Table 1.

Characteristics and challenges of MJ

	Characteristics	Challenges
Method	Droplets of ink are deposited from the nozzle into thin layers, then cured with cooling air and in the presence of high-energy light, such as ultraviolet (UV)[10]. The droplet flight path, droplet impact, and surface wetting can change the geometry of the product[11]. MJ can tune the drug composition during the printing process[12]. MJ can work with thermal or piezoelectric nozzle[13].	In some cases, MJ needs support structure[14]. It is necessary to perform a post-processing for removing the support structure[15].
Material	MJ works with melted polymers and waxes, UV curable resins, solutions, suspensions, and complex multicomponent fluids[11]. MJ used waxes as the first materials[10]. This process can use photosensitive polymers but requires further processing to remove the photoinitiator[10]. This process can use multimaterials and full color[10].	The viscosity can affect the optimization requirement[12]. The materials are photosensitive (e.g., sensitive to daylight), and the mechanical properties degrade over time[14].
Quality	The quality and the curing method depend on material properties[10]. The final product has homogeneous mechanical and thermal properties[14].	The final product has poor mechanical properties[14].

MJ: Material jetting, UV: Ultraviolet