Sub-100 nm IR spectromicroscopy of living cells.

We have performed IR spectromicroscopy of cells immersed in liquid water, with a lateral resolution better than 100 nm. Here, we use the motion of an atomic force microscope tip, probing the local transient deformation induced by an IR pulsed laser tuned at a sample absorbing wavelength. By Fourier analysis of the vibration of the cantilever tip, we can discriminate frequencies that are characteristic of the object, thus eliminating the influence of the water absorption. This opens the door of chemical imaging of living species in vivo, with spatial resolution of the order of the size of cell components.