Microassembly Systems Research Articles

Acoustic rotation of multiple subwavelength cylinders for three-dimensional topography reconstruction

Accurate rotation of microparticles is of great significance in micro-rotors, multi-angle microscopic observation, microbial three-dimensional phenotyping, and microsystem assembly. However, most methods can only rotate a single object, thus limiting the throughput. In this study, we realized the simultaneous rotation of many trapped and aligned subwavelength glass cylinders inside an evanescent wave field excited by a resonant phononic crystal plate. The unique feature of the rotation lies in its periodic distribution as well as the rotation axis being perpendicular to the acoustic axis. The rotary power originates from viscous torque generated by the evanescent wave-induced near-boundary acoustic streaming's asymmetry distribution on the trapped cylinder. Furthermore, the three-dimensional topographies of rotated cylinders can be reconstructed from the microscopic images under different rotating angles. Our findings can pave the way toward developing simple, disposable, and scalable microfluidic devices for massive subwavelength acoustic rotation by carefully designing acoustic metamaterials.

Depth estimation method of surface of micropart in microassembly space based on microscopic vision tomographic scanning images.

Three-dimensional (3D) morphology of microparts has an important influence on performance of microassembly system that mainly assembles microparts in millimetre and micron scale. Because 3D morphology of microparts cannot be accurately obtained by conventional microscopic vision system, a depth estimation method of surface of micropart in microassembly space based on microscopic vision tomographic scanning (MVTS) images is proposed in this paper. The proposed method uses the positions of pixels with the largest focus values in MVTS image to construct the isodepth contours of surface of micropart and obtains the depth values of micropart's surface at the positions of MVTS by assigning depth values to corresponding isodepth contours. The MVTS images are obtained by MVTS and pixels with the largest focus values in MVTS image are obtained by focus measurement of MVTS images of micropart in microassembly space. On these bases, 3D spatial interpolation method is applied to map depth value of space between adjacent isodepth contours and to obtain depth values of all surface of micropart. Simulation experiments are carried out to verify the proposed method by generating simulated MVTS image array from two simulation objects, and the influence parameters of the proposed method are analysed. In established experimental setup of microassembly that can realise MVTS, experimental verification for the proposed depth estimation method are carried out by using cone cavity and end jaws of microgripper. 3D morphologies of depth maps of cone cavity and end jaws of microgripper are registered with their respective CAD models using iterative nearest point registration algorithm to quantify accuracy of depth estimation. The research results show that 3D morphology of micropart can be obtained by the proposed method and has better accuracy than those by conventional shape from focus method. This method provides a new way to obtain the morphology of microparts and lays a foundation for improving the accuracy and efficiency of gripping, alignment and approaching microparts in microassembly systems.

Three-Dimensional Trapping and Assembly of Small Particles with Synchronized Spherical Acoustical Vortices

Three-dimensional harmless contactless manipulation and assembly of micro-objects and micro-organisms would open new horizons in microrobotics and microbiology, e.g. for microsystems assembly or tissue engineering. In our previous work [Gong and Baudoin, Phys. Rev. Appl., 12: 024045 (2019)], we investigated theoretically the possibility to trap and assemble in two dimensions small particles compared to the wavelength with synchronized acoustical tweezers based on cylindrical acoustical vortices. However, since these wavefields are progressive along their central axis, they can only push or pull (not trap) particles in this direction and hence are mainly limited to 2D operations. In this paper, we extend our previous analysis and show theoretically that particles can be trapped and assembled in three-dimensions with synchronized spherical vortices. We show that the particles can be approached both laterally and axially and we determine the maximum assembly speed by balancing the Stokes' drag force and the critical radiation force. These theoretical results provide guidelines to design selective acoustical tweezers able to trap and assemble particles in three dimensions.

Model-Free Control for Dynamic-Field Acoustic Manipulation Using Reinforcement Learning

Dynamic-field acoustic manipulation techniques benefit numerous applications in microsystem assembly, pattern formation, biological research, tissue engineering, and lab-on-a-chip. These techniques generally rely on a theoretical dynamic model of particle motion in the acoustic field. Accordingly, success of the manipulation task highly depends on the accuracy of the employed dynamic model. However, modelling such dynamic behavior is a great challenge in more advanced acoustic manipulation devices and requires significant simplifications. Here, we introduce a model-free control method based on reinforcement learning for highly-dynamic acoustic manipulation devices. In our method, the controller does not need a prior knowledge of the acoustic field and learns the optimal control policy for each manipulation task by merely interacting with the acoustic field. As a proof-of-concept, we apply our method to a classic acoustic manipulation device, a Chladni plate consisting of a centrally-actuated vibrating plate. By employing the controller, we demonstrate successful manipulation of single and multiple particles towards target locations on the plate surface. The model-free control method is not limited to the Chladni plate and can be potentially applied to a broad range of acoustic manipulation devices as well as other forms of field-based micromanipulation systems, where accurate theoretical modelling of the field is challenging.

