Paper Number
VP10
Session
Pre-recorded Flash Presentations (virtual)
Title
Sculpting hydrogels using additive advective processing
Presentation Date and Time
All Week (Asynchronous) Any Time
Track / Room
Pre-recorded Presentation / Virtual
Authors
- Bayles, Alexandra V. (ETH Zürich, Materials)
- Pleij, Tazio (ETH Zürich, Materials)
- Hofmann, Martin (ETH Zürich, Materials)
- Vermant, Jan (ETH Zurich, Materials Departement)
Author and Affiliation Lines
Alexandra V. Bayles, Tazio Pleij, Martin Hofmann and Jan Vermant
Materials Departement, ETH Zurich, Zurich 8093, Switzerland
Speaker / Presenter
Bayles, Alexandra V.
Keywords
experimental methods; additive manufacturing; microfluidics
Text of Abstract
Polymer hydrogels find broad application as advanced functional materials due to their biocompatibility, stimuli responsiveness and affordability. In these materials, crosslinking density reports critical properties such as elasticity, permeability and swelling propensity. Patterning this design parameter across the volume polymerized is an attractive means by which to engineer hydrogel performance. Here, we report a novel processing scheme that uses custom millifluidic devices as 3D printheads to direct the organization of crosslinking density across a single gel. Inspired by techniques used to structure polymeric melts, we design serpentine devices that force disparate streams through splitting, rotation and recombination elements. These elements multiply the incoming macromer concentration field across the cross-sectional area while preserving its relative spacing and orientation. Successful operation of these ‘advective assemblers’ requires that the advective path trace the contour of curvilinear channels with minimal distortion. Viscoplastic materials are ideally suited for this task: yielding is localized in high-shear regions near the wall, while unyielded, layered streams flow as a stable plug. To prepare a viscoplastic hydrogel ink, we blend poly(ethylene glycol) diacrylate with poly(acrylic acid) microgels. The arrested structure of the microgel suspension dominates ink rheology, allowing flow stability to be tuned independently of macromer concentration. This formulation enables extrusion of hydrogel filaments with laminated concentration distributions, which are subsequently arranged via the 3D printing path and secured via photopolymerization. The sculpted gradients cause the hierarchical gels to swell differentially in water, giving rise to predictable shape changes that persist over tens of centimeters. The unique structures achieved, and the geometrically dictated additive manufacturing principles used to achieve them, provide a new means to engineer hydrogels for various applications.