Self-alignment Capability Research Articles

A polyamide-facilitated soldering approach for Mini LED precise alignment leveraging 3D interfacial networks

Driven by the need for improved quality, energy efficiency, and visual innovation, display technology has evolved from CRT to Mini LED. However, the transfer process in Mini LED assembly poses challenges in precision. This study addressed the displacement issue during the transfer process by investigating the synergistic effects of solder and functional organic chemicals. Through the Mini LED assembly process, with the Mini LED size measuring 150 μm (length) ∗ 100 μm (width) ∗ 70 μm (thickness), polyamide was identified as a facilitator for precise alignment, which enhanced self-alignment capabilities by 68.8 % and improved the accuracy on self-aligned distance from 12.5 μm to 21.1 μm in Mini LED packaging. Through the powder coalescence approach, further extensive analysis using XPS, SEM, FTIR, and DSC reveals the synergistic effects. It supports the proposed three-dimensional polyamide-tin ion coordination interfacial network construction mechanism that facilitates solder-to-solder self-alignment and coalescence. This study provides insight into such a polymer-metal ion 3D coordination network for Mini LED precise alignment, which is promising for mass production.

Concept design of automatic connector for maintenance cask of EU-DEMO and CFETR

For both CFETR and EU-DEMO remote handling system, maintenance casks are critical systems to provide storage and sealing functions. The maintenance devices and tools inside a cask receive power and signals during operation from the cask automatic connectors which are located at both sides of the Hot Cell Docking ports and the Tokamak machine Docking ports, respectively. For perfect transmission of power and signals, the automatic connector should have self-alignment capability and reasonable cable routing. Structural flexibility should be designed for the connector to compensate for the engagement misalignment induced by the structure and the control of the cask transporter. Moreover, the automatic connector should be connecting electric wires for motors, sensors, fiber optics, etc. The automatic connector must have high reliability to ensure that there will be no damage during the life cycle of the fusion reactor. A conceptual design of the connector has been developed. This will be presented together with prototype and validation works that are currently being implemented in close collaboration between European laboratories and the Comprehensive Research facility for Fusion Technology (CRAFT) at ASIPP in Hefei.

Development and Validation of a Self-Aligning Knee Exoskeleton With Hip Rotation Capability.

The self-aligning capability of an exoskeleton is important to ensure wearing comfort, and the delicate motion ability of the exoskeleton is essential for motion assistance. Designing a self-aligning exoskeleton that offers improved wearing comfort and enhanced motion-assistance functions remains a challenge. This paper proposes a novel spatial self-aligning mechanism for a knee exoskeleton to enable simultaneous assistance in the flexion and extension (FE) of the knee joint and the internal and external rotation (IER) of the hip joint. Additionally, considering the misalignment of the human-robot joint axes, a kinematic model of the knee exoskeleton is established and analyzed to demonstrate the kinematic compatibility of the exoskeleton. Furthermore, a global torque manipulability (GTM) index is proposed to evaluate the effects of dimensional parameters on the exoskeleton's performance, and then the knee exoskeleton is optimized according to the GTM index. Finally, experiments are conducted to validate the performance of the proposed exoskeleton. The experimental results show that during knee FE and hip IER, the proposed exoskeleton exhibits lower interaction forces and torques than existing exoskeletons.

A Robust Wireless Power Transfer System With Self-Alignment Capability and Controllable Output Current for Automatic-Guided Vehicles

A Robust Wireless Power Transfer System With Self-Alignment Capability and Controllable Output Current for Automatic-Guided Vehicles

Self-Alignment Capability Analysis and Self-Attraction Dipole Solution of Spacecraft Electromagnetic Docking

Spacecraft electromagnetic docking has many potential advantages, such as no propellant consumption and plume contamination, while providing high-precision, continuous, reversible, synchronous, and noncontacting control capabilities. With these advantages, there are strong dynamic nonlinearity and coupling, which are not friendly to controller design. Electromagnetic actuation has capabilities of force/torque symmetry and self-alignment, which could be exploited not only to simplify the controller but also to reduce the demand of relative motion measurement and improve control precision. In this paper, based on the theoretical derivation of nonlinear relative motion dynamic models, the magnetic force/torque symmetries and the self-alignment capability are analyzed, and then the self-attraction magnetic dipoles are solved. In addition, several numerical simulation cases are given to verify these capabilities and dipole solutions.

