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

Design, evaluation, and control of nexus: a multiscale additive manufacturing platform with integrated 3D printing and robotic assembly.

Additive manufacturing (AM) technology is an emerging approach to creating three-dimensional (3D) objects and has seen numerous applications in medical implants, transportation, aerospace, energy, consumer products, etc. Compared with manufacturing by forming and machining, additive manufacturing techniques provide more rapid, economical, efficient, reliable, and complex manufacturing processes. However, additive manufacturing also has limitations on print strength and dimensional tolerance, while traditional additive manufacturing hardware platforms for 3D printing have limited flexibility. In particular, part geometry and materials are limited to most 3D printing hardware. In addition, for multiscale and complex products, samples must be printed, fabricated, and transferred among different additive manufacturing platforms in different locations, which leads to high cost, long process time, and low yield of products. This thesis investigates methods to design, evaluate, and control the NeXus, which is a novel custom robotic platform for multiscale additive manufacturing with integrated 3D printing and robotic assembly. NeXus can be used to prototype miniature devices and systems, such as wearable MEMS sensor fabrics, microrobots for wafer-scale microfactories, tactile robot skins, next generation energy storage (solar cells), nanostructure plasmonic devices, and biosensors. The NeXus has the flexibility to fixture, position, transport, and assemble components across a wide spectrum of length scales (Macro-Meso-Micro-Nano, 1m to 100nm) and provides unparalleled additive process capabilities such as 3D printing through both aerosol jetting and ultrasonic bonding and forming, thin-film photonic sintering, fiber loom weaving, and in-situ Micro-Electro-Mechanical System (MEMS) packaging and interconnect formation. The NeXus system has a footprint of around 4m x 3.5m x 2.4m (X-Y-Z) and includes two industrial robotic arms, precision positioners, multiple manipulation tools, and additive manufacturing processes and packaging capabilities. The design of the NeXus platform adopted the Lean Robotic Micromanufacturing (LRM) design principles and simulation tools to mitigate development risks. The NeXus has more than 50 degrees of freedom (DOF) from different instruments, precise evaluation of the custom robots and positioners is indispensable before employing them in complex and multiscale applications. The integration and control of multi-functional instruments is also a challenge in the NeXus system due to different communication protocols and compatibility. Thus, the NeXus system is controlled by National Instruments (NI) LabVIEW real-time operating system (RTOS) with NI PXI controller and a LabVIEW State Machine User Interface (SMUI) and was programmed considering the synchronization of various instruments and sequencing of additive manufacturing processes for different tasks. The operation sequences of each robot along with relevant tools must be organized in safe mode to avoid crashes and damage to tools during robots’ motions. This thesis also describes two demonstrators that are realized by the NeXus system in detail: skin tactile sensor arrays and electronic textiles. The fabrication process of the skin tactile sensor uses the automated manufacturing line in the NeXus with pattern design, precise calibration, synchronization of an Aerosol Jet printer, and a custom positioner. The fabrication process for electronic textiles is a combination of MEMS fabrication techniques in the cleanroom and the collaboration of multiple NeXus robots including two industrial robotic arms and a custom high-precision positioner for the deterministic alignment process

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

Mechanical de-tethering technique for Silicon MEMS etched with DRIE process.

International audienceGetting Micro-Electro-Mechanical Systems (MEMS) out of a wafer after fabrication processes is of great interest in testing, packaging or simply using these devices. Actual solutions require special machines like wafer dicing machines, increasing time and cost of de-tethering MEMS. This article deals with a new solution for manufacturing mechanical de-tetherable silicon MEMS. The presented solution could be done with DRIE process, already used in silicon MEMS fabrication, without additional time or cost. We are proposing a new way to create a notch on tethers linking both wafer and millimetric MEMS, especially designed to break with a specified mechanical force. A theoretical silicon fracture study, the experimental results and dimensional rules to design the tethers are presented in this article. This new technique is particularly useful for microscopic MEMS parts, and will find applications in the field of the MEMS components micro-assembly

