arXiv subjects

Noah Eckman

Publications and source records attributed to Noah Eckman.

2 recordsLinked to original sources

arXiv2025

Evolving transport properties of dynamic hydrogels enable self-tuning of short- and long-term cargo delivery

Hydrogels are crosslinked polymer networks with high water content, widely employed in biomedical applications such as drug delivery, tissue engineering, and regenerative medicine. Injectable, depot-forming hydrogels enable sustained release of therapeutic agents by modulating macromolecular diffusion through dynamic polymer networks. However, achieving reliable control over release kinetics remains a challenge, as the injection process induces shear-mediated disruption of transient crosslinks, leading to an initial burst release that can cause local toxicity and compromise therapeutic efficacy. Here, we present a hydrogel formulation strategy designed to restore network structure post-injection through rapid reformation of dynamic crosslinks, enabling time-dependent regulation of diffusion properties. By tuning viscoelastic parameters, including stress relaxation time and network recovery rate, we reduced the extent of burst release without compromising sustained delivery. Using model protein cargo, we demonstrate in both $in~vitro$ and $in~vivo$ settings that hydrogels with faster crosslink reformation kinetics exhibit significantly lower early-phase release while maintaining long-term delivery comparable to unmodified formulations. These results establish a mechanistic framework for decoupling short- and long-term release behavior, offering a broadly applicable strategy for precise drug delivery in soft tissue environments.

cond-mat.soft↗

arXiv2021

A Swimming Rheometer: Self-propulsion of a freely-suspended swimmer enabled by viscoelastic normal stresses

Self-propulsion at low Reynolds number is notoriously restricted, a concept that is commonly known as the "scallop theorem". Here we present a truly self-propelled swimmer (force- and torque- free) that, while unable to swim in a Newtonian fluid due to the scallop theorem, propels itself in a non-Newtonian fluid as a result of fluid elasticity. This propulsion mechanism is demonstrated using a robotic swimmer, comprised of a "head" sphere and a "tail" sphere, whose swimming speed is shown to have reasonable agreement with a microhydrodynamic asymptotic theory and numerical simulations. Schlieren imaging demonstrates that propulsion of the swimmer is driven by a strong viscoelastic jet at the tail, which develops due to the fore-aft asymmetry of the swimmer. Optimized cylindrical and conic tail geometries are shown to double the propulsive signal, relative to the optimal spherical tail. Finally, we show that we can use observations of this robot to infer rheological properties of the surrounding fluid. We measure the primary normal stress coefficient at shear rates less than 1 Hz, and show reasonable agreement with extrapolated benchtop measurements (between 0.8 to 1.2 Pa sec2 difference). We also discuss how our swimmer can be used to measure the second normal stress coefficient and other rheological properties. The study experimentally demonstrates the exciting potential for a "swimming rheometer", bringing passive physics-driven fluid sensing to numerous applications in chemical and bioengineering.

physics.flu-dyn↗