Wenjiang Shen

University of California, Los Angeles, Los Angeles, CA, United States

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Publications (3)3.86 Total impact

  • Source
    Wenjiang Shen, R.T. Edwards, Chang-Jin Kim
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    ABSTRACT: The dominance of surface tension over inertia in microscale and favorable scale effect for electrostatic actuation allow electrostatically driven metal-droplet systems practical. Because of such potential advantages as low contact resistance, naturally bistable operation, and high switch density, the liquid-metal droplet switch is an excellent candidate for reconfigurable circuit interconnections. Following earlier droplet microswitch examples and related studies of metal-droplet behavior, we report the first functioning droplet switch directly integrated on top of a functional CMOS circuit. While the surface tension dominance makes the droplet switches practical as a mechanical system and also brings bistability, it also requires a high electric field to move the droplet. We implement the concept of physical surface modification to lower the driving voltage to a value that a commercial CMOS process can provide. Unlike previous droplet switches, the reported device is planar-processed to allow the integration with the underlying CMOS circuits. The integrated switch is made functional by such provisions as self-limiting actuation and by optimizing the electrostatic force in the planar configuration and avoiding liquid-metal "flooding" into surface patterns. A fabrication process for low driving voltage and high compatibility is developed to integrate the droplet switch on the custom-developed CMOS chip. A packaging method adapted from well-established microelectronic packaging isolates the active switch space from the surrounding environment. Low driving voltage (as low as 15 V) and millisecond switching speed are achieved by the current on-chip device. While the current device uses ~150 mum droplets for demonstration, additional theoretical and experimental results indicate that further miniaturization would lead to smaller devices and lower operation voltage
    Journal of Microelectromechanical Systems 09/2006; · 1.92 Impact Factor
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    ABSTRACT: This paper presents the use of a microscale liquid-metal droplet as a contact and moving part in a micromechanical switch with electrostatic actuation. Design, FEM analysis, fabrication and testing of the device are reported. The droplet is driven by a given voltage bias that induces electrostatic force between a grounded liquid-metal and an imbedded actuation electrode. The electrodes and the liquid-metal droplet are placed inside of an anisotropically etched silicon cavity. A novel technique to make shadow masks utilizing thin wafers is used to pattern the electrodes inside the silicon cavity.
    Sensors and Actuators A Physical 04/2002; · 1.94 Impact Factor
  • Wenjiang Shen, Joonwon Kim, Chang-Jin Kim
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    ABSTRACT: Under electrostatic actuation, mercury droplet can act as a contact and moving part in a microswitch system. In order to reduce the actuation voltage while keeping the electrical advantages of liquid-solid contact, the contact properties of mercury droplet on structured surfaces are investigated in this paper. Forces to actuate a mercury droplet on different structured surfaces are theoretically analyzed and experimentally tested. Both results confirm our claim that the adhesion forces of liquid metal droplets on a solid surface can be designed by physical modification of the surface. The criteria for detaching a mercury droplet from solid surface was predicted and verified by experimental results
    Micro Electro Mechanical Systems, 2002. The Fifteenth IEEE International Conference on; 02/2002

Publication Stats

27 Citations
3.86 Total Impact Points


  • 2002–2006
    • University of California, Los Angeles
      • Department of Mechanical and Aerospace Engineering
      Los Angeles, CA, United States