Manipulation Capabilities Research Articles

Ultrathin Dual‐Band Wide‐Angle Beam Scanning Metalens Based on High‐Efficiency Meta‐Atom

Metasurfaces composed of planar subwavelength‐scaled meta‐atoms demonstrate unprecedented wavefront manipulation capabilities. However, the wavelength‐dependent property of the metasurface could severely reduce the design freedom, and most metasurfaces require multilayer structure for high efficiency. Herein, a single‐layered‐substrate meta‐atom is proposed to achieve independent phase manipulations as well as high transmission efficiencies at two frequencies. Specifically, the full 2π phase coverages can be individually realized through rotating the corresponding resonators. As a proof‐of‐concept demonstration, a dual‐band high‐efficiency metalens with wide field‐of‐view (FoV) under the circular polarization incidence is simulated, fabricated and measured at Ka‐band for satellite communications. Both simulation and experimental results agree well with each other, demonstrating that wide scanning coverages of ±60° can be achieved at both 20 and 30 GHz. The proposed method can be a competitive candidate for designing dual‐band high‐efficiency meta‐devices.

Transmission–Reflection‐Integrated Quadratic Phase Metasurface for Multifunctional Electromagnetic Manipulation in Full Space

AbstractMetasurface has shown significant advantages in full‐space multifunctional electromagnetic (EM) manipulation due to its strong design capability. Here, a novel transmission–reflection‐integrated metasurface is proposed, which can simultaneously manipulate beam direction and polarization states. Through ingenious design based on the quadratic phase distribution, such a metasurface can dynamically control the beam deflection direction in both transmission and reflection modes by shifting the position of the feeding source. In addition, arbitrarily polarized EM waves can be generated based on the dual‐beam coherent interference method. The above EM functions are experimentally demonstrated at microwave frequencies. The wide‐angle beam steering performance is realized in full space, and its scanning range is beyond ±60°. More remarkably, the deflecting beam with different polarization states can be obtained by simultaneously illuminating the metasurface from the reflection and transmission sides with a specific phase difference. The measured results are in excellent accordance with the numerically simulated results, thus verifying the EM manipulation capability of the metasurface. The proposed design provides a new approach to achieve multifunctional beam manipulation in full space, which holds great promise in integrated optics, radar detection, and wireless communication.

A seamless anonymous authentication protocol for mobile edge computing infrastructure

Mobile Edge Computing (MEC) accommodates processing and data storage and manipulation capabilities across the scope of wireless network. In MEC environment, MEC servers along with the computing and storage capabilities are distributed at the edge of the network. However, due to the broad range of wireless communication, the fulfillment of security requirements still remain a challenging task in the for MEC environment. With the expeditious traffic expansion and growing end user requirements, the classic security protocols cannot encounter the innovative requirements of lightweightness and real-time communication. To meet these requirements, we have proposed an authentication protocol for the MEC environment. Our proposed protocol stipulates secure and efficient communication for all of the intended entities. Meanwhile, during its execution user anonymity remains intact. Moreover, our protocol is proven to be secure under the assumptions of formal security model. Additionally in this article, we have described the security properties of our protocol that it offers resistance against impersonation, session key computation and forward and backward secrecy attacks. The comparative analysis of time consumption and computation overheads are presented at the end of the paper, which is an evidence that our proposed protocol outperforms prior to various existing MEC protocols.

Penerapan Sistem E-Learning untuk Meningkatkan Produktifitas Kerja Karyawan di Era Pandemi Covid-19

E-learning is a training and development delivery system for online education. This system is advantageous in terms of the speed of memory, and the data manipulation capabilities of the computer for greater flexibility in instructions. The purpose of this study are: i) To determine the process of implementing E-learning to increase employee productivity in the Covid-19 pandemic at PT. Asia Talenta Manajemen; ii) To explain E-learning system to increase employee productivity in the Covid-19 pandemic at PT. Asia Talenta Manajemen; iii) To find out the obstacles and constraints obtained from the E-learning system. This research takes a qualitative descriptive approach. The population in this study were all employees of PT. Asia Talenta Manajemen, amounting to 50 people. The sample in this study used the nonprobability sampling method, which is a sampling technique that does not provide equal opportunities for each element or member of the population to be selected as samples, using a purposive sampling approach. The results showed that: (i) E-learning process which is applied at PT. Asia Talenta Manajemen Tangerang provides information or flow that is quite clear and understandable to participants through a fairly long but regular process that is easily understood by employees or E-learning participants. (ii) PT. Asia Talenta Manajemen Tangerang tends to have a positive impact on employees or participants who are involved in training carried out by means of E-learning because participants or employees can implement the skills they have acquired in the available forums as well as in their respective work lines, according to the material presented obtained. (iii) Obstacles and challenges that are obtained from the E-learning system depend on the participants themselves, the participants cannot fulfil the deadline that has been determined, for example, it has been determined that the deadline is one month but the participants cannot fulfil it for up to one year.

