Virtual valve in a MEMS-based cooling system

An active cooling system comprising:

• a plurality of piezoelectric cooling cells, each of the plurality of piezoelectric cooling cells including a chamber and a cooling element, the chamber having sidewalls, at least a portion of a bottom plate including a plurality of orifices therein, and a vent in a top of the chamber, the cooling element residing in the chamber between the vent and the bottom plate and defining a top chamber and a bottom chamber in the chamber, the cooling element being in communication with a fluid, the cooling element being actuated to undergo vibrational motion to draw fluid into the chamber through the vent and to drive the fluid through the plurality of orifices, the cooling element being actuated to alternately open and close a virtual valve of at least one virtual valve, the virtual valve being between the top chamber and the bottom chamber, the at least one virtual valve being open for a low flow resistance and closed for a high flow resistance, the virtual valve remaining physically open when the virtual valve is closed.

A method of cooling a heat-generating structure, comprising:

• driving a cooling element to induce vibrational motion, a piezoelectric cooling cell including a chamber and the cooling element, the chamber having sidewalls, a bottom plate including a plurality of orifices therein, and a vent in a top of the chamber, the cooling element residing in the chamber between the vent and the bottom plate and defining a top chamber and a bottom chamber in the chamber, the cooling element being in communication with a fluid, the cooling element being driven to undergo the vibrational motion to draw fluid into the chamber through the vent and to drive the fluid through the plurality of orifices, the cooling element being actuated to alternately open and close a virtual valve of at least one virtual valve, the virtual valve being between the top chamber and the bottom chamber, the at least one virtual valve being open for a low flow resistance and closed for a high flow resistance, the virtual valve remaining physically open when the virtual valve is closed.