Large Dynamic Response Research Articles

3D‐Printed Mechano‐Optic Force Sensor for Soft Robotic Gripper Enabled by Programmable Structural Metamaterials

Rapid deployment of automation in today's world has opened up exciting possibilities in the realm of design and fabrication of soft robotic grippers endowed with sensing capabilities. Herein, a novel design and rapid fabrication by 3D printing of a mechano‐optic force sensor with a large dynamic range, sensitivity, and linear response, enabled by metamaterials‐based structures, is presented. A simple approach for programming the metamaterial's behavior based on mathematical modeling of the sensor under dynamic loading is proposed. Machine learning models are utilized to predict the complete force–deformation profile, encompassing the linear range, the onset of nonlinear behavior, and the slope of profiles in both bending and compression‐dominated regions. The design supports seamless integration of the sensor into soft grippers, enabling 3D printing of the soft gripper with an embedded sensor in a single step, thus overcoming the tedious and complex and multiple fabrication steps commonly applied in conventional processes. The sensor boasts a fine resolution of 0.015 N, a measurement range up to 16 N, linearity (adj. R2–0.991), and delivers consistent performance beyond 100 000 cycles. The sensitivity and range of the embedded mechano‐optic force sensor can be easily programmed by both the metamaterial structure and the material's properties.

Multiplexable all-optical nonlinear activator for optical computing

As an alternative solution to surpass electronic neural networks, optical neural networks (ONNs) offer significant advantages in terms of energy consumption and computing speed. Despite the optical hardware platform could provide an efficient approach to realizing neural network algorithms than traditional hardware, the lack of optical nonlinearity limits the development of ONNs. Here, we proposed and experimentally demonstrated an all-optical nonlinear activator based on the stimulated Brillouin scattering (SBS). Utilizing the exceptional carrier dynamics of SBS, our activator supports two types of nonlinear functions, saturable absorption and rectified linear unit (Relu) models. Moreover, the proposed activator exhibits large dynamic response bandwidth (∼11.24 GHz), low nonlinear threshold (∼2.29 mW), high stability, and wavelength division multiplexing identities. These features have potential advantages for the physical realization of optical nonlinearities. As a proof of concept, we verify the performance of the proposed activator as an ONN nonlinear mapping unit via numerical simulations. Simulation shows that our approach achieves comparable performance to the activation functions commonly used in computers. The proposed approach provides support for the realization of all-optical neural networks.

Statics and dynamics of pulley-driven tensegrity structures with sliding cable modeling

This article introduces the concept of Pulley-Driven Clustered Tensegrity Structures (PD-CTS) and develops nonlinear and linearized static and dynamic equations using the Lagrangian method. The generalized coordinates utilized in this framework comprise the nodal coordinates of the tensegrity structure and the string sliding distances. The governing equations are specifically constructed, considering situations with and without boundary constraints. The developed method can be applied to nonlinear and linearized static and dynamic analysis of any PD-CTS, covering various research domains such as load analysis, form-finding, large deformation analysis, modal analysis, and dynamic response to various inputs. The substructure method is used to lower the order of the equations to reduce computational costs and facilitate the study of actuation strategies of tensegrity structures. The effectiveness of the suggested methods is validated through the analysis of two case studies: a 2D T-bar and a 3D tensegrity tower. Furthermore, the methodologies established in this paper can also be employed to examine deployable cable net structures and pulley-driven robotic systems.

The preparation of a fluorescent dual-modality nanosensor for the discrimination and determination of biothiols in real samples and its practical detection kit.

