Showing papers by "Yanju Liu published in 2023"
TL;DR: Shape memory polymer (SMP) and SMP composites (SMPC) have become possible materials to solve the problems currently faced by space deployable structures, biomedical devices, mold manufacturing, release devices, etc as discussed by the authors .
Abstract: Shape memory polymer (SMP) and SMP composites (SMPC) can memorize the permanent shape and recover from the temporary shape to the permanent shape when stimulated by the appropriate stimuli. Because of the unique shape memory effect, coupled with its low cost, low density, high specific strength, biodegradability, biocompatibility, and other characteristics, SMP and SMPC have become possible materials to solve the problems currently faced by space deployable structures, biomedical devices, mold manufacturing, release devices, etc. This work reviews the research and developments of SMP and SMPC, including the achievements in constitutive theory, the applications, and prospects in aerospace, biomedical medicine, intelligent mold, and release devices.
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TL;DR: In this paper , a series of 3D kirigami-inspired honeycomb (TW3KH) structures with different mechanical properties were designed and fabricated on the exploration and optimization of geometric parameters of 2D honeycomb structures.
Abstract: Kirigami arts have provided a more promising method for building multiscale structures, which can shape two-dimensional (2D) sheets into three-dimensional (3D) configurations by cutting and folding. Here, we first carried out a theoretical analysis of the mechanical properties of 2D honeycomb lattice structures and experimental verification combined with finite element (FE) simulation. Furthermore, a series of thick-walled 3D kirigami-inspired honeycomb (TW3KH) structures with different mechanical properties were designed and fabricated on the exploration and optimization of geometric parameters of 2D honeycomb structures. The investigations of folding feasibility, self-expansion, and self-folding performance experimentally showed that our designed four-dimensional (4D) printing structure had good programmability and shape memory capability and a large volume change ratio during shape change. Meanwhile, research on its compression deformation behavior found that the TW3KH structures can recover load-bearing capacity very well when the angle is positive. Therefore, these TW3KH structures have great advantages in space-saving smart load-bearing equipment.
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TL;DR: In this article , the authors investigated the effect of temperature and fiber volume content on fiber buckling and showed that the higher the temperature and volume content, the easier the fiber buckles.
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TL;DR: In this paper , a shape memory biocomposite with controllable transition temperature was developed through facile manufacturing technology, and the shape memory process of triggering printed constructs under NBT was realized.
Abstract: Despite the burgeoning interest in manufacturing highly complex and dynamically reconfigurable implants using the 4D printing technique, one of the most critical challenges is to develop near-body temperature (NBT)-triggered 4D printing materials in a facile and scale-up manner. The currently reported 4D printed biomaterials for implants have inappropriate transition temperatures or are limited to demonstration production of small amounts of materials in the laboratory. Here, 4D printed shape memory biocomposites with controllable transition temperature were developed through facile manufacturing technology, and the shape memory process of triggering printed constructs under NBT was realized. Customized, reconfigurable, biodegradable, and biocompatible 4D printed biomimetic intestinal stents were developed using NBT-triggered biocomposites, filling the blank of 4D printed intestinal stents. The 4D printed biomimetic intestinal stents were designed based on wavy biomimetic networks that can mimic the nonlinear stress-strain response of biological tissues, demonstrating high flexibility and facilitating reduced irritation of the intestinal wall. More importantly, the biodegradability of the 4D printed biomimetic intestinal stent can avoid the secondary endoscope removal required by the metal intestinal stent. This work not only offers an efficient and facile methodology to fabricate NBT-triggered 4D printing shape memory biocomposites but also demonstrates the attractive application potential of 4D printed intestinal stents in next-generation intelligent implants.
1 citations
TL;DR: In this article , a structure-level smart deployable truss (SDT) was further studied for on-orbit verification on the SJ18 Geostationary Satellite in this work on the basis of a material-level validation of a shape-memory polymer composite (SMPC) sheet.