Pareto optimization-based trade-off between the visual resolvability and the intersection space of view of binocular microscopic vision system for microassembly systems

Visual resolvability and intersection space of view of a binocular microscopic vision system (MVS) in microassembly systems have influences on each other via analyzing theoretically. According to requirements of various microassembly tasks, it is an explicit problem how to find the best compromise between the visual resolvability of binocular MVS and its intersection space of view in three-dimensional space. A Pareto optimization-based method to make the trade-off between the visual resolvability and the intersection space of view of binocular MVS with relevant fixed parameters in microassembly systems is proposed. Through modeling and analyzing on the visual resolvability and intersection space of view of a binocular MVS, the topology and optical magnifications of two MVSs are considered as the key parameters to optimize its physical properties. A multiobjection optimization model based on a Pareto optimization method is formulated and used to find the Pareto optimal cure, namely the Pareto front, which represents the best trade-off between the visual resolvability and the intersection space of view of a binocular MVS. On these bases, the physical properties of a binocular MVS with structural parameters corresponding to the optimization solutions are numerically simulated. Accordingly, a binocular MVS with different parameters is established on an automatic microassembly system with a single manipulator with five degree-of-freedom and experimentally tested. The simulation and experimental results indicate that all of the optimal solutions, which locate on the Pareto front, are the best trade-off between the visual resolvability and the intersection space of view of a binocular MVS. According to the Pareto front, physical parameters of a binocular MVS can be chosen to get the optimal visual resolvability with a certain intersection space of view and vice versa.

Системы высокоточной микросборки для фотоники и оптоэлектроники

Системы высокоточной микросборки для фотоники и оптоэлектроники

Robust Impedance Control of a Compliant Microgripper for High-Speed Position/Force Regulation

High-speed simultaneous position and contact force control is vital for microgrippers dedicated to automated high-throughput microassembly tasks. This paper presents the design and validation of a new robust impedance control for high-speed position and force regulation of a compliant gripper which is driven by a piezoelectric stack actuator. Unlike traditional position/force switching control, the proposed scheme enables a smooth transition between the free and constrained motions of the gripper. A single controller is devised to regulate both the gripper tip position and the contact force, rendering a simplification in control design. The stability of the closed-loop system in the presence of piezoelectric nonlinearities is guaranteed by a digital sliding mode impedance control algorithm. Moreover, the proposed control scheme is applicable to high-order systems, and the control algorithm simplification enables a high-speed loop rate. The high-speed control is realized by deploying the algorithm to a field-programmable gate array controller. The effectiveness of the proposed scheme is verified through experimental studies on grasp-hold-release operation of a graphite microrod. The control scheme can be extended to other microassembly systems as well.

A Review of Haptic Feedback Teleoperation Systems for Micromanipulation and Microassembly

This paper presents a review of the major haptic feedback teleoperation systems for micromanipulation. During the last decade, the handling of micrometer-sized objects has become a critical issue. Fields of application from material science to electronics demonstrate an urgent need for intuitive and flexible manipulation systems able to deal with small-scale industrial projects and assembly tasks. Two main approaches have been considered: fully automated tasks and manual operation. The first one require fully pre determined tasks, while the later necessitates highly trained operators. To overcome these issues the use of haptic feedback teleoperation where the user manipulates the tool through a joystick whilst feeling a force feedback, appears to be a promising solution as it allows high intuitiveness and flexibility. Major advances have been achieved during this last decade, starting with systems that enable the operator to feel the substrate topology, to the current state-of-the-art where 3D haptic feedback is provided to aid manipulation tasks. This paper details the major achievements and the solutions that have been developed to propose 3D haptic feedback for tools that often lack 3D force measurements. The use of virtual reality to enhance the immersion is also addressed. The strategies developed provide haptic feedback teleoperation systems with a high degree of assistance and for a wide range of micromanipulation tools. Based on this expertise on haptic for micromanipulation and virtual reality assistance it is now possible to propose microassembly systems for objects as small as 1 to 10 micrometers. This is a mature field and will benefit small-scale industrial projects where precision and flexibility in microassembly are required.

