A device configured to jet a plurality of separate droplets of a viscous medium over a period of time, the device comprising: a nozzle including an outlet , the nozzle configured to jet the plurality of droplets of the viscous medium through the outlet of the nozzle; a viscous medium conduit configured to direct a flow of the viscous medium to the outlet of the nozzle, the viscous medium conduit including an eject chamber in fluid communication with the outlet of the nozzle; an acoustic transducer configured to emit an acoustic signal that transfers acoustic waves into at least a portion of the viscous medium located in the eject chamber; an actuator configured to extend into the eject chamber to move viscous medium located within the eject chamber through the outlet of the nozzle; and a control device configured to: control the actuator to extend into the eject chamber to move viscous medium located within the eject chamber to jet the plurality of separate droplets through the outlet of the nozzle over the period of time, and control the acoustic transducer to emit the acoustic signal during the jetting of the plurality of droplets over the period of time, to transfer acoustic waves into the portion of the viscous medium to adjust at least one rheological property of the portion of the viscous medium located in the eject chamber during the jetting of the plurality of droplets. a nozzle including an outlet , the nozzle configured to jet the plurality of droplets of the viscous medium through the outlet of the nozzle; a viscous medium conduit configured to direct a flow of the viscous medium to the outlet of the nozzle, the viscous medium conduit including an eject chamber in fluid communication with the outlet of the nozzle; an acoustic transducer configured to emit an acoustic signal that transfers acoustic waves into at least a portion of the viscous medium located in the eject chamber; an actuator configured to extend into the eject chamber to move viscous medium located within the eject chamber through the outlet of the nozzle; and a control device configured to: control the actuator to extend into the eject chamber to move viscous medium located within the eject chamber to jet the plurality of separate droplets through the outlet of the nozzle over the period of time, and control the acoustic transducer to emit the acoustic signal during the jetting of the plurality of droplets over the period of time, to transfer acoustic waves into the portion of the viscous medium to adjust at least one rheological property of the portion of the viscous medium located in the eject chamber during the jetting of the plurality of droplets. control the actuator to extend into the eject chamber to move viscous medium located within the eject chamber to jet the plurality of separate droplets through the outlet of the nozzle over the period of time, and control the acoustic transducer to emit the acoustic signal during the jetting of the plurality of droplets over the period of time, to transfer acoustic waves into the portion of the viscous medium to adjust at least one rheological property of the portion of the viscous medium located in the eject chamber during the jetting of the plurality of droplets. <EOS>