Biothiols widely exist in living organisms and have a crucial function of maintaining redox balance in the human body. It is vital yet difficult to develop probes that can simultaneously detect and distinguish biothiols. In this study, a highly sensitive dual-modality nanosensor, NBD-Nap@NCC, was developed for the discrimination and determination of biothiols in real samples, and its practical application was elucidated based on RGB analysis using a smartphone. The sensitive nanosensor was successfully prepared through the surface modification of nanocrystalline cellulose (NCC), combining NBD and naphthalene fluorophores. Owing to the high electron-withdrawing behavior of the NBD group, which led to a PET mechanism between the fluorophores, the prepared NBD-Nap@NCC nanosensor had a very weak fluorescence response. However, after treatment with Hcy or Cys, NBD-Nap@NCC quickly provided remarkable and different rates of fluorescence "turn-on" responses in both blue and green channels, which was attributed to naphthalene and NBD fluorophores as a result of the inhibition of the PET mechanism. However, after treatment with GSH, only a significant blue-channel emission, which was attributed to the naphthalene fluorophore was obtained, indicating the inhibition of the PET mechanism. Furthermore, the NCC platform demonstrated improved sensitivity and selectivity because of the increased surface area and higher number of binding sites due to modification of the NBD group on the surface. The detection limit ranged from 0.910 to 1.150 μmol L-1 for biothiols with a large dynamic response range. The accuracy of the sensor in determining the concentrations of Hcy, Cys, and GSH in real samples was evaluated via HPLC and spike/recovery analysis. Additionally, paper-based analysis kits were fabricated for the practical detection of biothiols based on RGB changes using a smartphone application.

Interface Engineering to Drive High-Performance MXene/PbS Quantum Dot NIR Photodiode.

The realization of a controllable transparent conducting system with selective light transparency is crucial for exploring many of the most intriguing effects in top-illuminated optoelectronic devices. However, the performance is limited by insufficient electrical conductivity, low work function, and vulnerable interface of traditional transparent conducting materials, such as tin-doped indium oxide. Here, it is reported that two-dimensional (2D)titanium carbide (Ti3 C2 Tx ) MXene film acts as an efficient transparent conducting electrode for the lead sulfide (PbS) colloidal quantum dots (CQDs) photodiode with controllable near infrared transmittance. The solution-processed interface engineering of MXene and PbS layers remarkably reduces the interface defects of MXene/PbS CQDs and the carrier concentration in the PbS layer. The stable Ti3 C2 Tx /PbS CQDs photodiodes give rise to a high specific detectivity of 5.51×1012 cmW-1 Hz1/2 , a large dynamic response range of 140dB, and a large bandwidth of 0.76MHz at 940nm in the self-powered state, ranking among the most exceptional in terms of comprehensive performance among reported PbS CQDs photodiodes. In contrast with the traditional photodiode technologies, this efficient and stable approach opens a new horizon to construct widely used infrared photodiodes with CQDs and MXenes.

A hybrid polymer–water peridynamics model for ballistic penetration damage of soft materials

Numerically understanding the dynamic response of soft materials subject to high-speed penetration is crucial for advancing transdermal delivery technologies and analyzing injuries related to ballistics. Due to the complexity in material correspondence models and the difficulty of simulating high-speed impact damage problems using traditional mesh-based numerical techniques, precisely capturing mechanical behaviors of soft materials following ballistic penetration remains challenging. This work proposes a novel hybrid polymer–water model within the peridynamics (PD) framework to accurately clarify the complex damage process of soft materials subject to ballistic penetration. We propose the hybrid interactions comprising of water–water, polymer–polymer, and polymer–water interactions, which embodies the subscale nature of various components and captures the constitutive features of soft materials. A novel decomposition scheme for the deformation gradient is proposed to overcome the limitations in traditional non-ordinary state-based PD where only homogeneous particles are involved in the influence domain, extending the scope of PD theory to mixed material systems. The superior effectiveness and applicability of proposed model are demonstrated through compression, shear, fracture tests. Regarding to the case of high-velocity penetration, both motion profiles of projectile and pressure profiles of gelatin after penetration can be captured in line with physics awareness. The proposed model offers a reasonable and practical representation of soft material from the perspective of a particle-based approach and enhances the potential applications of PD framework for simulating large deformation and dynamic response of soft materials.

