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Friction behavior and serious wear of the stator/slider pair are critical to restrict the development and commercialization of standing-wave linear ultrasonic motors. Owing to the effective friction regulation of laser surface microtextures, a multi-connected vesicle-like microarray consisting of the micropits and microgrooves was prepared on the slider surface. Finite element analysis at the microscale showed the proposed micro-textures were prone to cause the stator tip to sink, resulting in an increase of horizontal impact effect of ultrasonic vibration and the alternately regulating of static-dynamic friction boundary, which enhances the tangential force and improves the driving effect. The experimental results approved that the composite microtextures combining the pits of 100 μm and the grooves of 50 μm are positive for friction drive and output performance enhancement. Specifically, the output power of the low-voltage driving linear piezoelectric motor with the complex texturing array is 66% higher than that of non-textured ones. This study provides a reliable approach to enhancing the friction-driving performance and operation stability of piezoelectric motors or actuators. [Display omitted] [ABSTRACT FROM AUTHOR]

Coulomb friction model is modified with considering the preliminary distance of rigid bristles and shear stiffness of the contact surface. The degeneration in friction drive and wear behavior induced by nonlinear contact (i.e., impact, intermittent, and fretting) is outlined. Wear tests of LUSMs with V-shape transducers are conducted by a homemade reciprocating apparatus. Results show that chemical inertness, thermotolerance, elasticity as well as surface topography are critical for the contact interface of LUSMs A systematic approach involving, for instance, dynamic contact, friction model, and wear behavior provides new perspectives in improving service performances and promoting practical applications. [ABSTRACT FROM AUTHOR]

• A home-made measured simple system for output performances of linear piezoelectric motors were constructed. • A prototype of SWUMs is manufactured and the mechanical characteristics were tested. • A basic measurement approach for service performances of linear ultrasonic motors was presented. • Static and dynamic performances of linear motor can be measured simultaneously in real time. A prototype of the linear standing-wave ultrasonic motors having arc tip is designed and manufactured, and the output performances and mechanical characteristics were tested and evaluated using a home-made measured simple system in this study. Results show that the flexible design of the driving foot is interesting for the performance improvement and simplification design of standing-wave ultrasonic motors. The measured system is simple and is available to evaluate the output performances (thrust and speed) and mechanical characteristics curves of linear motors. The influence trend of preload and driving voltage on output speed is opposite, while the influence trend of thrust is parabola. The peak value of applied voltage is critical for the mechanical characteristic curve of piezoelectric motor. This study also supports a basic measurement approach for service performances of linear ultrasonic motors and the tribological behaviors of motor and/or actuator devices using piezoelectric vibration. [ABSTRACT FROM AUTHOR]

A homemade testing device is used to measure the operating speed of linear piezoelectric motors with different friction couples that consist of ceramic stator tip and slider. The dynamic variations of motor performance are analyzed using a statistical method, and the attenuation mechanism is discussed using the energy method during the periodic contact between the driving tip of the stator and the slider. Study of the operating characteristics of piezoelectric motors can clarify the change and transformation of the stator/slider contact by reflecting the driving process, wear, and service lifespan of the contact interface of friction couples under ultrasonic vibration. This study is significant for the performance evaluation of the operations and alternation of friction materials for standing-wave piezoelectric motors. • The dynamic variations of motor performance are analyzed using a statistical method. • The attenuation mechanism is discussed using the energy method during the periodic contact. • The factors to evaluate the steady-state operations of piezoelectric motors is defined. • Friction characteristics of ceramic couples are compared for SWUM operations. [ABSTRACT FROM AUTHOR]

