SpringWorm: A Soft Crawling Robot with a Large-Range Omnidirectional Deformable Rectangular Spring for Control Rod Drive Mechanism Inspection.

In this article, a cable-driven elastic backbone worm-like robot (named "SpringWorm") of decimeter-level size is designed, which has high adaptability in crack inspection of the weld between reactor pressure vessel (RPV) and control rod drive mechanisms. The robot consists of a body that adopts a rectangular helix spring backbone driven by four cables and the flexible claws embedded with distributed electromagnets. Combining the omnidirectional deformation of the backbone and the passive deformation adsorption of the claws, the robot can achieve a variety of gaits. Based on the approaches of geometric analysis and transformation matrices of the coordinate frame, a kinematic model of the cable-driven backbone has been established. Moreover, a mechanical model considering the friction between the cable and the backbone has also been established. The top position and the bending angle of the backbone obtained by the theory, simulation, and experiment are in good agreement. In addition, the errors of the driving force between simulation and experimental results are also small. SpringWorm is 670 g, measures 206 × 65 × 75 mm, has a maximum speed of 8.9 mm/s, and has a maximum payload of 1 kg. The robot can climb over 2-cm-tall steps and 4-cm-deep ditches, and climb and turn on the vertical wall, on the pipe with a radius of 31 cm, and on the spherical surface of RPV.

A Super-Lightweight and Soft Manipulator Driven by Dielectric Elastomers.

Some applications are very sensitive to the weight of the robot, such as space manipulation or any untethered mobile manipulation. In this article, we designed a five-module unilaterally bending serial manipulator with length of 32 cm and a weight of only 18 g. The manipulator is driven by dielectric elastomer actuators (DEAs). Each module consists of a spatially closed tubular structure, which has the capability of large deformation while simultaneously maintaining torsional rigidity. The design is based on the buckling of columns. To achieve global deformation continuously, each module was controlled independently by a multichannel high-voltage power supply. As a demo, the manipulator was able to enter and exit a narrow L-shaped pipe. Experiments demonstrate that the manipulator driven by spatial DEAs can be super lightweight and can realize large continuous deformation.

Soft and Fast Hopping-Running Robot with Speed of Six Times Its Body Length Per Second.

Existing robots capable of hopping or running mostly rely on rigid actuators, but soft hopping or running robots based on muscle-like actuators have not yet been achieved. In this article, we report a tethered soft robot capable of hopping-running on smooth and rough surfaces with high speed. The hopping-running robot is composed of two soft joints that simulate the foreleg and hind leg driven by dielectric elastomer. The mass, length, width, and height of the robot are 6.5 g, 8.5 cm, 4.8 cm, and 50 cm, respectively. The robot can run at a speed of 51.83 cm/s (6.10 body lengths/s), which is much faster than previously reported locomotion robots driven by soft responsive materials. The robot also shows good adaptability to different terrains, such as marble, wood, rubber, sandpaper, and slopes. The robot can carry a load equal to its weight, can maintain a high locomotion speed, and demonstrates the potential ability to carry its power supply and control circuitry.

Rapid mineralization of hierarchical poly(l-lactic acid)/poly(ε-caprolactone) nanofibrous scaffolds by electrodeposition for bone regeneration.

Introduction: Hierarchical nanofibrous scaffolds are emerging as a promising bone repair material due to their high cell adhesion activity and nutrient permeability. However, the existing method for hierarchical nanofibrous scaffolds fabrication is complicated and not perfectly suitable for further biomedical application in view of both structure and function. In this study, we constructed a hierarchical nanofibrous poly (l-lactic acid)/poly(ε-caprolactone) (PLLA/PCL) scaffold and further evaluated its bone healing ability. Methods: The hierarchical PLLA/PCL nanofibrous scaffold (PLLA/PCL) was prepared by one-pot TIPS and then rapidly mineralized at room temperature by an electrochemical deposition technique. After electrode-positioning at 2 V for 2 hrs, a scaffold coated with hydroxyapatite (M-PLLA/PCL) could be obtained. Results: The pore size of the M-PLLA/PCL scaffold was hierarchically distributed so as to match the biophysical structure for osteoblast growth. The M-PLLA/PCL scaffold showed better cell proliferation and osteogenesis activity compared to the PLLA/PCL scaffold. Further in vivo bone repair studies indicated that the M-PLLA/PCL scaffold could accelerate defect healing in 12 weeks. Conclusion: The results of this study implied that the as-prepared hydroxyapatite coated hierarchical PLLA/PCL nanofibrous scaffolds could be developed as a promising material for efficient bone tissue repair after carefully tuning the TIPS and electrodeposition parameters.

Self-Assembled Hydroxyapatite-Graphene Scaffold for Photothermal Cancer Therapy and Bone Regeneration.

