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Modeling and control of MEMS tweezers for the characterizations of enzymateic reactions on DNA molecules

Authors
  • Lafitte, Nicolas
Publication Date
Apr 04, 2012
Source
HAL-UPMC
Keywords
Language
English
License
Unknown
External links

Abstract

The main objective of this Ph.D. is to achieve biological experiments on DNA molecules with versatile silicon nanotweezers. Experiments on single molecule rely on elaborated tools that have a low throughput since preparations are done one at a time. To move towards systematic and real-time analysis, design and fabrication of MEMS tweezers have been made by ourselves in the lab of Pr. H Fujita (U. of Tokyo, Japan). DNA molecules are firstly trapped in solution by dielectrophoresis. Then biological reaction on the DNA bundle is characterized in real-time by monitoring the mechanical resonance of the system {tweezers + DNA bundle}. The resolution of the measurements allowed the sensing of mechanical stiffness of about 30 of lambda-DNA molecule (i.e. about 20 mN/m). As it remains problematic to design and fabricate a new micro mechanical device with extremely low stiffness (< 1 N/m), state feedback control has been developed to emulate a system more sensitive to mechanical stiffness parameter detection. By simulations, it was demonstrated an enhancement of the sensitivity of about 10 when the resonant frequency of the closed-loop system is designed to be 10 times lower than the tweezers resonant frequency (i.e. reducing the equivalent stiffness of the system). Experimentally we demonstrated an improvement of the sensitivity superior to 2. However the issue is here to obtain stability and robustness with respect to disturbances and unmodeled dynamics. Before to attain the sensitivity of the single molecule, problematic about the model of the device or about the several dynamics of the device have been tackled in order to control and fit the improvement with the theory.

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