Xiantao Sun

A novel flexure-based microgripper with double amplification mechanisms for micro/nano manipulation

This paper describes the design, modeling, and testing of a novel flexure-based microgripper for a large jaw displacement with high resolution. Such a microgripper is indispensable in micro∕nano manipulation. In achieving a large jaw displacement, double amplification mechanisms, namely, Scott-Russell mechanism and leverage mechanism arranged in series, are utilized to overcome the limited output of microgrippers driven by piezoelectric actuators. The mechanical performance of the microgripper is analyzed using the pseudo rigid body model approach. Finite element analysis is conducted to evaluate the performance and validate the established models for further optimum design of the microgripper. The prototype of the developed microgripper is fabricated, with which experimental tests are carried out. The experimental results show that the developed microgripper is capable of handling various sized micro-objects with a maximum jaw displacement of 134 μm and a high amplification ratio of 15.5.

A force-decoupled compound parallel alignment stage for nanoimprint lithography

This paper presents the development of a force-decoupled compound parallel alignment stage for nanoimprint lithography. Parallel alignment stage is a critical component of nanoimprint machine to implement the uniform surface contact between the template with predefined micro/nano patterns and the substrate that accepts the patterns. A combination of a high-stiffness spherical air bearing and a multi degree-of-freedom flexure-based mechanism is adopted in the parallel alignment stage. Apart from the parallel alignment function, the proposed stage can also endure a large imprinting force (more than 1000 N) but does not cause any damage to the delicate flexure-based mechanism. The stage performance is evaluated to satisfy the alignment requirement through the theoretical modeling and finite element analysis. Experiments are conducted on the parallel alignment stage to verify its performance on the transferred grating patterns with linewidth of 2.5 μm. This result demonstrates that the proposed approach can enhance the load capacity of the parallel alignment stage without degrading its alignment accuracy for nanoimprint lithography.

Design of compliant parallel mechanism for Nanoimprint Lithography

Nanoimprint Lithography (NIL) is an emerging alternative lithography technology that can be repeated to print nanometer-scale geometries which have very good uniformity and repeatability. The compliant mechanism is a novel mechanism which has been utilized in many accurate mechanisms and precise instruments because of its obvious advantages such as easy assembly, zero friction, zero lubrication, low cost, monolithic manufacturing and reduced weight, etc. This paper mainly introduces the application of compliant mechanisms in NIL and analysis and design of several novel compliant mechanisms.

Design of a novel passive flexure-based mechanism for microelectromechanical system optical switch assembly

In microelectromechanical system (MEMS) optical switch assembly, the collision always exists between the optical fiber and the edges of the U-groove due to the positioning errors between them. It will cause the irreparable damage since the optical fiber and the silicon-made U-groove are usually very fragile. Typical solution is first to detect the positioning errors by the machine vision or high-resolution sensors and then to actively eliminate them with the aid of the motion of precision mechanisms. However, this method will increase the cost and complexity of the system. In this paper, we present a passive compensation method to accommodate the positioning errors. First, we study the insertion process of the optical fiber into the U-groove to analyze all possible positioning errors as well as the conditions of successful insertion. Then, a novel passive flexure-based mechanism based on the remote center of compliance concept is designed to satisfy the required insertion condition. The pseudo-rigid-body-model method is utilized to calculate the stiffness of the mechanism along the different directions, which is verified by finite element analysis (FEA). Finally, a prototype of the passive flexure-based mechanism is fabricated for performance tests. Both FEA and experimental results indicate that the designed mechanism can be used to the MEMS optical switch assembly.

Development of a flexure-based XY positioning stage for micro/nano manipulation

This paper presents the design and modeling methodologies of a novel flexure-based positioning stage with capable of traveling along two translational directions. A 4-PP parallel configuration is utilized to implement two planar translational motions. Each prismatic joint is achieved using a translational flexure hinge with a large deformation for smooth motion. The two layers are assembled in a top-down and stacked manner for a compact structure. Furthermore, the flexure-based stage has a totally decoupled kinematic characteristic in theory, which is crucial in micro/nano scale manipulation. Classical beam theory is utilized to conduct the statics, stiffness and dynamics modeling to predict the primary response of the flexure-based stage. Finite element analysis (FEA) is performed to examine the mechanical performances and validate the established models. The finite element simulation shows that the proposed flexure-based stage can achieve a large displacement within the millimeter level, and high natural frequencies of about 134 Hz for two translational vibrations.

Design of a force-decoupled compound parallel alignment stage for high-resolution imprint lithography

Parallel surface contact between the template and the substrate is very important in imprint lithography. In this paper, a novel force-decoupled compound parallel alignment stage is proposed for high-resolution imprint lithography. It mainly consists of a high-stiffness spherical air bearing (SAB) and a multi-degree-of-freedom (multi-DOF) flexure-based mechanism that functions for both the active and passive alignments. Apart from the function of the parallel alignment, the proposed stage can also endure a large imprinting force of more than 1000 N but does not cause any damage to the delicate components, which is mainly attributed to its force-decoupled characteristic. Through the stiffness modeling and finite element analysis (FEA), the performance is evaluated to satisfy the design requirement. Finally, experimental tests are conducted on the parallel alignment stage for the hot embossing process, and the grating patterns with linewidth of 2.5 μm are successfully transferred from the silicon template to the polymethy methacrylate (PMMA) substrate. This result demonstrates that the proposed stage can be used in the hot embossing process without degrading its alignment accuracy.

A novel positioning stage with resolution enhancement functionality for nano manipulation

With the rapid development of nano science and precision engineering, a positioning system with high resolution is indispensable to meet the requirement of precise positioning. This paper presents the design and modeling of a flexure-based positioning stage with the functionality of resolution enhancement. To achieve high enhancement ratio, two sets of displacement reduction mechanisms are incorporated and configured serially in a monolithic symmetrical design. Following the assumption that the flexure hinge can be equivalent to an ideal revolute joint with a torsional spring, theoretical models are established to analyze the resolution enhancement ratio and dynamic performance of the positioning stage. Moreover, finite element analysis (FEA) is conducted to study the performances of the mechanism and verify the theoretical models. The results show that the proposed mechanism can achieve a resolution enhancement ratio of 18.75 to improve the positioning performance, and the first order natural frequency of the mechanism is 535.5Hz, which guarantees the bandwidth of the positioning operation.

Design and analysis of a new flexure-based XY micropositioning stage with decoupled motion characteristic

In this paper, a new two translational degrees of freedom (DOFs) flexure-based micromotion stage (FMMS) is presented. Two flexure-beam joints are used to design the stage for large motion range and meanwhile the symmetric layout of four kinematic chains restricts its parasitic motion in the XY plane. A detailed analytical model is established to evaluate the parasitic motion and dynamic property of the stage. Finite element simulations are carried out to inspect the performance and verify the theoretical model. Finally, the prototype is fabricated for performance tests. Linear and circular trajectory tests indicate that the proposed stage has a large workspace of about ±300 × ±300 μm2 with the maximum relative coupling error of 0.6%, and good positioning and tracking performances. In addition, the results from dynamic tests show that the natural frequencies for two translational vibrations are 209.7 Hz and 212.4 Hz, respectively.