Tomotake Furuhata

Design, fabrication, and operation of submicron gap comb-drive microactuators

Making submicron interelectrode gaps is the key to reducing the driving voltage of a micro comb-drive electrostatic actuator. Two new fabrication technologies, oxidation machining and a post-release positioning method, are proposed to realize submicron gaps. Two types of actuator (a resonant type and a nonresonant type) with submicron gaps were successfully fabricated and their operational characteristics were tested experimentally. The drive voltage was found to be lower than that of existing actuators. The stability of comb-drive actuators is discussed. >

An integrated lateral tunneling unit

A micromachined device developed to perform displacement-controlled tunneling is described. Its performance was experimentally confirmed. The lateral tunneling unit (LTU), composed of a comb-drive actuator, a tunneling tip, and an opposing wall integrated on the same wafer was fabricated using surface micromachining with only one photomask. Integration of the tip and its opposing wall eliminated coarse positioning of the specimen, and realized a fully micromachined tunneling unit. The lateral configuration is easy to fabricate and suitable for integrating other structures such as an atomic force microscope (AFM) tip. The LTU can be used as an extremely sensitive position detector. Possible applications, such as an accelerometer and an integrated AFM/LTU chip, are discussed.<<ETX>>

Face Clustering of a Large-scale CAD Model for Surface Mesh Generation

A detailed CAD model needs manual clean-up, or simplifying operations, before a finite element mesh can be automatically generated because such a model consists of hundreds or thousands of faces many of which may be smaller than a desired mesh element size. We propose an automated face clustering method used as a pre-process of surface mesh generation. By decomposing a model into face clusters so that each region can be projected onto a simple parametric surface such as a plane, we obtain a final mesh as an aggregate of sub-meshes for respective clusters without time-consuming manual preparation work. The projection onto a surface realises re-parameterisation as well as suppression of small details. The main contribution of this work is the integration of (1) a greedy algorithm for combining faces into clusters, and (2) geometric indices that reflect various aspects of a preferable shape for a cluster. The validity of the approach is demonstrated with results of clustering and mesh generation for a realistic-scale CAD model.

Array-driven ultrasonic microactuators

The authors present the design of an array-driven ultrasonic microactuator. Unlike a conventional ultrasonic motor, the array-driven ultrasonic microactuator consists of many distributed modules, using a concept similar to that of the distributed microactuator array. With a conventional ultrasonic motor, it is difficult to control an object locally and to obtain sufficient resolution of the rotor position and orientation without closed-loop control, since the motion of the rotor is produced by traveling waves on the whole diaphragm. However, an array-driven ultrasonic microactuator can control the motion with high accuracy even in open-loop control, because it can control the motion of each distributed module. It uses perpendicular motion, which is suitable for an electrostatic-force-type actuator. Perpendicular motions produced by two transducers in each module are mechanically transformed into circular motion, and a set of circular motions of the micromodules induces motion in the object.<<ETX>>

Operation of sub-micron gap electrostatic comb-drive actuators

Resonant and nonresonant operation of submicron gap, electrostatic, comb-drive actuators is reported. Using a single-mask process and a 4- mu m-thick phosphorus-doped polysilicon layer as the structural material, a resonant actuator and a nonresonant, linear actuator were fabricated and tested. Resonant displacement amplitude of +or-5.2 mu m was observed in a resonant actuator with 0.3- mu m gaps when an AC drive voltage of 11.5 V (peak) without bias was applied. Maximum displacements of 3.6 mu m were observed in a nonresonant linear actuator with 0.2- mu m gaps when a DC drive voltage of 11.1 V was applied. A postrelease assembly technique is used to position and fix the comb-drive suspension such that the drive electrodes of the nonresonant linear actuator are in the submicron gap region prior to the application of the drive voltage. Measured displacements of linear actuators with 0.2-0.65- mu m gaps show little hysteresis and observed performance parameters which are in good agreement with theoretical predictions.<<ETX>>

