Droplets with diameters from a few to hundreds of micrometers have found increasing applications in various fields. For inkjet printing, there is always a great need to control and reduce the droplet size for a given nozzle diameter and print viscous fluids by avoiding clogging. This study investigates the electric field-assisted droplet formation process under piezoactuation-based drop-on-demand (DOD) inkjet printing. For better control of droplet monodispersity, the Taylor cone is intentionally suppressed to avoid undesirable satellite droplets. The droplet formation process of deionized water is investigated, and some main conclusions are drawn as follows: (1) with an increase of applied voltage, the droplet velocity increases and the droplet size decreases, (2) the pinch-off location may be different depending on the applied voltage; and (3) the combination effect of the electric field and meniscus oscillation can be utilized to significantly reduce the droplet diameter to less than one-fifth of the orifice diameter. The electric field also demonstrates its capability in facilitating the DOD inkjet printing of high-concentration cell-alginate suspensions.
- Inkjet printing