Mechanical model and characteristics of deep-water drilling riser-wellhead system under internal solitary waves

Internal solitary waves with a huge amount of energy easily trigger the large dynamic responses of riser-wellhead system and threaten its structural safety. However, previous studies have only focused on the dynamic response of the riser under internal solitary waves. The riser may experience excessive traction from the platform, especially from the mooring platform, in response to the arrival of internal solitary waves. The bottom of the riser connects to the wellhead system, which in turn exerts a reaction force on the riser. To address this problem, a coupled dynamic model of deep-water drilling mooring platform-riser-wellhead system under internal solitary waves is developed in this paper. A dynamic response analysis method based on the fourth-order Runge-Kutta method and finite element method is also proposed for the mooring platform-riser-wellhead system. A dynamical solver for the coupled system is then developed using MATLAB. The dynamic response characteristics of the riser-wellhead system under internal solitary waves are calculated. Results show that the displacement and bending moment of the system initially increases and then decreases along with the propagation of internal solitary waves, and finally reach equilibrium position. The displacement and bending moment reach their peak before the trough of internal solitary waves passes through the riser-wellhead system. The dynamic responses of the riser-wellhead system under the influence of internal solitary wave loads are much larger than those without the effect of internal solitary wave loads. The riser system experiences shearing loads at the interface of internal solitary waves, which trigger a step-like bending moment variation. The bending moment of the conductor under the mudline is greatly increased by the internal solitary waves.

Regular Wave Seakeeping Analysis of a Planing Hull by Smoothed Particle Hydrodynamics: A Comprehensive Validation

In this work, the dynamics of a planing hull in regular head waves was investigated using the Smoothed Particle Hydrodynamics (SPH) meshfree method. The simulation of the interaction of such vessels with wave trains features several challenging characteristics, from the complex physical interaction, due to large dynamic responses, to the likewise heavy numerical workload. A novel numerical wave flume implemented within the SPH-based code DualSPHysics fulfills both demands, guaranteeing comparable accuracy with an established proprietary Computational Fluid Dynamics (CFD) solver without sharpening the computational load. The numerical wave flume uses ad hoc open-boundary conditions to reproduce the flow characteristics encountered by the hull during its motion, combining the current and waves while adjusting their properties with respect to the vessel’s experimental towing speed. It follows a relatively small three-dimensional domain, where the potentiality of the SPH method in modeling free-surface flows interacting with moving structures is unleashed. The results in different wave conditions show the feasibility of this novel approach, considering the overall good agreement with the experiments; hence, an interesting alternative procedure to simulate the seakeeping test in several marine conditions with bearable effort and satisfying accuracy is established.

Mixed-potential-function-based large-signal stability analysis of DC microgrid with constant power loads

With the development of power grid technology, a large number of constant power loads (CPL) are introduced into the power grid system. The negative damping characteristic of CPL poses a great challenge to the stability of power grid under the condition of large signal disturbance. This paper focuses on the large signal stability and dynamic response characteristics of DC microgrid with CPL. The mixed potential function (MPF) method is adopted to model the large signal characterstic of load converter controlled by the traditional PI control strategy and the new virtual DC motor (VDM) control strategy. The large signal stability criteria and the asymptotic stability region of the DC microgrid system under the two control strategies are derived. The dynamic response characteristics of the DC microgrid are compared under three large signal operation conditions of the load step, load linear change and the load fault. The results show that VDM control strategy can effectively improve dynamic response characteristics of the DC microgrid system compared with those of PI control, and enhance the stability and anti-interference ability of the DC microgrid system.

Bridge Static Influence Line Identification Based on Structural Dynamic Responses Under High-Speed Trains

Bridge influence lines can reflect the performance status of bridge structures and are an important tool to evaluate high-speed railway bridges. Because a high-speed train can cause large dynamic response on a bridge, it is difficult to identify the static influence line of the bridge. To extract the static bridge influence lines for bridge evaluation, this paper proposes a low-pass filter design method for static influence line identification. By maximizing the difference in bridge static and dynamic energy, the relationship between the frequency domain characteristics of the bridge dynamic response and the filter parameters is established. Based on this relationship, reasonable values of the low-pass filter parameters can be determined. After filtering the dynamic response, the quasi-static response can be effectively obtained, and the bridge static influence line can be identified through the least square regularization method. Finally, a numerical example of the vehicle–bridge interaction model is used to verify the effectiveness of the proposed method. The results show that the low-pass filter designed through the proposed principle can accurately remove the dynamic effects, and its stability and robustness are good. The research results provide a reliable method for the static influence line identification of high-speed railway bridges.

