A switching circuit includes: a transistor having a first electrode, a second electrode and a control electrode; a zener diode; and a capacitor. The panel unit includes a series of planar panels assembled in an enclosing arrangement defining an enclosed area and is movable between an installation position where the sharp outer end of the Huber needle projects from the panel unit and a safety position where the sharp outer end is covered by the panels. The surface modifying polymer is combined with the bulk polymer, and, due to the presence of the moiety that favors migration, concentrates primarily on the surface of the bulk polymer such that the moiety that provides the activity of interest is located primarily on the surface of the bulk polymeric article which is produced.