Self-Aligning Capability of IPT Pads for High-Power Wireless EV Charging Stations

This article studies magnetic forces between transmitter (Tx) and receiver (Rx) coils in an inductive power transfer (IPT) system aiming to use those forces to align the coils and, consequently, improve power transfer. Due to its popularity, the analysis is conducted on a series–series compensated IPT system with planar spiral coils. The proposed method utilizes the bifurcation operation mode of the system and unloaded resonating receiver to maximize attractive force between magnetic couplers. Three-dimensional finite-element method simulations indicate that high-power IPT systems can develop enough attractive force to align coils even under nominal current. Regardless of the coil shape, e.g., spiral or Double-D (DD), the attractive forces tend to align the coils. Hence, a smart charging station can be devised based on self-aligning capability. Furthermore, this article proposes a mechanical structure to facilitate the attractive lateral force for the alignment of high power applications, i.e., wireless fast-charging stations. The forces are analyzed, modeled, and simulated for a 100-kW IPT system with an operating frequency of 20 kHz, while the self-aligning capability is experimentally verified on a downscale 11-kW prototype.

Design and Validation of a Self-Aligning Index Finger Exoskeleton for Post-Stroke Rehabilitation.

Rehabilitation of hand functions is necessary to improve post-stroke patients' quality of life. There is initial evidence that hand exoskeletons should exercise flexion/extension (f/e) and abduction/adduction (a/a) of the fingers to rebuild hand functions. However, designing a self-alignment mechanism of the metacarpophalangeal (MCP) joint to improve its wearing comfort is still a challenge. In this paper, a novel index finger exoskeleton with three motors is proposed to help post-stroke patients perform finger a/a and f/e training. A spatial mechanism with passive degrees of freedom for the MCP joint is designed to realize human-robot axes self-alignment. The proposed mechanism's kinematic compatibility is analyzed to show its self-aligning capability, and the kineto-statics analysis is performed to present the exoskeleton's static characteristics. Finally, kinematic and static experiments have been conducted, and the results indicate that the standardized reaction forces square sum of the exoskeleton to the MCP joint can be reduced by 65.8% compared with the state-of-the-art exoskeleton. According to the experimental results, the exoskeleton can achieve the a/a and f/e training and human-robot axes self-alignment, and improve its comfortability. In the future, clinical trials will be further studied to test the exoskeleton.

A self-attachable and self-alignable micro electromagnetic linear actuator

This paper presents the design, fabrication and characterization of a novel micro electromagnetic linear actuator, which exhibits two highlights: slider self-alignment and self-attachment capability. Such characters are realized by deliberately utilizing the attractive force between the permanent magnets (Nd2Fe14B) of the slider and nickel ferromagnetic cores embedded in the stator. Actuation is achieved via thrust from both meander micro copper coils and nickel ferromagnetic cores in the stator to the permanent magnets of the slider. The actuator is fabricated by the micro machining process. The surface magnetic property of the slider is simulated and experimentally measured. The eccentric experiment is conducted to evaluate the attraction force between the slider and stator, which proves its self-attachment characteristics. The device is actuated by two-phase sinusoidal currents with a 0.5 A amplitude under an open-loop condition. The slider demonstrates self-alignment movements before moving forward when misalignment occurs. The actuation experimental results show that the average velocity of the slider reaches 4 mm s–1 and 12 mm s–1 at 10 Hz and 30 Hz, respectively. Further increasing the input frequency to 50 Hz leads to the unsteady actuation state, indicating the actuator bandwidth is less than 50 Hz under an open-loop condition.

Passive self-aligning of a floating offshore wind turbine

The development of floating offshore wind turbines opens the way for various new design types, and the platform, tower and turbine can benefit from its floating foundation. Self-aligning platforms, where the entire structure follows the wind direction are a promising concept. A single point mooring with turret system allows for free rotation around the vertical axis. Aerodynamic forces of rotor and tower induce the self-aligning moment. In the present study, the operating principle of a passive platform design with airfoil-shaped tower and downwind rotor is analyzed under steady conditions using a boundary element method (BEM). Rotor cone angle and the tower dimensions have a major influence on the yawing moment. They must be large enough to dominate the hydrodynamic forces induced by seaway and current. The passive self-aligning capability is shown in an integrated simulation for various current velocities and wind-current offset angles.

Experimental Investigation of a Downwind Coned Wind Turbine Rotor under Yawed Conditions: Preliminary Results

The growing number of Floating Offshore Wind Turbine (FOWT) concepts that utilize a single point mooring and therefore rely on the self-alignment capabilities of the wind turbine (e.g. SCD nezzy or SelfAligner by CRUSE Offshore) demands an extension of the simulation methods used for their development. A crucial issue for these concepts is the accurate prediction of forces and moments, which contribute to the self-alignment. In contrast to the well-studied behaviour of torque and thrust, yaw moment and lateral forces on a rotor under yawed conditions have not been in focus of previous experimental tests for the validation of aerodynamic simulation tools. In the present work, a model turbine equipped with a 6-axis force/moment sensor to capture the complete load on the rotor is presented. A detailed study of the two-bladed model turbine’s aerodynamic behaviour under yawed conditions was carried out within a range of yaw angles between -55 to + 55° with steps of 1 – 2.5°.

