title: Model-based estimation of 3-D stiffness parameters in photonic-force microscopy.
abstract: We propose a system to characterize the 3-D diffusion properties of the probing bead trapped by a photonic-force microscope. We follow a model-based approach, where the model of the dynamics of the bead is given by the Langevin equation. Our procedure combines software and analog hardware to measure the corresponding stiffness matrix. We are able to estimate all its elements in real time, including off-diagonal terms. To achieve our goal, we have built a simple analog computer that performs a continuous preprocessing of the data, which can be subsequently digitized at a much lower rate than is otherwise required. We also provide an effective numerical algorithm for compensating the correlation bias introduced by a quadrant photodiode detector in the microscope. We validate our approach using simulated data and show that our bias-compensation scheme effectively improves the accuracy of the system. Moreover, we perform experiments with the real system and demonstrate real-time capabilities. Finally, we suggest a simple adjunction that would allow one to determine the mass matrix as well.
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne(EPFL), EPFL/School of Engineering (STI)/Institut de Microtechnique(IMT)/Laboratoire d'Imagerie Biomédicale (LIB), CH-1015 Lausanne VD, Switzerland. philippe.thevenaz@epfl.ch
authors.forename: P
authors.initials: P
authors.lastname: Thévenaz
authors.forename: A S G
authors.initials: AS
authors.lastname: Singh
authors.forename: E
authors.initials: E
authors.lastname: Bertseva
authors.forename: J
authors.initials: J
authors.lastname: Lekki
authors.forename: A J
authors.initials: AJ
authors.lastname: Kulik
authors.forename: M
authors.initials: M
authors.lastname: Unser
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004548:Elasticity; D008853:Microscopy / Q000295:instrumentation / Q000379:methods; D009010:Monte Carlo Method; D052898:Optical Tweezers; D015203:Reproducibility of Results; D012984:Software