Carbon Deposition on Blade Surfaces of Laser Microactuator for Optical MEMS

A laser opto-microactuator has been proposed as an Optical Micro-Electro-Mechanical-Systems (OMEMS). The rotational or twisting mechanisms of the microactuator have been discussed. For increasing the sensitivity of the actuator, the temperature difference between the front and rear blade surfaces of the actuator should be increased. Therefore, high absorption rates on the blade surface with laser beam irradiation and low heat conductivities of blade materials are needed. In the present paper experimental and numerical approaches have been carried out. For increasing the absorption rates of a laser beam on the blades of the microactuator, carbon molecules were deposited from a heated carbon fiber to substrates in a vacuum deposition machine. The deposition rates were experimentally measured and are compared with the numerical results by DSMC. INTRODUCTION With the coming of the 21 century, because electronic technology and the industry of mechanical information merging developed to high performance, mechanical technology is being developed and carried on to the micro mechanical technology that has the characteristic of lightweight and detailed technology. A laser opto-microactuator has been proposed as an Optical Micro-Electro-Mechanical-Systems (OMEMS) [1], [2], [3]. In order to prove a non-wiring type of energy supplying method, a kind of energy absorption film has been studied for improving the rotational characteristics of the laser beam micro-actuator. Carbon black powder that was used conventionally on the actuator turns round, so it is easy to make the carbon come off and then reduce the rotational characteristics because the carbon cannot be coated evenly. In order to solve the problem above-mentioned, a new vacuum deposition device was adopted to make a carbon film, a laser energy absorption film. The characteristics of the energy absorption film were appraised by an optical method meaning transmittance, reflectance and absorption. The numerical analysis with DSMC method was carried; meanwhile a film thickness was evaluated. VACUUM DEPOSITION EXPERIMENTS In the vacuum deposition experiments, deposition materials were heated in vacuum conditions under a low-voltage for heating, and the particles produced were sent towards a glass substrate, on which a film was condensed and produced in this study. CC-40F carbon coater was used instead of a conventional method fixed carbon black powders with an adhesive medicine. The carbon fiber heated by electric current evaporated carbon particles and then produced the energy absorption film for a laser beam. The photo of a deposition machine is shown in Figure 1. After being furnished with 4 electrodes in a vacuum chamber, an alternating current was used between each electrode. The carbon fiber fixed at the electrodes evaporated the carbon particles after heating the fiber. After setting up a stage that can be moved freely in the vacuum chamber, the deposition distance between the fiber and a substrate (glass) can be fixed. According to the film thickness of reference data, the deposition distance and the deposition pressure were designed, and then the deposition experiments were carried out. The amounts of the deposition decrease with increasing the deposition distance. In order to absorb the light energy effectively, the light energy of transmission should be reduced. Therefore the method of increasing the thickness film can be reached. The deposition experiments must be repeated many times. As shown in the figure 2, the total thickness of the film increases with increasing the deposition times. With increasing the times of the deposition, the deposition distance increases also. As shown in Figure 3, with the increment of deposition times, the amounts of the deposition increase. On the other hand, the transmittance and reflectance of the light from the deposited surface decrease, and the absorption increases. The temperature of the deposition film surface increases with the increment of the deposition times. Figure 1 Photo of deposition machine Electrode Chamber Roof Vacuum Stage