Intracellular Nanomanipulation by a Photonic-Force Microscope with Real-Time Acquisition of a 3D Stiffness Matrix

E. Bertseva, A.S.G. Singh, J. Lekki, P. Thévenaz, M. Lekka, S. Jeney, G. Gremaud, S. Puttini, W. Nowak, G. Dietler, L. Forró, M. Unser, A.J. Kulik

Nanotechnology, vol. 20, no. 28, paper no. 285709, July 15, 2009.

A traditional photonic-force microscope (PFM) results in huge sets of data, which requires tedious numerical analysis. In this paper, we propose instead an analog signal processor to attain real-time capabilities while retaining the richness of the traditional PFM data. Our system is devoted to intracellular measurements and is fully interactive through the use of a haptic joystick. Using our specialized analog hardware along with a dedicated algorithm, we can extract the full 3D stiffness matrix of the optical trap in real time, including the off-diagonal cross-terms. Our system is also capable of simultaneously recording data for subsequent offline analysis. This allows us to check that a good correlation exists between the classical analysis of stiffness and our real-time measurements. We monitor the PFM beads using an optical microscope. The force-feedback mechanism of the haptic joystick helps us in interactively guiding the bead inside living cells and collecting information from its (possibly anisotropic) environment. The instantaneous stiffness measurements are also displayed in real time on a graphical user interface. The whole system has been built and is operational; here we present early results that confirm the consistency of the real-time measurements with offline computations.

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AUTHOR="Bertseva, E. and Singh, A.S.G. and Lekki, J. and Th{\'{e}}venaz,
        P. and Lekka, M. and Jeney, S. and Gremaud, G. and Puttini, S. and
        Nowak, W. and Dietler, G. and Forr{\'{o}}, L. and Unser, M. and
        Kulik, A.J.",
TITLE="Intracellular Nanomanipulation by a Photonic-Force Microscope
        with Real-Time Acquisition of a 3D Stiffness Matrix",
JOURNAL="Nanotechnology",
YEAR="2009",
volume="20",
number="28",
pages="",
month="July 15,",
note="{Paper no.\ 285709}")

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