Workshop on "Robotic assembly of 3D MEMS".

Proceedings of a workshop proposed in IEEE IROS'2007.The increase of MEMS' functionalities often requires the integration of various technologies used for mechanical, optical and electronic subsystems in order to achieve a unique system. These different technologies have usually process incompatibilities and the whole microsystem can not be obtained monolithically and then requires microassembly steps. Microassembly of MEMS based on micrometric components is one of the most promising approaches to achieve high-performance MEMS. Moreover, microassembly also permits to develop suitable MEMS packaging as well as 3D components although microfabrication technologies are usually able to create 2D and "2.5D" components. The study of microassembly methods is consequently a high stake for MEMS technologies growth. Two approaches are currently developped for microassembly: self-assembly and robotic microassembly. In the first one, the assembly is highly parallel but the efficiency and the flexibility still stay low. The robotic approach has the potential to reach precise and reliable assembly with high flexibility. The proposed workshop focuses on this second approach and will take a bearing of the corresponding microrobotic issues. Beyond the microfabrication technologies, performing MEMS microassembly requires, micromanipulation strategies, microworld dynamics and attachment technologies. The design and the fabrication of the microrobot end-effectors as well as the assembled micro-parts require the use of microfabrication technologies. Moreover new micromanipulation strategies are necessary to handle and position micro-parts with sufficiently high accuracy during assembly. The dynamic behaviour of micrometric objects has also to be studied and controlled. Finally, after positioning the micro-part, attachment technologies are necessary

Micromanipulation and Micro-Assembly Systems.

International audienceThe needs to manipulate micrometer sized objects keeps growing and concerns numerous and various fields like microsystems (MEMS1 and MOEMS2), micromechanics, optics, biology or pharmacy. The specificities of size, material, geometry and consistency of manipulated micro-objects, their surrounding, the kind of task to perform and the free size are all the more specific parameters that strongly influence the design and working of micromanipulation and micro-assembly systems. These systems are widely developing because they correspond both to industrial needs and really challenging scientific problematics. For these reasons, the present paper aimed at dealing with a review that mainly focuses on systems recently developed to assemble small series of microcomponents. The paper especially points out different solutions of carriers structures, gripping principles, sensors, other peri-microrobotic systems and control systems presenting the main solution and justifying their use and interest

Radix-2r Arithmetic for Multiplication by a Constant.

International audienceIn this paper, radix-2r arithmetic is explored to minimize the number of additions in the multiplication by a constant. We provide the formal proof that for an N-bit constant, the maximum number of additions using radix-2r is lower than Dimitrov's estimated upper-bound (2.N/log(N)) using double base number system (DBNS). In comparison to canonical signed digit (CSD) and DBNS, the new radix-2r recoding requires an average of 23.12% and 3.07% less additions for 64-bit constant, respectively

Modeling the trajectory of a microparticle in a dielectrophoresis device.

International audienceMicro- and nanoparticles can be trapped by a nonuniform electric field through the effect of the dielectrophoretic principle. Dielectrophoresis DEP is used to separate, manipulate, and detect microparticles in several domains, such as in biological or carbon nanotube manipulations. Current methods to simulate the trajectory of microparticles under a DEP force field are based on finite element model FEM, which requires new simulations when electrode potential is changed, or on analytic equations limited to very simple geometries. In this paper, we propose a hybrid method, between analytic and numeric calculations and able to simulate complex geometries and to easily change the electrode potential along the trajectory. A small number of FEM simulations are used to create a database, which enables online calculation of the object trajectory as a function of electrode potentials

Modeling of a new SMA micro-actuator for active endoscopy applications.

International audienceShape memory alloys (SMA) are good candidates to actuate endoscope heads but the cooling problem must be solved particularly in confined situations. For these reasons, a new SMA micro-actuator specially designed for active endoscopy applications has been developed in our laboratory. This work is a new step in the approach of using integrated thermoelectric cooling with SMA actuators. In fact, the Peltier effect is very attractive in such a case because this reversible phenomenon reduces the overheating of the external environment and provides forced cooling that decreases the response time. In this paper the actuator design and its working principle are presented. A fine modeling of the coupled mechanical and thermal behaviors gives a better understanding of the physical phenomenon involved in the actuator. Finally an experimental prototype has been developed and tested in order to verify the model predictions

Modeling and control of non-contact micromanipulation based on dielectrophoresis.

International audienceMicro and nano-particles can be trapped by a non uniform electric field through the effect of the dielectrophoretic force. Dielectrophoresis (DEP) is used to separate, manipulate and sense micro particles in several domains, such as in biological or Carbon Nano-Tubes (CNTs) manipulations. This paper tackles the creation of a closed loop strategy in order to control, using DEP, the trajectory of micro objects using vision feedback. A modeling of the dielectrophoresis force is presented to illustrate the non linearity of the system and the high dynamics of the object under dielectrophoresis . A control strategy based on the generalized predictive control method is proposed with the aim of controlling the trajectory, taking advantage of the high dynamics despite the non linearity. Simulated results are shown to evaluate our control strategy

Modeling, Identification and Control of a Thermal glue based temporary fixing system : Application to the Micro-Robotic field.

International audienceThe purpose of this paper is to present a temporary fixing system based on a thermal glue that is well-adapted to micro-robotics. In the paper, ths system is used to design a tool changer but can be generalized to other micro-robotic applications. A thermal modeling and an identification procedure are presented to propose a strategy to control the system. This system takes place into a micromanipulation station to gain flexibility, space and complexity. Indeed, to perform sequences of micromanipulation tasks (i.e. micro-assembly sequences), only one manipulator, able to use sequentially several end-effectors, has to be used instead of several dedicated to one specific task

Flexible micro-assembly system equiped with an automated tool changer.

International audienceThis paper deals with the design, fabrication and experimental validation of several modules of a micro-assembly system. On one hand, a microgripper is integrated in a four degrees of freedom system. On the other hand, a tool changer is designed. It enables to exchange automatically the tip part of the microgripper and then dedicated tools can be used to achieve specific tasks. The principle of this tool changer relies on a thermal glue whose phase (liquid or solid) is controlled by heat generators. This system is based on the modeling of thermal phenomena in the tools during a cycle of tool exchange. A compliant system is added to limit micromanipulation forces applied during assembly tasks like insertions. Finally, the successful assembly of several microcomponents is detailed, highlighting the capabilities and benefits of the whole system

Temporary fixing systems for applications in Microrobotics.

International audienceThis paper focuses on temporary fixing systems for microrobotics. Several solutions from the art are presented and compared : solutions based on mechanical bending, electromagnetic elements, electrostatic forces, glues, polymers or Van der Waals forces. From this analysis, we designed and developed a new system based on thermal glue (that permits to exchange the tip part of a microgripper) for microassembly stations. This system brings a high flexibility and compactness for microrobotic applications

Open loop control of dielectrophoresis non contact manipulation.

International audienceThe framework of this paper is the study of "No Weight Robots-NWR" that use non-contact transmission of movement (e.g. dielectrophoresis) to manipulate micro-objects enabling significant throughput (1Hz). Dielectrophoresis (DEP) is currently used to separate, manipulate and detect micro particles in several domains with high speed and precision, such as in biological cell or Carbon Nano-Tubes (CNTs) manipulations. A dielectrophoresis system can also be considered as a robotic system whose inputs are the voltages of the electrodes and output is the object trajectory. This "No Weight Robots" enables the positionning of the manipulted object in a 3D space. This paper is summarized the modeling principle of this new type of robots and some first results on trajectory control in 2D space