Planar Platform Research Articles

Predicting development of AD clinical symptoms and their progression through a collection of novel plasma Aβ immunoassays

AbstractBackgroundFor many years, fluid biomarkers for amyloid β‐protein were described exclusively for Aβ42 and Aβ40, with Aβ40 being the major secreted form and Aβ42 being the predominant component of amyloid‐plaques in AD brain. However, the C‐termini of these two Aβ peptides and the N‐terminus of the AICD are not aligned. It is now clear that secreted Aβ peptides are produced along two proteolytic pathways by γ‐secretase: Aβ49→46→43→40→37 and Aβ48→45→ 42→39/38. We now asked whether a more comprehensive analysis of Aβ peptides in plasma and CSF will help understand and predict brain amyloid pathology and its consequences.MethodWe designed novel immunoassays to detect essentially all the secreted forms of Aβ (Aβ x‐37, 38, 39, 40, 42 and 43), initially on the MesoScale‐Discovery platform (sensitive enough for human CSF samples). To measure same analytes in plasma, we built ultrasensitive immunoassays on the Quanterix SP‐X planar platform with 10‐20 folds enhanced sensitivity. We term Aβ37‐39 short and 40‐43 long Aβs.ResultWe quantified 6 Aβ‐variants in 79 CSF samples from Mayo‐Clinic divided into three diagnostic groups: cognitively normal (CN), mild cognitive impairment (MCI) and Alzheimer's disease (AD). In contrast to Aβ42/40, the short/long Aβ ratios in CSF distinguished CN from AD & MCI more effectively, with AUC (ROC‐analysis) of 0.9609 for Aβ37/42 in distinguishing CN and AD, while AUC is 0.8623 for Aβ42/40. Moreover, both 37/42 and 38/43 correlated significantly with the MMSE scores of these subjects. Next, we tested 88 plasma samples from same cohort, the Aβx‐37/1‐42 ratio in plasma clearly distinguished AD and CN (AUC of 0.8572), while the traditional Aβ1‐42 analyte could not. Currently, we are testing the Aβ37/42 and other ratios in a longitudinal Harvard‐Aging‐Brain‐Study (HABS) cohort.ConclusionCompared to the classic Aβ42/40 ratio in CSF or the Aβ1‐42 absolute level in plasma, a comprehensive analysis of Aβ peptides in plasma and CSF yields better Aβ biomarkers to distinguish CN and AD. Moreover, both 37/42 and 38/43 ratios in CSF correlated significantly with MMSE scores. Importantly, we are assessing whether plasma Aβ37/42 correlates most tightly with the development of AD clinical symptoms and their progression, using longitudinal aging cohorts.

All-dielectric silicon metalens for two-dimensional particle manipulation in optical tweezers

Dynamic control of compact chip-scale contactless manipulation of particles for bioscience applications remains a challenging endeavor, which is restrained by the balance between trapping efficiency and scalable apparatus. Metasurfaces offer the implementation of feasible optical tweezers on a planar platform for shaping the exerted optical force by a microscale-integrated device. Here we design and experimentally demonstrate a highly efficient silicon-based metalens for two-dimensional optical trapping in the near-infrared. Our metalens concept is based on the Pancharatnam–Berry phase, which enables the device for polarization-sensitive particle manipulation. Our optical trapping setup is capable of adjusting the position of both the metasurface lens and the particle chamber freely in three directions, which offers great freedom for optical trap adjustment and alignment. Two-dimensional (2D) particle manipulation is done with a relatively low-numerical-aperture metalens ( NA ML = 0.6 ). We experimentally demonstrate both 2D polarization-sensitive drag and drop manipulation of polystyrene particles suspended in water and transfer of angular orbital momentum to these particles with a single tailored beam. Our work may open new possibilities for lab-on-a-chip optical trapping for bioscience applications and microscale to nanoscale optical tweezers.

Fabricating 3D Metastructures by Simultaneous Modulation of Flexible Resist Stencils and Basal Molds.

Metamaterials have gained much attention thanks to their extraordinary and intriguing optical properties beyond natural materials. However, universal high-resolution fabrications of 3D micro/nanometastructures with high-resolution remain a challenge. Here, a novel approach to fabricate sophisticated 3D micro/nanostructures with excellent robustness and precise controllability is demonstrated by simultaneously modulating of flexible resist stencils and basal molds. This method allows arbitrary manipulations of morphology, size, and orientation, as well as contact angles of the objects. Combined with a new alignment strategy of high-resolution, previously inaccessible architectures are fabricated with ultrahigh precision, leading to an excellent spectra response from the fabricated metastructures. This method provides a new possibility to realize true 3D metamaterial fabrications featuring high-resolution and direct-compatibility with broad planar lithography platforms.

