that is monotonically dependent on microcantilever deflection. The measured differential signal matches simulation when microcantilever rotation is properly accounted for. The measured differential signal sensitivity is 1.4×10-4 nm-1 and the minimum detectable deflection is 0.35 nm.
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Photonic Readout of Microcantilevers for Sensor Applications
Frontiers in Optics, 2007Co-Authors: Ryan R. Anderson, Gregory P. NordinAbstract:We have developed an in-plane photonic transduction method for microcantilever sensors that permits high sensitivity readout of microcantilever deflection and is scalable to large numbers of Microcantilevers on a single chip.
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In-plane photonic transduction for microcantilever sensor arrays
Proceedings of SPIE, 2007Co-Authors: Gregory P. NordinAbstract:Microcantilevers show significant promise in sensing minute quantities of chemical and biological analytes in vapor and liquid media. Much of the reported work on microcantilever sensors has made use of single functionalized Microcantilevers, usually derived from commercially available atomic force microscope (AFM) cantilevers. However, arrays with hundreds to thousands of Microcantilevers on a single chip are required to create sophisticated, broad spectrum chemical and biological sensors in which individual Microcantilevers have different bio- or chemoselective coatings. Unfortunately, the most sensitive microcantilever readout mechanisms (such as laser beam reflection as used in atomic force microscopy) are not readily scalable to large arrays. We therefore introduce a new microcantilever transduction mechanism for silicon-on-insulator (SOI) Microcantilevers that is designed to scale to large arrays while maintaining a very compact form factor and high sensitivity. This mechanism is based on in-plane photonic transduction of microcantilever deflection in which the microcantilever itself forms a single mode rib waveguide. Light from the end of the microcantilever is directed across a small gap to an asymmetric receiving waveguide with two outputs that enables differential detection of microcantilever deflection. Initial noise and optical power budget calculations indicate that deflection sensitivities in the 10's of picometer range should be achievable.
Isabelle Dufour - One of the best experts on this subject based on the ideXlab platform.
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Resonant microcantilever devices for gas sensing
Advanced Nanomaterials for Inexpensive Gas Microsensors, 2019Co-Authors: Hélène Debéda, Isabelle DufourAbstract:Abstract This chapter is first devoted to the theory behind the detection principle of microcantilever gas sensors used in the dynamic mode. A microcantilever is covered with a sensitive layer for chemical detection, and the sorbed species can be detected by measuring the resonant frequency drop as mass increases. The importance of damping and, consequently, of the design of Microcantilevers for gas detection achieving low limits of detection is shown. Secondary effects such as temperature affecting the response of the gas microsensor are also discussed. Then, the materials and associated processes for the fabrication of Microcantilevers and their sensitive coatings are described, with emphasis on solutions proposed for low-cost and actuation/readout integration. Finally, examples of successful gas detection are shown.
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Resonant characteristics of rectangular hammerhead Microcantilevers vibrating laterally in viscous liquid media
2013 Joint European Frequency and Time Forum & International Frequency Control Symposium (EFTF IFC), 2013Co-Authors: Jinjin Zhang, Isabelle Dufour, Fabien Josse, Stephen Heinrich, Nicholas Nigro, Oliver BrandAbstract:The resonant characteristics of laterally vibrating rectangular hammerhead Microcantilevers in viscous liquid media are investigated. The rectangular hammerhead microcantilever is modeled as an Euler-Bernoulli beam (stem) and a rigid body (head). A modified semi-analytical expression for the hydrodynamic function in terms of the Reynolds number, Re, and aspect ratio, h/b, is proposed to rapidly evaluate the sensing characteristics. Using this expression, the resonance frequency, quality factor and normalized surface mass sensitivity are investigated as a function of the dimensions of the microcantilever and liquid properties. Guidelines for design of hammerhead microcantilever geometry are proposed to achieve efficient sensing platforms for liquid-phase operation. The improvement in the sensing area and characteristics are expected to yield higher sensitivity of detection and improved signal-to-noise ratio in liquid-phase chemical sensing applications.