Generation of high-uniformity and high-resolution Bessel beam arrays through all-dielectric metasurfaces

Abstract Bessel beam arrays are progressively attracting attention in recent years due to their remarkable non-diffracting nature and parallel manipulation capabilities in diverse applications. However, the poor phase discretization of conventional approaches such as spatial light modulators leads to low numerical aperture (NA) beam arrays due to the limitation imposed by the Nyquist sampling theorem and poor uniformity of the beam intensity. The key contribution of this study is to experimentally demonstrate the generation of high-uniformity and high-resolution Bessel beam arrays by utilizing all-dielectric metasurfaces. This is attained by optimizing the design of the supercell of a Dammann grating, particularly decreasing each supercell of the grating to a proper size. We demonstrate a 4 × 4 array of Bessel beams with a subwavelength transverse dimension (570 nm, ∼0.9λ) and a large NA of 0.4 for each beam in the array, while maintaining a relatively high uniformity intensity (52.40%) for the array. Additionally, the Bessel beam arrays are generated in a broadband range through the proposed all-dielectric metasurfaces. Our results are of great significance and particularly useful for applications of metasurface-based Bessel beam arrays in multidisciplinary fields such as laser fabrication, biomedical imaging, data storage, and multi-particle trapping.

Characterizing the body morphology of the first metacarpal in the Homininae using 3D geometric morphometrics

AbstractObjectivesThe morphological characteristics of the thumb are of particular interest due to its fundamental role in enhanced manipulation. Despite its possible importance regarding this issue, the body of the first metacarcapal (MC1) has not been fully characterized using morphometrics. This could provide further insights into its anatomy, as well as its relationship with manipulative capabilities. Hence, this study quantifies the shape of the MC1's body in the extant Homininae and some fossil hominins to provide a better characterization of its morphology.Materials and methodsThe sample includes MC1s of modern humans (n = 42), gorillas (n = 27), and chimpanzees (n = 30), as well as Homo neanderthalensis, Homo naledi, and Australopithecus sediba. 3D geometric morphometrics were used to quantify the shape of MC1's body.ResultsThe results show a clear distinction among the three extant genera. H. neanderthalensis mostly falls within the modern human range of variation. H. naledi varies slightly from modern humans, although also showing some unique trait combination, whereas A. sediba varies to an even greater extent. When classified using a discriminant analysis, the three fossils are categorized within the Homo group.ConclusionThe modern human MC1 is characterized by a distinct suite of traits, not present to the same extent in the great apes, that are consistent with an ability to use forceful precision grip. This morphology was also found to align very closely with that of H. neanderthalensis. H. naledi shows a number of human‐like adaptations, while A. sediba presents a mix of both derived and more primitive traits.

Metasurface-assisted multidimensional manipulation of a light wave based on spin-decoupled complex amplitude modulation.

Achieving arbitrary manipulation of the fundamental properties of a light wave with a metasurface is highly desirable and has been extensively developed in recent years. However, common approaches are typically targeted to manipulate only one dimension of light wave (amplitude, phase, or polarization), which is not quite sufficient for the acquisition of integrated multifunctional devices. Here, we propose a strategy to design single-layer dielectric metasurfaces that can achieve multidimensional modulation of a light wave. The critical point of this strategy is spin-decoupled complex amplitude modulation, which is realized by combining propagation and geometric phases with polarization-dependent interference. As proofs of concept, perfect vector vortex beams and polarization-switchable stereoscopic holographic scenes are experimentally demonstrated to exhibit the capability of multidimensional light wave manipulation, which unlocks a flexible approach for the multidimensional manipulation of a light wave such as complex light-wave control and vectorial holography in integrated optics and polarization-oriented applications.

Polarization-independent broadband achromatic metalens in the mid-infrared (3–5 μm) region

With superior capabilities for light manipulation and wavefront shaping, the metasurface recently has caught growing attention. However, the presence of chromatic aberration hinders metasurfaces, especially metalenses, from wider applications. Here, we design a polarization-independent broadband achromatic focusing metalens in the mid-infrared region, which covers continuous bands in 3–5 μm. Numerical simulation shows that different wavelengths can be focused to the same plane with a nearly diffraction-limited resolution, and can achieve an average focusing efficiency of nearly 70% in the whole bandwidth. We expect that our approach can underpin the development of integrated and mid-infrared imaging and detection.