Trade-off between resolution and frame rate of visual tracking of mini-robots on an experimental planar platform

Accurate and fast visual localization is required in many applications of mini-robotics. Obtaining the best possible result for a given platform requires a balanced combination of camera settings and efficient image processing of the acquired image. In this paper, we study the trade-off between a high-resolution and a high-speed acquisition mode of a conventional camera for an experimental platform of magnetically-propelled mini-robots. Specifically, we propose a two stage localization algorithm based on fast pre-location using block matching followed by optical flow correction for subpixel accuracy of localization. In the experimental evaluation, we show that the difference in localization using two images of the same scene in resolutions 1000 × 1000px and 200 × 200px is only 0.2px of the higher resolution. The computational cost of the lower resolution is 16times lower than that of the higher resolution. This allows greater accuracy localization at a higher frame rate, which significantly improves the dynamics of control. Experimental results demonstrate the precision and speed of the proposed algorithm in the task of tracking a magnetically propelled robot on the platform.

Robust waveguiding in substrate-integrated topological photonic crystals

Recent development of topological photonics has enabled photonic energy flow robust against disorders. On the other hand, waveguiding in substrate-integrated planar platforms is significant for microwave and mm-wave technology. Here, we propose substrate-integrated topological photonic crystals (PhCs) that support robust pseudospin-dependent edge states. We verify the robustness of pseudospin-dependent electromagnetic-wave (EM-wave) energy transport through sharply twisted corners, random defects, or a channel intersection both numerically and experimentally at microwave frequencies. The present topological PhCs with planar forms, small thicknesses, and excellent electrical shielding pave the way toward manipulation of EM topological pseudospins in an integrated platform.

Large scale 3D bioreactor technology: linear scale up of mesenchymal stromal cell expansion with tidexcell™ system

Background & Aim Tissue and bone marrow aspirate generally contain only a small amount of mesenchymal stromal cells (MSCs), yet a typical dose of 10-200 million cells or more is required for cell therapy. As such, alternatives to traditional planar culture platforms are preferred for efficient cell expansion. The extensive quantity demands for MSCs for allogeneic therapy further pushes the need for scaling up culture with bioreactors. In bioreactors, automation, single use and linearly scalable capabilities are desirable. However, this scaling up in bioreactors and bioprocesses is complex and requires extensive understanding experience and knowledge. Methods, Results & Conclusion Here, we performed upstream process development in a series of Tide Motion bioreactors that offer a culture environment with high oxygen transfer, low shear stress and no sparging. P4 bone marrow MSCs were recovered in planar cultures, seeded into a small benchtop bioreactor, the CelCradle, and harvested and reseeded into the TideXcell™ bioreactor with 1 L packed bed volume. Within a culture period of 15 days, the cells expanded by 9.6 doubling population levels, achieving 2 billion cells from 2.5 million cells. Real time monitoring of media/metabolites and sampling of cells ensured the culture was at optimal conditions throughout cell growth. Using the automated, closed TideXcell™ Cell Harvesting System, 97.7% harvesting efficiency was achieved with a cell viability of 93.8%. The criterial quality parameters (identity, purity, potency and safety) of the final cell product were inspected. As per ISCT recommendations, the MSCs demonstrated trilineage differentiation and immunophenotyping of > 95% for CD105, CD90, CD73, and <2% for CD34, CD45, HLA-DR, CD11b and CD19. T-cell suppression assay and IDO quantification also demonstrated intact immunomodulatory capabilities of the expanded MSCs. By coupling the automated TideXcell™ system together with its closed automated cell harvester, we were able to obtain high cell numbers with low labour cost. The bioprocess route to determining optimal culture parameters for the TideXcell™ was simplified by optimizing culture parameters in CelCradle™, with a 0.1 L packed-bed volume, before moving to larger capacities. The cell yield obtained in a 1 L packed bed TideXcell system was as projected from the CelCradle™ system. As such, the cost of bioprocess development was greatly reduced using the Tide Motion bioreactos. Tissue and bone marrow aspirate generally contain only a small amount of mesenchymal stromal cells (MSCs), yet a typical dose of 10-200 million cells or more is required for cell therapy. As such, alternatives to traditional planar culture platforms are preferred for efficient cell expansion. The extensive quantity demands for MSCs for allogeneic therapy further pushes the need for scaling up culture with bioreactors. In bioreactors, automation, single use and linearly scalable capabilities are desirable. However, this scaling up in bioreactors and bioprocesses is complex and requires extensive understanding experience and knowledge. Here, we performed upstream process development in a series of Tide Motion bioreactors that offer a culture environment with high oxygen transfer, low shear stress and no sparging. P4 bone marrow MSCs were recovered in planar cultures, seeded into a small benchtop bioreactor, the CelCradle, and harvested and reseeded into the TideXcell™ bioreactor with 1 L packed bed volume. Within a culture period of 15 days, the cells expanded by 9.6 doubling population levels, achieving 2 billion cells from 2.5 million cells. Real time monitoring of media/metabolites and sampling of cells ensured the culture was at optimal conditions throughout cell growth. Using the automated, closed TideXcell™ Cell Harvesting System, 97.7% harvesting efficiency was achieved with a cell viability of 93.8%. The criterial quality parameters (identity, purity, potency and safety) of the final cell product were inspected. As per ISCT recommendations, the MSCs demonstrated trilineage differentiation and immunophenotyping of > 95% for CD105, CD90, CD73, and <2% for CD34, CD45, HLA-DR, CD11b and CD19. T-cell suppression assay and IDO quantification also demonstrated intact immunomodulatory capabilities of the expanded MSCs.

