In-vivo nano-scale infrared imaging and spectroscopy of cells in liquid environment

We report a breakthrough in observing living cells with infrared s-SNOM (scattering near-field microscope).(1, 2) To keep cells "happy" it is mandatory to avoid evaporation, oxygen attack, and mechanical distortion. We reported at IRMMW-THz 2019 that we successfully analyzed E. coli cells protected by graphene, but later had to realize that strong van der Waals forces squeeze cells and thus impair their metabolic functions.Here we demonstrate a new, satisfactory method of letting cells in nutrient broth adhere weakly to a biocompatible surface, SiN, where they can develop freely. We choose this material in form of an extremely thin (10 nm), free-standing membrane so that the s-SNOM tip can work on and probe through it from the other side at atmospheric conditions, while the tip-confined infrared near field reaches through this membrane largely unaffected.