Thermoplastic Dielectric Elastomer of Triblock Copolymer with High Electromechanical Performance.

Dielectric elastomer (DE) actuators have been shown to have promising applications as soft electromechanical transducers in many emerging technologies. The DE actuators, which are capable of large actuation strain over a wide range of excitation frequencies, are highly desirable. Here, the first single-component DE of a triblock copolymer with attractive electromechanical performance is reported. Symmetric poly(styrene-b-butyl acrylate-b-styrene) (SBAS) is designed and synthesized. The SBAS actuator exhibits about 100% static actuation area strain and excellent dynamic performance, as evidenced by a wide half bandwidth of 300 Hz and a very high specific power of 1.2 W g-1 within the excitation frequency range of 300-800 Hz.

The application of a new type of titanium mesh cage in hybrid anterior decompression and fusion technique for the treatment of continuously three-level cervical spondylotic myelopathy.

PURPOSE: To evaluate the efficacy and safety of a new type of titanium mesh cage (NTMC) in hybrid anterior decompression and fusion method (HDF) in treating continuously three-level cervical spondylotic myelopathy (TCSM). METHODS: Ninety-four cases who had TCSM and accepted the HDF from Jan 2007 to Jan 2010 were included. Clinical and radiological outcomes were compared between cases who had the NTMC (Group A, n = 45) and traditional titanium mesh cage (TTMC, Group B, n = 49) after corpectomies. Each case accepted one polyetheretherketone cage (PEEK) after discectomy. RESULTS: Mean follow-up were 74.4 and 77.3 months in Group A and B, respectively (p > 0.05). Differences in cervical lordosis (CL), segmental lordosis (SL), anterior segmental height (ASH) and posterior segmental height (PSH) between two groups were not significant preoperatively, 3-days postoperatively or at final visit. However, losses of the CL, SL, ASH and PSH were all significantly larger in Group B at the final visit, so did incidences of segmental subsidence and severe subsidence. Difference in preoperative Japanese Orthopedic Association (JOA), visual analog scale (VAS), neck disability index (NDI) or SF-36 between two groups was not significant. At the final visit, fusion rate, JOA, and SF-36 were all comparable between two groups, but the VAS and NDI were both significantly greater in Group B. CONCLUSIONS: For cases with TCSM, HDF with the NTMC and TTMC can provide comparable radiological and clinical improvements. But application of the NTMC in HDF is of advantages in decreasing the subsidence incidence, losses of lordosis correction, VAS and NDI.

Adhesive cryogel particles for bridging confined and irregular tissue defects.

BACKGROUND: Reconstruction of damaged tissues requires both surface hemostasis and tissue bridging. Tissues with damage resulting from physical trauma or surgical treatments may have arbitrary surface topographies, making tissue bridging challenging. METHODS: This study proposes a tissue adhesive in the form of adhesive cryogel particles (ACPs) made from chitosan, acrylic acid, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The adhesion performance was examined by the 180-degree peel test to a collection of tissues including porcine heart, intestine, liver, muscle, and stomach. Cytotoxicity of ACPs was evaluated by cell proliferation of human normal liver cells (LO2) and human intestinal epithelial cells (Caco-2). The degree of inflammation and biodegradability were examined in dorsal subcutaneous rat models. The ability of ACPs to bridge irregular tissue defects was assessed using porcine heart, liver, and kidney as the ex vivo models. Furthermore, a model of repairing liver rupture in rats and an intestinal anastomosis in rabbits were established to verify the effectiveness, biocompatibility, and applicability in clinical surgery. RESULTS: ACPs are applicable to confined and irregular tissue defects, such as deep herringbone grooves in the parenchyma organs and annular sections in the cavernous organs. ACPs formed tough adhesion between tissues [(670.9 ± 50.1) J/m2 for the heart, (607.6 ± 30.0) J/m2 for the intestine, (473.7 ± 37.0) J/m2 for the liver, (186.1 ± 13.3) J/m2 for muscle, and (579.3 ± 32.3) J/m2 for the stomach]. ACPs showed considerable cytocompatibility in vitro study, with a high level of cell viability for 3 d [(98.8 ± 1.2) % for LO2 and (98.3 ± 1.6) % for Caco-2]. It has comparable inflammation repair in a ruptured rat liver (P = 0.58 compared with suture closure), the same with intestinal anastomosis in rabbits (P = 0.40 compared with suture anastomosis). Additionally, ACPs-based intestinal anastomosis (less than 30 s) was remarkably faster than the conventional suturing process (more than 10 min). When ACPs degrade after surgery, the tissues heal across the adhesion interface. CONCLUSIONS: ACPs are promising as the adhesive for clinical operations and battlefield rescue, with the capability to bridge irregular tissue defects rapidly.

Manta Ray Inspired Soft Robot Fish with Tough Hydrogels as Structural Elements.

