Elastohydrodynamic friction of robotic and human fingers on soft micropatterned substrates.

Frictional sliding between patterned surfaces is of fundamental and practical importance in the haptic engineering of soft materials. In emerging applications such as remote surgery and soft robotics, thin fluid films between solid surfaces lead to a multiphysics coupling between solid deformation and fluid dissipation. Here, we report a scaling law that governs the peak friction values of elastohydrodynamic lubrication on patterned surfaces. These peaks, absent in smooth tribopairs, arise due to a separation of length scales in the lubricant flow. The framework is generated by varying the geometry, elasticity and fluid properties of soft tribopairs and measuring the lubricated friction with a triborheometer. The model correctly predicts the elastohydrodynamic lubrication friction of a bioinspired robotic fingertip and human fingers. Its broad applicability can inform the future design of robotic hands or grippers in realistic conditions, and open up new ways of encoding friction into haptic signals.

A Strategy for Rapid Construction of Blood Vessel-Like Structures with Complex Cell Alignments.

A method is developed that can rapidly produce blood vessel-like structures by bonding cell-laden electrospinning (ES) films layer by layer using fibrin glue within 90 min. This strategy allows control of cell type, cell orientation, and material composition in separate layers. Furthermore, ES films with thicker fibers (polylactic-co-glycolic acid, fiber diameter: ≈3.7 µm) are used as cell-seeding layers to facilitate the cell in-growth; those with thinner fibers (polylactic acid, fiber diameter: ≈1.8 µm) are used as outer reinforcing layers to improve the mechanical strength and reduce the liquid leakage of the scaffold. Cells grow, proliferate, and migrate well in the multilayered structure. This design aims at a new type of blood vessel substitute with flexible control of parameters and implementation of functions.