Modeling for effective computer support to MEMS product development

Microelectromechanical systems (MEMS) are miniaturized devices with high functionality. In recent years, MEMS products have become increasingly dominant in every aspect of the commercial market place. As the MEMS technology is in its infant stage and has several unique features compared to macro-scale products, it is faced with several challenges. One of them is that design and fabrication knowledge is very intrigue and thus very difficult to be accessible. An effective computer support to the MEMS product development is thus very important. This thesis study undertakes a thorough investigation into the MEMS product development process and its computer support. Specifically, the study examines the state-of-the-art in computer aided design systems in light of the support of product functionality. It is shown that MEMS product development involves high degree of uncertainty, which calls for an unconventional computer support. At this point, this study proposes an approach to construct a knowledge base in a fairly flexible and real-time manner. This approach is based on the extended function-behavior-structure framework and the template technique proposed in this thesis. The other finding is that the MEMS product development resembles the one-of-a-kind product (OKP) development. Therefore software tools for the OKP product development process can be applied to the MEMS product development process. These tools are examined, and further extensions upon them are proposed. Throughout the thesis, a microdispensing system is used as an example for illustration of concepts described in this thesis

Positioning accuracy characterization of assembled microscale components for micro-optical benches

International audienceThis paper deals with the measurement of microscale components' positioning accuracies used in the assembly of Micro-Optical Benches (MOB). The concept of MOB is presented to explain how to build optical MEMS based on out-of-plane micro-assembly of microcomponents. The micro-assembly platform is then presented and used to successfully assemble MOB. This micro-assembly platform includes a laser sensor that enables the measure of the microcomponent's position after its assembly. The measurement set-up and procedure is displayed and applied on several micro-assembly sets. The measurement system provides results with a maximum deviation less than +/- 0.005°. Based on this measurement system and micro-assembly procedure, the article shows that it is possible to obtain a positioning errors down to 0.009°. These results clearly state that micro-assembly is a possible way to manufacture complex, heterogeneous and 3D optical MEMS with very good optical performances

Integrated Micro Gas Chromatographs with High-Flow Knudsen Pumps.

Environmental gas sensing typically requires both sensitivity and specificity; target vapor species must not only be detected and quantified, but also differentiated from interferents. This mission can be accomplished by micro gas chromatographs (μGCs), which allow preconcentration of samples and subsequent separation of complex vapor mixtures into individual constituents by their specific retention times. This thesis focuses on the system-level design, fabrication, and integration of μGCs, with the ultimate goal of fully microfabricated systems that can be easily manufactured and distributed to end-users. This thesis also explores the optimization of a micro gas pump – a critical μGC component, and generally recognized as a challenge for microsystems. Three generations of integrated µGC systems have been designed, fabricated, and evaluated. The iGC1 system demonstrates the feasibility of a low-cost three-mask fabrication approach for a µGC including a Knudsen pump, a preconcentrator, a separation column and a microdischarge-based detector, which are integrated in a 4-cc stack. The iGC2 system demonstrates a valveless µGC architecture, in which a bi-directional Knudsen pump provides reversible gas flow for (multi-stage) preconcentrators, which is essential for quantitative analysis. The iGC3 system replaces the microdischarge-based detectors in iGC1 and iGC2 with complementary capacitive detectors, facilitating a purely electronic interface for the fluidics. Additionally, it is compatible with the use of room air as the carrier gas. The quantitative analysis of 19 chemicals with concentration levels of well below 100 ppb is demonstrated, showing the promise of automated, continuous monitoring of indoor air pollutants. The pumps used in the iGCx systems are Knudsen pumps that use thermal transpiration provided by nanoporous media and have no moving parts. This thesis also describes an exploratory effort in which lithographically fabricated channels in silicon substrates provide the thermal transpiration. The Si-micromachined Knudsen pumps demonstrate >200 sccm flow rate. To increase the output pressure head, these pumps are arrayed in series, using both a stacked configuration and a planar one. The results show that the pressure and flow characteristics can be tailored over a wide performance range, extending the possible applications beyond µGC systems.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113581/1/yutaoqin_1.pd

