Bending States Research Articles

Vibrational relaxation of D2O induced by collision with He: A rigid bender close coupling study.

The vibrational relaxation of the first excited bending state ofD2O induced by collision with He is studied at the close coupling level and using the Rigid Bender approximation. A new 4D potential energy surface is calculated and reported for this system. It is then used to determine the low-lying bound states of the D2O-He van der Waals complex and to perform scattering calculations. Colli- sion rates are determined for pure rotational transitions as well as for rovibrational transitions within the first excited bending state. The results are compared with those obtained for the collision of D2O with other noble gases such as Ne and Ar. We also analyse the differences observed with respect to the H2O + He collisions and compare our results with experiment.

Tunable Nano-Bending Structures of Loosened/Tightened Lassos with Bi-Stable Vibration-Induced Emissions for Multi-Manipulations of White-Light Emissions and Sensor Applications.

The first tunable nano-bending structures of [1]rotaxane containing a single-fluorophoric N,N'-diphenyl-dihydrodibenzo[a,c]phenazine (DPAC) moiety (i.e., [1]RA) are developed as a loosened lasso structure to feature the bright white-light emission [CIE (0.27, 0.33), Φ = 21.2%] in THF solution, where bi-stable states of bending and twisted structures of DPAC unit in [1]RA produce cyan and orange emissions at 480 and 600nm, respectively. With acid/base controls, tunable loosened/tightened nano-loops of corresponding [1]rotaxanes (i.e., [1]RA/[1]RB) can be achieved via the shuttling of macrocycles reversibly, and thus to adjust their respective white-light/cyan emissions, where the cyan emission of [1]RB is obtained due to the largest conformational constraint of DPAC moiety in its bending form of [1]RB with a tightened lasso structure. Additionally, the non-interlocked analog M-Boc only shows the orange emission, revealing the twisted form of DPAC fluorophore in M-Boc without any conformational constraint. Moreover, the utilization of solvents (with different viscosities and polarities), temperatures, and water fractions could serve as effective tools to adjust the bi-stable vibration-induced emission (VIE) colors of [1]rotaxanes. Finally, tuning ratiometric emission colors of adaptive conformations of DPAC moieties by altering nano-bending structures in [1]rotaxanes and external stimuli can be further developed as intelligent temperature and viscosity sensor materials.

Fabrication of highly flexible, wearable, free-standing symmetric supercapacitors with high voltage operation enabled by hierarchical graphene/cerium oxide/polypyrrole hybrid films

Flexible, free-standing supercapacitors play a significant role in the development of future wearable energy storage devices. Herein, we successfully fabricated the highly flexible and free-standing graphene/cerium oxide/polypyrrole hybrid films by thermal reduction of graphene oxide (GO) followed by the sol–gel synthesis of CeO2 and then the addition of PPy. By regulating oxygen functional groups in GO, the electronic conductivity and electroactive sites of the hybrid films are significantly controlled, leading to enhanced energy storage capability. Finally, a symmetric flexible supercapacitor (FSC) device was developed using the prepared films as electrodes. Resulting, the integrated symmetric GO-400/CeO2/PPy FSC manifests excellent areal capacitance of 49.0 mF cm−2 at 1 mA cm−2, with a durability of 83.1 % over 10,000 cycles. Specifically, the FSC exhibited capacitance retention of 77.2 % after 10,000 cycles under bending state with exceptional rate ability. Meanwhile, an impressive energy density of 19.69 µW h cm−2 was attained at a power density of 0.85 mW cm−2. Evidently, the synergistic interactions between GO and PPy nanosheets, along with CeO2 favour the rapid electron movement of electrode material for next-generation wearable, portable electronics.