Expansion of human mesenchymal stromal/stem cells in xeno-free conditions

Background & Aim The long-term outlook for stem cell therapy predicts a shift toward better defined media and high-quality raw materials. Additionally, there is an increased need for cell therapy reagents compatible with microcarrier-based suspension culture platforms, allowing for both small scale studies and large-scale therapeutic manufacturing. Methods, Results & Conclusion Here, we examine the scale up process of human mesenchymal stromal/stem cells (hMSCs) using a novel high-quality xeno-free medium. We highlight the growth and characterization of hMSCs in planar and stirred-tank bioreactor growth platforms using xeno-free conditions throughout the entire process. Different xeno-free materials such as microcarriers and surface coatings are investigated to identify the best conditions compatible with our xeno-free MSC medium. In addition, certain steps and procedures are optimized because the xeno-free environment requires some adjustments. Results indicate that our newly developed medium delivers improved cell growth performance and supports a xeno-free process in both planar and microcarrier-based suspension culture. This xeno-free medium developed for hMSC expansion reliefs the immediate need for suspension-based clinical production, as well as future implementation of large-scale commercial manufacturing solutions for cell therapies. The long-term outlook for stem cell therapy predicts a shift toward better defined media and high-quality raw materials. Additionally, there is an increased need for cell therapy reagents compatible with microcarrier-based suspension culture platforms, allowing for both small scale studies and large-scale therapeutic manufacturing. Here, we examine the scale up process of human mesenchymal stromal/stem cells (hMSCs) using a novel high-quality xeno-free medium. We highlight the growth and characterization of hMSCs in planar and stirred-tank bioreactor growth platforms using xeno-free conditions throughout the entire process. Different xeno-free materials such as microcarriers and surface coatings are investigated to identify the best conditions compatible with our xeno-free MSC medium. In addition, certain steps and procedures are optimized because the xeno-free environment requires some adjustments.

2D Waveguided Bessel Beam Generated Using Integrated Metasurface-Based Plasmonic Axicon

Near-field imaging of the propagation of a diffraction-free Bessel-type beam in a guided wave configuration generated by means of a metasurface-based axicon lens integrated on a silicon waveguide is reported. The operation of the axicon lens with a footprint as small as 11µm2 is based on local engineering of the effective index of the silicon waveguide with plasmonic nanoresonators. This generic approach, which can be adapted to different types of planar lightwave circuit platforms, offers the possibility to design nano-engineered optical devices based on the use of plasmonic resonators to control light at the nanoscale.

Realization of Nanolene: A Planar Array of Perfectly Aligned, Air-Suspended Nanowires.

