The invention relates to an injection device, designed in particular for injecting fluid into an exhaust tract of an internal combustion engine, having a valve needle, an injection chamber having at least one injection opening, and a control chamber. The area for detecting water contact is formed on the rechargeable battery or its component parts by applying water-soluble ink on a surface thereof. The sol-gels can be fabricated to produce complex waveguide structures directly onto silica-on-silicon substrates with low bending losses.