Photoelectric properties of glass-ceramics containing KTb2F7 nanocrystals for UV detection.

In this work, a glass ceramics (GC) containing KTb2F7 nanocrystals was fabricated by controlled crystallization of an fluorosilicate glass via heat-treatment. The microstructure, luminescence, and photoelectric properties of the GCs are systematically studied by X-ray diffraction, transmission electron microscopy, spectral analysis, and current-voltage (I-V) curves. The results show that the GC containing KTb2F7 nanocrystals exhibit intense visible emission due to the 4f transition of Tb3+: 5Di (i = 3, 4) → 7Fj (j = 0-6) upon excitation of ultraviolet (UV) light. In addition, a UV detector device based on the GC was fabricated, which has a large dynamic linear response range, fast response speed and high sensitivity. This study not only provides a new material for UV detector that can simplify the process of UV detection, but also highlight a new strategy for UV detection.

Deciphering the atomic-scale structural origin for large dynamic electromechanical response in lead-free Bi0.5Na0.5TiO3-based relaxor ferroelectrics

Despite the extraordinary electromechanical properties of relaxor ferroelectrics, correlating their properties to underlying atomic-scale structures remains a decisive challenge for these “mess” systems. Here, taking the lead-free relaxor ferroelectric Bi0.5Na0.5TiO3-based system as an example, we decipher the atomic-scale structure and its relationship to the polar structure evolution and large dynamic electromechanical response, using the direct atomic-scale point-by-point correlation analysis. With judicious chemical modification, we demonstrate the increased defect concentration is the main driving force for deviating polarizations with high-angle walls, leading to the increased random field. Meanwhile, the main driving force for deviating polarizations with low-angle walls changes from the anti-phase oxygen octahedral tilting to the multidirectional A-O displacement, leading to the decreased anisotropy field. Benefiting from the competitive and synergetic equilibrium of anisotropic field versus random field, the facilitated polarization rotation and extension versus facilitated domain switching are identified to be responsible for the giant electromechanical response. These observations lay a foundation for understanding the “composition-structure-property” relationships in relaxor ferroelectric systems, guiding the design of functional materials for electromechanical applications.

Nonlinear interaction of the damped large dynamic deformations of the Mooney–Rivlin hyperelastic plates with the viscoelastic and shear reactions of the supporting substrate

In this research, the interaction between the damped large deformation dynamic responses of the Mooney–Rivlin hyperelastic plates and the viscoelastic and shear characteristics of the supporting substrate (that constitute a visco-hyperelastic system) is investigated for various distributions and various time variations of the transverse loads and different boundary conditions. A viscoelastic Winkler–Pasternak model is chosen for the supporting substrate to account for the dissipative, shearing, and supporting features of the foundation. The governing equations of motion are obtained by using Hamilton’s principle, von Karman assumptions, left Cauchy–Green deformation tensor, and a modified classical plate theory whose accuracy is enhanced through the incorporation of an appropriate high-order incompressibility condition. The combination of the nonlinear and coupled motion equations and boundary conditions is solved by an iterative 2D differential quadrature (DQ) spatial-discretization and Newmark’s time-marching methods. The effects of the constitutive parameters of the hyperelastic material, magnitude and type of the distributed loads, the thickness and aspect ratios of the plate, parameters of the Winkler–Pasternak viscoelastic foundation, and boundary conditions on the dynamic lateral deflections of the plate are studied examined during the parametric studies. Results emphasize the role of the visco-hyperelasticity features interaction of the combined plate-substrate system on the vibration suppression and dynamic performance of the structure in different spatial and time-variation patterns of the distributed loads and various boundary conditions.

