According to an aspect, there is disclosed a hot runner system (100), comprising: a first surface (205) being elastically deformable; a second surface (210) forming, in cooperation with the first surface (205), a melt-leakage gap (215) being located between the first surface (205) and the second surface (210); and an active material (220) being: (i) coupled with the first surface (205), (ii) held normally stationary, (iii) configured to be operatively coupled with a signal source (225), and (iv) configured to elastically deform in response to receiving a signal from the signal source (225), upon elastic deformation of the active material (220), the first surface (205) becomes moved toward the second surface (210) such that a size (235) of the melt-leakage gap (215) becomes controlled.