The invention is directed to methods for the propagation or cultivation of cells including preparing a cell culture substrate, wherein the cell culture substrate includes a substrate and a layer formed by surface modification. According to a preferred embodiment of the present invention, the electric knife also includes a shield that that is adapted to prevent fruit or vegetable matter from entering the housing of the electric knife. Respective internal electrodes are located on internal surfaces of the through holes and an outer conductor is formed on at least some of the outer surfaces.