• A measuring system for electromechanical multi-parameters of linear piezoelectric motors was constructed. • Signal conditioning and measurement circuits were designed for physical signals processing, A/D conversion, and transmission. • The principle and structures of the synchronous testing system were demonstrated based on the virtual instrument. • The calculation principle of the transient characteristic of multi-parameters of piezoelectric motors was proposed. Due to the time-dependent correlations, the measurement and characterization of electronic and mechanical parameters are critical for linear piezoelectric ultrasonic motors (USMs) during the running process. This study constructed a homemade system to measure the electromechanical multi-parameters and kinetics performances agilely, transiently, and synchronously. The principles and structures of the test system were demonstrated based on virtual instrument technology. A signal conditioning circuit is designed and used for physical signal processing, A/D conversion, and transmission. The difference in resonant frequencies was discovered for the synchronization acquisition of mechatronic parameters, and the instantaneous characteristics of electromechanical parameters for SWUM (e.g., driving voltage, input current, thrust force, and speed during the start-up and power-off process) were established based on the experimental data. This study is significant for the measurement/evaluation of the dynamic and transient performances of linear piezoelectric motors and actuators. [ABSTRACT FROM AUTHOR]

• T-phage-inspired multilegged design for microrobot. • A rotationally asymmetric structure. • Multiple working modes: forward motion, backward motion, steering, climbing, and swimming. • The maximum velocity of 120 mm/s under a driving voltage of 50 V p-p and the maximum carrying weight of 10.6 gs, 6 times more than the weight of the microrobot. • Miniaturization capability and ability to work in various environments, i.e., a narrow tube and water. T-phages use contractile tails to recognize host bacterial and move on the surface of bacterial. This virus demonstrates remarkable locomotive capabilities in recognition and infection progress. The field of microrobotics focuses on achieving these functions in mobile robotic systems of centimeter size. However, owing to the structure size and weight, it has been a challenge to satisfy high robustness, fast motion, adequate carrying capacity, low driving voltage, and versatile environmental adaptability in one robot. In addition, functional microrobots require multimodal locomotive strategies that reconcile the constraints imposed by different applications. Inspired by the unique structure of T-phage in the micro-world, we develop a T-phage Mimic MicroRobot (TMMR), which is composed of a triangular prism core with piezoelectric elements and legs attached on bases, mimicking the core and the tail fibers of the T-phage, respectively. The triangular prism structure avoids rollover while moving, indicating the robustness of the design. TMMR of 2.5 × 2.5 × 2.6 mm3 weighs 1.74 gs and can be easily further miniaturized. It is capable of moving forward, backward, and steering at a low voltage of 25 V. Working mechanisms for each type of motion are analyzed using the finite element method. Results show that TMMR reaches 120 mm/s, 4.8 body lengths per second (BL/s), and carry an object weighing 10.6 gs, 6 times more than its weight. By sealing the body and adding passive flaps, TMMR achieves a "swimming" motion with a velocity of 16 mm/s. TMMR shows potential for versatile applications in a narrow and constrained environment. [Display omitted] [ABSTRACT FROM AUTHOR]

• The effects of laser parameters on the surface temperature field were evaluated. • The phase transition in the processed region was analytically modelled. • The effects of the process parameters on the geometrical features were analyzed. Surface micro-texturing paves the way for surface functionalization of material and engineering parts with abrasion resistance, hydrophilicity, anti-reflectivity, and antimicrobial properties. Nevertheless, the morphological control of micro-textures with high precision and efficiency is still challenging for advanced applications, especially for lightweight design and corrosion resistance in aerospace and transportation. Despite many stumbling blocks in achieving high-precision micro-textures, the serviced surface properties relate to their surface asperities and micro-textures. Laser surface texturing can be used for surface-functionalization and structuration control of counterparts with textured micro-pits and micro-grooves. With the interaction of pulse laser and materials, the influence of the laser process on the geometrical configuration of the alloy's surface micro-textures was investigated by altering the laser processing parameters. We found that the depth and width of micro-textures are positively correlated with the laser power and scanning times, and negatively correlated with the laser frequency and scanning speed. This research is significant in enabling the active design of non-ferrous metal surface micro-textures, regulating surface properties, and enhancing unique applications in mechanics, biology, medicine, and physiochemistry fields. [ABSTRACT FROM AUTHOR]

