Huadong Yu

Fabrication and applications of two- and three-dimensional curved surfaces with robust underwater superoleophobic properties

In this work, a method for the fabrication of two- and three-dimensional curved surfaces with robust underwater superoleophobicity is reported for the first time on light alloys (including 5083 Al and TC4 Ti alloys) through the high speed wire electrical discharge machining (HS-WEDM). The surface morphology and compositions were characterized by scanning electron microscope and energy-dispersive X-ray spectrometer. The results showed that rough structures and a layer of oxidization were created on the light alloys by HS-WEDM cutting. The two- and three-dimensional structured curved surfaces after an ethanol immersion exhibited the extreme underwater superoleophobic property with the high oil contact angle and low oil sliding angle. More importantly, the underwater superoleophobic surfaces with the three-dimensional curved features could have many new applications. In order to use the potential functions, the durability of the fabricated samples was tested and the results showed that the samples still exhibited the underwater superoleophobic property after the underwater storage and physical mechanism tests. Additionally, this method is versatile, simple, environment-friendly, and cost-effective.

Superhydrophobic surface prepared by micromilling and grinding on aluminium alloy

An efficient method for processing superhydrophobic surface is presented in this paper, which can realise the microstructure machining on a large area. First, the microgroove arrays were processed by high speed precision micromilling machine on the surface of the aluminium alloy. Then, the surface of the microgroove was ground by 1000 # electrostatic sand alumina water resistant abrasive belt. The machined surface topography was observed by SEM, which showed that the microgroove arrays were uniform. The contact angles of the water on the microgroove arrays were measured in different directions. In the parallel direction, the contact angle of microgroove arrays is 142±0·5°, whereas in the vertical direction, it arrives 160±0·6°. The above values of contact angle mean that a stable superhydrophobic metallic surface was prepared by the micromilling and grinding.

Design and performance evaluation of collision protection-based safety operation for a haptic robot-assisted catheter operating system

The robot-assisted catheter system can increase operating distance thus preventing the exposure radiation of the surgeon to X-ray for endovascular catheterization. However, few designs have considered the collision protection between the catheter tip and the vessel wall. This paper presents a novel catheter operating system based on tissue protection to prevent vessel puncture caused by collision. The integrated haptic interface not only allows the operator to feel the real force feedback, but also combines with the newly proposed collision protection mechanism (CPM) to mitigate the collision trauma. The CPM can release the catheter quickly when the measured force exceeds a certain threshold, so as to avoid the vessel puncture. A significant advantage is that the proposed mechanism can adjust the protection threshold in real time by the current according to the actual characteristics of the blood vessel. To verify the effectiveness of the tissue protection by the system, the evaluation experiments in vitro were carried out. The results show that the further collision damage can be effectively prevented by the CPM, which implies the realization of relative safe catheterization. This research provides some insights into the functional improvements of safe and reliable robot-assisted catheter systems.

Design and principle analysis for electromagnetic brake clamping mechanism of a novel slave manipulator

Robotically assisted catheterization has attracted significant interest in recent years. However, few designs have taken the reasonable control of the clamping force into consideration. Additionally, limited research has been conducted in the damage of the clamping mechanism to the catheter. This paper presents a novel clamping mechanism for a slave manipulator that can be used in the minimally invasive surgery training system. The clamping mechanism utilizes the electromagnetic force which generated by the electrified coil to balance the pressure provided by the compression spring. Also the clamping force can be adjusted by the input current to prevent excessive clamping or inadequate clamping for the catheter. In addition, the modal analysis of the designed clamping structure is carried out. The results show that the modal frequency of the clamping structure is very small, so it does not resonate with the external excitation when the catheter is pushed forward. This clamping mechanism provides important insights into the design of compact and ergonomic robotic catheter manipulators incorporating effective and lossless clamping for intraoperative navigation.