Layer‑by‑layer assembled binder-free hydrated vanadium oxide-acetylene black electrode for flexible aqueous zinc ion battery

Vanadium oxides are potential positive electrode materials for aqueous zinc ion batteries (ZIBs) owing to their advantages of high theoretical capacity, low cost, and so on. Developments of methods for preparing binder-free vanadium oxide electrodes on a large scale and further investigation of their Zn2+ storage mechanisms are essential for expanding their uses in large-scale energy storage systems and wearable electronics. In this work, binder-free electrodes with hydrated vanadium oxide (V2O5·nH2O, denoted as VOH)-acetylene black (AB) on carbon cloth (VOH-AB/CC) are fabricated by a simple and scalable method which combined low-temperature hydrothermal treatment with layer-by-layer drop/spray-coating process. The AB can greatly improve the electrical conductivity of VOH, thereby enhancing the electrochemical performance. The as-prepared electrode with 20 wt% of AB (VOH-AB2/CC) delivers a high capacity of 280 mA h g−1 at 1 A/g and a good rate capability of 205 mA h g−1 at 4 A/g, which is better than many of the reported binder-free vanadium base electrodes. Besides, excellent cycling performance with 89 % retention rate after 3000 cycles at 4 A/g is achieved on the VOH-AB2/CC electrode. Furthermore, a storage mechanism of Zn2+/H+/H2O insertion accompanied by the formation of basic zinc salt precipitate during the discharging process is proposed by the aid of ex-situ XRD and XPS techniques. Additionally, the flexible Quasi-Solid-State ZIB constructed using VOH-AB/CC as positive electrode can work well at different bending states and two ZIBs connected in series can lighten a light-emitting diode even under bending state. This work provides a low-cost, time-saving, environmental-friendly and scalable method to fabricate binder-free hydrated vanadium oxide electrodes for flexible aqueous ZIBs.

Flexible piezoelectric pressure sensor based on BaTiO3-CNT/RTV composite film with filter paper microstructures for monitoring hand motions

Flexible piezoelectric sensors are widely used in various applications such as physiological signal monitoring and human-computer interaction. The present study introduces a BaTiO3-CNT/RTV piezoelectric sensor fabricated using a filter paper template. It incorporates micro-scale fiber stacking and a 1% CNT doping in the microstructure, resulting in a notable enhancement of sensor sensitivity, increasing it from 0.07 V N−1 to 0.69 V N−1, representing an almost tenfold improvement. Furthermore, the study investigates the influence of affecting factors like the flexible substrate of the sensing film, thickness, and mass fractions of various materials on the output voltage. The sensor exhibits superior characteristics such as good repeatability under 5000 cyclic loads, high elongation at break, fast response (80 ms) and recovery times (90 ms), and good linearity. It also demonstrates outstanding sensitivity (12 mV/10°) when monitoring different finger bending states, enabling real-time, sensitive, and reliable hand motion tracking. This sensor holds promising prospects for future developments in the fields of intelligent grasping and sign language translation.

Bendable, lamellar MXene membrane electrodes with diverse diffusion pathways for potential application in miniaturized capacitive deionization devices

Flexible devices have shown great application potential in portable and miniaturized devices. However, work on flexible electrodes for capacitive deionization (CDI) has not been well developed due to the issues of desalination property, processability, and availability under actual bending conditions. Herein, we constructed a kind of flexible lamellar MXene membrane by assembling Ti3C2Tx sheets with both crumpled and perforated structures and studied their desalination performance in conventional planar and bent configurations. The crumpled and perforated features in Ti3C2Tx (C-P-TC) nanosheets could optimize the in-plane and out-of-plane diffusion channels of the stacked samples, respectively, effectively improving the accessibility of membranes. As a result, the desalination performance of such C-P-TC electrodes was superior to that of those assembled from crumpled or perforated sheets alone. Significantly, this flexible C-P-TC electrode still showed excellent performance at real bend deformation, which possessed not only almost the same CDI capacity as the traditional planar configuration but also good cycling stability. This work not merely proposes an alternative strategy to improve the CDI performance of lamellar MXene electrodes by regulating the nanostructures of channels but also confirms their effective deionization ability under real bent state, greatly facilitating the potential use of flexible electrodes in miniaturized CDI devices.

