Atomic and close-to-atomic scale manufacturing (ACSM) aims to provide techniques for manufacturing in various fields, such as circuit manufacturing, high energy physics equipment, and medical devices and materials. The realization of atomic scale material manipulation depending on the theoretical system of classical mechanics faces great challenges. Understanding and using intermolecular and surface forces are the basis for better designing of atomic and close-to-atomic scale manufacturing. Transformation of atoms based on scanning tunneling microscopy (STM) or atomic force microscopy (AFM) is an essential process to regulate intermolecular interactions. Self-assemble process is a thermodynamic process involving complex intermolecular forces. The competition of these interaction determines structure assembly and packing geometry. For typical nanomachining processes including AFM nanomachining and chemical mechanical polishing, the coupling of chemistry and stress (tribochemistry) assists in the removal of surface atoms. Furthermore, based on the principle of triboelectrochemistry, we expect a further reduction of the potential barrier, and a potential application in high-efficiency atoms removal and fabricating functional coating. Future fundamental research is proposed for achieving high-efficiency and high-accuracy manufacturing with the aiding of external field. This review highlights the significant contribution of intermolecular and surface forces to ACSM, and may accelerate its progress in the in-depth investigation of fundamentals.

Polyether-etherketone (PEEK) is a corrosion-resistant material that has been widely used in aqueous lubrication. However, its anti-wear performance must be improved for its application in the industry. In this study, to improve the anti-wear performance of PEEK for aqueous boundary lubrication, PEEK/MoS2 composites were prepared by ball-milling and spark plasma sintering processes. A competitive MoS2 mechanism between the low shear strength property and the role of promoting wear debris generation influences the anti-wear performance of PEEK/MoS2 composites. Experiments demonstrated that the coefficients of friction (COF) and wear rate of PEEK composite with 0.25 wt% MoS2 were significantly reduced 68% and 94%, respectively. Furthermore, this was the first time that a PEEK composite could achieve a COF of less than 0.05 in aqueous boundary lubrication. Its anti-wear performance was verified to be better than that of PEEK/carbon fiber (CF) and Thordon composites. The PEEK/MoS2 composite may be a potential material for underwater equipment because of its outstanding anti-wear performance in aqueous boundary lubrication.

Traction stress between contact objects is ubiquitous and crucial for various physical, biological, and engineering processes such as momentum transfer, tactile perception, and mechanical reliability. Newly developed techniques including electronic skin or traction force microscopy enable traction stress measurement. However, measuring the three-dimensional distribution during a dynamic process remains challenging. Here, we demonstrated a method based on stereo vision to measure three-dimensional traction stress with high spatial and temporal resolution. It showed the ability to image the two-stage adhesion failure of bionic microarrays and display the contribution of elastic resistance and adhesive traction to rolling friction at different contact regions. It also revealed the distributed sucking and sealing effect of the concavity pedal waves that propelled a snail crawling in the horizontal, vertical, and upside-down directions. We expected that the method would advance the understanding of various interfacial phenomena and greatly benefit related applications across physics, biology, and robotics.

Wall attachment has great potential in a broad range of applications such as robotic grasping, transfer printing, and asteroid sampling. Herein, a new type of underactuated bionic microspines gripper is proposed to attach to an irregular, rough wall. Experimental results revealed that the gripper, profiting from its flexible structure and underactuated linkage mechanism, is capable of adapting submillimeter scale roughness to centimeter scale geometry irregularity in both normal and tangential attachment. The rigid-flexible coupling simulation analysis validated that the rough adaptation was achieved by the passive deformation of the zigzag flexible structure, while the centimeter-scale irregularity adaptation come from the underactuated design. The attachment test of a spine confirmed that a 5 mm sliding distance of the spine tip on the fine brick wall promises a saturated tangential attachment force, which can guide the stiffness design of flexible structure and parameter selection of underactuated linkage. Furthermore, the developed microspines gripper was successfully demonstrated to grasp irregular rocks, tree trunks, and granite plates. This work presents a generally applicable and dexterous passive adaption design to achieve rough wall attachment for flat and curved objects, which promotes the understanding and application of wall attachment.

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