A cooling fan comprises an impeller which includes a plurality of radially extending blades, each of which includes a blade hub, a blade tip and a blade midspan approximately midway between the hub and the tip. The acrylic adhesive is applied to the felt substrate in a dip and squeeze operation, which passes a felt web through a trough of adhesive and then through an excess adhesive removal station, after which, a protective releasable polymer film is applied to the exposed adhesive surfaces prior to curing step. And a discharge of the fast debris from the target material is also suppressed and extinguished by heating and then vaporizing them by a light beam for transpiration which is emitted at an adjusted time after the generation of the plasma.