Abstract
This work demonstrates the improvement of mass detection sensitivity and time response using a simple sensor structure. Indeed, complicated technological processes leading to very brittle sensing structures are often required to reach high sensitivity when we want to detect specific molecules in biological fields. These developments constitute an obstacle to the early diagnosis of diseases. An alternative is the design of coupled structures. In this study, the device is based on the piezoelectric excitation and detection of two GaAs microstructures vibrating in antisymmetric modes. GaAs is a crystal which has the advantage to be micromachined easily using typical clean room processes. Moreover, we showed its high potential in direct biofunctionalisation for use in the biological field. A specific design of the device was performed to improve the detection at low mass and an original detection method has been developed. The principle is to exploit the variation in amplitude at the initial resonance frequency which has in the vicinity of weak added mass the greatest slope. Therefore, we get a very good resolution for an infinitely weak mass: relative voltage variation of 8%/1 fg. The analysis is based on results obtained by finite element simulation.
Highlights
Over recent decades there has been a growing interest in multiplexed, miniaturized, automated and cost-effective analytical techniques for environmental control, medical research and pharmacological screening
The current study is based on the microcantilever structures which have been previously demonstrated as suitable and inexpensive compared with other structures for biological field applications
The operating range which is one of the criteria for transducer characterization is given by Equation (6). It can be deduced from the initial microcantilever mass m, the resonance frequency of the selected mode fR and the half-width of the resonance peak at 10% of the relative variation in amplitude: Range ≈
Summary
Over recent decades there has been a growing interest in multiplexed, miniaturized, automated and cost-effective analytical techniques for environmental control, medical research and pharmacological screening. Measurement mass techniques by conventional sensors require an important miniaturization to achieve sensitivity in the zeptogram range [1,2,3,4,5,6,7,8]. These manufacturing techniques remain complicated to develop and control. Coupled structures present other advantages such as the opportunity to perform on the same substrate differential measurements or to obtain a multiplexed analysis of a biological or chemical solution. We show the design of our device, describe the microfabrication process of the structure and present some preliminary results
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