Yongcun Hao

Bias Contribution Modeling for a Symmetrical Micromachined Coriolis Vibratory Gyroscope

This paper establishes a bias contribution model for a micromachined Coriolis vibratory gyroscope (MCVG). Eight bias sources, including stiffness imbalance, mass imbalance, and oscillation of the sense mode itself with their contributions, were analyzed and calculated. The calculation methods for key parameters, such as coupling stiffness, coupling damping, and offsets of center of mass based on the established process imperfection model, are presented in detail. Finally, the total bias of the MCVG is measured with an error of 18% compared with the theoretically calculated bias using the model. The acceptable error range of the bias model provides a solution to predict the bias behavior in the design stage before the costly fabrication.

Influences of the Feedthrough Capacitance on the Frequency Synchronization of the Weakly Coupled Resonators

Influences of the feedthrough capacitance on weakly coupled micromechanical resonators are theoretically analyzed and experimentally observed using current vector analysis and the Nyquist plots method for the first time. By analyzing the equivalent electric model of the weakly coupled resonators with feedthrough capacitance, it is found that the existence of the feedthrough capacitance will lead to frequency asynchronization and measurement error of the amplitude ratio of the mode localization based sensors. The variations of the transmission responses of the weakly coupled resonators with the influence of the feedthrough capacitance are experimentally demonstrated. The frequency asynchronization became less than 2.3 ppm, down from the previous 55.6 ppm, and the measurement error of the amplitude ratio was reduced from 25.9% to approximately 0 after compensating the feedthrough capacitance using the method presented in the paper. This enhancement lays the foundation for the accurate measurement of the eigenstate and the amplitude ratio of the mode localization based sensors.

A dicing-free SOI process for MEMS devices based on the lag effect

This paper presents a dicing-free process for silicon-on-insulator (SOI) microelectromechanical systems (MEMS). In the process, the lag effect in deep reactive ion etching (DRIE) is used to form the breaking trenches. In the backside DRIE, the wide backside cavities are etched down to the buried oxide layer. The narrow breaking trenches, in contrast, are not etched to the buried oxide layer. Therefore, the narrow trench can be used to break the wafer after the entire process; in addition, the handle layer can still act as a bracing structure before ?breaking?. Finally, the device layer is patterned, and a DRIE step is used to form the MEMS devices. In this way, the dicing step can be omitted to prevent further damages from high pressure water jets and silicon dust. Meanwhile, the process can also prevent notching simply because the insulating layer is removed before device etching. To demonstrate the feasibility of the proposed fabrication process, a micromachined gyroscope is designed and fabricated.

A Microgripper with a Post-Assembly Self-Locking Mechanism.

In this work, we report a new design for an electrostatically actuated microgripper with a post-assembly self-locking mechanism. The microgripper arms are driven by rotary comb actuators, enabling the microgripper to grip objects of any size from 0 to 100 μm. The post-assembly mechanism is driven by elastic deformation energy and static electricity to produce self-locking and releasing actions. The mechanism enables the microgripper arms to grip for long periods without continuously applying the external driving signal, which significantly reduces the effects and damage to the gripped objects caused by these external driving signals. The microgripper was fabricated using a Silicon-On-Insulator (SOI) wafer with a 30 μm structural layer. Test results show that this gripper achieves a displacement of 100 μm with a driving voltage of 33 V, and a metal wire with a diameter of about 1.6 mil is successfully gripped to demonstrate the feasibility of this post-assembly self-locking mechanism.

Design and Verification of a Structure for Isolating Packaging Stress in SOI MEMS Devices

This paper proposes and verifies a structure for the isolation of packaging stress in silicon-on-insulator-based microelectromechanical systems devices. The packaging-stress isolation structure resides on the handle layer and consists of a circular disk, eight elastic beams, and a support frame. The disk is located in the center of the die and occupies less than 5% of the handle-layer area; this can reduce packaging stress and avoid uneven stress distribution. The elastic beams are L-shaped and symmetrically distributed to decouple the deformation from the disk to the frame and suppress the stress evenly. The in-plane and out-of-plane deformation induced by packaging stress was modeled and experimentally measured. The comparison results demonstrate that the packaging stress was successfully isolated.

Design and fabrication of a rotary comb-actuated microgripper with high driving efficiency

This paper reports a novel microgripper with high driving efficiency. The proposed microgripper utilizes the rotational motion of rotary comb actuators to grip the target object directly. Therefore, the inefficient conversion system which is commonly used in recent works is avoided. The gripper is fabricated using a SOI process with a 60μm structural layer. Test results show that this gripper achieves a displacement of 94μm with a driving voltage of 100V and its driving efficiency is increased at least 12 times compared to the existing microgrippers.

A microgripper with a ratchet self-locking mechanism

This paper reports a new design for an electrostatic actuated microgripper with a ratchet self-locking mechanism. The self-locking mechanism enables long-time gripping without continuously applying the external driving signal, such as an electrical, thermal or magnetic field, which significantly reduces the effect and damage on the gripped micro-scale objects that are induced by the external driving signals. The microgripper is fabricated using a silicon-on-insulator (SOI) wafer with a 30μm device layer. The jaw gap is 100 μm, and the ratchet locking interval is 10 μm. A metal wire is successfully gripped to demonstrate the feasibility of the ratchet self-locking mechanism.

A rotary microgripper with locking function via a ratchet mechanism

This paper presents a rotary microgripper with locking function enabled by a ratchet mechanism. The ratchet mechanism enables long-time gripping without having to continuously apply the external excitation signal such as the electrical, thermal or magnetic field. Thus the damage to the gripped micro-scale objects caused by the external excitation signals can be significantly reduced. A logic control strategy is proposed to solve the wearing problems of the ratchet mechanism. The stability of the microgripper is improved by increasing the length of the engaged line. The microgripper is fabricated by an improved silicon-on-insulator dicing-free process to protect the delicate device structure from damage during fabrication. The microgripper has a discrete opening range and can handle micro-scale objects with a size of 20 μm, 40 μm and 60 μm based on the current design parameters. A pick-lock-release gripping experiment on a magnolia pollen cell is performed to form a triangle to prove the feasibility of the gripper in handling biological cells.

A novel packaging stress isolation structure for SOI based MEMS gyroscopes

In this paper, we propose a packaging stress isolation structure for the silicon-on-insulator (SOI) based microelectromechanical systems (MEMS) gyroscopes. The structure is designed on the handle layer and consists of a circular disk, eight “L-shape” elastic beams, and a support frame. The disk is located on the center of the die and occupies less than 5 percent of the whole handle layer area which can reduce the packaging stress and avoid the uneven stress distribution. The elastic beams are orthogonally distributed along the x and y axis connecting the disk with the support frame, which can further suppress stress evenly. The results reveal that the packaging stress transferred to the gyroscope is reduced by two orders of magnitude.

Correction: Yuan, G., et al. A Microgripper with a Post-Assembly Self-Locking Mechanism. Sensors 2015, 15, 20140-20151

Received: 7 January 2016; Accepted: 7 January 2016; Published: 8 January 2016Academic Editor: Vittorio M. N. PassaroKey Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education,Northwestern Polytechnical University, Xi’an 710072, China; yuangm@nwpu.edu.cn (G.Y.);yuanwz@nwpu.edu.cn (W.Y.); haoyongcun@126.com (Y.H.); xiaoy@nwpu.edu.cn (X.L.)