A discrete spring model for generating fair curves and surfaces

The ability to generate fair curves and surfaces is important in computer graphics (CG), computer-aided design (CAD), and other geometric modeling applications. In this paper, we present an iteration-based algorithm for generating fair polygonal curves and surfaces that is based on a new discrete spring model. In the spring model, a linear spring, whose length approximately represents a curvature radius, is attached along the normal line of each polygon node. Energy is assigned to the difference of the lengths, that is, the difference in curvature radius, of neighboring springs. Our algorithm then minimizes the total energy by an iterative approach. It accepts as inputs (1) an initial polygonal curve (surface), which consists of a set of polygonal segments (faces) and a set of nodes as polygon-vertices, and (2) constraints for controlling the shape. The outputs are polygonal curves (surfaces) with smooth shapes. We also describe a method for improving the performance of our iterative process to obtain a linear execution time. Our algorithm provides a tool for the fair curve and surface design in an interactive environment.

Sub-micron gaps without sub-micron etching

The authors present a processing technique consisting of polysilicon etching, thermal oxidation of polysilicon, and silicon dioxide wet-etching which results in the fabrication of operational, submicron gaps between the electrodes of side-drive actuators, without the need for submicron etching capability. As one example of an application of oxidation machining, this technique was used to define operational submicron gaps between the polysilicon electrodes of an electrostatic comb-drive actuator and a type of linear, side-drive actuator. Experimental results have verified the fundamental principle of the fabrication and indicate that it is possible to achieve operational gaps as small as 0.2 mu m with 10,000 AA resolution.<<ETX>>

Dry releasing of electroplated rotational and overhanging structures

Fabrication by the dry release of electroplated metallic structures is reported. This method results in thick structural height and high yield. It allows the micromechanism to be integrated with electrical circuits, and the needle-shaped residual of the sacrificial layer can be used as the bearing of the micromotor. As examples of this method, micromotors and overhanging structures are demonstrated. A new micromotor design is proposed. Its fabrication and successful testing are described. Overhanging structures such as an LTU (lateral tunneling unit) AFM (atomic force microscope) with overhanging AFM tip and a micro-flow sensor were designed and successfully fabricated.<<ETX>>

Interactive prostate shape reconstruction from 3D TRUS images

This paper presents a two-step, semi-automated method for reconstructing a three-dimensional (3D) shape of the prostate from a 3D transrectal ultrasound (TRUS) image. While the method has been developed for prostate ultrasound imaging, it can potentially be applicable to any other organ of the body and other imaging modalities. The proposed method takes as input a 3D TRUS image and generates a watertight 3D surface model of the prostate. In the first step, the system lets the user visualize and navigate through the input volumetric image by displaying cross sectional views oriented in arbitrary directions. The user then draws partial/full contours on selected cross sectional views. In the second step, the method automatically generates a watertight 3D surface of the prostate by fitting a deformable spherical template to the set of user-specified contours. Since the method allows the user to select the best cross-sectional directions and draw only clearly recognizable partial or full contours, the user can avoid time-consuming and inaccurate guesswork on where prostate contours are located. By avoiding the usage of noisy, incomprehensible portions of the TRUS image, the proposed method yields more accurate prostate shapes than conventional methods that demand complete cross-sectional contours selected manually, or automatically using an image processing tool. Our experiments confirmed that a 3D watertight surface of the prostate can be generated within five minutes even from a volumetric image with a high level of speckles and shadow noises.

Smoothing of Noisy Laser Scanner Generated Meshes Using Polynomial Fitting and Neighborhood Erosion

This paper presents a method for removing geometric noise from triangulated meshes while preserving edges and other intended geometric features. The method iteratively updates the position of each mesh vertex with a position lying on a locally fitted bivariate polynomial. The user selects the width of the vertex neighborhood, the order of the fitted polynomial, and a threshold angle to control the effects of the smoothing operation. To avoid smoothing over discontinuities, the neighborhood can be eroded by removing vertices with normals that deviate beyond a threshold from the estimated median normal of the neighborhood. The method is particularly suitable for use on laser scanner generated meshes of automobile outer body panels. Smoothing methods used on these meshes must allow C 2 continuous equilibrium surfaces and must minimize shrinkage. Despite the abundance of existing smoothing schemes, none addresses both of these specific problems. This paper demonstrates the effectiveness of our method with both synthetic and real world examples. @DOI: 10.1115/1.1737381#