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

Interconnection, Interface And Instrumentation For Micromachined Chemical Sensors

In realizing a portable chemical analysis system, adequate partitioning of a reusable component and a disposable is required. For successful implementation of micromachined sensors in an instrument, reliable methods for interconnection and interface are in great demand between these two major parts. This thesis work investigates interconnection methods of micromachined chip devices, a hybrid fluidic interface system, and measurement circuitry for completing instrumentation. The interconnection method based on micromachining and injection molding techniques was developed and an interconnecting microfluidic package was designed, fabricated and tested. Alternatively, a plug-in type design for a large amount of sample flow was designed and demonstrated. For the hybrid interface, sequencing of the chemical analysis was examined and accordingly, syringe containers, a peristaltic pump and pinch valves were assembled to compose a reliable meso-scale fluidic control unit. A potentiostat circuit was modeled using a simulation tool. The simulated output showed its usability toward three-electrode electrochemical microsensors. Using separately fabricated microsensors, the final instrument with two different designs--flow-through and plug-in type was tested for chlorine detection in water samples. The chemical concentration of chlorine ions could be determined from linearly dependent current signals from the instrument

Surface tension-powered self-assembly of micro structures - The state-of-the-art

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Engineering novel micro-scaffolds and bottom up strategies for in vitro building of vascularized hybrid tissues

There is a significant demand of de-novo engineered tissue grafts capable of replacing biological tissue and/or organ functions for clinical applications. The major obstacle to achieve this goal is the difficulty of recreating all of the complex biochemical and biomechanical functions of the tissue to regenerate, together with transport limitations into the bulk of these newly synthesized tissues. Oxygen and nutrients are supplied to cells and tissues naturally by the microvasculature, which is composed of branching, variable diameter blood vessels. Replicating the complex architecture and functionalities of native tissue vasculature is therefore one of the most important challenge in tissue engineering strategies. To date, bottom up techniques are strong powerful tools to build large viable tissue constructs by packing and sintering cell-laden scaffold-based micro-modules (μ-scaffolds) in a mould. In fact, after sintering and further μ-scaffolds degradation it is possible to achieve large viable tissues in vitro, replicating the composition and structure of native tissue and suitable for studying biological processes involved in new tissue genesis, maturation and remodelling. The aim of this work is to design and engineering novel μ-scaffolds and bottom up assembly techniques to fabricate vascularized layered tissues and to study the effect of μ-scaffolds spatial distribution and co-culture of human dermal fibroblasts (HDFs) together with human umbilical vein endothelial cells (HUVECs) on new tissue growth and vascularization in vitro. To achieve these aims, in first part of this study, we fabricated porous polycaprolactone (PCL) μ-scaffolds with bioinspired trabecular structure and we demonstrated that these newly developed μ-scaffolds supported the in vitro adhesion, growth, and biosynthesis of HDFs. The μ-scaffolds were fabricated by using a fluidic emulsion/porogen leaching/particle coagulation process and by using polyethylene oxide (PEO) as a biocompatible pore-generating agent. In particular, the effect of the composition of the polymeric solution and the flow rate of the continuous phase on μ-scaffolds size distribution, morphology and architectural properties were assessed with the aim to find the best preparation conditions for biological characterization. In vitro culture of HDFs showed that μ-scaffolds supported cells adhesion, colonization, proliferation and biosynthesis in the entire three-dimensional porosity up to 25 days. The second part of this study involved the development of a soft-lithography approach to control the spatial assembly of μ-scaffolds and to create two distinctive μ-scaffolds patterns, namely ordered and disordered. The as obtained patterns were used as substrate for culturing HDFs and 11 HUVECs aiming to develop viable monolayers and bilayers tissue constructs in vitro. The results of this study demonstrated that μ-scaffolds patterning directed cells colonization and biosynthesis and guided the morphology and distribution of newly formed vasculature. All of the findings reported in this work demonstrated the vital role of μ-scaffolds architectural features and assembly on in vitro tissue growth and, pay the way about the possibility to create in silico-designed vasculatures inside modularly engineered biohybrids tissues

A smart procedure for the femtosecond laser-based fabrication of a polymeric lab-on-a-chip for capturing tumor cell

Rapid prototyping methods for the design and fabrication of polymeric labs-on-a-chip are on the rise, as they allow high degrees of precision and flexibility. For example, a microfluidic platform may require an optimization phase in which it could be necessary to continuously modify the architecture and geometry; however, this is only possible if easy, controllable fabrication methods and low-cost materials are available. In this paper, we describe the realization process of a microfluidic tool, from the computer-aided design (CAD) to the proof-of-concept application as a capture device for circulating tumor cells (CTCs). The entire platform was realized in polymethyl methacrylate (PMMA), combining femtosecond (fs) laser and micromilling fabrication technologies. The multilayer device was assembled through a facile and low-cost solvent-assisted method. A serpentine microchannel was then directly biofunctionalized by immobilizing capture probes able to distinguish cancer from non-cancer cells without labeling. The low material costs, customizable methods, and biological application of the realized platform make it a suitable model for industrial exploitation and applications at the point of care. (19) (PDF) A smart procedure for the femtosecond laser-based fabrication of a polymeric lab-on-a-chip for capturing tumor cell. Available from: https://www.researchgate.net/publication/347278450_A_smart_procedure_for_the_femtosecond_laser-based_fabrication_of_a_polymeric_lab-on-a-chip_for_capturing_tumor_cell [accessed Sep 17 2021]

