Traction force microscopy : an inverse problem with pointwise observations

Orateur : Guido VITALE (Laboratoire de Mécanique des Solides - Ecole Polytechnique, Palaiseau, France)

Traction Force Microscopy is an inversion method that allows to obtain the stress field applied by a living cell on the environment on the basis of a pointwise knowledge of the displacement produced by the cell itself. This classical biophysical problem, usually addressed in terms of Green functions, can be alternatively tackled using a variational framework and then a finite elements discretization. In such a case, a variation of the error functional under suitable regularization is operated in view of its minimization. This setting naturally suggests the introduction of a new equation, based on the adjoint operator of the elasticity problem. In this talk we illustrate the rigorous theory of the two— and three— dimensional problem, involving in the former case a distributed control and in the latter case a surface control. The pointwise observations require to exploit the theory of elasticity extended to forcing terms that are Borel measures. Moreover, we also illustrate a numerical strategy of the inversion method that discretizes the partial differential equations associated to the optimal control problem by finite elements. A detailed discussion of the numerical approximation of a test problem (with known solution) that contains most of the mathematical difficulties of the real one, allows a precise evaluation of the degree of confidence that one can achieve by in the numerical results.

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