A hybrid-type electrostatically driven microgripper with an integrated vacuum tool
Introduction
Manipulation of microobjects is of great interest and challenge to the scientists and engineers which enables the assembly of microsystems. Due to recent development of microelectromechanical systems (MEMS), there is an increasing demand of micromanipulation techniques [1]. Microgripper is one of the key tools to realize the micromanipulation and microassembly of microobjects [2].
Since 1991 when Kim [3] designed a polysilicon electrostatic microgripper, which features a flexible cantilever comb-drive arm with bidirectional actuation and an over-range protector, research has been focused on the development of electrostatic comb-drive microgrippers. Volland and Heerlein [4] in 2002 designed an electrostatically driven microgripper with a system of elastic spring beams which is capable of converting the linear motion of the microactuator to rotational gripping motion. A microgripper based on silicon bulk micromachining was designed by Li [5] in 2003, and an electrostatically driven microgripper was designed and fabricated for blood vessel manipulation by Wierzbicki and Houston [6] in 2006.
At the microscale, adhesive forces such as van der Waals forces, surface tension forces and electrostatic forces are dominant in manipulating microobjects over the gravitational force [7]. Because of the existence of adhesive forces, the releasing of microobjects by a microgripper encounters a lot of difficulties [8].
Hence, several approaches have been proposed in the literature to solve the releasing problem.
- (1)
Reducing the adhesion such as roughing surface to reduce the van der Waals force [9], [10].
- (2)
Using inertial effects [11], [12] or by rolling [13].
- (3)
Using vacuum tool that generates positive pressure to overcome the adhesion between the tool and the microobject [14], [15], [16].
Comparing with others, vacuum tools are considered to be a good strategy to solve releasing problem. The positive pressure generated by the vacuum tool can overcome the adhesion between tools and microobjects. This approach has been successfully implemented by Zesch in 1997 [14] and Chen in 2004 [15].
However, vacuum tools are limited in microobject manipulation. One problem is that it cannot provide sufficient constraint force, especially the friction force, required in assembly operations. Another problem is that it does not satisfy different orientation operation requirements and different shapes of the microobjects. Hence, one possible solution is to use the direct mechanical gripping approach such as two-fingered electrostatic comb-drive gripper.
In order to handle microobjects effectively and efficiently, we design and fabricate a hybrid-type electrostatic comb-drive silicon microgripper integrated vacuum tool. This hybrid-type microgripper combines the advantages of both electrostatic comb-drive microgripper and vacuum tool.
Particularly, the arm tip of the hybrid-type microgripper actuated by the electrostatic comb fingers can satisfy the different orientation operation requirements and be suitable for different shapes of the microobjects. Bulk micromachining technology is used to fabricate the hybrid-type microgripper, integrating electrostatic comb drive and vacuum together. Vacuum gas pipes embedded in microgripper is used to realize stable and reliable pick and release manipulation of the microdevices.
In this paper, the structure and the working mechanism of the hybrid-type microgripper are introduced firstly. Finite element analysis (FEA) of the gripper is performed to predict both the static and dynamic performance of the microgripper. The structure of the vacuum tool is designed according to the analysis of the force acting on the microobjects during pick and place operations. In addition, the fabrication of the microgripper is also described in detail. Two control systems are designed with one for electrostatic drive control, and the other for working gas pressure control. Finally, microobjects ranging from 100 μm to 200 μm are picked and released by this microgripper to demonstrate the performance of this microgripper.
Section snippets
Design of general structure
The working principle of the microgripper is illustrated in Fig. 1. The bilateral gripper can realize a basic manipulation [17]. In addition, the vacuum tool with positive pressure can assist the gripper to release microobjects adhered to it.
Fig. 2 shows the prototype of the microgripper. This microgripper consists of the flexible beams, electrostatic comb fingers, gas pipes and glass based. Glass is the substrate and insulation of the gripper configuration. More importantly, as shown in Fig. 3
Electrostatic actuated control system
In order to solve destabilization problem of the comb-drive microgripper, the electrostatic actuated control system has been complemented. A controlling IC ADuC842 with digital analog converter (DAC) inside and signal acquisition circuit are used to constitute the final control signal system, which control the DC/DC converter to generate a wide range of voltage.
The tow-layered control architecture is designed in the comb-drive control system. ADuC842 is the lower layer controller, and the
Experiments of the microgripper
Voltages ranging from 0 V to 0.16 V are used to control the releasing pressure of the gas pipes. The relationship between the releasing voltage and the output pressure of the gas pipes is shown in Fig. 12.
