Jiang Hongyuan

Electrohydromechanical analysis based on conductivity gradient in microchannel

Fluid manipulation is very important in any lab-on-a-chip system. This paper analyses phenomena which use the alternating current (AC) electric field to deflect and manipulate coflowing streams of two different electrolytes (with conductivity gradient) within a microfluidic channel. The basic theory of the electrohydrodynamics and simulation of the analytical model are used to explain the phenomena. The velocity induced for different voltages and conductivity gradient are computed. The results show that when the AC electrical signal is applied on the electrodes, the fluid with higher conductivity occupies a larger region of the channel and the interface of the two fluids is deflected. It will provide some basic reference for people who want to do more study in the control of different fluids with conductivity gradient in a microfluidic channel.

Energy dissipation of a ring-like metal rubber isolator

Metal rubber (MR) is a kind of homogeneous poroelastic damping material made of metal wire. In this paper, by analyzing the forces on the MR isolator and the MR element, the hysteresis loops of the force and deformation are studied and verified by experiments. The results show that the force and displacement hysteresis loop of the MR isolator is described by the force and deformation hysteresis loops of the MR elements. In addition, the relationship between the energy dissipation coefficient of the MR element and that of the MR isolator is derived. The energy dissipation coefficient is programmed and calculated by MATLAB using experimental data, and the results are compared with the theoretical value. It is the basis for the design and applied research of the MR isolator in a future study.

Notice of Retraction Analysis of the basic mechanical parameters of Metal Rubber materials

Metal rubber is a porous material; it has characteristics of strong adaptability, corrosion resistance, radiation resistance and designability. In this paper, we have studied elastic modulus and stress of friction for compression and tension, energy dissipation coefficient for different directions and friction coefficient have been studied also. Research results are basic but essential for finite element analysis and engineering application of Metal Rubber materials.

Modeling of micro-friction in a multi-layer metal plate damper for a rotor support system

The energy dissipation of multi-layer metal plate damper is realized by dry friction caused by the micro-motion between adjacent layers when the damper is deformed. In the study, the damper is modeled with a single layer continuous beam with uniform thickness, in which the stress status is analyzed when the damper is deformed. The contact surface of the beam is simplified to discrete elements to analyze the energy dissipation based on Mindlin model. A finite element model is used to simulate the energy dissipation process to rectify the theoretical calculation. Considering the distribution and the intensity of the friction force at the contact area, the simulated results of micro friction on the contact surface have the good agreement with the experimental ones, which is beneficial to the wear and failure analysis of the multi-layer metal plate damper.

Study on automatic power control in FES cycling

In order to improve the performance of the lower-limb FES cycling, a method of measuring the automatic control Power in the cycling was developed based on the estimation of dynamic models of the response from muscle stimulation intensity to power. The identified models were used for analytical design of feedback controllers. The results showed that this method had ability to achieve an accurate control of power and track arbitrary signals obtained from healthy adults, which shows its feasibility to the experiment on the paraplegic.

Effects of thermal deformation of the head and the heater on the pressure of HDI

In this study the static characteristics are analyzed with consideration of the convection heat transfer between the fluent and the solid, and the thermal-induced deformation of solid. The pressure, temperature and thermal deformation at head/disk interface (HDI) are simulated. The steady state characteristics of the interface of the head and disk are obtained.

Effect of surface topography of disk on lubricant distribution and lubricant transfer between disk and slider

Lubricant transfer from the disk to the slider can affect the slider flying ability. Based on molecular dynamics simulation, we investigated the effects of the roughness of diamond like carbon (DLC) and disk surface protrusion on lubricant distribution on a disk surface and lubricant transfer between the disk and the slider using modified coarse-grained, bead-spring model. The simulation results showed that the effect of DLC roughness on the average lubricant thickness and on the disk surface roughness is small. However, the effect of disk surface protrusion on lubricant distribution on a disk surface is more significant. The roughness of DLC layer and disk surface protrusion result in an increase in the volume of lubricant transfer. Between these two, the effect of the disk surface protrusion is much more important than that of the DLC layer roughness.

AC electric field enhanced rapid serum immunoassay for Johne’s Disease

Early immunoassay is essential at the beginning of human/animal disease diagnosis. Due to limited concentration of antibody and slowly nature diffusion, it takes hours or more time to detect the disease specific antibody in serum using traditional diagnosis methods. A novel approach is proposed to enhance the convection and mass transfer in the micro channel based on AC electroth- ermal effect and dielectrophoresis, improving the antigen-antibody specific binding efficiency greatly, even the antibody in the serum at low concentration level. A platform with interdigited electrode array on silicon wafer and PDMS micro channel is developed for bovine paratuberculosis(Johnes Disease) rapid diagnosis. It only takes 2 minutes to distinguish positive serum from negative ones by measuring the change of electrode/serum interfatial electrical double layer capacitance at real time. Ac electric field enhanced rapid serum immunoassay diagnosis mechanism is presented based on AC electrolthermal and dielectrophoresis theory. Convection and mass transfer is greatly enhanced by AC electric field, leading to a rapid specific binding. The change of disease specific antibody concentration in the micro channel is simulated, showing validity of the novel rapid immunoassay diagnosis method.

Lubricant transfer mechanism and process between slider and disk

The increasing of areal density of hard disk drives promotes the decreasing of the slider flying height. Lubricant transfer between slider and disk, caused by reducing slider flying height, plays an important role in affecting slider flying stability. In this study, the improved coarse-grained, bead-spring model is used to investigate the mechanism of lubricant transfer between slider and disk by molecular dynamics simulation. The effects of lubricant thickness on disk surface, lubricant type, and local temperature difference on the slider surface on lubricant transfer are studied. We observe that the amount of lubricant transferred to the slider sharply increases with the increase of lubricant thickness value on the disk surface. Increasing the number of hydroxyl groups in an individual lubricant molecule can greatly reduce the volume of the lubricant transferred to the slider. In addition, the local temperature difference on the slider surface can increase the volume of lubricant transferred to slider. What is more, the increasing of the number of hydroxyl groups contained in an individual molecule can considerably improve the influence of the local temperature difference on the lubricant transfer between slider and disk.

Automatic microcircuit formation based on gold-coated SU-8 microrods via dielectrophoresis

To explore the application of the characteristics of metallic microparticles, alternating current electric trapping of the SU-8 microrods coated with a thin gold layer by the chemical approach is investigated. Positive dielectrophoresis is used to absorb the gold-coated SU-8 microrods at the edge of the parallel electrodes, thereby forming chains to connect the electrodes. This is a fast automatic microcircuit formation process. Moreover, a non-charged molecule is modified on the surface of the gold-coated SU-8 microrod, and the modified microrods are controlled by the alternating electric field to form a number of chains. The different chains between the parallel electrodes consist of various parallel circuits. In order to compare these chains with different electric surfaces, the impedances of the metallic and modified microrods are measured and compared, and the results show that the gold-coated microrods act as pure resistors, while the microrods functionalized by a non-charged molecule behave as good capacitors.