Repairing large tumor-related bone defects remains a difficult clinical problem because of the significant risk of locoregional relapse after surgical curettage. In this study, a composite scaffold of nano-hydroxyapatite (nHA) and reduced graphene oxide (rGO) sheets was fabricated by self-assembly, and a 20 wt% nHA-rGO sheet solution formed the most stable hydrogel. In vitro, nHA-rGO scaffolds killed all but 8% of osteosarcoma cells (MG-63) under 808 nm near-infrared laser irradiation for 20 min. SEM images and live/dead staining of MG-63 cells in nHA-rGO also confirmed the therapeutic efficacy of the scaffolds. Tumors implanted with nHA-rGO scaffolds reached 60 °C after 4 min. of irradiation; xenografted tumors stopped growth or even decreased in size after photothermal therapy. In vitro the scaffolds promoted adhesion, proliferation, and osteogenic mineralization of rat bone marrow stem cells (rBMSCs). Live cell staining and CCK-8 showed good proliferation for rBMSCs in nHA-rGO scaffolds. Alkaline phosphatase activity and qPCR demonstrated osteogenic mineralization of rBMSCs in nHA-rGO scaffolds. Micro-CT and histology verified that the scaffold promotes bone regeneration in rat cranial defects. At 8 weeks, 35% of the cranial defect area remained in the scaffold-implanted group, while 80% remained for the control. Bone mineral density of the scaffold-implanted group reached 284.58±20.78 mg/cm³, indicating new bone mineral deposition, versus only 96.04±2.67 mg/cm³ for the control. Histology showed scaffold stimulation of osteoblast mineralization and collagen deposition. Therefore, nHA-rGO scaffolds may be an effective treatment of large tumor-related bone defects due to their excellent photothermal and osteogenic effects.

One-Pot Synthesis of Silver Nanoparticle Incorporated Mesoporous Silica Granules for Hemorrhage Control and Antibacterial Treatment.

Hemostasis is of critical importance for damage control and the initiation of tissue repair in surgery and trauma. Mesoporous silica materials, due to their favorable biocompatibility and excellent surface properties, have attracted increasing attention for their outstanding hemostatic performance. In this study, silver nanoparticle-incorporated mesoporous silica granules (AgNP-MSG) were prepared by means of one-pot sol-gel processing, which brought about a highly blood-absorbent composite capable of prompt hemostasis. Detailed studies were performed to evaluate its structure, cellular compatibility, and adsorption capacity, emphasizing the influence of the composite on in vivo degradability and hemostasis efficacy. The as-prepared composite showed good compatibility and sustained antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Further in vivo experimentation demonstrated that hemorrhage in a rat liver injury model was effectively controlled within 7 s by 5% AgNP-MSG, much more rapidly than commercially derived hemostatic gauze. Histological analysis further demonstrated that the fabricated composites could completely degrade at the site of liver injury 2 weeks later. These results suggest that as-prepared AgNP-MSG has great potential as a hemostatic material with robust antibacterial activity for future therapeutic translation.

Wearable Stretch Sensors for Motion Measurement of the Wrist Joint Based on Dielectric Elastomers.

Motion capture of the human body potentially holds great significance for exoskeleton robots, human-computer interaction, sports analysis, rehabilitation research, and many other areas. Dielectric elastomer sensors (DESs) are excellent candidates for wearable human motion capture systems because of their intrinsic characteristics of softness, light weight, and compliance. In this paper, DESs were applied to measure all component motions of the wrist joints. Five sensors were mounted to different positions on the wrist, and each one is for one component motion. To find the best position to mount the sensors, the distribution of the muscles is analyzed. Even so, the component motions and the deformation of the sensors are coupled; therefore, a decoupling method was developed. By the decoupling algorithm, all component motions can be measured with a precision of 5°, which meets the requirements of general motion capture systems.

Coupled nonlinear oscillation and stability evolution of viscoelastic dielectric elastomers.

This article describes the development of an analytical model to study the coupled nonlinear oscillation and stability evolution of viscoelastic dielectric elastomers (DEs) under non-equibiaxial tensile forces by utilizing the method of virtual work. Numerically calculated results are employed to predict this nonlinear dynamic behavior. The resonant frequency (where the amplitude-frequency response curve peaks) and the amplitude-frequency response of the deformation in both in-plane directions are tuned by varying the values of tensile force. The oscillation response in the two in-plane directions exhibits strong nonlinearity and coupling with each other, and is tuned by the changing tensile forces under a specific excitation frequency. By varying the values of tensile forces, the dynamic viscoelastic creep in a certain in-plane direction can be eliminated. Phase diagrams and Poincaré maps under several values of tensile forces are utilized to study the stability evolution of the DE system under non-equibiaxial tensile forces.