Abstract: A structure-level smart deployable truss (SDT) was further studied for on-orbit verification on the SJ18 Geostationary Satellite in this work on the basis of a material-level validation of a shape-memory polymer composite (SMPC) sheet on the SJ17 Geostationary Satellite in 2016. In the SDT, a shape-memory alloy (SMA) mechanism was used to replace traditional pyrotechnic devices for locking and releasing, and SMPC actuation laminates were employed to replace traditional motor or spring driving mechanisms. With a strict parameter constrain of mass, size, and stiffness, the current form of the SDT flight hardware was finally obtained through several cycles of optimization design. Its systematical ground-based experiments were conducted, and the overall structural and functional performance met the demands of the aerospace standards of China. The locking force and expansion breaking force of the SMA releasing mechanism were [Formula: see text] and [Formula: see text], ensuring the locking and unlocking reliability for the movable parts with mass 5 kg. The actuation force of all SMPC laminates decreased from [Formula: see text] (0°) to [Formula: see text] (165°) with a recovery duration of [Formula: see text], which was strong enough for SDT deployment in space. The shape-memory materials show great prospects for smart deployable structures in space.
TL;DR: In this article , the shape fixed ratio of shape memory hydrogels (SMHs) increases monotonically with temperature, but first increases and then decreases with water content, and a constitutive model is developed to capture this thermo-aqueous coupling using the statistical theory of transient networks, from which they obtain an explicit evolution equation of deformation gradient.
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TL;DR: In this article , a variable stiffness model of flexible parallel electroadhesive structures under three-point bending, cantilever beam bending subjected to tip concentrated forces, and a fixed beam bending subject to uniformly distributed forces is presented.
Abstract: Electrostatic layer jamming represents a lightweight, low energy consumption, electrically tunable, and cost-effective variable stiffness structure. Flexible parallel electroadhesive structures are the simplest form of electrostatic layer jamming. There is a lack of comprehensive and experimentally validated theoretical variable stiffness models of flexible parallel electroadhesive structures. Here we present the first variable stiffness model of flexible parallel electroadhesive structures under three-point bending, cantilever beam bending subjected to tip concentrated forces, and cantilever beam bending subjected to uniformly distributed forces, using the Euler–Bernoulli beam theory and considering friction and slip between layers by integrating the Maxwell stress tensor into the model. We find that: (1) three-point bending and cantilever beam bending under tip concentrated forces only have pre-slip and full-slip, whereas cantilever beam bending under uniformly distributed forces has an additional partial-slip which can be used for stiffness modulation; (2) the stiffness during the pre-slip stage is four times larger than the stiffness in the full-slip stage; and (3) increasing the voltage, dielectric permittivity, and coefficient of friction can elongate the pre-slip stage, thus enhancing the structural load capability. A customized three-point bending and a cantilever beam bending experimental setup were developed and the experimental deflection–force curve agreed relatively well with the theoretical one. The model, which considered electrode thickness and Young’s modulus, and the results presented in this work are useful insights for understanding the variable stiffness mechanism of electroadhesive layer jamming and are helpful for their structural optimization towards practical applications.
TL;DR: Wang et al. as discussed by the authors developed a flexible deployable subsystem based on shape memory polymer composites (SMPC-FDS) with a large folding ratio, which incorporates a camera and two temperature telemetry points for monitoring the local state of the Mars orbiter and the deep space environment.
TL;DR: In this paper , surface modified upconversion nanomaterials (UCNPs) capable of aggregation by atom transfer radical polymerization (ATRP) were used as luminescent materials for the first time to achieve signal-stable, low-biological background, and sensitive detection of CYFRA21-1.
TL;DR: In this paper , the buckling loads and geometric imperfection sensitivities of shape memory polymer composite (SMPC) cylindrical shells at different temperatures are determined by means of numerical simulations and experimental analyses.
Abstract: The axial compressive buckling loads of shape memory polymer composite (SMPC) cylindrical shells are very sensitive to geometric imperfections and temperatures, but few studies have been conducted on this phenomenon. In this study, the buckling loads and geometric imperfection sensitivities of SMPC cylindrical shells at different temperatures are determined by means of numerical simulations and experimental analyses. The single perturbation displacement imperfection (SPDI), multiple perturbation displacement imperfection (MPDI) and linear buckling mode imperfection (LBMI) techniques are used to simulate the initial geometric imperfections and calculate the corresponding buckling loads and knock-down factors (KDFs) of SMPC cylindrical shells at different temperatures. In the experimental part, the [0/90/±45]s SMPC cylindrical shells are manufactured through the autoclave molding process. The load-bearing capacities at different temperatures are tested and compared with the numerical results. The results demonstrate that the buckling loads of the SMPC cylindrical shell obtained by numerical techniques are sensitive to temperature, while the KDFs are insensitive to temperature. Meanwhile, results indicate that brittle fracture is the main failure mode instead of buckling at low temperature, so there is a risk when using any numerical technique to design SMPC cylindrical shells in low-temperature region. At high temperatures, the SPDI method overestimates the KDFs, while the KDFs calculated by the MPDI and LBMI techniques are in good agreement with the experimental results. However, only the LBMI method can distinguish the influence of temperature on the post-buckling patterns, and the corresponding post-buckling pattern is more consistent with the experiment. In addition, the shape-recovery properties and repeatability of the SMPC cylindrical shells are good.
