Mechanical metamaterials have demonstrated broad application prospects in impact isolation and energy absorption due to their exceptional mechanical properties. However, existing metamaterials still face bottlenecks, such as limited stiffness adjustment range, insufficient impact resistance, and poor reusability. To address these challenges, this paper proposes a bio-inspired variable-stiffness metamaterial based on carbon fiber-reinforced polymer (CFRP). By integrating the design advantages of the Bouligand structure and S-shaped spring units, this structure innovatively achieves wide-range stiffness modulation and outstanding cushioning properties. In this study, a theoretical model of the S-shaped spring units was established and validated through finite element simulations and experimental tests. The variable-stiffness characteristics under compressive loading were systematically analyzed via simulations and experiments, confirming the structure’s variable stiffness behavior. Subsequently, drop hammer experiments were conducted on the metamaterial. In the experiments, this structure demonstrated excellent cushioning property. Finally, after 40 cycles of compression testing, the metamaterial retained excellent mechanical properties with a loss rate below 4.2 %, highlighting its durability and reliability.

The main purpose of this paper was to study the stress intensity factors of interface elliptical cracks and their correlations with bimaterial parameters ε and ν’ under uniform shear loadings. For non-oscillatory situation (ε=0), the analytical solutions for arbitrary planar interface crack were derived through the degenerated hypersingular integral equations. For ε≠0, one kind of element with coupled oscillatory characteristic of mode-1 and mode-2 was presented and the hypersingular integral equations were solved numerically. The stress intensity factors K1, K2 and K3 of interface elliptical cracks with b/a=0.2, 0.4, 0.6, 0.8, 1.0 and ε=0, 0.05, 0.06557, 0.1, 0.15 along the crack front were given and their correlations with bimaterial parameters ε and ν’ were discussed in detail. It is discovered that the normalized stress intensity factors under uniform shear are related only to ε through the suitable definition. The calculated energy release rates are consistent with the ones of Shifrin et al

Borderline Personality Disorder (BPD) is marked by emotional instability and intense negative affect. The Predictive Coding Model posits that impaired prediction of bodily signals may underlie such deficits, though empirical validation remains lacking. In this study, we compared a high BPD-trait group (score ≥ 6 on the Chinese Version of the McLean Screening Instrument for BPD, without a BPD diagnosis) with a low BPD-trait group (score ≤ 2). Participants were examined using the Multidimensional Assessment of Interoceptive Awareness-2 (MAIA-2) for interoceptive sensitivity (IS), the Heartbeat Counting Task (HBCT) for interoceptive accuracy (IA) and heartbeat-evoked potentials (HEP) as the neural correlates of cardiac interoceptive processing. Results showed that the high BPD-trait group scored lower in the two subscales of the MAIA-2 (Not-Worrying and Trusting); however, no differences were observed for the HBCT. Furthermore, HEP amplitudes were significantly modulated by attention in the low BPD-trait group, with higher amplitudes during the heartbeat-focused condition, whereas the high BPD-trait group exhibited consistently high amplitudes across both conditions. Within the predictive coding framework, the observed pattern (intact IA, low interoceptive trust and altered HEP responses) may indicate a rigidity in precision weighting that impairs adaptive interoceptive modulation in individuals with BPD traits.

An octopus-inspired soft gripper was proposed by combined pneumatic actuators and particle jamming units (PJUs), which enable the proposed gripper to generate helical deformation and enhance the stiffness of the gripper. The structure design of the octopus-inspired soft gripper and the fabrication process of the single finger are described. The platform of pneumatic experiments and the numerical model of pneumatic actuators were established to analyze the effects of geometrical sizes, including chamber angles and lengths of the pneumatic actuator on the helical deformation of the actuators. Experiments and simulations are used to analyze the effects of vacuum degree, membrane thickness, and jamming particles of the PJUs on the variable stiffness characteristics. The tests of envelope capability, grasping adaptability, and grasping force were used to analyze the grasping performance of the octopus-inspired soft gripper, exhibiting excellent helical envelope capabilities, strong adaptability, and a large bearing capacity of the proposed gripper. The proposed gripper has excellent potential for application in the field of soft robots.

