Molecular adsorption induces normal stresses at frictional interfaces of hydrogels

Soft Matter, Год журнала: 2025, Номер unknown

Опубликована: Янв. 1, 2025

Friction experiments were conducted on hydrogel thin films sliding against a rigid sphere in low velocity regime where molecular adsorption at the interface sets friction force, through dissipative adsorption-stretching-desorption mechanism initially postulated by Schallamach [A. Schallamach, Wear, 1963, 6, 375]. By carefully imaging contact from initial indentation step of into to steady state sliding, we evidence for first time that this very same also results normal force embedding further hydrogel. Observations tangential-normal coupling are made variety chemically modified silica spheres, over 3 decades and varied loads, thereby demonstrating its robustness. Quantitative measurements extra friction-velocity relationship versus load well rationalized within theoretical model based thermal actuation bonds. To do so, account finite non-zero thickness which stretching events produce an out-of-plane responsible both adhesive-like pull-in.

Язык: Английский

Analytical model of friction at low shear rates for soft materials in 3D printing

Technology and Health Care, Год журнала: 2024, Номер unknown, С. 1 - 20

Опубликована: Май 30, 2024

BACKGROUND: The biological properties of silicone elastomers such as polydimethylsiloxane (PDMS) have widespread use in biomedicine for soft tissue implants, contact lenses, robots, and many other small medical devices, due to its exceptional biocompatibility. Additive manufacturing materials still has significant challenges even with major advancements that occurred development these technologies customized devices engineering. OBJECTIVE: aim this study was develop a mathematical model tangential stress relation shear stress, rate, 3D printing pressure velocity, non-Newtonian gels fluids are used printing. METHOD: This FENE (finitely extensible nonlinear elastic model) model, define the dependences between pressure, considering viscosity, rates governing factors friction adhesion. Experimental samples were fabricated showcases, by SLA FDM technologies: polymer resembling PDMS thermoplastic polyurethane (TPU) samples. parameters developed analytical solution analyse relationships influential (tangential speed, rate coefficient). Maple software numerical modelling. RESULTS: Analytical applied on printed polymer, at low rates, exhibited values 0.208–0.216 N m - 2 velocities 0.9 1.2 mm s 1, while coefficient 0.09–0.16. These accordance experimental data literature. Printing did not significantly influence whereas it slightly influenced changes. Friction linearly increased stress. CONCLUSION: Simple showed good correspondence literature thus indicating possibility prediction towards desired dimensional accuracy objects. Further should enable regimes, well additional parameters.

Язык: Английский