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Researchers have been studying the pain sensation extensively in the past few decades. Quantitative simulation and theoretical modeling of pain sensation based on experimental results are necessary for pain research. Many theories have been proposed to explain the mechanism of pain from molecular, cellular, and neuron network perspectives. But some phenomena in pain sensation are not fully understood, including wind-up and ramp-off. This paper focused on the theoretical model of wind-up and ramp-off phenomena in the pain sensation. With the addition of the transduction model, the generation mechanism of wind-up and ramp-off is better explained. The simulations were carried out to analyze the skin pain sensation under the mechanical stimulus, consisting of four different parts: the mechanical model of skin, transduction, transmission, modulation, and perception. The stress distribution on the skin was obtained based on the elastic theory. And the modified Hodgkin and Huxley model and the mathematical model of gate control theory were utilized to analyze the process of transduction, modulation, and perception, respectively. The numerical experiments demonstrated the wind-up occurs with a frequent stimulus of 1 Hz and 2 Hz, and ramp-off appears with the withdrawal of constant mechanical stimulus, which could contribute to the understanding of the pain sensation mechanism.

Epidermal electronic systems (EESs) are a representative achievement for utilizing the full advantages of ultra-thin, stretchable and conformal attachment of flexible electronics, and are extremely suitable for integration with human physiological systems, especially in medical hyperthermia. The stretchable heater with stable electrical characteristics and a uniform temperature field is an irreplaceable core component. The inorganic stretchable heater has the advantage of maintaining stable electrical characteristics under tensile deformation. However, the space between the patterned electrodes that provides tensile properties causes uneven distribution of the temperature field. Aiming at improving the temperature distribution uniformity of stretchable thermotherapy electrodes, an orthotropic heat transfer substrate for stretchable heaters is proposed in this paper. An analytical model for transient heat conduction of stretchable rectangular heaters based on orthotropic transfer characteristics is established, which is validated by finite element analysis (FEA). The homogenization effect of orthotropic heat transfer characteristics on temperature distribution and its evolutionary relationship with time are investigated based on this model. This study will provide beneficial help for the temperature distribution homogenization design of stretchable heaters and the exploration of its transient heat transfer mechanism.

Compared with other physiotherapy devices, epidermal electronic systems (EES) used in medical applications such as hyperthermia have obvious advantages of conformal attachment, lightness and high efficiency. The stretchable flexible electrode is an indispensable component. The structurally designed flexible inorganic stretchable electrode has the advantage of stable electrical properties under tensile deformation and has received enough attention. However, the space between the patterned electrodes introduced to ensure the tensile properties will inevitably lead to the uneven temperature distribution of the thermotherapy electrodes and degrade the effect of thermotherapy. It is of great practical value to study the temperature uniformity of the stretchable patterned electrode. In order to improve the uniformity of temperature distribution in the heat transfer system with stretchable electrodes, a temperature distribution manipulation strategy for orthotropic substrates is proposed in this paper. A theoretical model of the orthotropic heat transfer system based on the horseshoe-shaped mesh electrode is established. Combined with finite element analysis, the effect of the orthotropic substrate on the uniformity of temperature distribution in three types of heat source heat transfer systems is studied based on this model. The influence of the thermal conductivity ratio in different directions on the temperature distribution is studied parametrically, which will help to guide the design and fabrication of the stretchable electrode that can produce a uniform temperature distribution.

As thermal protection substrates for wearable electronics, functional soft composites made of polymer materials embedded with phase change materials and metal layers demonstrate unique capabilities for the thermal protection of human skin. Here, we develop an analytical transient phase change heat transfer model to investigate the thermal performance of a wearable electronic device with a thermal protection substrate. The model is validated by experiments and the finite element analysis (FEA). The effects of the substrate structure size and heat source power input on the temperature management efficiency are investigated systematically and comprehensively. The results show that the objective of thermal management for wearable electronics is achieved by the following thermal protection mechanism. The metal thin film helps to dissipate heat along the in-plane direction by reconfiguring the direction of heat flow, while the phase change material assimilates excessive heat. These results will not only promote the fundamental understanding of the thermal properties of wearable electronics incorporating thermal protection substrates, but also facilitate the rational design of thermal protection substrates for wearable electronics.

