Towards a force-controlled microgripper for assembling biomedical microdevices

Abstract

This paper presents recent results on the development and control of a microgripper based on flexure joints, fabricated by LIGA and instrumented with semiconductor strain-gauge force sensors. The microgripper is the end-effector of a workstation developed to grasp and manipulate tiny objects such as the components of a typical biomedical microdevice. The development of the force control in the microgripper is of fundamental importance in order to achieve the dexterity and sensing capabilities required to perform assembly tasks for biomedical microdevices. As a step towards the definition of the force control strategy, system identification techniques have been used to model the microgripper. Results indicate that a proportional integral (PI) controller could be used to assure, at the same time, closed-loop stability of the system, and a bandwidth suitable for the intended applications. The force control is based on strain-gauge sensors which have been integrated in the microgripper and experimentally characterized. Sensor response in the idling condition and during grasp showed that they can provide useful information for force control of the microgripper.

A Micro-Opto-Electro-Mechanical System (MOEMS) for Microstructure Manipulation

“…In general, the goal has been to produce a system that would allow precise and controlled manipulation of structures of different kinds in the micrometer range. With this goal in mind, different Micro-Electro-Mechanical Systems (MEMS) microgrippers have been developed, with applications such microobject manipulation [1], microelectronic devices manipulation [2], assembly of biomedical microdevices [3], single biological cell manipulation [4][5][6][7], and micro-assembly of 3-D MEMS structures [8].…”

“…More sophisticated, or instrumented microgrippers, have been implemented in silicon, such as the microgripper presented by Beyeler [6] which is equipped with a monolithically fabricated force feedback sensor and is actuated electrostatically by means of a comb actuator, or the hybrid type microgripper presented by Park [9] which is implemented in silicon, actuated piezoelectrically and is equipped with a force sensor. Microgrippers have also been implemented in metal such as the one presented by Carrozza [3] which is implemented in nickel and is instrumented with a semiconductor strain-gauge force sensor. Microgrippers reported by Lu [10] are implemented in silicon dioxide, electrothermally actuated, and equipped with an optical sensor fabricated underneath the gripping facets.…”

“…Furthermore, different feedback mechanisms can provide different types of information about the microobject being manipulated. The types of feedback implemented in microgrippers are force sensing, implemented in silicon [6,9] and nickel [3], and a binary optical feedback implemented in SiO 2 through a CMOS process [10]. So, because of the limited feedback implemented so far, there is still physical, mechanical, optical and chemical information about the microstructure under study which requires the use of macroscopic instrumentation, such as confocal fluorescence microscopy, Raman spectroscopy, nanoindentation, among others [11].…”

Waveguide microgripper for identification, sensing and manipulation

“…In recent years, a variety of microgrippers have been developed for the manipulation of micro-sized objects. Different mechanisms of actuation have been used for microgripper applications such as piezoelectric by Carrozza [9], electrostatic by Kim [10], Volland [11], Wierzbicki [12], Shape Memory Alloy (SMA) by Roch [3], or electrothermal by Nguyen [2], Du [13], Chronis [9] and Ivanova [14]. Other important feature that can be integrated in a microgripper is feedback.…”

“…Not many microgripper have been developed with an integrated feedback. The types of feedback implemented in microgrippers are force sensing [9,15,16] and binary optical feedback [17]. Due to limited feedback implementation so far, it is important to integrate a feedback mechanism which would allow the analysis of physical, mechanical, optical and chemical information of the micro object under study.…”