TL;DR: Wang et al. as discussed by the authors designed and prepared a series of unique shape memory polyurethane (SMPU) microcapsules with stimuli-responsive functions for shape memory and solvent response.
Abstract: ABSTRACT Research on microcapsules has been conducted in recent years given trends in miniaturization and novel functionalization. In this work, we designed and prepared a series of unique shape memory polyurethane (SMPU) microcapsules with stimuli-responsive functions. The microcapsule has a core-shell structure in which the surface morphology can be adjusted, and it has a certain load-bearing capacity. In addition, the SMPU microcapsule has a stimuli-responsive function for shape memory and solvent response. The temperature of its shape recovery is approximately body temperature, and it can swell to rupture under the stimulation of organic solvents. Thus, the SMPU microcapsule has potential applications in biomedical fields, such as drug release. GRAPHICAL ABSTRACT
TL;DR: In this paper , the authors report an electrochemical analysis of human epidermal growth factor receptor 2 (HER2) in breast cancer patients, which is an important breast cancer marker that is abnormally expressed in 20 to 30% of patients.
Abstract: Human epidermal growth factor receptor 2 (HER2) is an important breast cancer marker that is abnormally expressed in 20 ~ 30% of breast cancer patients. Here, we report an electrochemical...
TL;DR: In this article , a new type of macro fiber composite (MFC) can be used to control the vibration of the structure and the state-space equations of the system were established based on the transfer function, and the frequency response was determined by sine sweep excitation of the SMPC specimen.
TL;DR: In this article , a programmable SMPC-based locking laminate was investigated, which is expected to replace initiating explosives, and the safe allowable area and damage modes were determined.
Abstract: Smart structures based on shape memory polymer composites (SMPCs) are gradually applied to the aerospace field hosting an ideal combination of properties. The damage behavior of SMPC-based smart structures with large deformations requires mechanism research to satisfy their reliability. In this study, a programmable SMPC-based locking laminate was investigated, which is expected to replace initiating explosives. Firstly, based on fiber buckling theory, fiber-reinforced SMPC locking laminate was designed and analyzed, and the safe allowable area and damage modes were determined. Additionally, the deformation test of the locking laminate based on fiber fabric reinforced SMPC showed that there is two typical damage behavior: matrix cracking and interlayer delamination. For this reason, theoretical analysis was performed to reveal the damage mechanism and initial damage location. The results indicated that the fiber bundle width, arc radius, and thickness were the influencing factors of matrix cracking, while the center angle was the influencing factor of delamination. Finally, finite element analysis shows the validity of the theoretical analysis. This research has potent inspiration and reference significance for the design of SMPC-based smart structures.
TL;DR: In this paper , a variable stiffness model of flexible parallel electroadhesive structures under three-point bending, cantilever beam bending subjected to tip concentrated forces, and a fixed beam bending subject to uniformly distributed forces is presented.
Abstract: Abstract Electrostatic layer jamming represents a lightweight, low energy consumption, electrically tunable, and cost-effective variable stiffness structure. Flexible parallel electroadhesive structures are the simplest form of electrostatic layer jamming. There is a lack of comprehensive and experimentally validated theoretical variable stiffness models of flexible parallel electroadhesive structures. Here we present the first variable stiffness model of flexible parallel electroadhesive structures under three-point bending, cantilever beam bending subjected to tip concentrated forces, and cantilever beam bending subjected to uniformly distributed forces, using the Euler–Bernoulli beam theory and considering friction and slip between layers by integrating the Maxwell stress tensor into the model. We find that: (1) three-point bending and cantilever beam bending under tip concentrated forces only have pre-slip and full-slip, whereas cantilever beam bending under uniformly distributed forces has an additional partial-slip which can be used for stiffness modulation; (2) the stiffness during the pre-slip stage is four times larger than the stiffness in the full-slip stage; and (3) increasing the voltage, dielectric permittivity, and coefficient of friction can elongate the pre-slip stage, thus enhancing the structural load capability. A customized three-point bending and a cantilever beam bending experimental setup were developed and the experimental deflection–force curve agreed relatively well with the theoretical one. The model, which considered electrode thickness and Young’s modulus, and the results presented in this work are useful insights for understanding the variable stiffness mechanism of electroadhesive layer jamming and are helpful for their structural optimization towards practical applications.