Mussel-inspired multifunctional hydrogel dressing with hemostasis, hypoglycemic, photothermal antibacterial properties on diabetic wounds.

To meticulously establish an efficient photothermal multifunctional hydrogel dressing is a prospective strategy for the treatment of diabetic chronic wounds. Herein, glucose oxidase (GOx) was added to polydopamine/acrylamide (PDA/AM) hydrogels to reduce hyperglycemia to a normal level (3.9-6.1 mmol L-1) and enhance compressive properties (55 kPa) and adhesive properties (32.69 kPa), which are capable of hemostasis in the wound. Then, MnO2 nanoparticles were encapsulated into a polydopamine/acrylamide (PDA/AM) hydrogel, endowing it with excellent antibacterial properties (E. coli and S. aureus were 97.87% and 99.99%) under the irradiation of 808 nm NIR; meanwhile, the biofilm was eliminated completely. Besides, O2 was generated (18 mg mL-1) by the decomposition of H2O2 under the catalysis of MnO2, which could accelerate the formation of angiogenesis and promote the crawling and proliferation of cells. Furthermore, the diabetic wound in vivo treated with the PDA/AM/GOx/MnO2 hydrogel had a less inflammatory response and faster healing speed, which was completely healed in 14 days. Therefore, the multifunctional hydrogels with the capability of high compressible, hemostasis, antibacterial, hyperglycemia manipulation, and O2 generation, demonstrate promise in diabetic chronic wound dressing.

Adaptive CLF-MPC With Application to Quadrupedal Robots

Modern robotic systems are endowed with superior mobility and mechanical skills that make them suited to be employed in real-world scenarios, where interactions with heavy objects and precise manipulation capabilities are required. For instance, legged robots with high payload capacity can be used in disaster scenarios to remove dangerous material or carry injured people. It is thus essential to develop planning algorithms that can enable complex robots to perform motion and manipulation tasks accurately. In addition, online adaptation mechanisms with respect to new, unknown environments are needed. In this work, we impose that the optimal state-input trajectories generated by Model Predictive Control (MPC) satisfy the Lyapunov function criterion derived in adaptive control for robotic systems. As a result, we combine the stability guarantees provided by Control Lyapunov Functions (CLFs) and the optimality offered by MPC in a unified adaptive framework, yielding an improved performance during the robot's interaction with unknown objects. We validate the proposed approach in simulation and hardware tests on a quadrupedal robot carrying un-modeled payloads and pulling heavy boxes.

Modulated Metasurfaces for Microwave Field Manipulation: Models, Applications, and Design Procedures

Metasurfaces (MTSs) have emerged in the last years as a promising platform for next generation planar devices in a broad range of frequencies, thanks to their unique field manipulation capability. In particular, in the microwave range this solution is characterized by low-cost, lightweight, and simple integration with electronic circuits, since MTSs can be realized in PCB technology by printing electrically small patches over a dielectric slab. The MTS behavior can then be conveniently described in terms of homogenized boundary conditions of impedance type. Spatial modulation of these boundary conditions allows one to implement a broad class of functionalities, involving space wave or surface wave control, as well as conversion from surface waves to leaky waves. This paper reviews numerical and analytical models, design procedures and microwave applications of modulated MTSs, with particular emphasis on surface wave manipulation, and it discusses expected future developments of this technology.

Broadband convolutional scattering characteristics of all dielectric transmission Pancharatnam–Berrygeometric phase metasurfaces

In order to obtain the broadband scattering characteristics, we propose a superperiodic cell structure with all-dielectric material to construct Pancharatnam–Berry geometric phase encoding metasurfaces. Because we cannot design or prepare infinitesimal coding unit particles, according to the generalized Snell’s law, we can only obtain discrete scattering angle regulation for the basic coding metasurface sequence. In order to obtain multi-angle scattering characteristics, we introduce the Fourier convolution principle in digital signal processing on the Pancharatnam–Berry geometric phase encoding metasurfaces. By using the addition and subtraction operations on two encoding metasurface sequences, a new encoding metasurface sequence can be obtained with different deflection angle. Fourier convolution operations on the encoding metasurfaces can provide an efficient method in optimizing encoding patterns to achieve continuous scattering beams. The addition and subtraction methods are also applicable to the checkerboard coding mode. The combination of Fourier convolution principle and Pancharatnam–Berry phase coded metasurface in digital signal processing can realize more powerful electromagnetic wave manipulation capability.