Air suspension and alignment are fundamental requirements to make the best use of nanowires' unique properties; however, satisfying both requirements is very challenging due to the mechanical instability of air-suspended nanowires. Here, a perfectly aligned air-suspended nanowire array called "nanolene" is demonstrated, which has a high mechanical stability owing to a C-channel-shaped cross-section of the nanowires. The excellent mechanical stability is provided through geometrical modeling and finite element method simulations. The C-channel cross-section can be realized by top-down fabrication procedures, resulting in reliable demonstrations of the nanolenes with various materials and geometric parameters. The fabrication process provides large-area uniformity; therefore, nanolene can be considered as a 2D planar platform for 1D nanowire arrays. Thanks to the high mechanical stability of the proposed nanolene, perfectly aligned air-suspended nanowire arrays with an unprecedented length of 1 mm (aspect ratio ≈5100) are demonstrated. Since the nanolene can be used in an energy-efficient nanoheater, two energy-stringent sensors, namely, an air-flow sensor and a carbon monoxide gas sensor, are demonstrated. In particular, the gas sensor achieves sub-10 mW operations, which is a requirement for application in mobile phones. The proposed nanolene will pave the way to accelerate nanowire research and industrialization by providing reliable, high-performance nanowire devices.

Tunable Fractal Nanostructures for Surface-Enhanced Raman Scattering via Templated Electrodeposition of Silver on Low-Energy Surfaces

Here, we demonstrated a facile method for growing nanofeatured silver (Ag) structures on a planar microelectrode platform. The nanostructures were assembled along the electrically insulating substrate, growing from the microelectrode edge with the electrodes acting as the template. This was done by (a) limiting the nucleation to the edges of the electrodes and (b) chemically functionalizing the insulating substrate to promote an interaction between itself and the growing metallic structures. These structures were able to reach lateral lengths greater than 100 μm. Additionally, we performed an extended investigation into how the nanostructure morphology can be changed from spherical aggregates to fractal dendrites by altering the electrical signal and solution composition. We determined citrate to be a necessary additive and showed that it acts as a supporting electrolyte, capping agent, and oxidizing/complexing agent. Next, using optimal deposition conditions, we assembled Ag surface-enhanced Raman scattering (SERS) substrates with an enhancement factor up to 4.55 × 106. Finally, we demonstrated how these SERS nanostructures can also serve as concentration amplification devices, accelerating analyte deposition onto the detection site by means of electrohydrodynamics.

Coupling Si3N4 waveguide to SOI waveguide using transformation optics

Silicon nitride (Si3N4) planar waveguide platform combined with silicon-on-insulator (SOI) devices offer a whole new generation of system-on-chip applications. Therefore, efficient coupling of an Si3N4 waveguide to an SOI waveguide is essential. We present a coupler to interface a 1.8μm-wide Si3N4 waveguide to a 0.5μm-wide SOI waveguide based on the focusing property of the Luneburg lens. In order to match the refractive indices of the waveguides with the edges of the lens, one side of the lens is flattened with quasi-conformal transformation optics. The designed coupler is implemented by graded photonic crystals. The three-dimensional numerical simulations indicate that the 1.93μm-long coupler has an average coupling loss of 0.13 dB in the C-band.

Propentdyopents: Brief history of a family of dipyrrolic pigments

Propentdyopents are naturally occurring dipyrroles deriving from the metabolism of heme and characterized by a dipyrrin-1,9-dione motif. The unusual name propentdyopent is due to the first colorimetric method (the Stokvis reaction) for the detection of these compounds, which were initially isolated from urine samples. Upon reduction in alkaline solutions, they produced red species that were termed pentdyopents to describe with Greek numerals their absorption maximum (525 nm) in the visible range. The precursors to the red pentdyopents were thus indicated as propentdyopents.Over the course of several decades, these dipyrrolic compounds have appeared in several studies of human physiology, typically associated to conditions of abnormal heme metabolism and/or oxidative stress. Concurrently, synthetic investigations have confirmed their chemical structure, reactivity, and ability to coordinate metals as bidentate monoanionic ligands. Notably, the planar dipyrrindione platform can undergo reversible one-electron redox processes and thereby act as an electron reservoir in metal complexes. In combination with the documented ability of the carbonyl groups to act as hydrogen-bonding acceptors, the coordination chemistry of propentdyopents could lead to new applications for this old class of pigments. Furthermore, the observation of these pigments in several clinical contexts could potentially delineate a role of propentdyopents as diagnostic biomarkers. This mini-review summarizes both the chemistry and biology of propentdyopents while highlighting the ample space for new discoveries.

Planar Growth, Integration, and Applications of Semiconducting Nanowires.

