Paper Number
PO12 

Session
Poster Session

Title
No sagging, no cry

Presentation Date and Time
October 13, 2021 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom 1-2-3-4

Authors (Click on name to view author profile)

  1. Saengow, Chaimongkol (University of Illinois at Urbana-Champaign, Beckman Institute for Advanced Science and Technology)
  2. Aboutaleb, Sohaila (University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering)
  3. Haug, Nellie (University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering)
  4. Wagoner Johnson, Amy J. (University of Illinois at Urbana-Champaign, Beckman Institute for Advanced Science and Technology)
  5. Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Chaimongkol Saengow1, Sohaila Aboutaleb2, Nellie Haug2, Amy J. Wagoner Johnson1 and Randy H. Ewoldt1
1Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Champaign, IL 61801; 2Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, IL 61801

Speaker / Presenter 
Saengow, Chaimongkol

Keywords
additive manufacturing; applied rheology; biological materials; colloids

Text of Abstract
We test hypotheses of rheological property requirements and sensitivities for direct ink write 3D printing of suspended lattice structures, motivated by the fabrication of implantable scaffolds for bone regeneration after fracture. We focus on gravitational sagging of extruded end-supported horizontal cylinders and experimentally explore shape retention as a function of yield stress, complex moduli, thixotropy, and extensional viscosity. The primary component of the ink formulations is hydroxyapatite (HAp) particles (2-5 micron diameter) which is the main mineral of bone. Additionally, inks contain particles of polymethyl methacrylate (PMMA, sized 10-15 microns to create porosity), and polymeric components hydroxypropyl methylcellulose (HPMC, derivative of cellulose molecules), polyacrylic acid (PAA), and polyethylenimine (PEI); the latter two being polyelectrolytes that serve as electrostatic binding agents. A custom-built 3D printer, equipped with a laser scanner, is used for quantitative analysis of the interplay between ink rheology and sag to arrive at a rheology-sag-resistance map. This map will assist in ink design to achieve higher cell penetration within tolerable sagging distance and serves as a guide to other direct-write 3D printing processes to consider the sensitivity of shape retention to rheology beyond just the yield stress.