Rapid Prototyping Of Microfluidic Packages

In the area of MEMS there exists a tremendous need for communication between the micro-device and the macro world. A standard protocol or at least multiple standards would be of great use. Electrical connections have been standardized for many uses and configurations by the integrated circuit industry. Standardization in the IC industry has created a marketplace for digital devices unprecedented. In addition to the number of off the shelf products available, there exists the possibility for consumers to mix and match many devices from many different manufacturers. This research proposes some similar solutions as those for integrated circuits for fluid connections and mechanical configurations that could be used on many different devices. In conjunction with offering the capability to facilitate communication between the micro and macro worlds, the packaging solutions should be easy to fabricate. Many devices are by nature non-standard, unique, designs that make a general solution difficult. At the same time, the micro-devices themselves will inevitably need to evolve some standardization. In BioMEMS devices the packaging issue is concerned with delivering a sample to the device, conducting the sample to the sensor or sensors, and removing the sample. Conducting the sample to the sensor or sensors is usually done with microchannels created by standard MEMS fabrication techniques. Many current designs then utilize conventional machining techniques to create the inlet and outlet for the sample. This work proposes a rapid prototyping method for creating the microchannel and inlet / outlet in simplified steps. The packages developed from this process proved to be an effective solution for many applications

Development of novel micropneumatic grippers for biomanipulation

Microbjects with dimensions from 1 μm to 1 mm have been developed recently for different aspects and purposes. Consequently, the development of handling and manipulation tools to fulfil this need is urgently required. Micromanipulation techniques could be generally categorized according to their actuation method such as electrostatic, thermal, shape memory alloy, piezoelectric, magnetic, and fluidic actuation. Each of which has its advantage and disadvantage. The fluidic actuation has been overlooked in MEMS despite its satisfactory output in the micro-scale. This thesis presents different families of pneumatically driven, low cost, compatible with biological environment, scalable, and controllable microgrippers. The first family demonstrated a polymeric microgripper that was laser cut and actuated pneumatically. It was tested to manipulate microparticles down to 200 microns. To overcome the assembly challenges that arise in this family, the second family was proposed. The second family was a micro-cantilever based microgripper, where the device was assembled layer by layer to form a 3D structure. The microcantilevers were fabricated using photo-etching technique, and demonstrated the applicability to manipulate micro-particles down to 200 microns using automated pick-and-place procedure. In addition, this family was used as a tactile-detector as well. Due to the angular gripping scheme followed by the above mentioned families, gripping smaller objects becomes a challenging task. A third family following a parallel gripping scheme was proposed allowing the gripping of smaller objects to be visible. It comprises a compliant structure microgripper actuated pneumatically and fabricated using picosecond laser technology, and demonstrated the capability of gripping microobject as small as 100 μm microbeads. An FEA modelling was employed to validate the experimental and analytical results, and excellent matching was achieved

Enabling Capillary Self-Assembly for Microsystem Integration

Efficient and precise assembly of very-large quantities of sub-millimeter-sized devices onto pre-processed substrates is presently a key frontier for microelectronics, in its aspiration to large-scale mass production of devices with new functionalities and applications (e.g. thin dies embedded into flexible substrates, 3D microsystem integration). In this perspective, on the one hand established pick&place assembly techniques may be unsuitable, due to a trade-off between throughput and placement accuracy and to difficulties in predictably handling very-small devices. On the other hand, self-assembly processes are massively parallel, may run unsupervised and allow contactless manipulation of objects. The convergence between robotic assembly and self-assembly, epitomized by capillarity-enhanced flip-chip assembly, can therefore enable an ideal technology meeting short-to-medium-term electronic packaging and assembly needs. The objective of this thesis is bridging the gap between academic proofs-of- concept of capillary self-assembly and its industrial application. Our work solves several issues relevant to capillary self-assembly of thin dies onto preprocessed substrates. Very-different phenomena and aspects of both scientific and technological interest coexist in such a broad context. They were tackled both experimentally and theoretically. After a critical review of the state-of-the-art in microsystem integration, a complete quasi-static study of lateral capillary meniscus forces is presented. Our experimental setup enables also a novel method to measure the contact angle of liquids. Recessed binding sites are introduced to obtain perfectly-conformal fluid dip-coating of patterned surfaces, which enables the effective and robust coding of geometrical information into binding sites to direct the assembly of parts. A general procedure to establish solder-mediated electro-mechanical interconnections between parts and substrate is validated. Smart surface chemistries are invoked to solve the issue of mutual adhesion between parts during the capillary self-assembly process. Two chemical kinetic-inspired analytic models of fluidic self-assembly are presented and criticized to introduce a novel agent-based model of the process. The latter approach allows realistic simulations by taking into account spatial factors and collision dynamics. Concluding speculations propose envisioned solutions to residual open issues and further perspectives for this field of rapidly-growing importance