The suitability of GelMA/bPE hybrid hydrogels as bioinks, beyond their rheological screening (Figure ), was validated in extrusion-based 3D printing (Figure ). First, cell-free hybrid inks with 5 wt% GelMA precursor solutions supplemented with increasing amounts of DbPEs and TbPEs were extruded at 37 °C to create model structures to evaluate printing performance (Figure ). As expected, the low-viscosity GelMA ink was not printable at 37 °C. Increasing incorporation of electrostatically self-assembling bPEs improved extrudability of the GelMA ink and shape fidelity after deposition, commensurate with the expectations from the rheological screening. The printability of these hybrid hydrogel bioinks also emphasizes the high accuracy of the rheological screening methodology. Ink compositions which were considered below the lower limit of printability according to rheology screening (i.e., 5 wt% GelMA + 10 wt% DbPE and 5 wt% GelMA + 5 wt% TbPE inks) were too fluid-like for printing and immediately started to flow and spread on the glass slide after deposition. The best resolution was achieved with the 5 wt% GelMA + 40 wt% DbPE ink; however, such high micelle concentration impeded with photochemical crosslinking of the GelMA precursor, thus leading to reduced crosslink density and loss of structural integrity during swelling. Moreover, when comparing the two types of bPE additives, we observed that GelMA/DbPE formulations benefited from higher ink homogeneity during extrusion. Although both additives promoted fiber formation, printing of the GelMA/TbPE inks was less consistent with several fiber breaks during extrusion. Since these inhomogeneities persisted over a wide range of different extrusion rates, we attribute this to the challenge of extruding highly interconnected TbPE networks through a small orifice.