Moderately large vibrations of flexibly bonded layered beams with initial imperfections

In this paper, a beam theory is presented that allows to compute the moderately large dynamic response of slightly curved linear elastic layered beams with interlayer slip. The considered structural members are immovably supported, which leads to non-negligible membrane stresses at moderately large bending vibrations, and consequently to a geometrically nonlinear response. Based on a layerwise application of the Euler–Bernoulli theory, the boundary value problem is formulated for an arbitrary number of layers. A specification is then made for two- and three-layer beams. Several examples show the effect of an imperfect beam axis on the nonlinear dynamic response. A comparison of selected results with those of a much more expensive finite element analysis based on a plane stress state demonstrates the accuracy of the beam theory proposed.

Flexible capacitive three-dimensional force sensor for hand motion capture and handwriting recognition

Handwriting recognition has been widely studied as an important signal transmission method in the field of human–computer interaction. Flexible capacitive three-dimensional (3D) force sensor is widely used in this field because of its high sensitivity, large dynamic response range and good mechanical stability. However, traditional flexible capacitive 3D force sensors based on the array structure usually only sense 3D force with equivalent forward pressure rather than the decoupling of real 3D force in space. Herein, we design a flexible capacitive 3D force sensor with petal-like electrode to capture various hand movements in 3D space and further decouple 3D force to 1D force along [Formula: see text], [Formula: see text] and [Formula: see text] directions. The sensor presents a high sensitivity (1.1 kPa[Formula: see text]at the pressures below 1 kPa), a fast response (63 ms) and excellent repeatability under continuous pressure. In addition, the electrode with eight-petal structure helps simplify the decoupling process of 3D force. Through handwriting test, the sensor presents good sensing performance for hand motion capture and handwriting recognition, which is expected to be applied in the field of human–computer interaction.

Soil carbon consequences of historic hydrologic impairment and recent restoration in coastal wetlands

Coastal wetlands provide key ecosystem services, including substantial long-term storage of atmospheric CO2 in soil organic carbon pools. This accumulation of soil organic matter is a vital component of elevation gain in coastal wetlands responding to sea-level rise. Anthropogenic activities that alter coastal wetland function through disruption of tidal exchange and wetland water levels are ubiquitous. This study assesses soil vertical accretion and organic carbon accretion across five coastal wetlands that experienced over a century of impounded hydrology, followed by restoration of tidal exchange 5 to 14 years prior to sampling. Nearby marshes that never experienced tidal impoundment served as controls with natural hydrology to assess the impact of impoundment and restoration. Dated soil cores indicate that elevation gain and carbon storage were suppressed 30–70 % during impoundment, accounting for the majority of elevation deficit between impacted and natural sites. Only one site had substantial subsidence, likely due to oxidation of soil organic matter. Vertical and carbon accretion gains were achieved at all restored sites, with carbon burial increasing from 96 ± 33 to 197 ± 64 g C m−2 y−1. The site with subsidence was able to accrete at double the rate (13 ± 5.6 mm y−1) of the natural complement, due predominantly to organic matter accumulation rather than mineral deposition, indicating these ecosystems are capable of large dynamic responses to restoration when conditions are optimized for vegetation growth. Hydrologic restoration enhanced elevation resilience and climate benefits of these coastal wetlands.

Experimental realization of linearly polarized x-ray detected ferromagnetic resonance

We present the first theoretical and experimental evidence of time-resolved dynamic x-ray magnetic linear dichroism (XMLD) measurements of GHz magnetic precessions driven by ferromagnetic resonance in both metallic and insulating thin films. Our findings show a dynamic XMLD in both ferromagnetic Ni80Fe20 and ferrimagnetic Ni0.65Zn0.35Al0.8Fe1.2O4 for different measurement geometries and linear polarizations. A detailed analysis of the observed signals reveals the importance of separating different harmonic components in the dynamic signal in order to identify the XMLD response without the influence of competing contributions. In particular, RF magnetic resonance elicits a large dynamic XMLD response at the fundamental frequency under experimental geometries with oblique x-ray polarization. The geometric range and experimental sensitivity can be improved by isolating the 2ω Fourier component of the dynamic response. These results illustrate the potential of dynamic XMLD and represent a milestone accomplishment toward the study of GHz spin dynamics in systems beyond ferromagnetic order.

