Yamato Fukuta

Design, fabrication, and control of MEMS-based actuator arrays for air-flow distributed micromanipulation

This paper reports the design, fabrication and control of arrayed microelectromechanical systems (MEMS)-based actuators for distributed micromanipulation by generation and control of an air-flow force field. The authors present an original design of pneumatic microactuator, improving reliability and durability of a distributed planar micromanipulator described in the previous study. The fabrication process is based on silicon-on-insulator (SOI) wafer and HF (hydroflouric acid) vapor release, which also significantly increases the production yield of the 560 microactuator array device of 35times35 mm2. Minimization of the electrostatic actuation pull-in voltage through suspension shaping fabrication was also studied, and successfully validated for electrical efficiency improvement. A distributed control method to achieve good conveyance performance and reduce motion control instability was investigated. An emulation approach was chosen to validate a decentralized control strategy on the distributed active surface in order to conduct a proof-of-concept of a future smart structure, integrating sensors, intelligence, and microactuators. Thus, a centralized/decentralized control flow, inspired by autonomous mobile robot principles, was applied. It was modeled and implemented using C-programming language. Experimental and characterization results validate the control method for feedback micromanipulation with good velocity and load capacity performance

Vapor Hydrofluoric Acid Sacrificial Release Technique for Micro Electro Mechanical Systems Using Labware

We have developed a novel technique of sacrificial layer etching for micro electro mechanical systems (MEMS). Our technique uses vapor of hydrofluoric acid (HF) to etch sacrificial silicon oxide and to make freestanding silicon microstructures. The advantages of this technique are: (1) no subsequent water rinse is needed, (2) freestanding silicon microstructures can be successfully released without sticking to the substrate, (3) equipment for our vapor phase HF etching simply consists of Teflon beakers only. Conditions for the technique have been optimized by estimating etching rate with test patterns made of silicon-on-insulator (SOI) wafers and by observing water droplets condensation on the sample surface with thermally oxidized silicon chips. By this technique we have successfully obtained freestanding microstructures of SOI wafers. Microcantilevers of as long as 5000 µm (a 5-µm-wide, 10-µm-thick, and 5000-µm-long cantilever over a 0.6-µm-gap) have been successfully released without adhering to the base substrate or contacting the neighboring cantilevers. We have also fabricated and actuated electrostatic comb-drive actuators of 60 and 200 comb pairs to demonstrate high processing yield of our nonstick releasing technique.

Microactuated self-assembling of 3D polysilicon structures with reshaping technology

This abstract proposes and experimentally confirms the automatic self-assembling of 3D polysilicon structures, compatible with both mass production and IC based surface machining. This technique combines an integrated actuation based on the scratch drive actuator (SDA), for the structure raising up, and the reshaping technology to obtain the permanent 3D shapes. Complex 3D structures have been successfully realised and their electrostatic actuation have been obtained. This self-building capability of 3D devices from silicon surface micromachining opens new integration capabilities and new application field for MEMS.

FPGA-Based Decentralized Control of Arrayed MEMS for Microrobotic Application

In this paper, the authors have developed and implemented a decentralized decision-making strategy using field-programmable gate array (FPGA) technology as a prototype for an integrated controller of a microelectromechanical systems (MEMS) array for air-flow planar micromanipulation. The MEMS array was proposed to be integrated in a hybrid multichip module containing the FPGA-based controller. Algorithms and architectures, used for the decentralized control implementation and the hardware resource optimization, are described. A charge-coupled device camera was used to make each MEMS like an autonomous system when the distributed MEMS chip was tested. Finally, under air-flow condition, the FPGA-based decentralized control system successfully performed an object manipulation.