Transport studies in piezo-semiconductive ZnO nanotetrapod based electronic devices

ZnO nanotetrapods (ZnO NTs) with a non-centrosymmetric crystal structure consisting of four 1-D arms interconnected together through a central crystalline core, introduce interesting piezoelectric semiconducting responses in nanorods in the bent state. Considering the widespread applications of nanotetrapods in semiconductor devices, it becomes very crucial to establish a coupled model based on piezoelectric and piezotronic effects to investigate the carrier transport mechanism, which is being reported here in detail for the first time. In this work, we established a multiphysics coupled model of stress-regulated charge carrier transport by the finite element method (FEM), which considers the full account of the wurtzite (WZ) and zinc blende (ZB) regions as well as the spontaneous polarization dependence and the dependence of the material properties on the arm orientation. It is discovered that the forward gain of ZnO NT in the lateral force working mode is almost 50 % higher than that in the nanorod or in the normal force working mode while the reverse current is reduced to negligible. Through the simulation calculations and corresponding analysis, it is confirmed that the developed piezoelectric polarization charges are able to regulate the transport and distribution of carriers in ZnO crystal, which lays a theoretical foundation for the application of piezo-semiconductive ZnO NT devices in advanced technologies.

Highly tri-heteroatom doped porous carbon for aqueous and flexible quasi-solid-state zinc-ion hybrid supercapacitors

Porous carbon, a promising low-cost cathode material for zinc-ion hybrid supercapacitors (ZHSCs), is plagued by inferior hydrophilicity and insufficient active sites during charge/discharge process. Herein, a highly tri-heteroatom co-doped porous carbon material (HSACNS0.5) was prepared from the pyrolysis of Humulus scandens combining heteroatom doping. The high oxygen, nitrogen and sulfur content (total about 29.2 %) combining superior specific surface area (1505.9 m2 g−1) and hierarchical porous structure leads to superior wettability and abundant active sites, resulting in rapid kinetic behaviors and considerable ions adsorption capacity. Furthermore, the high content of heteroatoms provides extra pseudocapacitance. Consequently, the aqueous ZHSC based on HSACNS0.5 displays an excellent specific capacitance of 414.4 F g−1 at 0.5 A g−1, and energy density of 187.4 Wh kg−1 at a power density of 810 W kg−1. Moreover, the HSACNS0.5 cathode based flexible quasi-solid-state ZHSC operates well at different bending states. Even at a high mass loading of 17.3 mg cm−2, the ZHSC shows cycling stability and a superior areal capacitance of 4.27 F cm−2.

Multifunctional fiber-shaped flexible wearable strain sensor with high sensitivity and wide sensing range for detecting autonomous driving technology in automobiles

Flexible strain sensors have developed rapidly and shown enormous application prospects in human motion detection, intelligent robots, and other fields in recent years. However, developing satisfactory strain sensors that meet the requirements of high sensitivity, wide detection range and prominent durability remains a significant challenge. Herein, we developed a flexible and wearable multifunctional fiber-shaped carbon black (CB) and thermoplastic polyurethane (TPU) strain sensor (defined as CTSS) by combining wet spinning and ultrasound. The CTSS possesses characteristics of lightweight, wide sensing range (>390 %), high sensitivity (up to 1414), short response and recovery time (200 ms), ultralow detection limit (0.005 % strain) and good durability. These advantages endow the CTSS with good capability to monitor complicated human activities efficiently (e.g., joint bending, facial expression and breathing). CTSS can also clearly distinguish different bending states. It was then used to monitor the steering of a car in real-time, proving its tremendous potential as high performance flexible electronics device. CTSS is then encapsulated with Ecoflex (E-CTSS) as a single packaged fiber, exhibiting good triboelectric nanogenerator (TENG) performance, with a maximum output voltage beyond 12V for a single packaged fiber, and can maintain stable output. Indicating that E-CTSS has self powered sensing capability.

Influence of cladding tube structure on transmission characteristics of negative curvature terahertz fiber

A novel type of polarization negative curvature terahertz fiber has been designed, which has a cladding region composed of two long semi-circular cladding tubes in the horizontal direction and four long semi-elliptical cladding tubes in the oblique direction. The optimal fiber dimensions are determined to investigate the internal relationship between polarization characteristics and fiber cladding structure. The transmission performances of the negative curvature fiber are investigated by varying the thickness of fiber cladding tubes and adjusting the structural characteristics of cladding tubes in different directions. Relatively good transmission performances can be obtained with a cladding tube thickness of 80 μm. The birefringence can be stably maintained at the order of 10−4, and the confinement loss of the x-polarized mode at 2.55 THz is 0.036 dB cm−1. Moreover, the dispersion coefficient of the two polarized modes is stable between ±0.6 ps (THz·cm)−1 in the 2.3–2.6 THz band. The bent performance of the designed fiber at 2.52 THz is also discussed. The results show that the fiber has low bending sensitivity, and can still maintain excellent birefringence and low confinement loss in the bending state. For the y polarization, the birefringence can be basically stabilized at the order of 10−4 within a bending radius of 10–60 cm.

