A vehicle on-board charging assembly includes at least one power electronics module and a coolant channel in thermal contact with the at least one power electronics module. The charging assembly also includes a first reactive portion along a wall of the coolant channel defining a first reactive property and a second reactive portion along the wall of the coolant channel defining a second reactive property. The charging assembly further includes a plurality of emitters arranged to activate the first and second reactive portions. The charging assembly also further includes a controller programmed to sequentially activate the emitters to cause peristaltic pumping of coolant through the coolant channel.