  A subminiature mesoscopic cell, consisting of an asymmetric double quantum
dot capacitively coupled to a nearby mesoscopic circuit, is proposed, which can
transform disordered noise energy to ordered electric energy. Two schemes, the
noise originating from the nearby mesoscopic circuit and from the
electromagnetic wave disturbance in external environment, are investigated. We
found that the proposed cell can manifest as a good constant current source and
the output current may not reach its largest value even if the circuit is
shorted.
