Fast on-off jet control of aerosol jet printing (AJP) using internal rotary valve

Aerosol jet printing (AJP) has been used in additive manufacturing sectors because it has advantages over conventional printing due to its capability of micro-pattern printing on various surfaces including a non-flat (3D) substrate with higher aspect ratio. Since the aerosol systems rely on continuous jet stream, one of the key issues is how to control the on-off of the jets to obtain desired patterns. An external shuttering system outside the nozzle was used to block the jet on non-printing regions. However, there are some downsides, for example, non-optimal stand-off distance due to mechanical interference, unwanted accumulation of the ink on the shutter, and possible mechanical interference when printing on curved surface or surfaces with protrusions. The purpose of this study is to develop AJP system with an internal rotary valve to eliminate the problems of the external shutter. The proposed internal two-way rotary valve can select the jet direction for printing or diverting the jet stream to the air. However, there was jetting delay because it takes time to stabilize the internal pressure. This delay results in non-uniform printing especially when resuming printing from off. In this study, we investigate the pressure behaviors of the flow cell under internal shutter on-off conditions and proposed a new flow rate control method capable of fast on-off control for uniform printing.