Chronic wounds pose a significant challenge to healthcare professionals, not only due to their prolonged healing times but also because severe cases can lead to amputations and life-threatening risks for patients. However, existing wound monitoring sensors typically monitor only a single parameter of wound status and often experience crosstalk when detecting multiple types of information simultaneously. We propose a multifunctional wound monitoring sensor based on laser-induced graphene, which not only exhibits superior sensing performance and remarkable stability but also allows for non-interference monitoring of multiple wound-related parameters, such as pH, temperature, and strain. The sensor can detect a minimal strain of 0.3

Woven/unidirectional (UD) curved hybrid laminates have been widely applied in aerospace and automotive fields due to their excellent mechanical properties and design flexibility. The laser-assisted thermoplastic composite automated fiber placement has the advantages of fast forming speed and high heating efficiency. This study focuses on investigating the low-velocity impact behavior of glass fiber/polypropylene woven/UD composite curved hybrid laminates prepared by automated fiber placement molding. The automated fiber placement molded curved hybrid laminates were compared with those on UD laminates via automated fiber placement and woven/UD laminates molded by the autoclave process. Impact responses of specimens were determined through low-velocity impact tests with impact energies of 15 J, 20 J and 25 J. After the low-velocity impact tests, the damage to specimens was characterized and analyzed using a super-depth-of-field microscope. Also, the low-velocity impact damage behavior of the three types of specimens is quantitatively compared by using the impact contact force, impact peak force and absorbed impact energy. It is concluded that the layer structure plays an important role in determining the low-velocity impact behavior of composite laminates. Especially for GF/PP woven/UD curved hybrid laminates prepared by automated fiber placement, the woven layer plays an important role in reducing matrix cracking, delamination and fiber fracture, thus improving its low-velocity impact resistance.

Inspired by webbed feet, a bionic webbed foot soft gripper with variable stiffness was designed by integrating a pneumatic networks actuator with layer jamming skin. Layer jamming skin as the key component of bionic webbed foot soft gripper, its design and fabrication process were described. An experimental platform combining stretch/bend control was established to analyze the impact of activated negative pressure, different materials and shapes jamming units, and the number of jamming layers on the stiffness of the layer jamming skin. The layer jamming skin conforms to the characteristics of variable stiffness by evaluating the experimental and numerical results of the layer jamming skin under external loading. The curling and adaptability test demonstrated the layer jamming skin's adaptability and flexibility to various shapes and sizes of caught objects. The variable stiffness, adaptability, and gripping force of the bionic webbed foot soft gripper during object grasping were assessed through gripping experiments. This work presents an enveloping gripper with variable stiffness, high adaptability, and strong grasping force.

Laser-assisted thermoplastic composite automated placement method has been applied to the molding of composites due to its advantages of fast molding speed and high heating efficiency. This study focuses on designing a robot for laser-assisted thermoplastic composite automated fiber placement, employing a modular approach to create a versatile fiber placement head. Control functions, such as electrical circuits, a computer interface, and tension control, were developed. Hybrid laminates, combining GF/PP unidirectional and braided composites, were manufactured by independently adjusting laser power (275 W-400 W) and compression force (150 N-400 N). Bonding properties were analyzed using wedge peel tests and microscopic detection, revealing superior toughness in laser-assisted laminates compared to autoclave counterparts. Altering laser power and compression force impacted polypropylene resin distribution, influencing hybrid interlayer peel strength. The inclusion of braided materials and elevated mold temperature proved effective in minimizing lamination warpage in GF/PP laminates.

Replicating human somatosensory networks in robots is crucial for dexterous manipulation, ensuring the appropriate grasping force for objects of varying softness and textures. Despite advances in artificial haptic sensing for object recognition, accurately quantifying haptic perceptions to discern softness and texture remains challenging. Here, we report a methodology that uses a bimodal haptic sensor to capture multidimensional static and dynamic stimuli, allowing for the simultaneous quantification of softness and texture features. This method demonstrates synergistic measurements of elastic and frictional coefficients, thereby providing a universal strategy for acquiring the adaptive gripping force necessary for scarless, antislippage interaction with delicate objects. Equipped with this sensor, a robotic manipulator identifies porcine mucosal features with 98.44% accuracy and stably grasps visually indistinguishable mature white strawberries, enabling reliable tissue palpation and intelligent picking. The design concept and comprehensive guidelines presented would provide insights into haptic sensor development, promising benefits for robotics.