TL;DR: In this article , a shape memory composite used for cartilage defects is prepared by adding nanohydroxyapatite into a shape-memory polyurethane matrix, exhibiting good mechanical properties and biocompatibility.
Abstract: Repair of articular cartilage defects is a major challenge in orthopedic surgery due to the deficient self-regeneration capability. Cartilage tissue engineering scaffolds provide a promising approach to cartilage defect repair. Proper mechanical properties, interconnected internal structure, customized shape, and minimally invasive treatment are urgent requirements for a qualified cartilage scaffold. Here, a shape memory composite used for cartilage defects is prepared by adding nanohydroxyapatite into a shape memory polyurethane matrix, exhibiting good mechanical properties and biocompatibility. Based on its rheological properties, the composite melt can be printed into 4D printed structures with high precision and quality in a simple and clean way. Inspired by the structure of mangroves, a bionic 4D printed cartilage scaffold is designed and manufactured, presenting a good shape memory performance at a temperature close to body temperature. The 4D printed cartilage scaffold can expand from a conveniently insertional shape to a deployed shape to match defect, providing a novel idea for the personalized and minimally invasive treatment of cartilage defects.
TL;DR: In this paper , isocyanoethyl methacrylate (IEM) is used to functionalize the two ends of poly(ethylene glycol) (PEG) diol with acrylic acid groups through an urethanization reaction.
Abstract: In this paper, isocyanoethyl methacrylate (IEM) is used to functionalize the two ends of poly(ethylene glycol) (PEG) diol with acrylic acid groups through an urethanization reaction. The synthesized PEG/IEM resin is then photo‐cured with a 405 nm ultraviolet lamp. Ttrans of the PEG/IEM resin can be regulated by the different molecular weights of PEG and the use of plasticizer Triacetin to reach 44 °C, which is closer to the human body temperature. Cytotoxicity assay and DMA shape memory cycling testing show that the PEG/IEM resin has excellent biocompatibility and shape memory properties. The flower structure is prepared and its shape recovery process is demonstrated. The performance of 10wt% nano Fe3O4/PEG4000/IEM resin and its composite spring stent structure satisfy the requirement of the stent properties in vivo, and can quickly recover to the original shape under magnetically driven. This work provides a material option for developing new biological application devices such as ureter stents.
TL;DR: In this article , the shape memory polymers (SMPs) with intelligent deformability have shown great potential in the field of aerospace, and the research on their adaptability to space environments has far-reaching significance.
Abstract: Shape memory polymers (SMPs) with intelligent deformability have shown great potential in the field of aerospace, and the research on their adaptability to space environments has far-reaching significance. Chemically cross-linked cyanate-based SMPs (SMCR) with excellent resistance to vacuum thermal cycling were obtained by adding polyethylene glycol (PEG) with linear polymer chains to the cyanate cross-linked network. The low reactivity of PEG overcame the shortcomings of high brittleness and poor deformability while endowing cyanate resin with excellent shape memory properties. The SMCR with a glass transition temperature of 205.8 °C exhibited good stability after vacuum thermal cycling. The SMCR maintained a stable morphology and chemical composition after repeated high–low temperature cycle treatments. The SMCR matrix was purified by vacuum thermal cycling, which resulted in an increase in its initial thermal decomposition temperature by 10–17 °C. The continuous vacuum high and low temperature relaxation of the vacuum thermal cycling increased the cross-linking degree of the SMCR, which improved the mechanical properties and thermodynamic properties of SMCR: the tensile strength of SMCR was increased by about 14.5%, the average elastic modulus was greater than 1.83 GPa, and the glass transition temperature increased by 5–10 °C. Furthermore, the shape memory properties of SMCR after vacuum thermal cycling treatment were well maintained due to the stable triazine ring formed by the cross-linking of cyanate resin. This revealed that our developed SMCR had good resistance to vacuum thermal cycling and thus may be a good candidate for aerospace engineering.
