Experiments with polyacrylamide hydrogel spheres spanning a range of shear moduli and impact velocities reveal a transition between liquid-drop and elastic-solid behavior. Elastic number (El) separates two regimes: at El1, elastic behavior dominates and the contact foot is suppressed.
Key findings
- At El1, the foot was suppressed, deformation followed a neo-Hookean energy balance, and maximum spreading became wettability-independent. Normalized peak force saturated below El=1 and scaled approximately as El^0.38 above it.
Why this matters globally
Soft-material impact matters in 3D bioprinting, biomaterial-ink deposition, and processes where both shape and force must be controlled. The study offers a unifying parameter that bridges liquid and solid impact theories.
Thai researcher contribution
Researchers affiliated with Chulalongkorn University and the University of Waterloo contributed to the mechanical framework and analysis, linking Thai expertise to international work in interfacial and soft-material engineering.
Limitations to consider
Experiments used PAAm hydrogels and a limited set of model surfaces. Generalization to cell-laden bioinks, nonspherical geometries, or operational printers remains untested. This is fundamental mechanics evidence, not a biomedical performance trial.