Confocal Brillouin microscopy for the contactless mechanical characterization of biological cells

The mechanical characterization of cells is important to understand how cells react to changes in their microenvironment due to biochemical processes or injuries. Brillouin microscopy allows to determine a map of the local longitudinal modulus, which is an indicator of the local cell stiffness. For this purpose, the Doppler frequency shift of photons which were inelastically scattered on spontaneous acoustic phonons within the cell has to be evaluated with sub-GHz resolution. We present a confocal Brillouin microscopy setup capable of a volumetric and contactless characterization of highly scattering samples such as living cells and tissues. The setup is based on a two-stage virtually imaged phased array (VIPA) interferometer and a Rubidium absorption cell to achieve a sufficient frequency resolution and to suppress Rayleigh scattered light. As light source a 780 nm diode laser in combination with a Bragg grating is used. In our presentation, we will highlight the performance of the Brillouin microscope.