TL;DR: In this paper , a cost-effective liquid crystalline elastomer (LCE) design and fabrication method by dispersing continuous carbon fibers and carbon nanotubes into LCE composites, forming a new type of LCEC actuator was presented.
Abstract: Liquid crystalline elastomers (LCEs) are promising materials for soft actuations. LCE composites (LCECs), via the inclusion of fillers into LCEs, bring diverse functionalities and stimuli-responsive capabilities. It is still a challenge to improve the mechanical properties of LCEC and ensure that the material can perform reversible transformations. Here we present a cost-effective LCEC design and fabrication method by dispersing continuous carbon fibers and carbon nanotubes into LCEs, forming a new type of LCEC actuator. We found that through adjusting the angle (such as 45° and 90°) between the carbon fiber and the stretching axis of LCEC matrix, complex deformable geometries can be easily achieved including bending and twisting structures with enhanced storage modulus (400.9 MPa at 25 °C). Furthermore, the LCEC actuators could be driven by various stimuli including heat (120 °C), light (800 mW cm−2), and electricity (2.0 V). As a result, our new LCEC actuator outperforms other LCE actuators by having the largest number of morphing geometries and stimulus-responsive modes. Our LCEC design and manufacturing strategy represents a promising general methodology that can be easily extended to other continuous fibers (such as glass fiber, aramid fiber, etc.) filled LCECs, bringing even rich shape-changing capabilities that are needed for soft robots and beyond.
TL;DR: In this article , the authors proposed a novel theoretical model in which a non-buckling serpentine is characterized as a large-curvature beam and found that dimensionless geometrical parameters regulate the compliant mechanics of a serpentine, and there is a certain arc angle that produces abnormal stretchability.
TL;DR: In this paper , a novel type of multifunctional coating that could smartly reverse between super-hydrophobic and slippery properties on demand was proposed, which can effectively propel the water droplets, prolong the freezing time and enhance ice removal performance in an extremely cold environment.
TL;DR: Wang et al. as discussed by the authors proposed a shape memory sensor with functional and structural reconfiguration, enhanced sensitivity, and high flexibility by combining 4D-printed fractal-inspired metamaterials with micro-level biomimetic electrodes.
TL;DR: In this article , the authors presented a novel robotic stacking strategy, Netting-Rolling-Splicing (NRS) stacking, based on a dimensional raising method via 2D-to-3D rolling-and-splicing of netted stackable pneumatic artificial muscles to quickly and efficiently fabricate multifunctional soft robots.
Abstract: Soft robots equipped with multifunctionalities have been increasingly needed for secure, adaptive, and autonomous functioning in unknown and unpredictable environments. Robotic stacking is a promising solution to increase the functional diversity of soft robots, which are required for safe human-machine interactions and adapting in unstructured environments. However, most existing multifunctional soft robots have a limited number of functions or have not fully shown the superiority of the robotic stacking method. In this study, we present a novel robotic stacking strategy, Netting-Rolling-Splicing (NRS) stacking, based on a dimensional raising method via 2D-to-3D rolling-and-splicing of netted stackable pneumatic artificial muscles to quickly and efficiently fabricate multifunctional soft robots based on the same, simple, and cost-effective elements. To demonstrate it, we developed a TriUnit robot that can crawl 0.46 ± 0.022 body length per second (BL/s) and climb 0.11 BL/s, and can carry a 3 kg payload while climbing. Also, the TriUnit can be used to achieve novel omnidirectional pipe climbing including rotating climbing, and conduct bionic swallowing-and-regurgitating, multi-degree-of-freedom manipulation based on their multimodal combinations. Apart from these, steady rolling, with a speed of 0.19 BL/s, can be achieved by using a pentagon unit. Furthermore, we applied the TriUnit pipe climbing robot in panoramic shooting and cargo transferring to demonstrate the robot's adaptability for different tasks. The NRS stacking-driven soft robot here has demonstrated the best overall performance among existing stackable soft robots, representing a new and effective way for building multifunctional and multimodal soft robots in a cost-effective and efficient way.