Methods for controlling the flow of an aerosol in a print head of an aerosol jet printing system, and apparatuses for depositing an aerosol

Methods and apparatuses for controlling aerosol streams being deposited onto a substrate via pneumatic shuttering. The aerosol stream is surrounded and focused by an annular co-flowing sheath gas in the print head of the apparatus. A boost gas flows to a vacuum pump during printing of the aerosol. A valve adds the boost gas to the sheath gas at the appropriate time, and a portion of the two gases is deflected in a direction opposite to the aerosol flow direction to at least partially prevent the aerosol from passing through the deposition nozzle. Some or all of the aerosol is combined with that portion of the boost gas and sheath gas and is exhausted from the print head. By precisely balancing the flows into and out of the print head, maintaining the flow rates of the aerosol and sheath gas approximately constant, and keeping the boost gas flowing during both printing and shuttering, the transition time between printing and partial or full shuttering of the aerosol stream is minimized. The pneumatic shutterin