The disclosure relates to a sequential infiltration synthesis apparatus comprising: a reaction chamber constructed and arranged to accommodate at least one substrate; a first precursor flow path to provide the first precursor to the reaction chamber when a first flow controller is activated; a second precursor flow path to provide a second precursor to the reaction chamber when a second flow controller is activated; a removal flow path to allow removal of gas from the reaction chamber; a removal flow controller to create a gas flow in the reaction chamber to the removal flow path when the removal flow controller is activated; and, a sequence controller operably connected to the first, second and removal flow controllers and the sequence controller being programmed to enable infiltration of an infiltrateable material provided on the substrate in the reaction chamber. The apparatus may be provided with a heating system.