A gap method for increasing the sensitivity of cantilever biosensors

Leahy, Stephane; Lai, Yongjun

doi:10.1063/1.4989959

Cited by 8 publications

(3 citation statements)

References 29 publications

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“…We used the PiezoMUMPs micromachining process [16] to fabricate two identical 200 µm long cantilevers. We designed the cantilevers so that their free ends are facing each other and are separated by a 2.7 µm gap [17] (see Figure 1). Each cantilever has a piezoelectric strip (aluminum nitride sandwiched between gold and doped silicon) at its fixed end and is suspended above a trench.…”

Section: Designmentioning

confidence: 99%

Doubling the quality factor of cantilevers in liquid through fluid coupling-based actuation

Leahy

Lai

2018

Journal of Applied Physics

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Dynamic-mode cantilevers are a promising tool for real-time biosensing applications due to their high sensitivity and ability to perform label-free measurements. However, operating dynamic-mode cantilevers in liquid is challenging since viscous damping greatly reduces their quality factor and thus limit of detection. We reasoned through physical analysis that if the motion of the surrounding fluid is driven by an external force and not by the sensing cantilever itself, then the dissipative fluid force on the cantilever could be reduced and the quality factor of the cantilever could be increased. Here we demonstrate a new fluid coupling-based actuation method where one piezoelectric cantilever (directly excited) is used to excite another closely located cantilever (indirectly excited) through vibrations transferred through the surrounding medium. We performed measurements in several mediums, including air, water, ethanol, and acetone and observed that the viscosity of the medium influences the effectiveness of fluid coupling-based actuation. We also observed that fluid coupling-based actuation is more effective for the first bending mode of the cantilever, likely since fluid motion decays with distance from the tip of the directly excited cantilever. A significant result is that the indirectly excited cantilever has a quality factor that is double that of the directly excited one for the first bending mode in water. This method could improve the performance of dynamic-mode cantilevers operated in liquid.

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Section: Designmentioning

confidence: 99%

Doubling the quality factor of cantilevers in liquid through fluid coupling-based actuation

Leahy

Lai

2018

Journal of Applied Physics

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“…Several concepts have been developed to address this issue, including use of higher order bending modes or specifically tailored geometries [21][22][23]. Another approach is provided by a co-resonant concept, which makes use of coupling and eigenfrequency matching of a micro-and a nanocantilever [8].…”

Section: Introductionmentioning

confidence: 99%

Precisely controlled batch-fabrication of highly sensitive co-resonant cantilever sensors from silicon-nitride

Lampouras,

Holz,

Strehle

et al. 2023

J. Micromech. Microeng.

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Dynamic-mode cantilever sensors are based on the principle of a one-side clamped beam being excited to oscillate at or close to its resonance frequency. An external interaction on the cantilever alters its oscillatory state, and this change can be detected and used for quantification of the external influence (e.g. a force or mass load).A very promising approach to significantly improve sensitivity without modifying the established laser-based oscillation transduction is the co-resonant coupling of a micro- and a nanocantilever. Thereby, each resonator is optimized for a specific purpose, i.e. the microcantilever for reliable oscillation detection and the nanocantilever for highest sensitivity through low rigidity and mass. To achieve the co-resonant state, the eigenfrequencies of micro- and nanocantilever need to be adjusted so that they differ by less than approximately 20 %. This can either be realized by mass deposition and trimming of the nanocantilever, or by choice of dimensions. While the former is a manual and error-prone process, the latter would enable reproducible batch fabrication of coupled systems with predefined eigenfrequency matching states and therefore sensor properties.However, the approach is very challenging as it requires a precisely controlled fabrication process. Here, for the first time, such a process for batch fabrication of inherently geometrically eigenfrequency matched co-resonant cantilever structures is presented and characterized. It is based on conventional microfabrication techniques and the structures are made from 1 µm thick low-stress silicon nitride. They comprise the microcantilever and high aspect ratio nanocantilever (width 2 µm, thickness about 100 nm, lengths up to 80 µm) which are successfully realized with only minimal bending. An average yield of > 80 % of intact complete sensor structures per wafer is achieved. Desired geometric dimensions can be realized within ± 1 % variation for length and width of the microcantilever and nanocantilever length, ± 10 % and ± 20 % for the nanocantilever width and thickness, respectively, resulting in an average variation of its eigenfrequency by 11 %. Furthermore, the dynamic oscillation properties are verified by vibration experiments in a scanning electron microscope.The developed process allows for the first time the batch fabrication of co-resonantly coupled systems with predefined properties and controlled matching states. This is an important step and crucial foundation for a broader applicability of the co-resonant approach for sensitivity enhancement of dynamic-mode cantilever sensors.

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“…The persisting challenge is the demand for increased sensitivity while at the same time ensuring reliable and robust oscillation detection. Several innovative ideas are studied for that purpose, for example use of higher order bending modes [3,4] or specifically tailored geometries [5].…”

Section: Introductionmentioning

confidence: 99%

Co-Resonant Cantilevers for Materials Research and Sensor Applications

Körner

2022

2022 Solid-State, Actuators, and Microsystems Workshop Technical Digest

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Employing co-resonant coupling in dynamic-mode cantilever MEMS sensors has the potential for a significant increase in sensitivity while maintaining a reliable oscillation detection. However, the resulting complex interplay between the micro-and nanocantilever has to be carefully considered for applicationspecific sensor design as it impacts all relevant sensor properties, such as linearity, stability and detectivity. Here, an overview of key parameters, their dependence on the strength of co-resonance and resulting consequences for sensor performance is provided.

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A gap method for increasing the sensitivity of cantilever biosensors

Cited by 8 publications

References 29 publications

Doubling the quality factor of cantilevers in liquid through fluid coupling-based actuation

Doubling the quality factor of cantilevers in liquid through fluid coupling-based actuation

Precisely controlled batch-fabrication of highly sensitive co-resonant cantilever sensors from silicon-nitride

Co-Resonant Cantilevers for Materials Research and Sensor Applications

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