Development of a novel flexure-based microgripper for high precision micro-object manipulation

Abstract

Micro-scaled parts with dimension below 1 mm need to be manipulated with high precision and consistency in order to guarantee successful microassembly process. Often these requirements are difficult to be achieved particularly due to the problems associated with the structural integrity of the grasping mechanism which will affect the accuracy of the manipulation. Furthermore, the object's texture and fragility imply that small perturbation by the grasping mechanism can result in substantial damage to the object and leads to the degradation of its geometry, shape, and quality. This paper focuses on the unification of two designing approaches to develop a compliant-based microgripper for performing high precision manipulation of micro-objects. A combination of Pseudo Rigid Body Model (PRBM) and Finite Element Analysis (FEA) technique has proven to improve the design efficiency by providing the essential guideline to expedite the prototyping procedure which effectively reduces the cost and modeling time. An Electro Discharge Machining (EDM) technique was utilized for the fabrication of the device. Series of experimental studies were conducted for performance verification and the results are compared with the computational analysis results. A high displacement amplification and maximum stroke of 100 μm can be achieved.

Introduction

Grasping methodologies have been at the forefront among the subjects of interest by microsystem researches ever since the micro-scale products started to dominate the global market. It is undeniable that miniaturization in systems has implicated in every aspect of our life ranging from health, communication, entertainment, transportation, etc. Therefore, the demand to accomplish fully integrated multifunctional MEMS devices has stimulated extensive researches on micromanipulation methodologies and devices to ultimately achieve fully automated microassembly procedure. Most of the microsystem researchers in academia have been focusing on three critical assembly components that determine the accomplishment of microassembly procedure namely the development of high precision grasping devices, nano-measurement technologies and ultra precision stage positioning [1], [2], [3], [4], [5], [6]. The integration of these components will pave boundless opportunity for the establishment of wide range of microdevices that incorporate sensor, actuator and control architectures. Most of the microassembly procedures nowadays profoundly rely on human dexterities to operate the precision devices and instruments which technically account for large portion of production cost. Furthermore, the repetitive and intricately demanding assembly task will gradually afflict the operator's sensibility and focus and thus increases the susceptibility of human bound errors associated with the operator's stress and eye strain. Furthermore, the precision associated with assembling diminutive components determines the quality and reliability of the finished product and this stringent requirement should be meticulously considered when developing microtechnology based product. Extensive researches in haptics and virtual technology have also contributed to the advancement in microassembly system to enable better understanding towards microworld which involves different physics in contrary to macrodomain [7], [8].

As one of the essential components in microassembly process, the development of fully automated microhandling devices to enable accurate and high precision object manipulation has been undergoing for many years with promising results. It was found from the diverse micrograsping models in literature that researchers have predominantly emphasized on three major components during model development namely novel microfabrication techniques [9], [10], new actuation methodologies [11], [12], [13] and manipulation of different materials [14], [15], [16]. The establishment of novel microfabrication technique and the development of smart structures have advanced the grasping technologies and enable compact, highly compliant, and monolithic mechanism to be realized. The fabrication techniques such as Electro Discharge Machining (EDM), LIGA, surface, bulk and laser micromachining, and photo lithography have paved a decisive breakthrough to the persisting constraints in micrograsping methodology particularly associated with the object-gripper compatibility, surface to surface interaction between the object and the gripper's jaws and nonlinearity during operation [9], [10], [17], [18]. Furthermore, the realization of monolithic structure also demands the employment of different actuation strategy to satisfy the stringent requirements in precision microhandling operation since the application of conventional motor to drive the microgripper is insufficient to comply with the specifications. The development of novel actuation techniques over the years has proven to be decisive to enable model downsizing and further advancement in micrograsping technology. Common actuating techniques conventionally employed to provide the driving input to the grasping mechanism can be classified into four major categories namely thermal, piezoelectric, electrostatic and electromagnetic actuating concepts [12], [15], [19], [20], [21].