01948nas a2200157   4500008004100000022001400041245010400055210006900159300001600228490000700244520143900251653001901690100001501709700001801724856004801742       2012                        eng d  a1520-603300aThe impact of fabrication parameters and substrate stiffness in direct writing of living constructs0 aimpact of fabrication parameters and substrate stiffness in dire  a1315–13200 v283 a<p>Biomolecules and living cells can be printed in high-resolution patterns to fabricate living constructs for tissue engineering. To evaluate the impact of processing cells with rapid prototyping (RP) methods, we modeled the printing phase of two RP systems that use biomaterial inks containing living cells: a high-resolution inkjet system (BioJet) and a lower-resolution nozzle-based contact printing system (PAM(2) ). In the first fabrication method, we reasoned that cell damage occurs principally during drop collision on the printing surface, in the second we hypothesize that shear stresses act on cells during extrusion (within the printing nozzle). The two cases were modeled changing the printing conditions: biomaterial substrate stiffness and volumetric flow rate, respectively, in BioJet and PAM(2) . Results show that during inkjet printing impact energies of about 10(-8) J are transmitted to cells, whereas extrusion energies of the order of 10(-11) J are exerted in direct printing. Viability tests of printed cells can be related to those numerical simulations, suggesting a threshold energy of 10(-9) J to avoid permanent cell damage. To obtain well-defined living constructs, a combination of these methods is proposed for the fabrication of scaffolds with controlled 3D architecture and spatial distribution of biomolecules and cells. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012.</p>10aBioengineering1 aTirella, A1 aAhluwalia, A.  uhttp://www.ncbi.nlm.nih.gov/pubmed/22736619