Influence of shear thinning and material flow on robotic dispensing of poly(ethylene glycol) diacrylate/poloxamer 407 hydrogels

Robotic dispensing of hydrogels offers a direct way for generating complex hydrogel shapes. For this, there is a general need for hydrogel formulations with suitable rheological properties. In this contribution, hydrogel formulations containing poly(ethylene glycol) diacrylate (PEG-DA) and Poloxamer 407 are characterized regarding their flow behavior during robotic dispensing. Formulations contain between 15% and 20% PEG-DA and 22.5% and 25% Poloxamer 407. All formulations show shear thinning which can be described using a power law with a power law index between 0.10 and 0.11 and calculated shear rates at the wall of the dispensing needle of 379 s−1 with a dispensing speed of 8 mm s−1 and a dispensing needle inner diameter of 0.51 mm. Thus, facilitating the generation of smooth hydrogel strands, three-dimensional hydrogel objects can be prepared without flow after robotic dispensing and can be cured afterward to elastic hydrogels, retaining the shape of the dispensed object.