Despite good approval for excellent friction regulation, surface texturing seems to be a penalty area for gears mostly because of the traditional cognition of surface (micro-)pitting and structural similarity. Surface micro-textures were applied to the pinion flank to regulate the time-varying meshing stiffness and enhance the meshing characteristics. Results showed the stress regulation and smoothing capability of micro-textures in meshing process, the time-varying meshing stiffness increases by 4.75% and the frictional stability increased by 52%. Experiment results approve that the flank micro-textures can control friction and reduce torque by 26.2%. This study is significant for the systemic design of the dynamic performance and frictional meshing, especially for the gear engagement reliability in space without film lubrication. [Display omitted] • Surface pitting-like micro-textures were preset on flank surfaces of spur gears. • The symmetrical and continuous micro-textures near the pitch line were compared. • The micro-textures are capable to improve the meshing stiffness of gears. • Stress on flanks is rearranged for homogenize distribution after micro-texturing. • Micro-textures regulate the dynamic friction and increase friction stability. [ABSTRACT FROM AUTHOR]

Epoxy resin (EP) as a friction material suffers from serious friction and wear in high temperatures. Adding various carbon fillers into EP to form carbon/EP composites is one of the solutions to this concern. However, the correlation between the filler's dimensionality and their friction properties under high temperature conditions is missing. Herein we construct a comparable dimensional model system of carbon fillers (i.e., one- to three-dimensional carbon nanocage assemblies) to reveal the dimensional effect in high temperature lubrication. Compared with EP, a merely 0.10 wt% of one-dimensional filler can reduce the composite's friction coefficient and wear rate by 36% and 95% at 30 °C, respectively; while for those filled with other dimensionalities, the corresponding decreases are less than 24% and 60%. Even at very close to EP's glass transition temperature of 150 °C, it still maintains a low friction coefficient only with a slight increase in wear. The enhanced high temperature lubrication performance is first attributed to the advantage of one-dimensional fillers to suppress the EP matrix's creep and then easily sliding in the softened transfer film. This study provides a new view for the design of carbon fillers used in EP-based high temperature lubrication composites. [Display omitted] • A comparable dimensional model system for carbon fillers is fist constructed. • The dimensional effect of carbon fillers in EP is demonstrated and explained. • EP filled one-dimensional filler has the best high-temperature lubrication property. • Optimized carbon/EP has a maximum friction application temperature of 150 °C. • The possible high temperature friction mechanism of carbon/EP is revealed. [ABSTRACT FROM AUTHOR]

• A new filler of carbon nanocage is first proposed for epoxy resin nanocomposite. • Carbon nanocage filler shows prominent physical confinement and self-lubrication. • Relative to neat epoxy, wear rate is reduced by 51.9% for the optimized sample. • Friction coefficient is reduced by 55.6% for the optimized sample. • The performances are attributed to the unique hollow structure of carbon nanocage. Epoxy resin (EP) nanocomposite materials with excellent tribological properties are highly desired for many engineering applications requiring low friction and wear. Adding carbon nanofiller is regarded as one of the most potential solutions to solve the serious dry wear problem of epoxy matrix. Herein, we report a new filler of carbon nanocages (CNC) prepared by the method of MgO templates to improve its dry friction performance through filling epoxy into the internal hollow space of CNC. Relative to neat epoxy, the friction coefficient (0.249) and wear rate (7.98 × 10−7 mm3 Nm−1) are reduced by 55.6% and 51.9% for the optimized CNC/EP nanocomposites, respectively. Even compared to typical graphene/epoxy nanocomposites, the wear rate is also reduced by up to 21.8%, as well as greatly enhancing the mechanical properties, thereby effectively protecting epoxy matrix and improving its dry friction. Such great tribological performance is attributed to unique structure of CNC, enabling the multi-functional collaboration of physical confinement, self-lubrication and wear-debris collection for CNC fillers, and making it the most potential carbon-based nanofiller for EP-based nanocomposite material system. More than that, it also provides insights for designing other advanced carbon-based nanofillers. [ABSTRACT FROM AUTHOR]