Self-aligning behaviour of a passively yawing floating offshore wind turbine

ABSTRACTFloating offshore wind turbines are a promising concept for expanding offshore wind energy. In comparison with fix-founded offshore wind turbines, the overall costs are less dependent on water depths, which leads to a variety of potential locations and markets worldwide. Furthermore, floating platforms allow for new structural designs with the potential to save material and installation costs. In this paper, a self-aligning platform equipped with a 6 MW turbine is presented. The platform is moored on a single point and uses a turret buoy to be able to rotate freely around its anchor point. A downwind rotor and an airfoil-shaped tower induce self-aligning turning moments to passively follow changes of the wind direction. The first order boundary element method panMARE is used to simulate the motion behaviour considering aerodynamic, hydrodynamic and mooring loads. The self-aligning capability is demonstrated under partial turbine load for steady and dynamic conditions with waves and current.

A Disposable and Self-Aligned 3-D Integrated Bio-Sensing Interface Module for CMOS Cell-Based Biosensor Applications

This letter presents a disposable, self-aligned, and die-level socketed 3-D integrated biosensing-interface module (BIM) for biosensing applications. The enabling technologies of the BIM include: 1) mechanically flexible interconnects (MFIs) that provide temporary electrical interconnections to enable disposability; 2) sapphire precision balls and positive self-alignmentstructures, which in combination with KOH-etched pits provide the BIM self-alignment capabilities; and 3) a clamped socket that temporarily provides the necessary force for the MFIs to form and maintain electrical contact with the underlying test die during testing. Repeated alignment measurements show that the alignment of the BIM to the biosensor varies little between uses, hence demonstrating that the biosensor system can maintain accurate alignment. In addition, four-point resistance measurements were taken after assembly indicating that temporary electrical connections were formed and maintained.

Cellular immunity monitoring in long-duration spaceflights based on an automatic miniature flow cytometer

Monitoring cellular immunity is essential for long-duration spaceflight missions. To address this need, we developed an automatic miniature flow cytometer that is targeted to monitor the cellular immune function of astronauts or passengers during long-duration spaceflights. Automatic sample preparation, a disposable sheathless focusing chip, optical self-alignment, and side scatter (SSC) detection capability were developed to meet the strict requirements of spaceflight applications. SSC and four colors of fluorescence are measured to realize lymphocyte subsets counted from whole blood. This technology was used in four-subject 180-day controlled ecological life support system (CELSS) experiments to monitor the cellular immunity of four crewmembers by counting the lymphocyte subsets (total CD3+, CD3+CD4+, and CD3+CD8+ cells). The microgravity compatibility was successfully verified on a parabolic flight. Thus, the presented system was proven a feasible solution for health care applications during long-duration manned spaceflight.

Numerical simulation of self-alignment of chip resistor components for different silver content during reflow soldering

Three-dimensional simulation and experimental investigation of self-alignment phenomena during the reflow soldering process were presented. The multiphase flow model was developed using ANSYS Fluent to investigate the self-alignment effect of laminar melted lead-free solder during the reflow phase on board. User-defined function with c-code was integrated into the model, Volume of Fluid (VOF) method was applied to the melt front tracking, and solidification model was used for the phase change solder material. The material used in the study was SAC 105, SAC 305 and SAC 405. The specific heat, latent heat, solidus temperature, liquidus temperature of the lead-free solder and geometrical data for model input was determined experimentally. The model was validated experimentally. The self-alignment capability of different lead-free solder was presented. It has been observed that higher silver content solder (SAC 405) have higher self-alignment capability during reflow soldering compare to SAC 305 and SAC 105. Moreover, all cases show self-alignment in perpendicular to the longer sides of chip resistor travelled more towards the central position. The experimental and simulation results are in good conformity and can be extended for different cases.

Heterogeneous Integration of Thin-Film Optical Devices Utilizing Fluidic Self-Assembly and Micro-Pick-and-Place Technique

This paper demonstrates the heterogeneous integration of thin-film photonic devices onto a silicon-based host substrate by the combination of surface tension-driven fluidic self-assembly (FSA) and modified micro-pick-and-place (PAP) technique. FSA offers self-alignment and integration capability of thin-film devices onto a host substrate with high precision, while the PAP technique provides an efficient guiding mechanism by coarse positioning of the device and improves efficiency and yield of the integration by overcoming the stochastic limitation of FSA. An array integration of thin-film GaAs metal-semiconductor-metal photodetectors (PDs) onto a silicon-based host substrate has been successfully demonstrated with the proposed integration approach. Electrical measurement was performed to confirm the metal-to-metal contact between the integrated PD and its substrate. Misalignment of the PD from the optimal desired location was also analyzed. In addition, specific contact resistance of the Au-to-Au bonding was investigated. The proposed integration method can be further developed with the help of a high-speed automation technique for PAP to be compatible with batch wafer processing.

