Effect of Coating Viscoelasticity on Quality Factor and Limit of Detection of Microcantilever Chemical Sensors

“…The total displacement at the tip is the relevant response quantity for sensor applications that utilize optical (laser) monitoring of the tip position, while the tip's bending-deformation displacement at or near resonance will be approximately proportional to the beam's bending strain, i.e., it will correspond to the output signal of sensors that employ local piezoresistive elements for monitoring beam response (e.g., the piezoresistive Wheatstone bridge employed in [19] [20,[29][30][31]). …”

Section: Problem Statementmentioning

confidence: 99%

“…All of these studies were primarily motivated by the desire to reduce the detrimental effects of fluid damping and fluid inertia, thus providing higher resonant frequencies, fres , and quality factors, Q , the latter corresponding to sharper resonant peaks. Within the context of sensing applications, such improvements in the resonant characteristics correspond to enhancements in sensor performance metrics such as mass or chemical sensitivity and limit of detection, especially for liquid-phase detection (e.g., [20,[29][30][31]). …”

Section: Introductionmentioning

confidence: 99%

Lateral-Mode Vibration of Microcantilever-Based Sensors in Viscous Fluids Using Timoshenko Beam Theory

Schultz

Heinrich

Josse

et al. 2015

J. Microelectromech. Syst.

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To more accurately model microcantilever resonant behavior in liquids and to improve lateral-mode sensor performance, a new model is developed to incorporate viscous fluid effects and "Timoshenko beam" effects (shear deformation, rotatory inertia). The model is motivated by studies showing that the most promising geometries for lateral-mode sensing are those for which Timoshenko effects are most pronounced.Analytical solutions for beam response due to harmonic tip force and electrothermal loadings are expressed in terms of total and bending displacements, which correspond to laser and piezoresistive readouts, respectively. The influence of shear deformation, rotatory inertia, fluid properties, and actuation/detection schemes on resonant frequencies (fres) and quality factors (Q) are examined, showing that Timoshenko beam effects may reduce fres and Q by up to 40% and 23%, respectively, but are negligible for width-tolength ratios of 1/10 and lower. Comparisons with measurements (in water) indicate that the model predicts the qualitative data trends but underestimates the softening that occurs in stiffer specimens, indicating that support deformation becomes a factor. For thinner specimens the model estimates Q quite well, but exceeds the observed values for thicker specimens, showing that the Stokes resistance model employed should be extended to include pressure effects for these geometries.

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“…This decrease in the quality factor increases the frequency noise (which is proportional to f res /Q when operating in an oscillator configuration 40,67,68 ), thus increasing the limit of detection (LOD) in biochemical sensing applications. The quality factor is defined as 2p times the ratio of the maximum energy stored in a resonating system to the amount of energy dissipated in one cycle.…”

Section: Quality Factormentioning

confidence: 99%

Characteristics of laterally vibrating resonant microcantilevers in viscous liquid media

Cox

Josse

Heinrich

et al. 2012

Journal of Applied Physics

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The characteristics of microcantilevers vibrating laterally in viscous liquid media are investigated and compared to those of similar microcantilevers vibrating in the out-of-plane direction. The hydrodynamic loading on the vibrating beam is first determined using a numerical model. A semi-analytical expression for the hydrodynamic forces in terms of the Reynolds number and the aspect ratio (beam thickness over beam width) is obtained by introducing a correction factor to Stokes' solution for a vibrating plate of infinite area to account for the effects of the thickness. The results enable the effects of fluid damping and effective fluid mass on the resonant frequency and the quality factor (Q) to be investigated as a function of both the beam's geometry and liquid medium's properties and compared to experimentally determined values given in the literature. The resonant frequency and Q are found to be higher for laterally vibrating microcantilevers compared to those of similar geometry experiencing transverse (out-of-plane) vibration. Compared to transversely vibrating beams, the resonant frequency of laterally vibrating beams is shown to decrease at a slower rate (with respect to changes in viscosity) in media having higher viscosities than water. The theoretical results are compared to experimental data obtained for cantilevers completely immersed in solutions of varying aqueous percent glycerol. The increases in resonant frequency and Q are expected to yield much lower limits of detection in liquid-phase chemical sensing applications.

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Effect of Coating Viscoelasticity on Quality Factor and Limit of Detection of Microcantilever Chemical Sensors

Cited by 43 publications

References 21 publications

Theoretical Analysis of Strong-Axis Bending Mode Vibrations for Resonant Microcantilever (Bio)Chemical Sensors in Gas or Liquid Phase

Theoretical Analysis of Strong-Axis Bending Mode Vibrations for Resonant Microcantilever (Bio)Chemical Sensors in Gas or Liquid Phase

Lateral-Mode Vibration of Microcantilever-Based Sensors in Viscous Fluids Using Timoshenko Beam Theory

Characteristics of laterally vibrating resonant microcantilevers in viscous liquid media

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