A 79.7g Manipulator Prototype for E-Flap Robot: A Plucking-Leaf Application

The manipulation capabilities of flapping-wing flying robots (FWFRs) is a problem barely studied. This is a direct consequence of the load-carrying capacity limitation of the flapping-wing robots. Ornithopters will improve the existent multirotor unmanned aerial vehicles (UAVs) since they could perform longer missions and offer a safe interaction in proximity to humans. This technology also opens the possibility to perch in some trees and perform tasks such as obtaining samples from nature, enabling biologists to collect samples in remote places, or assisting people in rescue missions by carrying medicines or first-aid kits. This paper presents a very lightweight manipulator (79.7g) prototype to be mounted on an ornithopter. The distribution of the mass on the flapping-wing robot is sensitive and an extra lumped mass far from the center-of-mass (CoM) of the robot deteriorates the flight stability. A configuration was proposed to avoid changing the CoM. Flight experiments show that adding the arm to the robot only moved the CoM 6mm and the performance of the flight with the manipulator has been satisfactory. Plucking leaf is chosen as an application to the designed system and several experimental tests confirmed successful sampling of leaves by the prototype.

Compact Terahertz Dielectric Folded Metasurface

AbstractDespite modern terahertz (THz) systems benefit from the developments in metasurfaces with flexible wavefront manipulation capabilities, the large propagation space between the THz source/detector and metasurface component, as well as the inherent insertion loss of metasurfaces, are the two main bottlenecks that hinder metasurface‐based THz devices from becoming a practical technology. This article addresses these two problems by demonstrating a compact, high‐efficiency folded metasurface system in the THz band. The device comprises two parallel dielectric metasurfaces, between which the THz waves are confined to reduce the system volume. The bottom reflective metasurface consists of an array of anisotropic dielectric resonators, which can simultaneously manipulate THz waves’ phase and polarization properties. The upper metasurface is a dielectric Bragg polarizer that selects the desired linear polarization of THz waves to pass through. Low‐loss and nondispersive high‐resistivity silicon is used as the material for both metasurfaces in this design, which is essential to achieving high efficiency. The compact and high‐efficiency folded THz metasystem is further experimentally verified. The introduced folded device can be used in diverse applications such as high‐speed THz communications, non‐destructive detection, and imaging systems, significantly reducing their volume and increasing their radiation efficiency.

From grasping to manipulation with gecko-inspired adhesives on a multifinger gripper.

Anthropomorphic robotic manipulators have high grasp mobility and task flexibility but struggle to match the practical strength of parallel jaw grippers. Gecko-inspired adhesives are a promising technology to span that gap in performance, but three key principles must be maintained for their efficient usage: high contact area, shear load sharing, and evenly distributed normal stress. This work presents an anthropomorphic end effector that combines those adhesive principles with the mobility and stiffness of a multiphalange, multifinger design. Adhesive suspensions use buckling ribs to deliver shear load sharing and normal compliance in a deployable form factor. We use an elastic foundation model and fundamentals of grasping theory to motivate kinematic changes when shifting from Coulomb friction to adhesive manipulation. These design considerations integrate with the necessary control infrastructure in a prototype called farmHand, on which we perform tests to confirm shear load sharing and demonstrate adhesive use in manipulation beyond pick and place grasping.

Multiplexed sensing of biomolecules with optically detected magnetic resonance of nitrogen-vacancy centers in diamond

In the past decade, a great effort has been devoted to develop new biosensor platforms for the detection of a wide range of analytes. Among the various approaches, magneto-DNA assay platforms have received extended interest for high sensitive and specific detection of targets with a simultaneous manipulation capacity. Here, using nitrogen-vacancy quantum centers in diamond as transducers for magnetic nanotags (MNTs), a hydrogel-based, multiplexed magneto-DNA assay is presented. Near-background-free sensing with diamond-based imaging combined with noninvasive control of chemically robust nanotags renders it a promising platform for applications in medical diagnostics, life science, and pharmaceutical drug research. To demonstrate its potential for practical applications, we employed the sensor platform in the sandwich DNA hybridization process and achieved a limit of detection in the attomolar range with single-base mismatch differentiation.