Novel Railway Signal Control System Based on the Internet Technology and Its Distributed Control Architecture

We have developed a novel railway signal control system that operates as a distributed system. It consists of a central control unit (called LC) and terminal devices (called FC) that are distributed at the railroad wayside aid operate signal devices. The Internet technologies and optical LAN technologies have been used as communication methods between the LC and the FCs. While handling enormous amount of electric cables may cause human errors, the system is expected to reduce troubles of the current signal system at construction works thanks to the Internet technologies. The FC is a distributed terminal device that has its own processor and placed at the railroad wayside to control the field signal devices. The LC is a centralized computer device that has software arranged by the function of the field devices. An optical network system and multiple communication paths between the LC and the FCs realize durable transmissions. Moreover, the assure performance of controls and transmissions have been investigated, and the autonomous distributed signal control system is also discussed as the next steps of the system

Pneumatic two-dimensional conveyance system for autonomous distributed MEMS

We have proposed a micro conveyance system, which is based on the autonomous distributed MEMS. A controlling method suitable for our system has also been proposed. To realize a conveyance part of the system, we have developed an array of air-flow micro actuator by bulk micromachining technology. One-dimensional conveyance of a small object (2.1 mm/spl times/4.1 mm, approximately 4 mg weigh) was demonstrated with the help of the air-flow (17 kPa). A two-dimensional system composed of 560 micro actuators in a 35 mm/spl times/35 mm area was realized. Almost all the actuators were successfully driven by electrostatic force. We have achieve levitation-motion and transfer-motion of the object nevertheless full control of two-dimensional conveyance is under trial. We have also developed an integrated circuit composed of an array of sensors and processors by 0.8 /spl mu/m-rule CMOS fabrication process. The circuit works as a distributed processing system to recognize a shape of a micro object. Assembling of the present actuator array with control circuits is in progress.

A highly simple failure detection method for electrostatic microactuators: application to automatic testing and accelerated lifetime estimation

Reliability and testability are two important factors for the development of batch fabrication of microelectromechanical systems (MEMS) or mixed MEMS/IC applications. In that frame, an easy-to-implement electrical method of detection of failures is presented in this paper, valid for every kind of electrostatic microactuators showing pull-in behavior, with great expectation value in the case of arrayed MEMS. The method relies on the detection of a pull-in current peak at very low frequency. An experimental setup is described and results are shown obtained with prototypes of electrostatic microactuators with parallel capacitances created by deep reactive ion etching on silicon-on-insulator wafers. This method is really suitable for automation and application to on-line testing during mass production and reliability studies. The functional schematic of a test circuitry is proposed for implementation in an industrial tester or for built-in self-test purposes. Then, in order to illustrate the benefits of this method for reliability studies, it is used in conjunction with high voltage testing for accelerated lifetime measurements. A time gain factor of 20 is achieved with above-mentioned test structures.

A MEMS array for pneumatic conveyor and its control based on distributed system

In this paper, a pneumatic conveyor and its control mode are proposed for tiny object manipulation. The conveyor consists of a 2D array of 560 air-nozzle actuators realized by the silicon MEMS technology. A distributed control method, based on local air-flow force application, has been developed and successfully validated. Experimental and characterization results are finally presented and analyzed.

A Reshaping Technology With Joule Heat For Three Dimensional Silicon Structures

This paper presents a new basic reshaping technology which is efficient to realize real three dimensional silicon microstructures. In this process, the elastically deformed polysilicon structure is annealed by Joule heating generated by the current passing through the structure. Plastic deformation occurs resulting in permanent three-dimensional shapes. The application of this basic process to different polysilicon structures is successfully performed. Some quantitative characteristics of the annealing effects are also investigated by means of structure deformation measurements.

A Railway Signal Control System by Optical LAN and Design Simplification

When replace railway interlocking devices, setting up of large number of signal cables and confirming of wiring connections are required. So, it is worried that serious transport disorder caused by human error in wiring works would occur. We have developed a railway signal control system utilized optical LAN to reduce the signal cables and wiring works. Moreover, all signal devices operate independently, designers have to handle all devices one by one and pay great attention to avoid causing harmful influence each other. We propose the data-driven method to make easy to replace interlocking device. This logic is rearranged according to the field device in order to simplify and decrease design duties of designers. In this paper, we introduce this system, and describe network transmission, safety-related communication and software configuration of the system.