The interface between nanoscale films plays a very important role in semiconductor industry. In this paper, the interfacial thermal resistance (Kapitza resistance) of a crystalline and amorphous silicon carbide (SiC) heterojunction has been investigated by using molecular dynamics simulations. It is found that Kapitza resistance at crystalline and amorphous SiC interface depends on the interfacial coupling strength remarkably. Kapitza resistance in the strong interfacial coupling is significantly lower than that in weak coupling. The thickness of the heterojunction and temperature dependence of Kapitza resistance have also been examined. The results have shown that the Kapitza resistance decreases monotonically with the increase of temperature (from 300K to 800K). Moreover, Kapitza resistance can be effectively tuned by cross-plane strain. A 5% compressive strain is able to reduce the Kapitza resistance by 380% in weak coupling case. In contrast, a 5% tensile strain can increase Kapitza resistance by 13%. Our study provides useful guidance to the thermal management and heat dissipation across nanoscale crystalline and amorphous silicon carbide interface, in particular, for the design of silicon carbide nanowire based nano electronics devices.
Flexible electronics have revolutionized the field by overcoming the rigid limitations of traditional devices, offering superior flexibility and adaptability. Conductive ink performance is crucial, directly impacting the stability of flexible electronics. While metal filler-based inks exhibit excellent conductivity, they often lack mechanical stability. To address this challenge, we present a novel conductive ink utilizing a ternary composite filler system: liquid metal and two micron-sized silver morphologies (particles and flakes). We systematically investigated the influence of filler type, mass ratio, and sintering process parameters on the composite ink's conductivity and mechanical stability. Our results demonstrate that flexible wires fabricated with the liquid metal/micron silver particle/micron silver flake composite filler exhibit remarkable conductivity and exceptional bending stability. Interestingly, increasing the liquid metal content results in a trade-off, compromising conductivity while enhancing mechanical performance. After enduring 5000 bending cycles, the resistance change in wires formulated with a 4:1 mass ratio of micron silver particles to flakes is only half that of wires with a 1:1 ratio. This study further investigates the mechanism governing resistance variation during flexible wire bending. Additionally, we observed a positive correlation between sintering temperature and pressure with the conductivity of flexible wires. The significance of sintering parameters on conductivity follows a descending order: sintering temperature, sintering pressure, and sintering time. Finally, we demonstrate the practical application of this technology by integrating the composite ink-based flexible wires with conductive polymer-based strain sensors. This combination successfully achieved the detection of human movements, including finger and wrist bending.
The authors demonstrate that the micro magneto-rheological fluid device is designed by the method of outer magnetic coil to generate a mechanical loading less than 20 N. The results confirm that the method can obtain miniature device easily and control the magnetic field conveniently. The magnetic field, the channel gap, and the initial position of valve plug were optimized by finite element simulation and experimental test. Additionally, an impact force at the beginning can be eliminated by using a modeled synchronous linear current, which indicates that the micro-magnetorheological fluid damper has good soft-landing performance.
For the purpose of process R&D on inter-die vertical connection for 3D integration, the role of ultrasonic vibration in forming a low-temperature bonding joint needs to be studied in-depth. Rather than focusing on the ultrasonic-induced interfacial reactions by molten solder, this study used low power ultrasonics to bond solder with flat Ni and microcone-structured Ni substrates respectively under solid state temperature, and interpreted the mechanisms of ultrasonics functioning on the formation of interfacial adhesion. Results of joint shear tests and interfacial observations showed that ultrasonics worked in totally different ways on two types of Ni surfaces, the transverse vibration could either promote microscopic contact between two sides, or deteriorate the joint strength if lasted too long, depending on the type of Ni used. The effect of frictional heating brought by ultrasonics on bonding formation was less prominent.
In order to search for reasonable air-conditioned indoor control variables and save energy consumption and meet to need of personal thermal comfort,a method which is based on numerical simulation is employed to optimize indoor control variables.Computational fluid dynamics(CFD)is used to describe thermal state of office.An optimal method is proposed in this paper,dual neural network model is firstly used to acquire reliable information,data from CFD model are pre-processed,and the remaining data are used to train artificial neural networks(ANN),then CFD model is replaced by ANN model to reduce computational cost when is optimized,indoor control variables are optimized by genetic algorithm.Simulation results show that indoor thermal comfort is improved obviously,and the energy cost is decreased accordingly.
Abstract Conductive polymer composites (CPCs) are vital and indispensable for the emerging field of soft electronics. In this work, a new strategy for using carbon nanotubes (CNTs)/carbon nanofibers (CNFs) and liquid metal droplets as multiphase hybrid fillers for CPCs is presented. We found that CPCs with multiphase hybrid conductive fillers had advantages in electromechanical properties over those with single solid-phase conductive fillers. CNTs/CNFs can easily form conductive paths in the polymer due to their excellent electrical conductivity with large aspect ratio. Self-repair of conductive networks was realized since the exposed Galinstan under strains could bridge the gap between CNTs/CNFs to form new conductive pathways. In addition, the influences of the size and content of conductive fillers on the electromechanical properties of CPCs were investigated. We found CPCs with liquid metals can be served as a flexible strain sensor under mild strain, while as a conductor under large strain due to the robust stability of resistance, which has not been reported yet in the literature. The CPCs presented in this work could provide potential applications in wearable electronics and flexible electronics.
Mine seismic monitoring has been a kind of effective method for preventing rock-burst.Mainly through the arrangement of the mining area rock-burst monitoring system,it recorded the mine earthquake seismic wave,then processed and analyzed the seismic wave form,thus determined location and energy size of the rock-burst seismic source.Based on Matlab software,and through wavelet analysis of rock-burst signal,according to continuous wavelet transform to detect mutant site of the signals,thus it able to determine the original time of the rock-burst signal P-wave.Finally,it can effectively get rid of the noise from rock-burst signal through wavelet denoising.
Benefit from the development of micro/nano manufacturing and flexible electronics technology, soft micro-actuators which could be potentially applied in drug delivering and environment monitoring have developed rapidly in recent years. Due to the simplicity of fabrication process and flexibility of control strategies, magnetic-controlled soft actuators based on magnetic-responsive composites have attracted intensive interests. In literature, lots of works focus on the structure and manufacturing process of the micro-actuators in order to enhance their driving performance. However, as fully soft micro-actuators, the driving efficiency of the soft parts is comparatively low, and the stability is poor in a liquid environment. In this work, a micro-actuator combined with rigid and flexible parts was presented to improve the driving force as well as the stability. We proposed a method of using substrates with higher stiffness to manufacture the nonuniform stiffness composites. The magnetic unit is made of magnetic particles mixed with rigid substrate, and then embedded in or connected with the flexible body. Following this strategy, the rigid sections take responsible for quick magnetic response while the soft area have desired deformation performance. Firstly, the magnetic response of magnetic composite made of epoxy resin was analyzed. Then, hysteresis loop test was deployed to investigate the effect of magnetic particle concentration on magnetic properties. Furthermore, the deformation of the composite actuator is analyzed by simulation with respect to the different positions and quantity of the rigid parts. Finally, the fabricated soft micro-actuator is controlled by external magnetic field to demonstrate the potential applications. It was believed that the combination of rigid and flexible components in micro electro mechanical system is beneficial to improve the driving ability and broaden the application range of micro actuators.
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