Silicon and other inorganic semiconductor nanowires (NWs) have been extensively investigated in the last two decades for constructing high-performance nanoelectronics, sensors, and optoelectronics. For many of these applications, these tiny building blocks have to be integrated into the existing planar electronic platform, where precise location, orientation, and layout controls are indispensable. In the advent of More-than-Moore's era, there are also emerging demands for a programmable growth engineering of the geometry, composition, and line-shape of NWs on planar or out-of-plane 3D sidewall surfaces. Here, the critical technologies established for synthesis, transferring, and assembly of NWs upon planar surface are examined; then, the recent progress of in-plane growth of horizontal NWs directly upon crystalline or patterned substrates, constrained by using nanochannels, an epitaxial interface, or amorphous thin film precursors is discussed. Finally, the unique capabilities of planar growth of NWs in achieving precise guided growth control, programmable geometry, composition, and line-shape engineering are reviewed, followed by their latest device applications in building high-performance field-effect transistors, photodetectors, stretchable electronics, and 3D stacked-channel integration.

Fourier-transform spectrometer chip covering visible band on silica planar waveguide

To minimise a spectrometer maximally, using a micro-electro-mechanical system or planar waveguide chip, has aroused interest in both academia and industry. This is because a portable and inexpensive spectral analysis tool has tremendous potential in various applications including scientific exploration, industrial inspection, and environmental protection. Here, we design, fabricate, and characterise a Fourier-transform spectrometer (FTS) chip consisting of 101 Mach–Zehnder interferometers (MZIs) with gradually varying optical path differences on a silica planar waveguide platform, aiming to cover the entire visible band. To ensure a wide-band operation while simultaneously compressing the size of the chip, wide-bending arm waveguides that can support high-order modes in a short wavelength range are employed in the design of the MZI array. The experimental result of our FTS chip shows its ability to analyse the visible spectrum with a minimum resolution of better than 10 nm and to reproduce the original spectrum with an accuracy of less than 0.5 nm. The successful implementation of the FTS chip based on a matured and low-cost silica planar lightwave circuit process makes it quite promising to realise mass production and widespread application.

Fabrication of integrated spectrometer module based on optical waveguide platform with planar nano diffraction grating using UV imprint lithography

We proposed a simple and attractive integrated polymeric spectrometer module based on a planar optical waveguide platform that can be easily manufactured at a low cost. The proposed integrated spectrometer module comprises a planar optical waveguide with a concave mirror, a planar nano diffraction grating with a non-uniform pitch, an optical fiber, and a photodiode array. The nano diffraction grating and optical waveguide platform were precisely fabricated using the UV imprint lithography suitable for mass production. To provide uniform diffraction efficiency in the wavelength range of 400–650 nm, the nano diffraction grating had a quasi-three-dimensional V-shaped groove with a blazing angle of 22.5° and non-uniform pitches, maximum of 0.406 μm and minimum of 0.393 μm. In addition, the optical waveguide platform focuses the optical source to the nano diffraction grating using the concave mirror. The alignment guide pattern is used to align the nano diffraction grating and optical fiber. Through the packaging process of nano grating device, photo diode array and fiber on the planar optical waveguide platform, we manufactured the polymeric integrated polymeric spectrometer module. We confirmed that the fabricated planar spectrometer module had a resolution of 5 nm or less for spectral bandwidth of 250 nm, and it can be used widely in portable spectrometer sensors.

Long-duration direct drive hydrodynamics experiments on the National Ignition Facility: Platform development and numerical modeling with CHIC

We report on a novel planar direct-drive platform for hydrodynamics experiments on the National Ignition Facility (NIF). Its commissioning has been performed as part of the NIF Discovery Science Program. This platform enables the use of a 30 ns drive at an average intensity of 200 TW/cm2, creating a planar shock and ablation front over a 2 mm radius. To benchmark the performance of this design, the planarity of both the shock and ablation fronts has been measured between 26 ns and 28 ns after the start of the laser drive in a 3 mm-thick CH foil. The platform was then used to measure late-time Rayleigh-Taylor instability (RTI) growth at the ablation front for a 2D-rippled 300 μm-thick CH foil. Simultaneously, a numerical platform has been developed with the CHIC radiation hydrodynamics code at the CELIA laboratory. The CHIC numerical platform allows, for the first time, a complete simulation of the experiments over 30 ns to be performed. Large-scale simulations recover the trajectory and the 2D RTI growth measurements. They are further compared with half-mode simulations performed with identical parameters. We show that both numerical techniques fit with analytical modeling of RTI growth and discuss plans for future campaigns.