A modular approach to high throughput microsystems

A modular high throughput microsystem was developed using microfabrication technology and nucleic acid analysis. The purpose of developing this microsystem is to identify acute infectious disease and prevent contagious outbreak in a matter of time. This microsystem included three major components, a reagent distribution device, a 96 CFPCR array, and a multi-zone thermal system, to efficiently amplify specific DNA fragments to determine the disease status or precisely pinpoint a disease from multiple patients. Polymerase chain reaction (PCR) is the key component in the nucleic acid analysis for disease because it can be used to amplify interested DNA fragments by repeatedly thermal cycles. Temperature distribution is critical to the PCR reaction, and thermal management was studied; the approaches which reached good biochemical results were applied to the design of a 96 CFPCR array and a multi-zone thermal system. Protein adsorption is another issue when PCR is realized in a micro device because of the increased surface-to-volume ratio, which might terminate the biochemical reaction. A series of experiments were carried out to understand the protein adsorption in the microchannels with different geometries. A disposable 96 CFPCR was designed and fabricated on a polycarbonate substrate by double-sided hot embossing and its requirement of multiple temperature zones was fulfilled by building a multi-zone thermal system. Their thermal performance was characterized by numerical simulations and validated by infrared camera experiments. To evenly distribute the analyte with reducing pipetting steps, a reagent distribution device was designed to assemble with the 96 CFPCR array by using passive alignment structures to perform a systematic performance. The passive alignment structures including three pairs of v-groove and hemisphere-tipped post was studied and modified to ensure a smooth passage for mass, momentum, and energy of chemical analyte. Biochemical experiments demonstrated parallel amplifications of both identical and different DNA fragments from the multiple CFPCRs on the multi-zone thermal system, which implied the potential to detect acute infectious disease with acceleration, accuracy, specificity, and high throughput

Analog Front-End Circuits for Massive Parallel 3-D Neural Microsystems.

Understanding dynamics of the brain has tremendously improved due to the progress in neural recording techniques over the past five decades. The number of simultaneously recorded channels has actually doubled every 7 years, which implies that a recording system with a few thousand channels should be available in the next two decades. Nonetheless, a leap in the number of simultaneous channels has remained an unmet need due to many limitations, especially in the front-end recording integrated circuits (IC). This research has focused on increasing the number of simultaneously recorded channels and providing modular design approaches to improve the integration and expansion of 3-D recording microsystems. Three analog front-ends (AFE) have been developed using extremely low-power and small-area circuit techniques on both the circuit and system levels. The three prototypes have investigated some critical circuit challenges in power, area, interface, and modularity. The first AFE (16-channels) has optimized energy efficiency using techniques such as moderate inversion, minimized asynchronous interface for data acquisition, power-scalable sampling operation, and a wide configuration range of gain and bandwidth. Circuits in this part were designed in a 0.25μm CMOS process using a 0.9-V single supply and feature a power consumption of 4μW/channel and an energy-area efficiency of 7.51x10^15 in units of J^-1Vrms^-1mm^-2. The second AFE (128-channels) provides the next level of scaling using dc-coupled analog compression techniques to reject the electrode offset and reduce the implementation area further. Signal processing techniques were also explored to transfer some computational power outside the brain. Circuits in this part were designed in a 180nm CMOS process using a 0.5-V single supply and feature a power consumption of 2.5μW/channel, and energy-area efficiency of 30.2x10^15 J^-1Vrms^-1mm^-2. The last AFE (128-channels) shows another leap in neural recording using monolithic integration of recording circuits on the shanks of neural probes. Monolithic integration may be the most effective approach to allow simultaneous recording of more than 1,024 channels. The probe and circuits in this part were designed in a 150 nm SOI CMOS process using a 0.5-V single supply and feature a power consumption of only 1.4μW/channel and energy-area efficiency of 36.4x10^15 J^-1Vrms^-1mm^-2.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/98070/1/ashmouny_1.pd