Experimental study of surface roughness effects on wettability

In this paper, we present a method to fabricate aluminum alloy 5083 surfaces with different surface roughness using reciprocating type high speed wire cut electrical discharge machining (HS-WEDM). Observe the processed surface by ultra-depth three-dimensional scanning system, obviously notice that craters and bumps were uniformly distributed in the surface which is machined by HS-WEDM. And the size of craters and bumps are relevant to the parameters of the pulse power supply. Then we obtain a surface with static contact angle of 136° and draw a changing trends curve of the static contact angle along with surface roughness by measuring the surface roughness and static contact angle respectively. It has provided experimental basis and theoretical foundation for fabricating aluminum alloy super-hydrophobic surface by HS-WEDM.

Nanosecond Laser-Induced Underwater Superoleophobic and Underoil Superhydrophobic Mesh for Oil/Water Separation

Materials with special wettability have drawn considerable attention especially in the practical application for the separation and recovery of the oily wastewater, whereas there still remain challenges of the high-cost materials, significant time, and complicated production equipment. Here, a simple method to fabricate the underwater superoleophobic and underoil superhydrophobic brass mesh via the nanosecond laser ablation is reported for the first time, which provided the micro-/nanoscale hierarchical structures. This mesh is superhydrophilic and superoleophilic in air but superoleophobic under water and superhydrophobic under oil. On the basis of the special wettability of the as-fabricated mesh, we demonstrate a proof of the light or heavy oil/water separation, and the excellent separation efficiencies (>96%) and the superior water/oil breakthrough pressure coupled with the high water/oil flux are achieved. Moreover, the nanosecond laser technique is simple and economical, and it is advisable for the large-area and mass fabrication of the underwater superoleophobic and underoil superhydrophobic mesh in the large-scale oil/water separation.

An investigation on drilling micro holes in different processes using micro-EDM

Microparts are widely used for aerospace, medical and other special industries. Due to the limitation of cutting tools and processing technology, and cost a lot, it is difficult to machining for conventional mechanical process especially for the micro holes in the materials with high strength and hardness. Yet it is a highly efficient machining process using micro-EDM, because of its non-contact mode. SUS 304 possess excellence corrosion resistance and heat resistance while it is hard to machine, this paper will do a series of research on the SUS 304 material about drilling micro holes using micro-EDM. From the comparative analysis of three different processes about drilling holes, it shows that using cutting edge electrode and layered milling processes effectively decrease the taper angle under keeping the precision of holes, the cutting edge electrode produces better material removal rate(MRR), and layered milling with different layered numbers have different influence on the machining performance.

A comparative investigation of drilling and milling micro holes using micro-EDM

Micro Electrical Discharge Machining (micro-EDM), is one of the most important technologies for the machining of difficult-to-cut materials, and it can be considered as one of the most promising manufacturing process for fabricating micro holes. Micro-EDM is suitable for machining micro holes, while it is still hard to machining holes with high depth. The study will make a research on drilling and milling holes using micro-EDM, the milling process shows better performance especially for the holes with high depth to diameter ratio; while drilling process could gain higher processing speed and better geometrical properties of the micro-holes.

Research on the post-processing method for CNC program oriented to miniature five-axis machining system

In this paper, an approach of converting the APT file generated by the CAM software to the CNC machining program, executed by the CNC system based on the UMAC control platform for the self-developed 5-axis micro-milling system, is presented. The transformation of the cutter location coordinate between workpiece coordinate system and machine coordinate system during processing is obtained by analyzing the motion topological structure of the micro-milling system. And the flow of writing the CNC program is also proposed according to the features of the CNC system. Then, the conversion of APT file to UMAC file is established and the auto-generation of the CNC milling program is realized through using the text processing functions in Matlab and the display of the tool-path is also realized by Matlabs functions.

An EO pump-based new type of micro fluidic system

This paper proposes an EO pump based novel type of micro fluidic control system, which can control both the output pressure and the output flow velocity. This system consists of an EO pump, a flow sensor, a pressure sensor and a fuel cell. By changing the driving voltage, the material of pipe and the two kinds of liquid, we get different output pressure and output flow velocity data. We proposed the mechanism using one fuel cell to solve the problem of gases generated by the EO pump. The characteristic evaluations have been carried out. The maximum flow velocity in the oil is 6.34µl/min at the driving voltage 7.02V.