The design of soft robots capable of navigation underwater has received tremendous research interest due to the robots' versatile applications in marine explorations. Inspired by marine animals such as jellyfish, scientists have developed various soft robotic fishes by using elastomers as the major material. However, elastomers have a hydrophobic network without embedded water, which is different from the gel-state body of the prototypes and results in high contrast to the surrounding environment and thus poor acoustic stealth. Here, we demonstrate a manta ray-inspired soft robot fish with tailored swimming motions by using tough and stiff hydrogels as the structural elements, as well as a dielectric elastomer as the actuating unit. The switching between actuated and relaxed states of this unit under wired power leads to the flapping of the pectoral fins and swimming of the gel fish. This robot fish has good stability and swims with a fast speed (∼10 cm/s) in freshwater and seawater over a wide temperature range (4-50 °C). The high water content (i.e., ∼70 wt %) of the robot fish affords good optical and acoustic stealth properties under water. The excellent mechanical properties of the gels also enable easy integration of other functional units/systems with the robot fish. As proof-of-concept examples, a temperature sensing system and a soft gripper are assembled, allowing the robot fish to monitor the local temperature, raise warning signals by lighting, and grab and transport an object on demand. Such a robot fish should find applications in environmental detection and execution tasks under water. This work should also be informative for the design of other soft actuators and robots with tough hydrogels as the building blocks.

Global Vision-Based Formation Control of Soft Robotic Fish Swarm.

Possessing the attributes of high adaptability and low cost, soft robotic individuals can further coordinate and form into a swarming system, enhancing the performances as well as functions in practical applications. However, the formation control of soft robotic swarm remains challenging mainly due to the limitation in relatively low precision and slow response of the soft actuators. In this work, a soft robotic fish swarm system with global vision positioning was studied. The soft robotic fish used in the project is driven by a hybrid power-control system, in which the soft dielectric elastomers and the rigid electrical servo provide forward propulsion and controllable steering function, respectively. Results show that soft robotic fish swarm can quickly shift their formations, mimicking three typical swarming behaviors of natural creatures: highly parallel group, encircling, and torus. The system design and controlling principles of the soft robotic fish swarm may guide the future research of soft robots and robotic swarms, specifically for underwater applications.

Surgical Treatment for Odontoid Fractures in Patients with Long-Standing Ankylosing Spondylitis: A Report of 3 Cases and Review of the Literature.

BACKGROUND: Ankylosing spondylitis (AS) is classified as a chronic inflammatory seronegative rheumatic arthritis. Patients with AS are more likely to sustain a fracture of the cervical spine compared with the general population. Most fractures occur in the lower cervical spine and manifest at the level of the intervertebral disc. There have been few reports about the surgical treatment for upper cervical spine fractures in patients with AS, especially odontoid fractures. We present 3 cases of odontoid fracture in patients with long-standing AS. METHODS: Odontoid fracture with atlantoaxial displacement was identified on radiologic imaging in 3 patients. In 1 patient, fracture was a missed diagnosis after initial trauma, and the fracture and displacement were discovered 3 months later owing to aggravation of symptoms. Posterior occipitocervical fusion with iliac autograft was performed under general anesthesia in all cases. RESULTS: All 3 patients recovered postoperatively without any complications related to surgery. Cervical radiographs obtained at 12-month follow-up demonstrated healed fracture and replacement of the atlantoaxial joint. CONCLUSIONS: Odontoid fracture with atlantoaxial dislocation in patients with long-standing AS is uncommon. Clinicians must be cautious in assessing such patients with any episode of trauma. Computed tomography and magnetic resonance imaging can be helpful in demonstrating occult odontoid fractures. Posterior occipitocervical fusion with internal fixation may benefit these patients, although at the cost of sacrificing the last motion segment.

Soft Artificial Bladder Detrusor.

Developing soft devices for invasive procedures bears great importance for human health. The softness and large strain actuation of responsive hydrogels promise the potential to fabricate soft devices, which can attach on and assist to the function of organs. The key challenges lie in the fabrication of soft devices with robust actuating ability and biocompatibility to the attached organ. This paper presents a solution that integrates the thermoresponsive hydrogel membrane with flexible electronics and silk scaffold into a balloon-like soft device. As an example, the actuation assisting function of this soft device for shrinking an animal bladder is presented. The mechanical behaviors of the balloon-like soft device are experimentally and theoretically investigated. The concepts are applicable to other applications such as soft implants, soft robotics, and microfluidics.

A soft artificial muscle driven robot with reinforcement learning.

Soft robots driven by stimuli-responsive materials have their own unique advantages over traditional rigid robots such as large actuation, light weight, good flexibility and biocompatibility. However, the large actuation of soft robots inherently co-exists with difficulty in control with high precision. This article presents a soft artificial muscle driven robot mimicking cuttlefish with a fully integrated on-board system including power supply and wireless communication system. Without any motors, the movements of the cuttlefish robot are solely actuated by dielectric elastomer which exhibits muscle-like properties including large deformation and high energy density. Reinforcement learning is used to optimize the control strategy of the cuttlefish robot instead of manual adjustment. From scratch, the swimming speed of the robot is enhanced by 91% with reinforcement learning, reaching to 21 mm/s (0.38 body length per second). The design principle behind the structure and the control of the robot can be potentially useful in guiding device designs for demanding applications such as flexible devices and soft robots.