• Journal of Electrochemical Science and Technology
• /
• v.8 no.3
• /
• pp.215-221
• /
• 2017

The electroless plating process largely consists of substrate cleaning, seed formation (activator formation), and electroless plating. The most widely used activator in the seed formation step is Pd, and Sn ions are used to facilitate the formation of this Pd seed layer. This is problematic because the Sn ions interfere with the reduction of Cu ions during electroless plating; thus, the Sn ions must be removed by a hydrochloric acid cleaning process. This method is also expensive due to the use of Pd. In this study, Cu electroless plating was performed by forming a seed layer using a silver nanosol instead of Pd and Sn. The effects of the Ag nanosol concentration in the pretreatment solution and the pretreatment time on the thickness and surface morphology of the Cu layer were investigated. The degrees of adhesion to the substrate were similar for the electroless-plated Cu layers formed by conventional Pd activation and those formed by the Ag nanosol.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.11
• /
• pp.119-125
• /
• 2008

The objective of this study was to compare micro-scale friction coefficients with and without synovial fluid, and micro-scale measurements were performed using atomic force microscopy (AFM) with a $5{\mu}m$ spherical probe. Four cylindrical cartilage specimens were harvested from two fresh bovine humeral heads (4-6 months old). $Average{\pm}standard$ deviation values of the micro-scale AFM frictional coefficients calculated from the liner fit of friction versus normal force was $0.177{\pm}0.012$ and $0.130{\pm}0.010$ with and without synovial fluid coating on AFM probe respectively, showing its reduction by ${\sim}27%$ with synovial fluid. To the best of our knowledge, this experimental study investigates the first such comparisons of frictional response of articular cartilage with and without synovial fluid coating on AFM probe, and provides significant insights into the role of synovial fluid in the articular cartilage friction and lubrication independently of the confounding effect of fluid pressurization in the articular cartilage.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.04a
• /
• pp.45-48
• /
• 2007

Conventional force sensors such as piezoelectric sensor has limitations for measuring micro/nano-scale thrust. In this study we developed nano-scale measurement system using laser displacement sensor and cantilever. And electrospray microthruster was fabricated by using stainless capillary and extraction electrode, to generate nano-scale thrust. The measurement system can measure the around 90 nN thrust from this thruster. In addition, we designed and fabricated electrospray micro thruster based on PMMA(Polymethyl methacrylate), which has a nozzle protruded from the substrate.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.711-712
• /
• 2009

The fabrication of micro-scale irregular holes by using PMMA (Poly Methyl Methacrylate) beads in the front dielectric layer was proposed to improve luminous efficacy of an ac plasma display panel. Through the firing process of front dielectric layer, bowl shaped holes with a depth of $2.5{\mu}m$, a top diameter of $8-12{\mu}m$, and a bottom diameter of $4-7{\mu}m$ were fabricated. The proposed ac plasma display panel with the irregular micro-scale holes improved the luminous efficacy by 18 % due to the decrease in the minimum sustain voltage.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2005.05a
• /
• pp.424-428
• /
• 2005

This paper shows a non-contact optical method to inspect micron scale parts which will be manufactured in micro-factory system. This inspection system should have some characteristics like a small size, flexibility, and high measuring speed. In the viewpoint of measuring capabilities, it also has resolution under micron scale with measuring range over millimeter scale. Two methods will be presented in this paper, one is Moire and the other is white-light scanning interferometry. Also some experimental results will be presented to show the possibilities of the proposed inspection system.

• Structural Engineering and Mechanics
• /
• v.71 no.3
• /
• pp.223-232
• /
• 2019

Since the actuators with small- scale structures may be exposed to external reciprocal actions lead to create undesirable loads causing instability, the buckling behaviors of them are interested to make reliable or accurate actions. Therefore, the purpose of this paper is to analyze plastic buckling behavior of the micro beam structures by adopting a Conventional Mechanism-based Strain Gradient plasticity (CMSG) theory. The effect of length scale on critical force is considered for three types of boundary conditions, i.e. the simply supported, cantilever and clamped - simply supported micro beams. For each case, the stability equations of the buckling are calculated to obtain related critical forces. The constitutive equation involves work hardening phenomenon through defining an index of multiple plastic hardening exponent. In addition, the Euler-Bernoulli hypothesis is used for kinematic of deflection. Corresponding to each length scale and index of the plastic work hardening, the critical forces are determined to compare them together.

• Journal of Sensor Science and Technology
• /
• v.32 no.5
• /
• pp.280-284
• /
• 2023

In this study, a prototype micro-scale photomask and microfluidic channel mold were fabricated using the thermal shrinkage of the polymer. A polystyrene (PS) sheet was used as the heat-shrink polymer, and the patterns of the photomask and microchannel are interdigitated electrodes. Patterns were formed on the PS sheets using a commercial laser printer. The contraction ratio of the PS sheet was approximately 60% at a temperature of 150 ℃, and the transmittance was reduced by approximately 0% at a wavelength of 365 nm. The microfluidic channel had a round shape. The proposed technique is simple, facile, and inexpensive for fabricating a micro-scale photomask and microfluidic channel mold and does not involve the use of any harmful materials. Thus, this technique is well-suited for fabricating diverse micro-scale patterns and channels for prototype devices, including sensors.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.387-391
• /
• 2011

Since MEMS based micro actuators or generating devices have high efficiency per volume, plenty of research are ongoing. Among them, MEMS based millimeter-scale micro gas' turbine is one of the most powerful issue for replacing chemical batteries. However, since limiting of MEMS manufacturing technique, it is very difficult that makes wide turbine bearing area. It causes low DN number, so sufficient bearing force is hard to achieve. Thus, the most important issue on micro gas turbine is proper bearing design which can keep rotor stable during operation. In order to that, micro-scale gas-lubricated bearing is generally used. In this paper, basic feasibility study and design of journal bearing for 10mm diameter micro gas turbine is described Journal bearing is hydrostatic gas-lubricated type. Numerical simulation is performed with ANSYS CFX 11.0 which is commercial numerical tool. Repulsive force when there is radial displacement in bearing and returning time is calculated using steady and unsteady cases. Auto re-meshing technic is used for moving mesh unsteady cases which simulate displacement of axis and its movement. The simulation results are used for further design of micro gas turbine, and experiment will be done later.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.163-168
• /
• 2006

In a micro-unit of electronic-machine, vibration can be excited by a small impact, and this vibration acts as a fatigue load. To measure the vibration effect on the micro unit, a micro dynamic tester is needed to test a micro specimen. In this paper, it has confirmed a movement of the PZT(piezo actuator) to use a sine signal. And, it has confirmed a fracture of specimens by using a tension-tension input signal in PZT. A metal-material property in the micro scale has been tested to compare with the macro scale. A fatigue test has been conducted by using PZT actuator to give a bending-tension effect.

• Steel and Composite Structures
• /
• v.26 no.1
• /
• pp.89-102
• /
• 2018

This work investigates a novel plate formulation and a modified couple stress theory that introduces a variable length scale parameter is presented to discuss the static and dynamic of functionally graded (FG) micro-plates. A new type of third-order shear deformation theory of Reddy that use only 4 unknowns by including undetermined integral variables is proposed in this study. The equations of motion are derived from Hamilton's principle. Analytical solutions are obtained for a simply supported micro-plate. Numerical examples are presented to examine the effect of the length scale parameter on the responses of micro-plates. The obtained results are compared with the previously published results to demonstrate the correctness of the present formulation.