Processing parameters during the laser-radiated in-situ manufacturing process change the thermal history of the thermoplastic composite, which affects porosity and fiber-resin interfacial bonding quality, and hence the wedge peel strength of the laminate. The effect of different laser powers and consolidation forces on the wedge peel strength of the specimens was investigated. Due to the fiber-rich area on the tape surface during the laser heating phase as well as the insufficient consolidation force and consolidation length during the consolidation phase, the wedge peel strength decreased due to increased porosity and weak fiber-resin bonding at the interlayer bonding interface. A conformable consolidation roller of lower hardness was used to improve the wedge peel strength of the laminates, which reduced the initial temperature of the cooling phase, thus inhibiting the void rebound and increasing the bonding strength at the fiber-resin interface. The cross-section and peeling surface were characterized by optical microscope and scanning electron microscope. The wedge peel strength of the laminates, with reduced voids and increased interfacial bonding strength between the fibers and the resin, is improved. Highlights Mechanism of void formation and evolution in different phases of laser-radiated in-situ consolidated laminate. Effect of consolidation roller hardness and deformation on wedge peel strength.

The effect of automated fiber placement periodical gap and overlap defects on the microstructure, load-displacement curves, and out-of-plane displacements of bistable laminates due to the higher ratio of gap width to laminate thickness as well as the high sensitivity to imperfections is studied in this article. Results show that applying caul plates during curing can accurately predict snap loads and maximum out-of-plane displacements of the laminates, as well as prevent significant variations in curvature at the bending boundary. Gaps and overlaps of various widths embedded in a single layer facilitate the customization of the mechanical properties of bistable laminates.

Bistable laminates have potential applications in areas such as buffer and soft robotics due to their two stable states and ability to deform through both snap-through and snap-back processes. However, conventional orthotropic bistable laminates with two stable state configurations and snap loads are similar in magnitude. There is a problem that the deformation cannot be easily driven when the laminate stiffness is high. To solve this problem, a clever design is needed to reduce the snap-back load and increase the snap-through load so that the driven deformation can be realized more easily. In this paper, we propose a design method to suppress and control the deformation of bistable laminates by utilizing the shape memory of 3D-printed shape memory polymers (SMP), which enables the laminates to increase the stiffness while reducing the driving force. First, a numerical model of viscoelasticity of the laminate is established to study its deformation characteristics, and the numerical results are compared with experimental results with good agreement. The effect of SMPs on the snap load and principal curvature of bistable laminates is also investigated. Finally, the interlayer interface bonding of the bistable laminates is examined in microscopic perspective. The results demonstrate that 3D printed SMPs can effectively enhance the snap-through load and reduce the snap-back load of bistable laminates, achieving deformation suppression and control while maintaining good interlaminar bonding with carbon fiber composites. This study provides new insights and practical significance for the deformation suppression and active control of bistable structures.

Abstract The morphing characteristics of bistable laminates embedded with 4D printed shape memory polymers are investigated. Bistable laminates have potential applications in soft robotics due to their two stable states and ability to deform through both snap-through and snap-back processes. For example, a bistable laminate is triggered to snap back by a pneumatic-actuated method that allows it to grip objects. By reducing the snap-back load and increasing the snap-through load, the bistable laminate can be more easily driven to deform while maintaining good stiffness in its first stable state. 4D printed shape memory polymers have shape memory and recovery, A design method for suppressing and controlling the deformation of bistable laminates using 4D printed shape memory polymers is proposed in this paper. A numerical model of viscoelasticity of the laminate is established to study its deformation characteristics, and the numerical results are compared with experimental results with good agreement. The effect of shape memory polymers on the snap load and principal curvature of bistable laminates is also investigated. Finally, the interlayer interface bonding of the bistable laminates is examined in microscopic perspective. The results demonstrate that 4D printed shape memory polymers can effectively enhance the snap-through load and reduce the snap-back load of bistable laminates, achieving deformation suppression and control while maintaining good interlaminar bonding with carbon fiber composites. This study provides new insights and practical significance for the deformation suppression and active control of bistable structures.

