Papers by Author: Kai Leung Yung

Abstract: This paper demonstrates the comparisons of molding with micro molds made of different elastomeric polymers. Micro molds made of pure polydimethylsiloxane (PDMS), 0.3% carbon nanotube (CNT) enforced polydimethylsiloxane (PDMS), 2% carbon nanotube (CNT) enforced polydimethylsiloxane (PDMS) and commercial available high temperature silicon rubber sheet (Avon Group) were studied. Micro moldings using different molding pressures were performed. By comparing the dimensions of micro features produced with different molding pressures, molding accuracies of using micro molds made of different elastomeric polymers are obtained. Results of this study provide valuable information for the development of elastomer micro mold insert for micro injection molding.

Abstract: Micro overmolding is becoming more important with the rapid development and applications of microproducts in bioengineering, electronics and other areas in recent years. This paper presents our findings in studying polymer interfaces in micro channels of a micro mold during overmolding process. The bonding strengths between polycarbonate (PC) and thermoplastic polyurethanes (TPU) were examined and compared under different overmolding conditions. Results show bonding behaviors in micro channels are not only affected by temperatures, they are also influenced by surface roughness.

Abstract: The most apparent advantages of thermoplastics are the recyclability and processibility. To obtain recyclable and injectable conductive polymer, this paper studied the filling of carbon nanotubes (CNT) in polystyrene(PS) and the aligning of CNT in PS under high frequency electric field and ultrasonic vibration using an experimental set up developed in our laboratory. Results of these studies would be very useful to the development of a new generation of micro fabrication method for producing integrated micro electronic products using micro injection molding that is the most cost effective way to produce micro products massively.

Abstract: To fabricate high aspect ratio micro/nano features, demolding is more challenging than filling of melt into micro mold as solidified micro features can be easily peeled off when demolding resistance is high. Besides using anti-stick agent, using deformable mold is a new solution proposed by the authors. This paper presents a setup for testing the deformable active mold. Experimental results on micro thermal molding with the developed mold deforming system prove that the new system can successfully demold high aspect ratio micro features that can not be produced with traditional metal mold.

Abstract: In this paper, we demonstrate using laser induced forward transfer (LIFT) technology to deposit Ti/Ni alloy on a glass substrate with high precision. Here the photonic feature of laser energy is used to move the Ti/Ni particles forward and deposit them on the glass, while the wave feature of laser is used to turn part of the Ti/Ni particles into ions. The characteristics of deposited films and their relations with the processing conditions are studied. A new method of depositing materials using photons instead of electrons in electric field may bring about a series of new technologies on surface deposition, which can be used to produce shape memory alloys.

Abstract: Elastomeric polymers have been used as moulds for fabricating micro structures in the soft lithography technology due to their elastic features and unstickiness to polymer features. Previously, the micro moulds were normally produced by imprinting on micro prototypes, which are fabricated using deep reactive etching or photolithography. In this paper, we introduce a direct mould fabrication method, which uses pulsed laser drilling technology to directly generate high aspect ratio patterns in elastomeric polymers. The effects of laser parameters such as pulse repetition rate and average power on the drilling qualities are systematically studied. The techniques presented in this paper would provide a more flexible way to fabricate high aspect ratio micro features on elastomer mould efficiently.

Abstract: The purpose of this paper is to introduce a simplified yet efficient method to identify the critical parameter of MEMS device based on rapid computer experiments instead of expensive physical experiments. The prototype model of MEMS device is rapidly established by connecting reusable and parameterized element models based on developed element model library. Critical parameters are identified and optimal parameter assemblies are obtained using Taguchi method based on computational experiments of the prototype model. A typical MEMS device--micro resonator is used for demonstrating the design methodology. The method enables the designer to rapidly identify critical parameter of a new MEMS device in early stage of design.

Abstract: A method of fabricating nanotemplate and nanowires by the anodization of bulk aluminum at room temperature is reported in this paper. Details of manufacturing processes as well as some in-depth discussions on the formation mechanism of nano pores with reference to the phenomena observed in experiments are presented. Effects of fabricating conditions such as the anodization time, temperature, current intensity, voltage and features of solutions, were studied in the experiments.

Abstract: The precision control of the injection process in micro injection molding demands precise tracking of the moment that melt front passes through the nozzle so that accurate prediction of the amount of melt being injected into the mould can be achieved. The tracking accuracy, to large extent, depends on the processing of pressure signals followed by the identification of the critical moment that melt front reaches the nozzle. A new adaptive Kalman filter was introduced in this study to calculate and predict the amount of melt injected. The filter eliminated the delay error and was more robust than other filters. The adaptive Kalman filter switches between two Qs for steadystate and transient estimations, allowing resetting of the Kalman gain so that convergence is speeded up in calculations. Experimental and simulation results prove the effectiveness of the method proposed.

Abstract: The advances of wireless networking technologies and mobile devices has prompted many modern enterprises to look for management information systems to remotely monitor and control of their company operations in order to increase their flexibility and competitiveness in the market. Multi-agent modeling has emerged as a powerful technology for dealing with cooperation and decision-making processes in distributed information system applications. In this paper, we proposed a Mobile-enterprise Multi-Agent Paradigm (MMAP) which is an intelligent multiagent-based system combined with wireless VPN technology to provide various management operations to senior executives by PDA (Personal Digital Assistant) with wireless data networks. To demonstrate how the architecture can be built, the data collection agent, one of the primary component-ts of the proposed paradigm, is developed into a prototype implementation for part of the MMAP.