Precision Position/Force Interaction Control of a Piezoelectric Multimorph Microgripper for Microassembly

Precision position and force control is a critical issue for automated microassembly systems to handle micro-objects delicately. This paper presents two new approaches to regulating both position and contact force of a piezoelectric multimorph microgripper dedicated to microassembly tasks. One of the advantages of the proposed approaches lies in that they are capable of controlling the position and contact force of a gripper arm simultaneously. The methodology is easy to implement since neither a state observer nor a hysteresis model of the system is required. The first approach is a position-based sliding mode impedance control which converts the target impedance into a desired position trajectory to be tracked, and the second one is established on the basis of a proportional-integral type of sliding function of the impedance measure error. Their tracking performances are guaranteed by two devised discrete-time sliding mode control algorithms, whose stabilities in the presence of model uncertainties and disturbances are proved in theory. The effectiveness of both schemes are validated by experimental investigations on a glass microbead gripping task. Results show that both approaches are capable of accomplishing promising interaction control accuracy.

Robotic microassembly and micromanipulation at FEMTO-ST

This paper deals with a historical overview of the activities of the French FEMTO-ST institute in the field of microrobotic manipulation and assembly. It firstly shows tools developed for fine and coarse positioning: 4 DOF microgrippers, 2 DOF modules and smart surfaces. The paper then goes on the automation of tridimensional microassembly of objects measuring between 10 and 400 microns. We are especially focusing on several principles. Closed loop control based on micro-vision has been studied and applied on the fully automatic assembly of several 400 microns objects. Force control has been also analyzed and is proposed for optical Microsystems assembly. At least, open loop trajectories of 40 microns objects with a throughput of 1,800 unit per hour have been achieved. Scientific and technological aspects and industrial relevance will be presented.

Analysis and Prediction of the In-Plane Deformation in Laser Thermal Adjustment

Laser thermal adjustment as an application of laser forming in microsystems has received considerable attentions in recent years. This process is a noncontact and high precision forming method. The traditional mechanical microforming technologies for the adjustment step used in microsystem assembly are often limited in their accuracy and are also time consuming. This paper presents an analytical model for describing the in-plane deformation of actuators during laser thermal adjustment. A formula for calculating the in-plane bending angle of the actuator generated by the laser processing is derived. The proposed analytical model is demonstrated by the comparison of the predicted bending angles with the numerical and experimental results. Finally, a formula to predict the possible buckling of the actuator during the laser processing is also developed, from which one can design the opening of the actuator in order to avoid the buckling of the actuator during a heating stage of the process.

Controller Design for Automatic Micro-assembly Systems Under the Influence of Surface Forces, Hysteresis and Quantizer

AbstractIn this paper, we design nonlinear controllers for micro-magnetic levitation systems. The controller takes into account the influence of the surface forces and hysteresis/quantizer. We show the exponential convergence of the error signal and its time derivative to a compact set, which is determined by the uncertainty in the hysteresis and in the quantizer.

Challenges for Capillary Self-Assembly of Microsystems

Within the currently rising trend of heterogeneous microsystem integration and packaging, capillary self-assembly emerges as an innovative technique to enhance, complement and eventually replace pick-and-place assembly. Vast literature and experimental data support such claim. Still, the technique needs to overcome some important limitations in order to fully express its potential and earn wide industrial recognition. In this paper, we review and illustrate what are in our opinion the challenges ahead for making part-to-substrate capillary self-assembly reliable and seriously competitive with long-established assembly techniques. After setting self-assembly methods in the context of microsystem assembly and integration technologies, we focus on the standard embodiment of capillary self-assembly, and we describe in details the main, often novel technological steps required for its effective and reproducible performance. This preludes to an outline of what are presently, in our view, the major failure modes affecting the overall yield of the capillary self-assembly technique. Consequently, we propose solutions to face and overcome these challenges, which need to be met to foster the success of this technique.

Lateral capillary forces of cylindrical fluid menisci: a comprehensive quasi-static study

Capillarity is pivotal to many important technologies, including capillary self-alignment and self-assembly for heterogeneous microsystem integration and packaging. Lateral capillary forces ensuing from perturbed fluid menisci were the object of substantial theoretical and numerical modeling in recent years. Anyway, those studies were so far unsatisfactorily supported by direct experimental inspections. In this paper we present a comprehensive quasi-static study of lateral capillary forces arising from a constrained cylindrical fluid meniscus subjected to small lateral perturbations. We describe the novel experimental apparatus that we designed to accurately characterize such a fundamental system. We then reproduce our experimental data on lateral meniscus forces and stiffnesses by means of both a finite element and a novel analytical model. The agreement between our measurements and models, while confirming earlier reports, provides a solid foundation for the applications of lateral capillary forces to microsystem assembly. Moreover, our experimental apparatus may enable the exploitation of Gibbs’ inequality to measure the advancing contact angles of liquids, and it may be used as a reference testbed for further experimental investigations on constrained fluid menisci.

