Fig. 1: Overall concept, design, and effects.

a Schematic diagram of AJ printing assisted with acoustic focusing (AF). A piezoelectric tube is attached to the nozzle of the original AJ printing system, which is excited by a signal generator through a power amplifier. b The APS are transported into the printhead by the carrier gas, then focused and sprayed by the sheath gas, and further focused through the annular acoustic field generated by the piezoelectric tube. c Schematic drawing of focusing behavior for APS when passing through the acoustic field. V_flow is the velocity, D₀ is the original diameter, and D_A is the focused diameter, of the ink flow, respectively. d Schematic drawing of AJ printed trace during the AF process. e, f Top and cross-section view of the APS distribution under the radial radiation force in the nozzle channel. g Force distribution on APS during the jetting process. V_axial and V_radial are the axial and radial particle velocity, respectively. V_jet is the particle jetting velocity.