Table 2.

Some corresponding solutions for possible problems in EHD 3D printing

Existed problems	Alternative solutions
Reducing the size of droplet	For large conductivity (≥10−4 S/m)	Reducing flow rate, increasing voltage
	For small conductivity (<10−4 S/m)	Reducing flow rate, minimizing diameter of nozzle outlet
Increasing precision of placement	Keeping a small distance between nozzle and substrate
Increasing yielding rate	Increasing numbers of nozzle
Alleviating end effects from neighboring nozzle	Inserting nonconductive/dummy nozzles; inserting metal nozzles into nonconductive materialbased multinozzle structure; increasing distance between neighboring nozzle; changing the shape of nozzle array
Eliminating disturbance due to surface irregularity of the substrate, such as uneven surface, restriction of standoff distance, nonconductive material	Changing configuration of electrodes, such as nozzlering type; applying sinusoidal AC voltage and print droplet whose charge alternates between positive and negative charges