Experimental study on mechanical properties of conical head for bolted spherical joints

As a typical grid structure joint, bolted spherical joints are widely used in various engineering. However, as the key component of the bolted spherical joint, the conical head has not formed a unified specification and standard in China. At the same time, the mechanical properties and failure mode of the conical head are not clear. Therefore, this paper has carried out axial tension tests on 18 specimens with 6 kinds of conical heads. Combined with finite element analysis, the mechanical properties, failure mode, bearing capacity, and the factors affecting the bearing capacity of the conical head under axial tension were studied. The calculation formula of the bearing capacity of the conical head was proposed. The results show that the conical head is in a complex stress state of bending, shear and compression at the same time, and the failure mode of the conical head is the shear failure of the bottom plate. The thickness of the bottom plate of the conical head and the bolt specification will affect the bearing capacity of the conical head. The conical head's bearing capacity decreases with decreasing bottom plate thickness and bolt specification. However, the thickness of the bottom plate and the bolt specification will not affect the failure mode of the conical head.

Electrical/piezoresistive effects in bent Alpide MAPS

The ITS3 upgrade baseline design employs MAPS (Monolithic Active Pixel Sensor) in bent state. Bending experiments with the existing ITS2 MAPS (=Alpide chip) show it remains functional but with relative large analog supply current changes. It is shown that by the piezoresistive effect, rotation of current mirror FETs can be responsible which was confirmed after validating the layout. Measured Gauge Factor has proper sign but is 3 times lower than typical values derived from literature. The magnitude of the measured strain induced PMOS V th shift is as expected but the sign differs for compressive strain with some of the literature.

Mechanical performance of a kind of bolted joint for single-layer latticed shells under pure bending

In this paper, a kind of bolted joint with separated joint-body is creatively proposed. The mechanical properties of the bolted joints in the pure bending state are studied through theoretical calculation, test and finite element simulation. Based on the component method, a simplified mechanical model is proposed. The formulas of the initial rotational stiffness and the yield moment of the joint are derived. For the bolted joints, seven groups of test specimens with different typical parameters are designed. The mechanical performance tests of joints under pure bending are carried out. The influences of the joint-body form and the joint parameters on the mechanical properties of joints are obtained. Finally, the determination methods and the recommended values of the key parameters of the joint are given, which provides a basis for the design of the single-layer latticed shell with new bolted joints.

A High-Performance Flexible Hydroacoustic Transducer Based on 1-3 PZT-5A/Silicone Rubber Composite.

In recent years, hydroacoustic transducers made of PZT/epoxy composites have been extensively employed in underwater detection, communication, and recognition for their high energy conversion efficiency. Despite the ease with which these transducers can be formed into complex shapes, their lack of mechanical flexibility limits their versatility across various sizes of underwater vehicles. This study introduces a novel flexible piezoelectric composite hydroacoustic transducer (FPCHT) based on a 1-3 PZT-5A/silicone rubber composite and an island-bridge flexible electrode, which can break the limitations of existing hydroacoustic transducers that do not have flexibility. The finite element method is used to optimize the structural parameters of high-performance 1-3 FPC. A large-sized (187 mm × 47 mm × 5.12 mm) FPC is fabricated using an improved cutting-filling method and packaged into the FPCHT. Compared with the planar rigid PZT/epoxy composite hydroacoustic transducer (RPCHT) of the same size, the TVR (186.5 db) of the FPCHT has increased by about 7 dB, indicating that it has better acoustic radiation performance and electroacoustic conversion efficiency. Furthermore, its electroacoustic performance exhibits excellent stability under different bending states. Therefore, the FPCHT with high electroacoustic performance is an ideal substitute for the existing RPCHT and promotes the development of hydroacoustic transducers towards flexibility and portability.