Analysis of an electrically reconfigurable metasurface for manipulating polarization of near-infrared light

Integrating plasmonic metasurfaces with transparent conductive oxide (TCO) materials provides a new, to the best of our knowledge, opportunity to dynamically manipulate all degrees of freedom of light beams. Applying external stimuli to TCOs changes the plasmonic response of the nanostructure as a result of establishing an inhomogeneous optical property with deeply subwavelength films of epsilon-near-zero media, which is a challenge for better theoretical understanding of the dynamical tuning functionality. In this paper, we propose a dynamically reconfigurable reflective metasurface with the capability of electrical manipulation of the polarization state of near-infrared light. The structure behavior is investigated by numerical analysis and described based on the coupled-mode theory concept using the parameters of resonance wavelength, absorption, and radiation quality factors, altered by an external voltage. Variation of the applied bias voltage from − 0.7 to 4.2 V for p -polarized light leads to a wide range of absorption quality factors from 43 to two. This change causes a dramatic decrease in the equivalent surface impedance of the metasurface in the ratio 4.9:0.2, which may pave the way to tailor polarization-manipulating functions such as circular-to-linear polarization conversion and cross-polarization conversion.

Multifunctional metasurfaces integrating near-field display and 3D holography

Metasurfaces have versatile manipulation capabilities in the optical field and provide the possibility of building a compact optical device with various complex functions. They have been regarded as ideal candidates to construct a miniaturized optical system with high density and multi-channel information. In this work, reflective all-metallic multifunctional metasurfaces consisting of aluminum nanorods are designed by simultaneously realizing the near-filed display and three-dimensional (3D) holography. Specifically, in the proposed design, each nanorod acts as a complex amplitude modulator to provide continuous amplitude control and binary phase control. By carefully optimizing the orientations of nanorods, a multifunctional metasurface can be designed to display a near-field grayscale pattern and far-field 3D images simultaneously. Numerical results by a full-wave simulation validate the good performance of the proposed design. The proposed method could provide greater degree of freedom to designs of lightweight devices, which could be employed in optical applications, such as virtual or augmented reality displays and anti-counterfeiting technology.

High-Throughput and Controllable Fabrication of Helical Microfibers by Hydrodynamically Focusing Flow.

Due to the unique spiral geometry, different functional helical fibers are fabricated to perform vital tasks, including cargo transportation, medical treatment, cell manipulation, and so on. Although microfluidic techniques are widely used to fabricate helical fibers, the problems of channel blockage and spinning instability have not been well solved, which limits the mass preparation and practical application of spiral microfibers. In addition, the spinning mechanism is simply limited to liquid rope coiling, which has little impact on the design of microfluidic devices. Here, new types of microfluidic devices, which were easy to make and exhibited excellent spiral spinning performance, were designed. It was found that adding a sleeve layer outside the inner core needle in a coaxial microfluidic device could effectively promote the stable formation of helical microfibers. This novel microchannel could fabricate helical microfibers of more than 100 m in length continuously at one time with almost no blockage or deformation, and the key parameters of the fibers could be precisely adjusted. Combined with micro-particle image velocimetry (micro-PIV) measurements, it was confirmed that the improvement in the spinning performances was mainly attributed to the emergence of a focusing flow in the presence of the sleeve layer. After loading magnetic nanoparticles, the helical microfibers exhibited excellent motion manipulation capabilities, which showed great potential for drug delivery, cargo transportation, clogging removal, etc. This new design not only realized the high-throughput fabrication of helical microfibers but also provided deeper insights into the underlying mechanisms of spiral generation and new ideas for the design of microfluidic devices.

Interpreting and predicting tactile signals for the SynTouch BioTac

In the human hand, high-density contact information provided by afferent neurons is essential for many human grasping and manipulation capabilities. In contrast, robotic tactile sensors, including the state-of-the-art SynTouch BioTac, are typically used to provide low-density contact information, such as contact location, center of pressure, and net force. Although useful, these data do not convey or leverage the rich information content that some tactile sensors naturally measure. This research extends robotic tactile sensing beyond reduced-order models through (1) the automated creation of a precise experimental tactile dataset for the BioTac over a diverse range of physical interactions, (2) a 3D finite-element (FE) model of the BioTac, which complements the experimental dataset with high-density, distributed contact data, (3) neural-network-based mappings from raw BioTac signals to not only low-dimensional experimental data, but also high-density FE deformation fields, and (4) mappings from the FE deformation fields to the raw signals themselves. The high-density data streams can provide a far greater quantity of interpretable information for grasping and manipulation algorithms than previously accessible. Datasets, CAD files for the experimental testbed, FE model files, and videos are available at https://sites.google.com/nvidia.com/tactiledata.