3D bioprinting, in which living tissues are printed with cells mixed into soft hydrogels, or "bio-inks," is widely used in the field of bioengineering for modeling or replacing the tissues in our bodies. The print quality and reproducibility of tissues, however, can face challenges. One of the most significant challenges is created simply by gravity—cells naturally sink to the bottom of the bioink-extruding printer syringe because the cells are heavier than the hydrogel around them.