Influence of side chains on the self-alignment capability of electroluminescent polyfluorenes.

We report a significant role of side chains in the propagation of molecular orientation upon annealing the liquid crystal phase of polyfluorenes. Direct rubbing of poly(9,9-di(octyl)fluorene) led to the orientation of polymer segments in the top-most region of the film and enhanced propagation of this orientation along the rubbing direction was observed upon annealing. In contrast, the rubbing-induced molecular orientation of poly(9,9-di(ethylhexyl)fluorene) segments completely disappeared upon annealing in the nematic melt state. The higher order of the side chain structures in poly(9,9-di(octyl)fluorene) were found to allow the propagation of the three-dimensional molecular alignment. From integrated experimental and density functional theory studies, we propose that side chain interdigitation generates a unique alignment behavior of poly(9,9-di(octyl)fluorene).

Process Window for Forming of Micro Preforms at Different Temperatures

Parts, which dimensions do not exceed the micro range are gaining more importance in today´s goods due to miniaturization and function compaction of products. Thus, fabrication methods for these special, very small parts attract notice because whole processes or at least process parameters cannot be transferred into micro range. Nevertheless, this does not necessarily mean, that size-effects are always detrimental as there are some processes which can only be carried out in micro range such as the laser-based micro upsetting process. The basic characteristics of this process are presented in this paper such as its self-aligning capability. Due to the fact that the maximum achievable upset ratio in single stage upsetting decreases with decreasing sample size, the material accumulation represents a very good semi-finished product (preform) being formed in a succeeding upsetting process. A temperature- and time controlled forming unit has been developed which is directly adapted to the laser system which is required to generate the preform. Thus, either a pre-defined temperature of the preform or the down time gives the initial signal to start the forming process. In this paper, a mathematical model is very briefly presented to determine the process window for forming preforms at certain well defined temperatures regarding size-effects.

Picosecond Laser Machining of Metallic and Polymer Substrates for Fluidic Driven Self-Alignment

Fluidic self-alignment of micro-components relies on creating a receptor site that is able to confine a liquid droplet. When a micro-component is brought in contact with the droplet, capillary forces move the component to its final position. A method to stop the advancing of a liquid from a receptor site, consists of creating geometrical features, such as edges around the site. A picosecond pulsed laser source was used to create suitable edges in a metallic and a polyimide substrate. Subsequently, the self-alignment capabilities of these sites were tested. The receptor sites in polyimide showed the highest success rate.

Multi-functional nanopatterned optical films fabricated using capillary force lithography

We demonstrate anisotropic optical films based on liquid crystalline polymer (LCP) using a capillary force lithography (CFL). The fabricated optical films can be used as both an optical component and a self-aligning capability of liquid crystal molecules introduced on the film. Additionally, HA or PA LC can be induced on same material by controlling the water repellency of LCP surface. Moreover, surface anchoring transitions could be controlled by variation of pattern sizes and surface treatment. In this point of view, one thin optical film can act both retarder and alignment layer and then shows good retardation, LC alignment, and transmittance at the same time.

Novel approach for microassembly of three-dimensional rotary MOEMS mirrors

We present a novel approach to construct 3-D 1×N rotary micromirrors, which are fundamental components in optical switching systems. A rotary micromirror consists of two microparts: a rotary micromotor and a micromirror. Both of the two microparts are fabricated with PolyMUMPs,TM (MEMSCAP, Research Triangle Park, North Carolina), a surface micromachining process. A sequential robotic microassembly process is developed to join the two microparts together to construct the 3-D device. To achieve high positioning accuracy and strong mechanical connection, the micromirror is joined to the micromotor using an adhesive mechanical fastener. The mechanical microjoint has self-alignment capability and provides a temporary joint between the two microparts. The adhesive bonding creates a strong permanent connection between the two microparts. The adhesive mechanical fastener does not require extra supporting plates to fix the micromirror, which simplifies the microassembly process and makes it possible to automatically assemble the rotary micromirror. A hybrid manipulation strategy, which includes pick-and-place and pushing-based micromanipulations, is utilized to assemble the micromirror onto the micromotor. The pick-and-place manipulation has the ability to globally position the micromirror with multiple degrees of freedom. The pushing-based manipulation can achieve high positioning accuracy. This novel approach provides great flexibility and high accuracy for assembling the complex micromirror.