Although pneumatic soft crawling robots have made great progress, there are still several difficulties hindering their practical progress, the most important of which is the insufficient stiffness and the insufficient load capacity under large deformations. An inchworm-like soft crawling robot with load capacity and deformability is proposed in this paper. Bistable composite structures are typically smart morphing variable stiffness structures with lightweight, good stiffness under large deformations and possessing two stable configurations. Instead of traditional materials with high Young’s modular, the inchworm-like crawling robot, which consists of a stiffness-enhancing hybrid actuator integrating a bistable shell with a soft pneumatic actuator for the main body and two bristle structures for the feet, has lightweight, flexibility, and high stiffness under large deformations. By controlling the stiffness-enhanced hybrid actuator, the robot is capable of achieving crawling and reversing motions like an inchworm. Experimental results show that the tip output force of the inchworm-like deformed trunk was five times larger than a single pneumatic actuator, which means that the inchworm-like robot owns excellent driving performance and flexibility. The collapse of an inchworm-like deformed trunk with 100 g load is less than the collapse of a single pneumatic networks actuator. This also demonstrates that the bistable structure exactly improves the load capacity of the crawling robot. The periodic bending-flattening motion of the actuator is transformed into the unidirectional crawling motion of the robot by installing feet on both sides of the actuator. The crawling robot also can perform well in environments with different angles, heights, and surfaces, which is verified by experiments. The inchworm-like crawling robot provides a method to improve the load capacity while maintaining the flexibility of soft robots and demonstrating huge practicability in field exploration and goods transportation.

The morphing characteristics and damage analysis of variable stiffness bistable laminate fabricated by continuous fiber 3D printing technology are systematically studied. Conventionally, bistable structures used in morphing applications are achieved with straight fibers. With the application of fiber placement technology, it is now possible to prepare variable stiffness laminates with different directions and layup angles of fibers. Moreover, the structure will be damaged with the increase in deformation times. How to effectively suppress the failure of laminates is also a highlight for this composite structure. In this paper, three curvilinear fiber paths are designed and compared. And a semi-analytical model based on the Rayleigh-Ritz method is used to predict the curvature of stable configuration. In particular, continuous fiber thermosetting resin matrix composites 3D printing technology is proposed for preparing variable stiffness laminates, which has several advantages compared to other traditional preparation methods of variable stiffness laminates. The corresponding finite element model is also developed to investigate the bistable behavior and damage analysis. In addition, the influence of different angle parameters and fiber paths on the stable configuration and the snap-load are also discussed. Finally, the damage evolution and mechanical properties of straight-fiber laminates and variable stiffness laminates in tension and compression are carried out based on the Hashin failure criteria.

By inducing periodic gaps, conventional automated fiber placement avoids overlap defects, which are generally prohibited in composite component manufacturing. However, bistable laminates are highly sensitive to imperfections, and it is critical to explore the effect of periodic gaps on the performance of bistable laminates. The principal curvatures and load-displacement curves of thermoplastic composite laminates with manually embedded periodic gaps was studied using experimental and numerical methods in this paper. SEM microscopy was used to observe the gap areas of the cross section of laminates to assess the microstructure of gaps with width variations after curing. In addition, a numerical method was proposed based on the experimentally determined evolution of gap widths and thicknesses of laminate. Subsequently, the effects of gap width, single-layer thickness, and total thickness on the principal curvature were investigated. Gaps embedded in the 0 & DEG; and 90 & DEG; layers of bistable laminates demonstrated a substantial decrease in the snap load of the laminates. Interestingly, by embedding different gap widths in the 0 & DEG; layers of the laminates, the snap load discrepancy between the snap-through and snap-back processes increased as the gap width widened, and the same trend was also found in the curvatures in the two stable states.HighlightsBistable characteristics of laminates with periodic gap defects.Utilizing gaps embedding in 0 & DEG; layer to tailor the mechanical properties. Automated fiber placement periodic gaps were embedded in thermoplastic bistable composite laminates, and the effect on the principal curvature and load-displacement has been studied in this paper. Under SEM microscopy, the gaps were filled with polymer to make the resin-rich areas in the laminates with 0.5 mm gaps and only partially healed in the laminates with 1.6 and 3.2 mm gaps, which caused the thickness of the bistable laminates to decrease. A simplified numerical model was developed to investigate the effect of gap width and thickness of laminates on the mechanical performance of the specimens. As the gap width increases, the snap load of the snap-through increases and has a higher load bearing capacity, whereas the snap load of the snap-back decreases and necessitates less energy input to generate a snap process, which makes the application of bistable structures more favorable. Therefore, when manufacturing bistable composite structures with the AFP process is unable to eliminate gap defects, we can utilize this interesting phenomenon of periodic gaps embedding in the 0 & DEG; layer to control the mechanical properties of bistable laminates.image