Methodologies for the Assembly of a Fiber-Coupled MEMS Fourier Transform Spectrometer

This manuscript presents methodologies followed in the construction and packaging of a 3-D microelectromechanical system (MEMS) Fourier transform (FT) spectrometer based on integrated heterogeneous microassembly and packaging systems. We develop procedures, assembly, and packaging work-cells configured for sequential active alignment of miniaturized optical components. Component-to-system-level tolerance analysis is introduced to compensate for the misalignments associated. Furthermore, an inverse methodology based on the self-alignment of fibers is presented to counter the shifts resulting from the fiber packaging process.

Contact Micromanipulation—Survey of Strategies

This paper surveys contact micromanipulation strategies that are developed to tackle the microscale-related phenomena in microassembly. Strategies are divided according to how they take account of adhesion forces. Micromanipulation refers to handling of objects that have dimensions below hundreds of micrometers with handling accuracy down to submicrometers. The line between micro- and nanomanipulation is not definite but typically the object size in nanomanipulation is considered to reach from atomic and molecular scale to hundreds of nanometers. In contact micromanipulation, the tool physically touches the manipulated objects during handling. Scaling-effect-induced adhesion forces severely complicate micromanipulation when compared to conventional macromanipulation. At microscale, the most important adhesive forces are van der Waals force, electrostatic force, and capillary force. Adhesion forces are also the reason behind the fairly low level of automation in microassembly systems. Improved success rate of micromanipulation operations requires that the special features of microscale phenomena be taken into consideration.

Sliding Modes in Constrained Systems Control

In this paper, a sliding-mode-based design framework for fully actuated mechanical multibody system is discussed. The framework is based on the possibility to represent complex motion as a collection of tasks and to find effective mapping of the system coordinates that allows decoupling task and constraint control so one is able to enforce concurrently, or in certain time succession, the task and the constraints. The approach seems naturally encompassing the control of motion systems in interaction, and it allows application to bilateral control, multilateral control, etc. Such an approach leads to a more natural interpretation of the system tasks, simpler controller design, and easier establishment of the systems hierarchy. It allows a unified mathematical treatment of task control in the presence of constraints required to be satisfied by the system coordinates. In order to show the applicability of the proposed techniques, simulation and experimental results for high-precision systems in microsystem assembly tasks and bilateral control systems are presented.

Control of Interconnected Mechanical Systems

In this paper control systems design approach, based on siding mode methods, that allows maintain some functional relation – like bilateral or multilateral systems, establishment of virtual relation among mobile robots or control of haptic systems - is presented. It is shown that all basic motion control problems - trajectory tracking, force control, hybrid position/force control scheme and the impedance control for the interacting systems- can be treated in the same way while avoiding the structural change of the controller and guarantying stable behavior of the system In order to show applicability of the proposed techniques simulation and experimental results for high precision systems in microsystems assembly tasks are presented.

SMC framework in motion control systems

AbstractDesign of a motion control system should take into account both the unconstrained motion performed without interaction with environment or another system, and the constrained motion where the system is in contact with environment or has certain functional interactions with another system. In this paper control systems design approach, based on siding mode methods, that allows selection of control for generic tasks as trajectory and/or force tracking as well as for systems that require maintaining some functional relation—like bilateral or multilateral systems, establishment of virtual relation among mobile robots or control of haptic systems—is presented. It is shown that all basic motion control problems—trajectory tracking, force control, hybrid position/force control scheme and the impedance control—can be treated in the same way while avoiding the structural change of the controller and guaranteeing stable behaviour of the system. In order to show applicability of the proposed techniques simulation and experimental results for high precision systems in microsystems assembly tasks and bilateral control systems are presented. Copyright © 2007 John Wiley & Sons, Ltd.

Fluidic Heterogeneous Microsystems Assembly and Packaging

The nonrobotic fabrication of packaged microsystems that contain nonidentical parts has been accomplished by a directed self-assembly process. The self-assembly process uses geometrical shape recognition to identify different components and subsequent bond formation between liquid solder and metal-coated areas to form mechanical and electrical connections. We applied this concept of shape recognition and subsequent formation of contacts to assemble and package microsystems that contained nonidentical subunits. The self-assembly of three-component assemblies is demonstrated by sequentially adding device segments to the assembly solution including 200-mum-sized light-emitting diodes. Six hundred AlGaInP-GaAs light-emitting diode segments self-assembled onto device carriers in 2min without defects. Encapsulation units self-assembled onto the LED-carrier assemblies to form a three-dimensional (3-D) circuit path to operate the final device. The reported procedure provides a new route to the creation of autonomous heterogeneous microsystems including the realization of autonomous wireless sensor system that requires nonidentical units: CMOS circuitry, Non-CMOS sensor unit for sensing, III-V components for communication, and encapsulation units to form 3-D electrical interconnects. The creation of such systems is being discussed and a proof of concept experiment is being demonstrated