High-performance micro supercapacitor assembled by laser-induced graphene electrode and hydrogel electrolyte with excellent interfacial wettability for high capacitance

In this work, we demonstrate a facile, rational and novel strategy to assemble micro-supercapacitors (MSCs) via employing laser-induced graphene (LIG) microelectrodes and sodium alginate/polyacrylamide hydrogel electrolytes soaked in sulfuric acid solution (SA/PAAM-H2SO4). The microelectrodes are conductive graphene materials with porous structure that use laser direct writing technology to carbonize insulating polyimide (PI) sheets. The importance of good wetting of the electrode material by the electrolyte on the performance of the device is explained. There is good compatibility and interfacial contact between electrode and electrolyte. Impressively, the SA/PAAM-H2SO4 hydrogel electrolyte with high ionic conductivity (574.7 mS cm−1) also exhibit good water retention capability and performs normally even after 60 h of exposure to air. The capacitance of LIG-MSCs based on SA/PAAM-H2SO4 hydrogel is comparable to that of PVA/H2SO4 hydrogel. The LIG-MSCs exhibit high areal capacitance of 7.12 mF cm−2 and outstanding cycling stability. Moreover, our LIG-MSCs displays excellent mechanical flexibility and stable performance, the capacitance is almost unaffected even in highly bent states and during continuously hammering. Furthermore, the LIG-MSCs can be arbitrarily connected in series and in parallel without the requirement of metal-based interconnects for high-voltage and high-capacitance output. Our design strategy aims to provide new insights for the development of flexible MSCs.

Ultrafast laser one-step construction of 3D micro-/nanostructures achieving high-performance zinc metal anodes

Aqueous zinc-ion batteries provide a most promising alternative to the existing lithium-ion batteries due to their high theoretical capacity, intrinsic safety, and low cost. However, commercializing aqueous zinc-ion batteries suffer from dendritic growth and side reactions on the surface of metallic zinc, resulting in poor reversibility. To overcome this critical challenge, here, we report a one-step ultrafast laser processing method for fabricating three-dimensional micro-/nanostructures on zinc anodes to optimize zinc nucleation and deposition processes. It is demonstrated that the three-dimensional micro-/nanostructure with increased specific surface area significantly reduces nucleation overpotential, as well as preferentially absorbs zinc ions to prevent dendritic protuberances and corrosion. As a result, the presence of three-dimensional micro-/nanostructures on the zinc metal delivers stable zinc plating/stripping beyond 2500 h (2 mA cm-2/1 mAh cm-2) in symmetric cells, a high Coulombic efficiency (99.71%) in half cells, and moreover an improved capacity retention (71.8%) is also observed in full cells. Equally intriguingly, the pouch cell with three-dimensional micro-/nanostructures can operate across various bending states without severely compromising performance. This work provides an effective strategy to construct ultrafine and high-precision three-dimensional micro-/nanostructures achieving high-performance zinc metal anodes and is expected to be of immediate benefit to other metal-based electrodes.

Flexible light-stimulated artificial synapse based on detached (In,Ga)N thin film for neuromorphic computing

Because of wide range of applications, the flexible artificial synapse is an indispensable part for next-generation neural morphology computing. In this work, we demonstrate a flexible synaptic device based on a lift-off (In,Ga)N thin film successfully. The synaptic device can mimic the learning, forgetting, and relearning functions of biological synapses at both flat and bent states. Furthermore, the synaptic device can simulate the transition from short-term memory to long-term memory successfully under different bending conditions. With the high flexibility, the excitatory post-synaptic current of the bent device only shows a slight decrease, leading to the high stability. Based on the experimental conductance for long-term potentiation and depression, the simulated three-layer neural network can achieve a high recognition rate up to 90.2%, indicating that the system comprising of flexible synaptic devices could have a strong learning-memory capability. Therefore, this work has a great potential for the development of wearable intelligence devices and flexible neuromorphic systems.

