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

Automatic Microassembly of Tissue Engineering Scaffold

Ph.DDOCTOR OF PHILOSOPH

Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

A micromachined electrostatically suspended six-axis accelerometer, with a square plate as proof mass housed by a top stator and bottom stator, is presented. The device structure and related techniques concerning its operating principles, such as calculation of capacitances and electrostatic forces/moments, detection and levitation control of the proof mass, acceleration measurement, and structural parameters design, are described. Hybrid MEMS manufacturing techniques, including surface micromachining fabrication of thin film electrodes and interconnections, integration fabrication of thick nickel structures about 500 μm using UV-LIGA by successful removal of SU-8 photoresist mold, DRIE of silicon proof mass in thickness of 450 μm, microassembly and solder bonding, were employed to fabricate this prototype microdevice. A levitation experiment system for the fabricated microaccelerometer chip is introduced, and levitation results show that fast initial levitation within 10 ms and stable full suspension of the proof mass have been successfully demonstrated

Autofocusing-based visual servoing : application to MEMS micromanipulation.

International audienceIn MEMS microassembly areas, different methods of automatic focusing are presented in the literature. All these methods have a common point. Thus, the current autofocusing methods for microscopes need to perform a scanning on all the vertical axis of the microscope in order to find the peak corresponding to the focus (sharpen image). Those methods are time consuming. Therefore, this paper presents an original method of autofocusing based on a velocity control approach which is developed and validated on real experiments

Robust trajectory tracking and visual servoing schemes for MEMS manipulation.

International audienceThis paper focuses on the automation of manipulation and assembly of microcomponents using visual feedback controls. Trajectory planning and tracking methods are proposed in order to avoid occlusions during microparts manipulation and to increase the success rate of pick-and-place manipulation cycles. The methods proposed are validated using a five degree-of-freedom (DOF) microrobotic cell including a 3 DOF mobile platform, a 2 DOF micromanipulator, a gripping system and a top-view imaging system. Promising results on accuracy and repeatability of microballs manipulation tasks are obtained and presented

Automatic Microassembly System for tissue engineering- Assisted with top-view and force control

Master'sMASTER OF ENGINEERIN

Laser-driven micro-transfer printing for MEMS/NEMS integration

Heterogeneous materials integration, motivated by material transfer processes, has evolved to address the technology gap between the conventional micro-fabrication processes and multi-layer functional device integration. In its basic embodiment, micro-transfer printing is used to deterministically transfer and micro-assemble prefabricated microstructures/devices, referred to as “ink,” from donor substrates to receiving substrates using a viscoelastic elastomer stamp, usually made out of polydimethylsiloxane (PDMS). Thin-film release is, in general, difficult to achieve at the micro-scale (surface effects dominate). However, it becomes dependent on the receiving substrate’s properties and preparation. Laser Micro-Transfer Printing (LMTP) is a laser-driven version of the micro-transfer printing process that enables non-contact release of the microstructure by inducing a mismatch thermal strain at the ink-stamp interface; making the transfer printing process independent from the properties or preparation of the receiving substrate. In this work, extensive studies are conducted to characterize, model, predict, and improve the capabilities of the LMTP process in developing a robust non-contact pattern transfer process. Using micro-fabricated square silicon inks and varying the lateral dimensions and thickness of the ink, the laser pulse duration required to drive the delamination, referred to as “delamination time,” is experimentally observed using high-speed camera recordings of the delamination process for different laser beam powers. The power absorbed by the ink is measured to estimate the total energy stored in the ink-stamp system and available to initiate and propagate the delamination crack at the interface. These experiments are used as inputs for an opto-thermo-mechanical model to understand how the laser energy is converted to thermally-induced stresses at the ink-stamp interface to release the inks. The modeling approach is based on first developing an analytical optical absorption model, based on Beer-Lambert law, under the assumption that optical absorption during the LMTP process is decoupled from thermo-mechanical physics. The optical absorption model is used to estimate the heating rate of the ink-stamp system during the LMTP process that, in turn, is used as an input to the coupled thermo-mechanical Finite Element Analysis (FEA) model. Fracture mechanics quantities such as the Energy Release Rate (ERR) and the Stress Intensity Factors (SIFs) are estimated using the model. Then, the thermal stresses at the crack tip, evaluated by the SIFs, are decomposed into two components based on originating causes: CTE mismatch between the ink and the stamp, and thermal gradient within the PDMS stamp. Both the delamination time from the high-speed camera experiments and thermo-mechanical FEA model predictions are used to understand and improve the process’s performance under different printing conditions. Several studies are conducted to understand the effect of other process parameters such as the dimensions and materials of the stamp, the ink-stamp alignment, and the transferred silicon ink shape on the process performance and mechanism. With an objective of reducing the delamination time, the delamination energy, and the temperature of the ink-stamp interface during printing, different patterned stamp designs (cavity, preloading, and thin-walls) have been proposed. Cavity, preloading, and thin-wall stamps are designed to generate thermally-induced air pressure at the ink-stamp interface, to store strain energy at the interface, and to generate thermally-induced air pressure at the preloaded interface, respectively. Cohesive Zone Modeling (CZM) based models are developed to estimate the equilibrium solution of the collapsed patterned stamp after the ink pick-up process, and to evaluate the patterned stamps’ performance during the LMTP process. The patterned stamps show significant improvements in delamination times and delamination energies (up to 35%) and acceptable improvement of the interface temperature at the delamination point (up to 16%) for given printing conditions

Workshop on "Control issues in the micro / nano - world".