Voltages ranging from 0 V to 80 V are used for electrostatic actuation. This creates a maxim deflection of 25 μm at the arm tip. The gripping force can be increased with the growing of the driving voltage. The relationship between the square of driving voltage and arm tip deflection is shown in
Conclusion
This paper presented a novel MEMS hybrid microgripper which integrated both electrostatic mechanism and vacuum technology to fulfil the reliable and accurate pick and release manipulation of microobjects. The structure of the novel hybrid microgripper was detailed in this paper. The FEA method was conducted in order to obtain a full understanding of the working principle of the microgripper. With electrostatic actuator and the vacuum tool, this paper realized a miniaturized micromanipulation
Acknowledgements
This study is financially supported by the National Natural Science Funds for Distinguished Young Scholar under Grant Number 50725518, National Natural Science Foundation of China under Grant Number 50805040, and High Technology Research and Development Program of China under Grant Number 2007AA04Z315.
Tao Chen graduated with the Bachelor's degree and Master's degree in mechatronics engineering (Harbin Institute of Technology) in 2004 and 2006. He received his Ph.D. degree in mechatronics from Harbin Institute of Technology, China. His research interests include: MEMS 3D assembly, micromanipulation robot. Including mechanical analysis and material characterization in MEMS, system dynamics and control of mechatronics and MEMS, electrostatically actuated systems.
References (18)
- et al.
Polysilicon microgripper
Sens. Actuator A Phys.
(1992) - et al.
Electrostatically driven microgripper
Microelectron. Eng.
(2002) Design and fabrication of an electrostatically driven microgripper for blood vessel manipulation
Microelectron. Eng.
(2006)- et al.
Design, fabrication, and testing of a 3-DOF HARM micromanipulator on (1 1 1) silicon substrate
Sens. Actuator A Phys.
(2006) - et al.
Overview of microgrippers and design of a micromanipulation station based on a MMOC microgripper
- et al.
Development of microgripper technology
Optics Precision Eng.
(2000) - et al.
Fabrication process analysis for electrostatically actuated microgripper based on silicon bulk micromachining
Optics Precision Eng.
(2003) - et al.
Ambient environmental effects in micro/nano handling
- et al.
From “Macro” to “Micro” manipulation: models and experiments
IEEE/ASME Trans. Mechatronics
(2004)
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Tao Chen graduated with the Bachelor's degree and Master's degree in mechatronics engineering (Harbin Institute of Technology) in 2004 and 2006. He received his Ph.D. degree in mechatronics from Harbin Institute of Technology, China. His research interests include: MEMS 3D assembly, micromanipulation robot. Including mechanical analysis and material characterization in MEMS, system dynamics and control of mechatronics and MEMS, electrostatically actuated systems.
Lining Sun graduated with the Bachelor's degree in mechanical engineering and Master's degree in Harbin Institute of Technology in 1985 and 1988 and completed the Ph.D. degree in mechatronics engineering in 1993. His research interests have encompassed a number of related areas, including: robot control, design of actuators, design and control of high speed machines, MEMS 3D assembly, MEMS robotic task execution, micromanipulation robot, etc. He has published extensively in journals and conferences and has supervised over 50 masters and Ph.D. students and a number of Post-Doctoral Fellows and Research Engineers in these various research areas.
Liguo Chen received his Bachelor's and Master's degrees in mechanical engineering from Harbin Institute of Science and Technology in 1997 and 2000. He received his Ph.D. degree in mechatronics from Harbin Institute of Technology in 2003. Since 2003, he has been with the Robotics Institute at Harbin Institute of Technology, and is now an Associate Professor. Dr. Chen's research interests lie in robotics and automation, computer vision, MEMS 3D assembly, and micromanipulation robot.
Weibin Rong, born in 1972, received the B.S. degree in mechanical engineering, the M.S. degree, and the Ph.D. degree in mechatronics engineering from Harbin Institute of Technology, Harbin, China, in 1994, 1998, and 2002, respectively. He is a professor currently in the state key laboratory of robotics and systems, Robotics Institute, Harbin Institute of Technology. His main interests are nano-positioning technology and micro-nano-manipulating robot.
Xinxin Li received the M.S. and Ph.D. degrees in microelectronics from Fudan University, Shanghai, China, in 1995 and 1998, respectively. From 2001 to now, he has been a professor and now serves as the Director of the State Key Lab of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences. His research interest has been in the fields of micro/nano sensors and transducers, micro/nano electromechanical systems and micro/nano electromechanical integration technologies. He has invented more than 30 patents. He has published more than 150 papers in referred journals and academic conferences. He served as a TPC member for 2008 IEEE International Conference on Microelectromechanical Systems (IEEE MEMS-08) and IEEE International Conference on Sensors (IEEE Sensors) from 2002 to 2008. Dr. Li has been appointed as a program committee member for Transducers’09. He is an editorial board member for International Journal of Information Acquisition.