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Flexible materials with ideally designed structures and properties through direct ink writing (DIW) offer vast potential for flexible wearable devices, sensors, soft robots, and so on. Despite its common use as a flexible material, Sylgard‐184's poor rheological properties restrict its ability of printing precision models by DIW. Herein, we have improved the viscosity of Sylgard‐184 by adding suitable crosslinkers and silica, which produce inks with high printing quality and a low slump rate (3.75%). In addition, the DIW printing process was investigated, and a theoretical model relating to the basic printing parameters was developed. With the model, it is possible to predict printing parameters for various elastomers. To further demonstrate the application of this strategy to flexible wearable devices, a sensor was printed. The sensor allowed real‐time monitoring of bending angles through bending angle tests. A change from 0 to 135° was detected using this bending sensor. We believe that the results of this research will provide ideas for the high‐quality printing of silicone elastomers. [ABSTRACT FROM AUTHOR]

Although huge attentions are paid to the bionic robot research, preparing flexible actuators with high sensitivity, fast response, and long lifespan are still in great challenge. Herein, an enhanced actuator based on the ionic polymer–metal composite (IPMC) and carboxylic multi‐walled carbon nanotubes (CMWCNTs) is presented. The nanoscale decoration of MWCNT materials leads to the effectively application of doped and decorated carbon‐based devices for actuators. In the study, morphologies of CMWCNTs are evaluated with transmission electron microscope (TEM) and scanning electron microscope (SEM). By the home‐setup platform, the electrical conductivity and driving performance are evaluated. Using tensile‐testing machine, mechanical properties, such as the elastic modulus and tensile strength, are assessed. Results show that performances including electronic, mechanical, and driving activities of the ionic polymer–metal composite actuator are significantly improved. The maximum output force and sensitivity of the actuators are increased at rates of 24% and 130%, respectively. The mechanism is attributed to carboxylic groups in the acceleration of hydrated cations movement. Additionally, the surface conductivity, mechanical strength, and dispersion are far superior to those walled carbon nanotubes (WCNT)‐doped actuators reported previously. IPMC‐embedded nanotube designs provide a high potential for the development of robotic‐assisted manipulations, such as biomedical robots and microelectromechanical systems. [ABSTRACT FROM AUTHOR]

In the study, the hydrogen‐free diamond‐like carbon (DLC) coating was deposited on the surface of the Co‐Cr‐Mo alloy. Pin‐on‐plate tribotests were performed for the DLC‐coated CoCrMo specimen against un‐doped CoCrMo alloy under bovine serum albumin (BSA), NaCl solution, and distilled water. Results showed that the average coefficient of friction (COF) of the mating system was 0.08 under NaCl and 0.07 under distilled water, respectively. However, the dynamic COF under BSA lubrication was prone to increasing with testing time, and the average COF got to 0.12. The wear morphology of the pin was covered by the carbon transfer layer without BSA lubrication, and the formation of the transfer layer was a dynamic evolution process as wear debris adhesion, continuous transferring, and delamination. Oppositely, the transfer layer was inhibited under BSA lubrication due to the adsorption of the protein layer on the contact interface. [ABSTRACT FROM AUTHOR]

ABSTRACT: Injection of bionic synovial fluid (BSF) is a conventional method to improve the lubricity of artificial joints, but BSF cannot maintain long due to the dilution and degradation of BSF in human body. To prolong the effectiveness of hyaluronic acid (HA), which is the major component of BSF, this study applies a temperature‐sensitive poly(ɛ‐caprolactone)–poly(ethylene glycol)–poly(ɛ‐caprolactone) (PCEC) hydrogel loaded with HA to achieve long‐term lubrication. In addition, Fourier transform infrared, nuclear magnetic resonance analysis, X‐ray diffraction, scanning electron microscopy (SEM), and gel permeation chromatography spectra were used to analyze the structure of the synthetic hydrogel. Rheological test and test tube inverting method were used to characterize the thermosensitivity. The lubrication properties of the released solution were characterized by UV–vis, tribological tests, SEM, and 3D laser confocal scanning microscope. The experimental results reveal that the triblock PCEC hydrogel contains both hydrophilic block and hydrophobic block, and both PCEC and PCEC/HA hydrogels have phase‐changed effect when the temperature increases from room temperature to body temperature. Moreover, the friction coefficient of the released solution from PCEC/HA hydrogel is approximatively 38% lower than that of phosphate buffer saline. And the ability of shear resistance and creep recovery of PCEC/HA hydrogel are better than that of PCEC hydrogel. This study provides an effective approach to achieve long‐time lubrication effect for artificial joints. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46228. [ABSTRACT FROM AUTHOR]

3D printing has shown promise in the development of notable sensing and health detection devices. Nonetheless, challenges remain in the concurrent development of highly durable wearable sensors with low‐friction surfaces. This challenge serves as a limiting factor in the operational lifespans of these sensors. In this study, a magnetically assisted 3D printing technique is developed to fabricate composites reinforced with magnetic Fe3O4@SiO2 nanochains (NCs) with dimensions of 60.2 µm in length (L) and 0.2 µm in diameter (D), indicating an L:D ratio exceeding 300. By applying a vertical magnetic field and extrusion flow field to the sensor's surface layer, the NCs can be arranged differently (together with the printed textures), reducing the coefficient of friction by 27.7% and improving the wear resistance. This approach is inspired by nacre, known for its impressive durability and resilience. A motion monitoring sensor with an extended lifespan is successfully fabricated by using liquid metal ink integrated with an anti‐wear layer. These findings offer significant insights into the evolution of wearable sensors, demonstrating their adaptability to multi‐material printing and resulting in improved performance and service lives. [ABSTRACT FROM AUTHOR]