Fingerprint-inspired surface texture for the enhanced tip pinch performance of a soft robotic hand in lubricated conditions

The core capabilities of soft grippers/soft robotic hands are grasping and manipulation.At present,most related research often improves the grasping and manipulation performance by structural design.When soft grippers rely on compressive force and friction to achieve grasping,the influence of the surface microstructure is also significant.Three types of fingerprint-inspired textures with relatively regular patterns were prepared on a silicone rubber surface via mold casting by imitating the three basic shapes of fingerprint patterns(i.e.,whorls,loops,and arches).Tribological experiments and tip pinch tests were performed using fingerprint-like silicone rubber films rubbing against glass in dry and lubricated conditions to examine their performance.In addition to the textured surface,a smooth silicone rubber surface was used as a control.The results indicated that the coefficient of friction(COF)of the smooth surface was much higher than that of films with fingerprint-like textures in dry and water-lubricated conditions.The surface with fingerprint-inspired textures achieved a higher COF in oil-lubricated conditions.Adding the fingerprint-like films to the soft robotic fingers improved the tip pinch gripping performance of the soft robotic hand in lubricated conditions.This study demonstrated that the surface texture design provided an effective method for regulating the grasping capability of humanoid robotic hands.

Spatial evolution of friction of a textured wafer surface

Mechanical failure of integrated circuits and micro-electro-mechanical systems(MEMS)demands new understanding of friction in small devices.In present research,we demonstrated an in situ approach to measure sliding friction of a patterned surface composing multi-materials and structures.The effects of materials and surface morphology on friction and electrical contact resistance were investigated.The material transfer at the interface of dissimilar materials was found to play dominating roles in friction.The current work provides important insights from the fundamentals of friction that benefit the design of new micro-devices.

Sliding friction of shale rock on dry quartz sand particles

The sliding friction of rock, involving all kinds of particles at the contact surface, is relevant to many problems, ranging from those in artificial engineering to earthquake dynamics. In this work, the frictional performance of the shale rock–dry quartz sand contact was investigated using a self-developed testing device. The study showed that the coefficient of friction of the contact increases with nominal stress and that the corresponding friction force increases approximately linearly with nominal stress, which is directly related to the contact stress between each single sand particle and rock shale. An overall dynamic coefficient, γ, reflecting the response of friction force to nominal stress, first decreases and then increases with area ratio, which is determined by not only the contact stress but also the interparticle friction force. These have important repercussions for a preliminary understanding of the frictional properties of the shale rock–dry quartz sand contact in hydraulic fracturing and related industrial applications.