Understanding filling flow into micro-channels is important in designing micro-injection molding, micro-fluidic devices and an MIMIC (micromolding in capillaries) process. In this paper, we investigated, both experimentally and numerically, 'transient filling' flow into micro-channels, which differs from steady-state completely 'filled' flow in micro-channels. An experimental flow visualization system was devised to facilitate observation of flow characteristics in filling into micro-channels. Three sets of micro-channels of various widths of different thicknesses (20, 30, and 40 µm) were fabricated using SU-8 on the silicon substrate to find a geometric effect with regard to pressure gradient, viscous force and, in particular, surface tension. A numerical analysis system has also been developed taking into account the surface tension effect with a contact angle concept. Experimental observations indicate that surface tension significantly affects the filling flow to such an extent that even a flow blockage phenomenon was observed at channels of small width and thickness. A numerical analysis system also confirms that the flow blockage phenomenon could take place due to the flow hindrance effect of surface tension, which is consistent with experimental observation. For proper numerical simulations, two correction factors have also been proposed to correct the conventional hydraulic radius for the filling flow in rectangular cross-sectioned channels.

A micro heat flux sensor which can measure the thermal energy transfer per unit area has been designed, fabricated, and calibrated in a convective environment. The sensor which is based on a circular foil gage is composed of thermal paths and a thermopile. The thermal path is made in a LIGA-like process of SU-8 high aspect ratio microstructures and electroplated copper layers. The thermopile, a series of thermocouples, is used to amplify the output signal as a thermometer. When the sensor is placed on a high-temperature wall, heat flux from the wall flows through thermal paths and drains out to the environment, producing a temperature difference along its paths. Heat flux is obtained by calibrating this temperature difference in the thermopile of Ni-Cr or Al-Chromel pairs. The sensitivity of the heat flux sensor of Ni-Cr and Al-Chromel pairs is in the range of 0.1-2.0 and 0.4-2.0 µV mW −1 cm −2 , respectively, in the heat flux range of 0-180 mW cm −2 .

A novel electrostatic microgripper, which can grip and release micro objects with the electrostatic force, has been designed and fabricated. It consists of gripping part with one inner and two outer electrodes, and releasing part with an electrothermal actuator. It grips micro objects using electric field generated between the electrodes, and releases them using the backward motion of inner electrode with electrothermal actuation. The backward motion of inner electrode breaks the electric field and rapidly reduces the remaining charges of objects. The graspless work shows the safe object handling method and also suggests the solution for the releasing problem. The inner electrode achieves 23 μηι backward motion at 100mA, and the microgripper successfully grips glass beads with 170μηι diameter at 250V.

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A novel electrostatic microgripper, which can handle micro objects with the electrostatic force, is designed and fabricated. It consists of gripping piirt with one inner and two outer electrodes, and releasing part with an electrothermal actuator. It grips micro objects using electric field generated between the electrodes, and releases them using the backward motion of 'inner electrode with electrothermal actuation. The backward motion of inner electrode breaks the electric field and rapidly reduces the remaining charges of objects. The graspless work shows the safe object handling method and also suggests the solution for the releasing problem. The microgrippers are fabricated with 20pm and 40pm thick SO1 wafers, and they successfully grip glass beads with 170pm diameter at 250V and 1 OOV, respectively.