Directional sliding of water:biomimetic snake scale surfaces

Bioinspired superhydrophobic surfaces have attracted many industrial and academic interests in recent years.Inspired by unique superhydrophobicity and anisotropic friction properties of snake scale surfaces,this study explores the feasibility to produce a bionic superhydrophobic stainless steel surface via laser precision engineering,which allows the realization of directional superhydrophobicity and dynamic control of its water transportation.Dynamic mechanism of water sliding on hierarchical snake scale structures is studied,which is the key to reproduce artificially bioinspired multifunctional materials with great potentials to be used for water harvesting,droplet manipulation,pipeline transportation,and vehicle acceleration.

Calibration of Discrete Element Heat Transfer Parameters by Central Composite Design

The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.

Bio-inspired Attachment Mechanism of Dynastes Hercules:Vertical Climbing for On-Orbit Assembly Legged Robots

With the increasing size of space facilities,on-orbit assembly requires robots to move on different heights of trusses.This paper proposes a bio-inspired attachment mechanism for robot feet to enable climbing on different heights of trusses.Inspired by the attachment and grasping abilities of Dynastes Hercules,we utilize its foot microstructures,such as microhooks and setae,to achieve efficient contact and firm grip with the surface.The morphology and arrangement of these structures can inspire the design of robot feet to improve their grasping and stability performance.We study the biological structure of Dynastes Hercules,design and optimize the bio-inspired structure,analyze the influence of various factors from theoretical and experimental perspectives,and verify the feasibility of the scheme through simulation.We propose an ideal climbing strategy that provides useful reference for robot applications in practice.Moreover,the influence laws of various factors in this paper can be applied to robot foot design to improve their operation ability and stability performance in the space environment.This bio-inspired mechanism can improve robot working range and efficiency,which is critical for on-orbit assemblyin space.