Robot leg motion in a planarized-SOI, two-layer poly-Si process

With the ultimate goal of creating autonomous microrobots, we developed a five-mask process that combines two polysilicon structural layers with 50-/spl mu/m-thick SOI structures and a backside substrate etch. The polysilicon layers provide three-dimensional (3-D) hinged structures, high compliance structures, and electrical wiring. The SOI structural layer yields much stronger structures and large-force actuators. This process was developed as a part of a three-chip solution for a solar-powered 10-mg silicon robot. Here, we describe the fabrication of this planarized-SOI, two-layer poly-Si process (henceforth called the SOI/poly process), basic modules in the design of robot legs in this process, and lastly, the results of fabricated robot legs. In designing the leg structures, we developed guidelines and test structures to provide a better understanding of the robot leg performance. These guidelines include understanding the relationship between the lateral etch depth to the actuator spacing and performing static friction tests of polysilicon flaps to more accurately model the frictional forces of the linkages. Last, we report on the performance of the robot legs and inchworm motors. On an 8 mm /spl times/ 3 mm robot, we have demonstrated a 1 degree-of-freedom (DOF) robot leg, 1 mm in length, which demonstrates up to 60 /spl mu/N of vertical leg force with an angular deflection of almost 30/spl deg/. A two-DOF robot leg, also 1 mm in length, operated with at least 90/spl deg/ of angular deflection, and each inchworm motor demonstrated a shuttle displacement of 400 /spl mu/m with speeds up to 6.8 mm/s. In addition to robot legs, a bidirectional inchworm motor that produces equivalent forces in both directions was also fabricated in this SOI/poly process. This motor uses an additional set of gap-closing-actuator (GCA) arrays to prebias the drive frame.

[1]  Paolo Dario,et al.  Microactuators for microrobots: a critical survey , 1992 .

[2]  Norman C. Tien,et al.  Fabrication of thick silicon dioxide sacrificial and isolation blocks in a silicon substrate , 2002 .

[3]  Ronald S. Fearing,et al.  Development of PZT and PZN-PT based unimorph actuators for micromechanical flapping mechanisms , 2001, Proceedings 2001 ICRA. IEEE International Conference on Robotics and Automation (Cat. No.01CH37164).

[4]  Kristofer S. J. Pister,et al.  Surface-micromachined components for articulated microrobots , 1996 .

[5]  I. Shimoyama,et al.  Creation of an insect-based microrobot with an external skeleton and elastic joints , 1992, [1992] Proceedings IEEE Micro Electro Mechanical Systems.

[6]  Ho Nam Kwon,et al.  Design and characterization of a micromachined inchworm motor with thermoelastic linkage actuators , 2002 .

[7]  Göran Stemme,et al.  A WALKING SILICON MICRO-ROBOT , 1999 .

[8]  Norman C. Tien,et al.  Low voltage electrothermal vibromotor for silicon optical bench applications , 2000 .

[9]  Satoshi Konishi,et al.  Parallel Linear Actuator System with High Accuracy and Large Stroke , 2002 .

[10]  Ronald S. Fearing,et al.  Powering 3 Dimensional Microrobots: Power Density Limitations , 1998 .

[11]  K.S.J. Pister,et al.  Bidirectional inchworm motors and two-DOF robot leg operation , 2003, TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664).

[12]  Alun Harris,et al.  Actuators and their mechanisms in microengineering , 1996 .

[13]  Miko Elwenspoek,et al.  Modeling, design and testing of the electrostatic shuffle motor , 1998 .

[14]  Hiroyuki Fujita,et al.  A micromachined impact microactuator driven by electrostatic force , 2003 .

[15]  Don L. DeVoe,et al.  Large-force electrothermal linear micromotors , 2004 .

[16]  Kristofer S. J. Pister,et al.  Measurement of static friction in mechanical couplings of articulated microrobots , 1995, MOEMS-MEMS.

[17]  Miko Elwenspoek,et al.  Design, fabrication and testing of laterally driven electrostatic motors employing walking motion and mechanical leverage , 2000 .

[18]  Victor M. Bright,et al.  Prototype microrobots for micro-positioning and micro-unmanned vehicles , 2000 .

[19]  K. Pister,et al.  Solar powered 10 mg silicon robot , 2003, The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003. MEMS-03 Kyoto. IEEE.

[20]  Mehran Mehregany,et al.  Thick glass film technology for polysilicon surface micromachining , 1999 .

[21]  W. Benecke,et al.  Microtechnologies for microscaled robots and components , 1995, Proceedings 1995 INRIA/IEEE Symposium on Emerging Technologies and Factory Automation. ETFA'95.

[22]  R. Maboudian,et al.  High-performance surface-micromachined inchworm actuator , 2003, Journal of Microelectromechanical Systems.

[23]  K. Pister,et al.  Single mask, large force, and large displacement electrostatic linear inchworm motors , 2001, Technical Digest. MEMS 2001. 14th IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.01CH37090).