Efficient and Homogenous Precipitation of Sulfur Within a 3D Electrospun Heterocatalytic Rutile/Anatase TiO2-x Framework in Lithium–Sulfur Batteries

AbstractLithium–sulfur (Li–S) batteries can potentially outperform state-of-the-art lithium-ion batteries, but their further development is hindered by challenges, such as poor electrical conductivity of sulfur and lithium sulfide, shuttle phenomena of lithium polysulfides, and uneven distribution of solid reaction products. Herein, free-standing carbon nanofibers embedded with oxygen-deficient titanium dioxide nanoparticles (TiO2-x/CNFs) has been fabricated by a facile electrospinning method, which can support active electrode materials without the need for conductive carbon and binders. By carefully controlling the calcination temperature, a mixed phase of rutile and anatase was achieved in the TiO2-x nanoparticles. The hybridization of anatase/rutile TiO2-x and the oxygen vacancy in TiO2-x play a crucial role in enhancing the conversion kinetics of lithium polysulfides (LiPSs), mitigating the shuttle effect of LiPSs, and enhancing the overall efficiency of the Li–S battery system. Additionally, the free-standing TiO2-x/CNFs facilitate uniform deposition of reaction products during cycling, as confirmed by synchrotron X-ray imaging. As a result of these advantageous features, the TiO2-x/CNFs-based cathode demonstrates an initial specific discharge capacity of 787.4 mAh g−1 at 0.5 C in the Li–S coin cells, and a final specific discharge capacity of 584.0 mAh g−1 after 300 cycles. Furthermore, soft-packaged Li–S pouch cells were constructed using the TiO2-x/CNFs-based cathode, exhibiting excellent mechanical properties at different bending states. This study presents an innovative approach to developing free-standing sulfur host materials that are well suited for flexible Li–S batteries as well as for various other energy applications. Graphical Abstract

Achieving Low Cost and High Performance Flexible CsPbIBr2 Perovskite Photodetectors Arrays with Imaging System via Dual Interfacial Optimization and Structural Design

AbstractAll‐inorganic metal halide perovskites are competitive candidate as next‐generation flexible photodetectors (PDs) materials due to the remarkable photoelectric properties, enhanced heat stability, and mechanical flexibility. However, constructing low‐cost flexible perovskites PDs with high photodetection performance, good operation stability and mechanical robustness, and manufacturing corresponding flexible PDs array have been a challenge. Herein, the PbCl2 and Zinc(II) Dibenzyldithiocarbamate (Zn(DBDTC)2) are employed to modify bottom and top interface of CsPbIBr2 perovskite layer, respectively, to passivate surface trap state, enhance hydrophobicity and resist phase segregation, and improve interface contact. Consequently, the self‐powered champion PDs with low‐cost Bi2Te3 electrode reach a responsivity of 0.38 A W−1 and a maximum detectivity of 3.44 × 1013 Jones at 570 nm, and maintain the outstanding long‐term and operational stability without additional encapsulation. Meanwhile, the HTL‐free flexible PDs based on low‐temperature CsPbIBr2 perovskite layer exhibit impressive photodetection performance and mechanical robustness in bending test. More importantly, the flexible PDs array (5 × 5 pixels) and corresponding imaging system are fabricated with uniform and clear imaging results under flatting and bending state. This research is of great significance for the application of stable and high‐performance inorganic perovskites PDs and flexible array imaging systems.

Structural design of reinforced earthcrete (ReC) beams

This paper presents the results of an extensive experimental campaign aimed at evaluating the feasibility of using steel-reinforced earthen materials for load-bearing structural applications, with a focus on a new category termed "shot-earth". Addressing excavated soil, a major source of construction waste, shot-earth demonstrates remarkable properties, such as notable green strength and reduced water sensitivity. The experimental program includes four-point bending tests on steel-reinforced shot-earth beams, along with pull-out tests to assess the adherence between ribbed steel bars and shot-earth. A flexural design approach, traditionally suited for reinforced concrete, is presented and validated to establish a reliable model for reinforced shot-earth elements in bending state. These findings suggest that leveraging existing models for reinforced concrete can overcome some traditional challenges associated with earth-based constructions, promoting them as a viable and ecological alternative to conventional construction materials.