Trichromatic-color-sensing metasurface with reprogrammable electromagnetic functions

Visible light sensing technique has been developed and generally applied in communication, imaging, and display fields. In this paper, we propose a trichromatic-color-sensing (TCS) metasurface with reprogrammable electromagnetic (EM) functions, to establish an intelligent joint between light sensing and EM manipulations. The core innovation of this design is that it proposes a new regulation concept by combining color sensing sensors. The color sensor (TCS3200) has a large dynamic response range to light, with a standard output frequency range of 2Hz to 500 kHz. And for a full-scale output, data can be collected at twice the output frequency or at a rate of one data point per microsecond. By integrating four photodiode arrays (color sensors) on the metasurface, we achieve the active sensing on trichromatic colors and achieve the real-time response in the scattering field control. A 1-bit programmable unit is designed to regulate the reflected phase response of the scattering fields using the field-programmable gate array (FPGA) hardware system. We exhibit that the incident light of blue, green, and red components can be detected and transformed into the desired metasurface scattering patterns. Therefore, three color components in the incident light field can directly control the metasurface for various EM functions, establishing the flexible connection between light and microwave fields. Three typical coding patterns including dual-beam, four-beam, and radar-cross-section (RCS) reduction are designed and demonstrated. The presented concept will help to promote the fusion of optical and microwave systems and expand the application prospects in future new wireless communication systems and radar systems.

Study on dynamic response of slope under near-fault pulse-like ground motion

Compared with far-field ground motion, the most significant feature of near-fault pulse-like ground motion is the long-period, large-scale velocity pulse. This paper proves through statistical analysis that near-fault pulse-like ground motion is an important cause of slope damage and landslide. And use numerical simulation software FLAC3D to establish a homogeneous rock slope model, select near-fault ground motions with velocity pulses and non-pulse near-fault ground motions, and use an improved energy method to identify and extract the selected near-fault ground motions. The dynamic response of the slope under the action of near-fault ground motions with and without velocity pulses is comparatively studied, and the dynamic response law of the slope under the original records, pulse records, and residual records of pulse-like ground motions is explored. The research results show that the near-fault ground motions with velocity pulses can cause a greater dynamic response than ground motions without velocity pulses. There is an elevation magnification effect in the PGA distribution of the slope horizontally. The shorter-duration pulse record can cause a larger dynamic response, and the PGA magnification factor under the effect of the residual record is smaller than the original record. The velocity pulse strengthens the earthquake damage to the slope, and the slope produces a stronger dynamic response.

Extremely large static and dynamic nonlinear optical response of small superalkali clusters NM3M’ (M, M’=Li, Na, K)

Exploring novel nonlinear optical (NLO) materials with excess electron properties is essential for advancing the use of excess electron compounds in optics. The studied superalkali clusters NM3M’ (M, M′ = Li, Na, K) are thermodynamically stable and their binding energies range from −27.10 to −53.84 kcal mol−1. The observed significant values for VIPs suggest their electronic stabilities. Being excess electron candidate these clusters show significant βo value (3.9 × 107 au), which nicely correlates the hyperpolarizability reported by a two-level model (βtl). Furthermore, these clusters exhibit a remarkable static second hyperpolarizability (γo) value of 1.1 × 1010 au for the NK4 superalkali cluster. The hyper Rayleigh scattering (βHRS) is also computed where the highest value of 2.9 × 107 is recorded for NNa3K superalkali. The obtained values of βvec values (projection of hyperpolarizability on dipole moment vector) also signify the excellent nonlinearity of clusters. Besides, the calculated electro-optica pockel's effect β(-ω; ω,0) and second harmonic generation β(-2ω; ω, ω) values are much pronounced at larger dispersion frequency ω = 1064 nm. Moreover, the frequency-dependent second hyperpolarizability γ(ω) with dc-Kerr effect γ(-ω; ω,0,0) and electric field induced second harmonic generation γ(-2ω; ω,ω,0) show larger values at ω = 1064 nm. Thus the highest value of the dc-Kerr constant increases up to 1.0 × 1011 au which also signifies the larger nonlinear refractive index of the studied cluster. We hope this work could open up new possibilities using superalkali clusters as NLO materials for optoelectronics, laser, second harmonic generation and as frequency doubler.