Theoretical Study on the Surface Force in Microstructures

In microstructures such as microsensors and microactuators fabricated by semiconductor micromachining technologies, surface areas per unit volume are larger compared with those in conventional macroscopic structures. Further, when movable parts in the micromachined structures contact with counter parts separated by small gaps, contact areas per unit surface area are usually larger than those in the macroscopic structures, since the surfaces of the microstructures are usually smoother. Therefore, in the microstructures, interactions between the surfaces are relatively large compared with gravitational force and inertia force which are proportional to the volume and the surface force plays important roles in their fabrication processes and in their operations. For example, in some microstructures fabricated by surface micromachining technologies, they couldn’t operate because their movable parts adhered to counter parts separated by small gaps by the surface force . Further, in micro motors formed on substrates,