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Resonant Microcantilevers vibrating laterally in viscous liquid media
2010 IEEE International Frequency Control Symposium, 2010Co-Authors: Fabien Josse, Isabelle Dufour, Stephen Heinrich, Oliver BrandAbstract:The characteristics of Microcantilevers vibrating in the in-plane flexural mode (also known as lateral vibration) in viscous liquid media are investigated. A numerical model was utilized to determine a correction to Stokes' solution for an infinite plate to obtain an analytical expression for the hydrodynamic forces acting on a laterally vibrating microcantilever as a function of both Reynolds number and aspect ratio (thickness over width). The results allowed for the resonant frequency and quality factor to be investigated as a function of both beam geometry and medium properties. Trends in these characteristics can be used to optimize device geometry and maximize the frequency stability. As the thickness of a microcantilever is increased, both its stiffness and the medium's viscous damping increase. This will lead to an optimum quality factor in terms of the thickness. The characteristics of laterally and transversely vibrating Microcantilevers with similar geometries are also compared. It is found that the resonant frequency and quality factor are higher for laterally vibrating Microcantilevers (at least by a factor of 2 to 3 or higher for the Q-factor depending on the geometry) compared to those of similar beams under transverse (or out-of-plane) vibration. The improvement in sensitivity (due to the increase in frequency) and in the quality factor (thus a reduced frequency noise) are expected to yield much lower limits of detection in liquid-phase chemical sensing applications.
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Modeling and performance of uncoated microcantilever-based chemical sensors
Sensors and Actuators B: Chemical, 2010Co-Authors: Sébastien Tétin, Claude Pellet, Benjamin Caillard, Hélène Debéda, Claude Lucat, Francis Menil, Isabelle DufourAbstract:Chemical sensors based on vibrating silicon Microcantilevers without sensitive coating are investigated herein. The sensor signal is the relative variation of the microcantilever resonant frequency which depends on both the viscosity and the density of the fluid surrounding the microcantilever. This principle has been applied to the detection of binary gas mixtures. Experimental data for He/N2 and CO2/N2 environments are presented and compared to results of theoretical modeling. The advantages of such a gas sensor based on changes of physical properties are discussed (response time, sensitivity, selectivity, stability). © 2009 Elsevier B.V. All rights reserved.
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Chemical sensing using microcantilever without sensitive coating
2009 IEEE International Frequency Control Symposium Joint with the 22nd European Frequency and Time forum, 2009Co-Authors: Sébastien Tétin, Claude Pellet, Benjamin Caillard, Hélène Debéda, Claude Lucat, Francis Menil, Isabelle DufourAbstract:Chemical sensors based on vibrating silicon Microcantilevers without sensitive coating are investigated herein. The sensor signal is the relative variation of the microcantilever resonant frequency which depends on both the viscosity and the density of the fluid surrounding the microcantilever. This principle has been applied to the detection of binary gas mixtures. Experimental data for He/N2 and CO2/N2 environments are presented and compared to results of theoretical modeling. The advantages of such a gas sensor based on changes of physical properties are discussed.
Tadatomo Suga - One of the best experts on this subject based on the ideXlab platform.
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self excited piezoelectric pzt Microcantilevers for dynamic sfm with inherent sensing and actuating capabilities
Sensors and Actuators A-physical, 1999Co-Authors: Toshihiro Itoh, Tadatomo SugaAbstract:Abstract Currently three crucial components are necessary for the dynamic SFM, they are the microcantilever, oscillator, and cantilever deflection sensor. We demonstrate a piezoelectric microcantilever made of PZT thin films for SFM. This PZT microcantilever can perform the same functions which have to be done by the three crucial components. It is able to excite itself when an ac voltage is applied to it, and actuate itself in z -directional displacement by a superimposed dc voltage, while force sensing is executed concurrently. Since the motional admittance can be derived from the piezoelectric current output when the PZT microcantilever is vibrated at resonance frequency, the motional admittance will vary as the change of vibrational amplitude. Thus the topography of the sample can be recorded as the trace of the difference between output signals of motional admittance. The piezoelectric coefficient d 31 of the PZT layer is about −58 pC/N. The dimensions of piezoelectric Microcantilevers used are 125×50×3.8 μm. The actuating ability is estimated as 75 nm/V. The vertical resolution of the self-excited PZT microcantilever can be derived as 1.2 A at the bandwidth of 125 Hz. Very clear images of a 1.0 μm pitch Au coated SiO 2 grating and an evaporated gold film on a smooth glass plate are obtained by an SFM using this self-excited force sensing PZT microcantilever. The invention of this smart PZT microcantilever endows the possibility of constructing a stand-alone micro SFM system and a multiprobe SFM system.