International audienceDuring the last decade, the need of systems with micro/nanometers accuracy and fast dynamics has been growing rapidly. Such systems occur in applications including 1) micromanipulation of biological cells, 2) micrassembly of MEMS/MOEMS, 3) micro/nanosensors for environmental monitoring, 4) nanometer resolution imaging and metrology (AFM and SEM). The scale and requirement of such systems present a number of challenges to the control system design that will be addressed in this workshop. Working in the micro/nano-world involves displacements from nanometers to tens of microns. Because of this precision requirement, environmental conditions such as temperature, humidity, vibration, could generate noise and disturbance that are in the same range as the displacements of interest. The so-called smart materials, e.g., piezoceramics, magnetostrictive, shape memory, electroactive polymer, have been used for actuation or sensing in the micro/nano-world. They allow high resolution positioning as compared to hinges based systems. However, these materials exhibit hysteresis nonlinearity, and in the case of piezoelectric materials, drifts (called creep) in response to constant inputs In the case of oscillating micro/nano-structures (cantilever, tube), these nonlinearities and vibrations strongly decrease their performances. Many MEMS and NEMS applications involve gripping, feeding, or sorting, operations, where sensor feedback is necessary for their execution. Sensors that are readily available, e.g., interferometer, triangulation laser, and machine vision, are bulky and expensive. Sensors that are compact in size and convenient for packaging, e.g., strain gage, piezoceramic charge sensor, etc., have limited performance or robustness. To account for these difficulties, new control oriented techniques are emerging, such as[d the combination of two or more ‘packageable' sensors , the use of feedforward control technique which does not require sensors, and the use of robust controllers which account the sensor characteristics. The aim of this workshop is to provide a forum for specialists to present and overview the different approaches of control system design for the micro/nano-world and to initiate collaborations and joint projects

Autofocusing-based visual servoing : application to MEMS micromanipulation.

International audienceIn MEMS microassembly areas, different methods of automatic focusing are presented in the literature. All these methods have a common point. Thus, the current autofocusing methods for microscopes need to perform a scanning on all the vertical axis of the microscope in order to find the peak corresponding to the focus (sharpen image). Those methods are time consuming. Therefore, this paper presents an original method of autofocusing based on a velocity control approach which is developed and validated on real experiments

Hybrid Microassembly with Surface Tension Driven Self-alignment: Handling Strategies and Micro-fabricated Patterns

Hybrid microassembly combines self-assembly technology with traditional robotic pick-and-place technology or other robotic feeding mechanics to construct microsystems. In a typical hybrid microassembly process, a micro part is brought adjacent to the assembly site by a robot handling tool at a high speed but with a relatively low precision, and liquid droplets dispensed by a dispenser at the assembly site align the part at a higher precision. By combing both the robotic pick-and-place technique and self-assembly technique, hybrid microassembly technique can achieve high speed and high precision simultaneously. This thesis explores the adaptability of hybrid microassembly technique by investigating different hybrid microassembly methods and different types of the patterns. Three hybrid microassembly approaches have been investigated: 1) droplet assisted hybrid microassembly, 2) water mist induced hybrid microassembly and 3) hybrid microassembly with forced wetting. The droplet assisted hybrid microassembly has been studied using patterns with segments and patterns with jagged edges. Parallel microassembly of microchips with water mist induced hybrid microassembly has also been explored. Hybrid microassembly on hydrophobic receptor site with super-hydrophobic substrate has been experimentally investigated with two forced wetting techniques. Four different types of patterns have been investigated for hybrid microassembly technique: (a) oleophilic/phobic patterns, (2) hydrophobic/super-hydrophobic patterns, (3) segmented patterns and (4) patterns with jagged edges. Hybrid microassembly has been studied on a new patterned oleophilic/oleophobic surface using adhesive droplet in ambient air environment. A patterned hydrophobic/super-hydrophobic surface has also been investigated and hybrid microassembly has been demonstrated with both water and adhesive. Application relevant patterns such as segmented patterns and patterns with jagged edges have been investigated. In summary, this thesis shows that hybrid microassembly can adapt to large varieties of patterns. Several new hybrid microassembly methods are developed and demonstrated. Such a wide adaptability and a variety of the processes indicate that hybrid microassembly can be a very promising approach for many potential applications, such as integration of surface emitting lasers, integration of small dies and 3D integration of chips with high density pin counts