Cell Imaging by Phonon Microscopy

Variation in the mechanical properties of a cell such as stiffness often provides little or no optical contrast when illuminated with light. Mechanical information is directly related to cell characteristics such as cell mobility, adherence or division and there is an interest in measuring these properties with the aim of revealing underlying mechanisms. Current methods for this purpose include acoustic microscopy [1], atomic force microscopy [2], Brillouin microscopy [3] and photoacoustic microscopy [4] where the last two, for single cell applications, are still in their infancy. Given the dimensions of a cell, extraction of useful mechanical information is challenging – cells are very sensitive to environmental stimulus and they are very difficult to measure without causing an undesired reaction. In that sense, conventional mechanical imaging systems often struggle, while at the same time their resolution often remains below that of conventional optical microscopy. Despite this, mechanical characterization of cells has been shown to be significant. For instance, in the field of cancer research, diseased cells were found to have different mechanical properties compared to healthy cells [5].