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Characterization of micromachined piezoelectric PZT force sensors for dynamic scanning force microscopy
Review of Scientific Instruments, 1997Co-Authors: Chengkuo Lee, Ryutaro Maeda, Toshihiro Itoh, Tadatomo SugaAbstract:The key component for the piezoelectric scanning force microscopy (SFM) is the piezoelectric force-sensing microcantilever. In this article, the resonance frequency and quality factor of Pb(Ti,Zr)O-3 (PZT) Microcantilevers; effective Young's modulus and piezoelectric Pb(Ti,Zr)O-3 property of PZT layer of piezoelectric Microcantilevers are discussed. The PZT Microcantilevers after poling have quality factors such as 204 to 248 in air, and 608 to 1094 in vacuum. The calculated spring constants are in the range of 1.0-30.0 N/m for cantilevers with 0.64-1.7-mu m-thick PZT layer and 125-300 mu m length. The force sensitivity and resolution of the PZT microcantilever are studied when it is oscillated by an external oscillator and applied to the cyclic contact SFM. Then the real transverse piezoelectric coefficient d(31) Of piezoelectric PZT thin films is derived from the measured sensitivity and effective Young's modulus. The derived effective Young's moduli of PZT layers slightly increases from 53.5 to 58 GPa as the thickness of the PZT layer increases. The d(31) is around -35 pC/N which is about 8 times larger than the value of ZnO, and half the value of bulk PZT ceramics. The sensitivity of 0.98 fC/nm can be obtained by PZT force sensors. The longitudinal resolution obtained is 1.5 Angstrom at a bandwidth of 125 Hz. Cantilevers with proper characteristics for different applications can be predicted, designed, and fabricated via the adjustment of the thickness ratio of each layer and the total thickness of the cantilever. Very clear images of an evaporated Au film on a smooth glass plate are obtained by an SFM with a PZT force sensor. (C) 1997 American Institute of Physics.
Sri Venkata Surya Siva Rama Krishna Garimella - One of the best experts on this subject based on the ideXlab platform.
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hydrodynamic loading of Microcantilevers vibrating in viscous fluids
Journal of Applied Physics, 2006Co-Authors: Sudipta Basak, Arvind Raman, Sri Venkata Surya Siva Rama Krishna GarimellaAbstract:The hydrodynamic loading of elastic Microcantilevers vibrating in viscous fluids is analyzed computationally using a three-dimensional, finite element fluid-structure interaction model. The quality factors and added mass coefficients of several modes are computed accurately from the transient oscillations of the microcantilever in the fluid. The effects of microcantilever geometry, operation in higher bending modes, and orientation and proximity to a surface are analyzed in detail. The results indicate that in an infinite medium, microcantilever damping arises from localized fluid shear near the edges of the microcantilever. Closer to the surface, however, the damping arises due to a combination of squeeze film effects and viscous shear near the edges. The dependence of these mechanisms on microcantilever geometry and orientation in the proximity of a surface are discussed. The results provide a comprehensive understanding of the hydrodynamic loading of Microcantilevers in viscous fluids and are expected to be of immediate interest in atomic force microscopy and microcantilever biosensors. © 2006 American Institute of Physics. DOI: 10.1063/1.2202232
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hydrodynamic loading of Microcantilevers vibrating in viscous fluids
Journal of Applied Physics, 2006Co-Authors: Sudipta Basak, Arvind Raman, Sri Venkata Surya Siva Rama Krishna GarimellaAbstract:The hydrodynamic loading of elastic Microcantilevers vibrating in viscous fluids is analyzed computationally using a three-dimensional, finite element fluid-structure interaction model. The quality factors and added mass coefficients of several modes are computed accurately from the transient oscillations of the microcantilever in the fluid. The effects of microcantilever geometry, operation in higher bending modes, and orientation and proximity to a surface are analyzed in detail. The results indicate that in an infinite medium, microcantilever damping arises from localized fluid shear near the edges of the microcantilever. Closer to the surface, however, the damping arises due to a combination of squeeze film effects and viscous shear near the edges. The dependence of these mechanisms on microcantilever geometry and orientation in the proximity of a surface are discussed. The results provide a comprehensive understanding of the hydrodynamic loading of Microcantilevers in viscous fluids and are expected to be of immediate interest in atomic force microscopy and microcantilever biosensors.