Hai Feng Zhang

Fabrication of self-healing super-hydrophobic surfaces on aluminium alloy substrates

We present a method to fabricate a super-hydrophobic surface with a self-healing ability on an aluminium alloy substrate. The coatings are obtained by combining a two-step process (first, the substrate is immersed in a solution of HCl, HF and H2O, and then in boiling water) and succeeding surface fluorination with a solution of poly(vinylidene-fluoride-co-hexafluoropropylene) and a fluoroalkyl silane. The morphological features and chemical composition were studied by scanning electron micrometry and energy-dispersive X-ray spectroscopy. The prepared super-hydrophobic aluminium surfaces showed hierarchical structures forming pores, petals and particles with a contact angle of 161° and a sliding angle of 3°.

Fabrication of super-hydrophobic surfaces on aluminum alloy substrates by RF-sputtered polytetrafluoroethylene coatings

In this work, we present a method of fabricating super-hydrophobic surface on aluminum alloy substrate. The etching of aluminum surfaces has been performed using Becks dislocation etchant for different time to create micrometer-sized irregular steps. An optimised etching time of 50 s is found to be essential before polytetrafluoroethylene (PTFE) coating, to obtain a highest water contact angle of 165±2° with a lowest contact angle hysteresis as low as 5±2°. The presence of patterned microstructure as revealed by scanning electron microscopy (SEM) together with the low surface energy ultrathin RF-sputtered PTFE films renders the aluminum alloy surfaces highly super-hydrophobic.

Fabrication of Super-Hydrophobic Surface on Stainless Steel Using Chemical Etching Method

Superhydrophobic surface have many applications such as drag reduction in the micro-electromechanical systems. A novel method of fabricating superhydrophobic surface is proposed using the simple wet chemical etching in this paper. Firstly, the surface of steel disc is polished by abrasive paper and then treated with chemical etching. Secondly, the surface of steel is modified with 1H,1H,2H,2H-Perfluorooctyltrimethoxysilane. The superhydrophobic surface was obtained on the stainless steel surface. Finally, the effects of the etching time and etching solution concentration were analyzed to the superhydrophobic performance. The experimentation results show that superhydrophobic performance is the best when the HCl concentration is 2mol/L, the etching time is 20 minute respectively. The water contact angle (CA) of the rotor surface is 152°. The water droplets are hardly able to stick to the steel surface．

Field-portable Capillary Electrophoresis Instrument with Conductivity Detection

In this paper a novel capillary electrophoresis chip (CEC) is presented with integrated platinum electrodes and simplified conductivity detector. CEC is fabricated by the method of mechanical modification with probe on organic glass. Capillary electrophoresis chip can rapidly completed ion separation by simulation of concentration distribution and zone-broadening. Detection circuit is simple which can detect pA order current. This system has those advantages such as small volume, low power consumption and linearity, and well suit for field analysis.

The Fracture Mechanism of As-Cast and Extruded SiCp/AZ91 Composites Fabricated by Stir Casting

The fracture mechanisms of SiCp/AZ91 composites were investigated by scanning electron microscopy (SEM). For the as-cast composites, the decohesion at SiCp/matrix interface is the main fracture mechanism because of the high stress concentration resulting from the segregation of particles in grain boundaries formed during solidification process. But for the extruded composites, the main fracture mechanism is the particle crack or ductile rupture of the matrix between the particles. So the fracture mechanism of SiCp/AZ91 composites is altered by extrusion because the segregation of particles and defects in the grain boundaries are largely eliminated by extrusion.

Facile Fabrication of Super-Hydrophobic Surfaces by Spray PTFE

We have developed a combination of electro –deposition and spraying methods to prepare water-repellent tin oxide/ polytetrafluoroethylene(SnO2/PTFE) coating. The coating has a high water contact angle. The resulting porous and lowest surface energy hydrophobic groups (－CF3) has a water contact angle of 165° and a sliding angle of 7°, showing super-hydrophobic property. The coating with good adhesion on substrates and the long-term stability can be fabricated on various metal substrates.

High Resolution Micro-Displacement Sensing Circuit for Rotor Micro-Gyroscope

A novel CMOS interface circuit with high resolution is designed and realized to achieve the integration of interface circuit for liquid suspended rotor micro-gyroscope. The detecting circuit adopts continuous-time current sensing circuit for capacitance measurement. The equivalent output noise power spectral density of phase-sensitive demodulation is 120 nV/Hz1/2. The whole circuitry is realized with 0.5 μm 2P2M CMOS process and its testing results show the circuit has a relative capacitance resolution of 1×10-8, in which the power supply is 18 V and the power consumption is 30 mW. The area of the chip is merely 18.5 mm2.

Two Benches PDMS Free Flow Electrophoresis Chip

This paper puts forward a kind of two benches structure of the glass-PDMS free flow electrophoresis chip. We use die casting method to produce microstructure, and use PDMS as its structure layer. The mold is made in tape-PMMA by micro cementing technology. During the progress of PDMS curing, gold wires are directly integrated in the electrode groove to form the chips electrodes. PDMS and glass are sealed in natural bonding method. Chips glass surface of separation chamber realizes the modification through sticking polyimide tape. Visual technology is conducted for chip electrophoresis separation. The sample is the mixture of methyl green and Rhodamine B. The separation effect of methyl green and Rhodamine B is obvious when the electric field is 31 V/cm. the two benches between the electrode groove and the separation chamber block the electrolytic bubbles into the separation chamber. When the separation chamber height is 70 μm and the electric field is 50 V/cm, the air bubbles can be glidingly discharged from electrode groove. The samples steady separation time is more than 2 hours, and this free flow electrophoresis chip realizes continuous work.

Effect of the Surface Roughness on the Detecting Capacitance

With the MEMS technology advancement, electronic devices are miniaturized at every development node. The surface roughness is affecting the detecting capacitance of MEMS device because surface to volume ratio is increasing rapidly. A novel model with one rough electrode is investigated in this paper. The impacts of surface roughness on detecting capacitance are analyzed. The image of height percentage is used to describe the surface roughness of electrode sample. The function of the surface roughness is obtained according the method of curve fitting. The effect of surface roughness on the capacitance is calculated. The results demonstrate the capacitance increases with the surface roughness.

Liquid-Suspended Rotor Gyroscope Multiphase Driving Technology

Liquid-suspended rotor micro-mechanical gyroscope uses a high-speed rotating hollow rotor in response to the density of the liquid as the mass to do the angular velocity detection. In order to improve the liquid-suspended gyroscopes performance, this paper suggested a new high performance magnetic driving technology. In this technology, the driving performance is optimized by applying six-phase overlapped driving signal to the twelve driving coils of the stator. With this driving technology, the rotating speed of rotor in 3# industrial white oil can go up to 8700rpm.