Light effective hole mass in undoped Ge/SiGe quantum wells

We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities ($2.0-11\times10^{11}$ cm$^{-2}$) in top-gated field effect transistors by positioning the strained buried Ge channel at different depths of 12 and 44 nm from the surface. From the thermal damping of the amplitude of Shubnikov-de Haas oscillations, we measure a light mass of $0.061m_e$ at a density of $2.2\times10^{11}$ cm$^{-2}$. We confirm the theoretically predicted dependence of increasing mass with density and by extrapolation we find an effective mass of $\sim0.05m_e$ at zero density, the lightest effective mass for a planar platform that demonstrated spin qubits in quantum dots.

Generalized Optical Signal Processing Based on Multioperator Metasurfaces Synthesized by Susceptibility Tensors

This paper theoretically proposes a multichannel functional metasurface computer characterized by Generalized Sheet Transition Conditions (GSTCs) and surface susceptibility tensors. The study explores a polarization- and angle-multiplexed metasurfaces enabling multiple and independent parallel analog spatial computations when illuminated by differently polarized incident beams from different directions. The proposed synthesis overcomes substantial restrictions imposed by previous designs such as large architectures arising from the need of additional subblocks, slow responses, and most importantly, supporting only the even reflection symmetry operations for normal incidences, working for a certain incident angle or polarization, and executing only single mathematical operation. The versatility of the design is demonstrated in a way that an ultra-compact, integrable and planar metasurface-assisted platform can execute a variety of optical signal processing operations such as spatial differentiation and integration. It is demonstrated that a metasurface featuring non-reciprocal property can be thought of as a new paradigm to break the even symmetry of reflection and perform both even- and odd-symmetry mathematical operations at normal incidences. Numerical simulations also illustrate different aspects of multichannel edge detection scheme through projecting multiple images on the metasurface from different directions. Such appealing findings not only circumvent the major potential drawbacks of previous designs but also may offer an efficient, easy-to-fabricate, and flexible approach in wave-based signal processing, edge detection, image contrast enhancement, hidden object detection, and equation solving without any Fourier lens.

Electrochemistry of cyclic triimidazoles and their halo derivatives: A casebook for multiple equivalent centers and electrocatalysis

A family of cyclic triazines, based on the triimidazo[1,2-a:1′,2′-c:1″,2″-e][1,3,5]triazine scaffold, has recently caught attention due to its variegated solid state photoluminescent properties (e.g., crystallization induced emission, fluomechanochromism, dual fluorescence, room temperature ultralong phosphorescence), tuned by proper functionalization of the cyclic core. From an electrochemical point of view, this family of heteroaromatic cyclic triazines is unexplored. A cyclic voltammetry study is here performed aiming to clarify structure/electroactivity relationship. The peculiar molecular structure of this class of molecules offers a multi-approach case study, spanning from multiple equivalent redox site interactions in small hoops (due to ideally C3h symmetry) to carbon-halogen bond reactivity in the presence of catalytic metal electrode surfaces (for –Br and –I derivatives). Results point to a poor heteroannular aromaticity along the rigid, planar cyclotrimer, with each equivalent redox site acting quite independently. An unusually higher electrocatalytic performance of gold with respect to silver electrode for the electrocleavage of carbon-halogen bonds (that decreases by increasing number of halo substituents) is tentatively explained in term of a specific interaction between gold and the nitrogen-rich planar cyclotrimer platform.

Relevance and Transferability for Parallel Mechanisms With Reconfigurable Platforms

The parallel mechanism with a reconfigurable platform retains all advantages of parallel mechanisms and provides additional functions by virtue of the reconfigurable platform, leading to kinematic coupling between limbs that restricts development of the mechanism. This paper aims at dealing with kinematic coupling between limbs by investigating the transferability of limb constraints and their degrees of relevance to the platform constraints based on the geometric model of the mechanism. The paper applies screw-system theory to verifying the degree of relevance between limb constraint wrenches and platform constraint wrenches, and reveals the transferability of limb constraints, to obtain the final resultant wrenches and twists of the end effector. The proposed method is extended to parallel mechanisms with planar n-bar reconfigurable platforms, spherical n-bar reconfigurable platforms, and other spatial reconfigurable platforms and lends itself to a way of studying a parallel mechanism with a reconfigurable platform.