A method to preparing suspensions of metal or metal alloy nanoparticles in an ionic liquid involves the physical vapor deposition of a metal or a mixture of metals onto an ionic liquid. Various solid or liquid ingestible compositions are provided for determining storage temperature, temperature of the user, temperature of the ingestible, particularly comestibles, and the like. The plug includes tungsten and fills up the opening. A twisted bitline may be used for array arrangement. Also, as will be described, the pre-erase of a servo channel and writing to a servo channel may be done by making two passes over a single head or by using two or more heads to perform both steps.