Papers by Author: Zheng Han Hong

Abstract: Molecular dynamic simulation for Fe sliding on Fe substrate with textured surface is investigated in this work. The textured surfaces on sliding are discussed to elucidate the physics of friction at the small scale. The modified embedded-atom method many-body potential is modeled to describe the interaction of Fe-Fe atoms. We find that a textured surface can reduce the friction because the former can entrap wear particles, effectively reducing the contact area. In addition, the friction force increases almost linearly in the low sliding speed with the increasing of sliding speeds. However, the friction force decreased as the increasing speed exceeds the 300 m/s.

Abstract: Molecular dynamic simulation for Co cluster deposition on Si substrate was investigated in this work. The surface roughness and the interface mixing will be evaluated for the deposited film quality under different incident energies and substrate temperatures. The effect of thermal annealing on the ability of gap filling will be discussed by a slip vector. The results indicate that the incident energy has dominant effect on the surface roughness, and there is a minimum surface roughness value around the incident energy of 8 eV. However, the substrate temperature has little effect on the surface roughness. For interface mixing, the simulation indicates the easy diffusion of Co atoms into Si substrate. However, increasing either the incident energy or the substrate temperature could not change much the mixing conditions. As for the ability of gap filling, it is clear that the thermal annealing does improve this ability and obtains better surface roughness and interface mixing.

Abstract: A molecular dynamic (MD) method is used to simulate Al atom depositing on Cu substrate by controlling the incident energy and the deposition rate for dual-target magnetron sputtering. At the interface, functional graded material (FGM) will be created to reduce the residual stress after the deposition process. The results indicate that the surface roughness of the deposited film will be reduced with the assistance of FGM, and more layers of FGM will reduce more the root-mean-square (RMS) value and the residual stress to obtain excellent quality of the deposited film.

Abstract: The mixing situation of Co atoms implanting onto Cu(001) substrate is investigated with regard to incident energy and substrate temperature by molecular dynamics. The results indicate that higher substrate temperature and/or incident energy will result in higher intermixing between the incident atoms and the substrate atoms. Furthermore, the value of the first peak of the radial distribution function (RDF) becomes lower and wider for the Co-Cu system as the substrate temperature and/or incident energy are increased.

Abstract: Valve-less micropumps with one or two piezoelectric buzzers are manufactured and tested. Piezoelectric buzzers are chosen as actuation elements because they are cheap and with high actuation amplitude. The micro-chamber with nozzle and diffuser is fabricated by employing UV photolithography and film mask. A negative photoresistive material, SU8-50, is used as a structure material, and exact angles in the inlet/outlet elements can be obtained. PDMS is chosen to bond different parts of the micropump. The piezoelectric buzzer does have nice actuation amplitude of 40.4 μm after the assembly with the chamber. The results indicate that the micropump with one piezoelectric buzzer has a maximum flow rate of 90.28μl/min when the buzzer is actuated at 100 V and 20 Hz. A maximum backpressure of 50 mm H2O occurs as the buzzer is actuated at 100 V and 30 Hz. For the micropump with two piezoelectric buzzers, it has a maximum flow rate of 165.32 μl/min when the buzzer is actuated at 100 V and 20 Hz and has a maximum backpressure of 84 mm H2O as the buzzer is actuated at 100 V and 30 Hz.