As a kind of lightweight composite structure, thin-walled lenticular booms made of fiber reinforced composite are widely used in the aerospace field because of its high stiffness in the unfolded state. In this paper, the loadbearing and coiling characteristics of the thin-walled lenticular composite booms were studied, and the effects of different design parameters and material properties were compared. Thin-walled lenticular composite booms with different ply numbers, ply angles, fiber types and fiber contents were prepared. Free-end loading experiments and coiling experiments were conducted to obtain the load-displacement curves, coiling torques and binding forces. The finite element model was established and the simulation results were compared with those of experiments. It is shown that increasing the ply number, increasing the fiber content and using fibers with lower elastic modulus can significantly enhance the load-bearing capacity of thin-walled lenticular composite booms, meanwhile reducing its coiling capacity. The booms with orthometric ply angle have greater load-bearing capacity, but the ply angle has less effect than the ply numbers, fiber types and fiber contents. The results provide feasibility for the design of thin-walled lenticular composite booms suitable for the aerospace field.

This study proposes a magnetorheological elastomer actuated multi-stable gripper reinforced stiffness with twisted and coiled polymer. The multi-stable gripper can conform objects with different sizes by means of its stable and adaptive characteristics. The multi-stable gripper is composed of a multi-stable laminated composite shell as the grab unit for supporting, a twisted and coiled polymer as the deformation element for variable stiffness and a magnetorheological elastomer as the smart material for actuation. The magnetorheological elastomer was activated by external magnetic field inducing the gripper change from the first stable state to the second or the third stable state to complete the gripping action. The driving force of the multi-stable laminated composite shell was discussed by the experimental and numerical methods, then the width of deformation and transition element was designed to reduce the driving force. Furthermore, the stiffness of the multi-stable gripper is analysed with respect to the compression, extraction, and gripping performance of the gripper through experiments, and then, the gripping performance was compared with current soft grippers. The experimental results show that the multi-stable gripper exhibits sufficient compliance and adaptability. That is, the multi-stable gripper has a faster response time and larger grasping weight compared with soft grippers.

Somatosensory networks that provide sophisticated sensory feedback and enable the dexterous manipulation of the human grasp remain difficult to replicate in robots, which is attributed to the grand challenge of densely covering the hand with tactile arrays. Here, a multisensory tactile glove is reported that is capable of object recognition with dense coverage of pressure and temperature sensing arrays. The synergistic effect of the multimodal configuration allows the tactile arrays to perceive contact pressure and thermal conductivity of an object involved in grasping motion, thus enhancing the accuracy via the combination of the mechanical features with thermal properties. By leveraging the multiple scanning technology and wireless transmission system, the tactile glove achieves a recognition accuracy of 94.2% in differentiating 20 types of objects with a modified deep learning algorithm. The large-area sensing arrays with high spatiotemporal resolution and multimodal sensing capabilities, which paves the way for the development of robot grasping tools, human-machine interfacing, and advanced prosthetics.

For complex diseases, beyond the main effects of genetic (G) and environmental (E) factors, gene-environment (G-E) interactions also play an important role. Many of the existing G-E interaction methods conduct marginal analysis, which may not appropriately describe disease biology. Joint analysis methods have been developed, with most of the existing loss functions constructed based on likelihood. In practice, data contamination is not uncommon. Development of robust methods for interaction analysis that can accommodate data contamination is very limited. In this study, we consider censored survival data and adopt an accelerated failure time (AFT) model. An exponential squared loss is adopted to achieve robustness. A sparse group penalization approach, which respects the "main effects, interactions" hierarchy, is adopted for estimation and identification. Consistency properties are rigorously established. Simulation shows that the proposed method outperforms direct competitors. In data analysis, the proposed method makes biologically sensible findings.