Skin pain resulting from mechanical compression is one of the most common pains in daily life and the indispensable information for electronic skin to perceive external signals. The external mechanical stimuli are transduced into impulses and transmitted via nerve fiber, and finally, the sensation is perceived via the procession of the nerve system. However, the mathematical mechanism for pain sensation due to mechanical stimuli remains unclear. In this paper, a mathematical model for skin pain sensation under compression is established, in which the Flament solution, the revised Hodgkin–Huxley model, and the mathematical model gate control theory are considered simultaneously. The proposed model includes three parts: a mechanical model of skin compression, a model of transduction, and a model of modulation and perception. It is demonstrated that the pain sensation degree increases with the compression amplitude and decreases with deeper nociceptor location in the skin. With the help of the proposed model, the quantitative relationship between compression pain sensation and external mechanical stimuli is revealed, which has a significant benefit in promoting the design and mechanism research of electronic skin with pain perception function.

Microelectromechanical systems (MEMS) that are based on flexible substrates are widely used in flexible, reconfigurable radio frequency (RF) systems, such as RF MEMS switches, phase shifters, reconfigurable antennas, phased array antennas and resonators, etc. When attempting to accommodate flexible deformation with the movable structures of MEMS, flexible RF MEMS are far more difficult to structurally design and fabricate than rigid MEMS devices or other types of flexible electronics. In this review, we survey flexible RF MEMS with different functions, their flexible film materials and their fabrication process technologies. In addition, a fabrication process for reconfigurable three-dimensional (3D) RF devices based on mechanically guided assembly is introduced. The review is very helpful to understand the overall advances in flexible RF MEMS, and serves the purpose of providing a reference source for innovative researchers working in this field.

As phase change functional polymer composites, polydimethylsiloxane (PDMS) and paraffin composites exhibit excellent performance on temperature dependent thermal and mechanical properties. In this paper, PDMS/paraffin composites with uniform microstructure are prepared by the melting mixing method with paraffin as filler and PDMS as matrix. The modification of PDMS by paraffin components owns both advantages on excellent flexibility and heat absorption capacity. Systematic experiments results are performed to illustrate the DSC specter, stress-strain curves and other properties varying with temperature. The obtained composites can be an ideal material for soft thermal management substrate of flexible electronics or phase change heat sink of batteries and this study might be helpful for the design and fabrication in the wide potential applications. Keywords: Phase change polymer composites, Thermal properties, Thermal management, Mechanical properties, Temperature sensitive

The concept of mimicking natural materials to design novel lightweight structures with high capacity of energy absorption is of great interest at present. Enormous natural structures exhibit fascinating mechanical performance after hundreds of millions of years of convergent evolution. Odontodactylus scyllarus, known as the peacock mantis shrimp, whose dactyl strike is recognized as one of the rapidest and powerful creatures found in nature, has an enormous potential to act as excellent biomimetic protective system. In this paper, a novel lightweight bio-inspired double-sine corrugated (DSC) sandwich structure has been proposed to enhance the impact resistance. The out-of-plane uniform compression of the bio-inspired bi-directionally sinusoidal corrugated core sandwich panel has been conducted under the quasi-static crushing load. Compared with the regular triangular and sinusoidal corrugated core sandwich panels, the bio-inspired DSC core sandwich panels significantly improve the structural crashworthiness as well as reducing the initial peak force greatly. Finally, the influences of the wave amplitude, wave number and corrugated core layer thickness on the mechanical performance of the bio-inspired DSC core sandwich panel are investigated to seek for the appropriate structural parameters to optimize the energy absorption behavior. Keywords: Bio-inspired, Sandwich structure, Crashworthiness, Energy absorption, FE simulation

EAST upper divertor has been upgraded to ITER-like actively-cooled W/Cu components in May 2014. In the manufacture, assembling and disassembling of this W/Cu divertor, it was found that more than 10 support legs have dropped from the W/Cu-monoblock. In this work, the welding technique and drop reason of the support leg have been summarized and analyzed. To replant the dropped legs, some weld methods, including the middle-temperature brazing, electric resistance welding and 3D printing, have been performed and compared. Finally, the replantation technique based on 3D printing with laser beam has been developed and the nickel leg has successfully been printed on W block without the copper interface. In the development of the replantation technique, the microstructure and mechanical properties of the nickel leg have been researched to modify the printing technique. It is considered that this replantation technique also could be used in the ITER W divertor project.

In order to avoid the occurrence of two types of longitudinal defects (strain localization and folding flaws), which were observed in the CuCrZr tubes of EAST W/Cu upper divertor components, in the future manufacturing of monoblock components using hot isostatic pressing (HIP), a new CuCrZr tube forming protocol is proposed. The evolution of Cu grains and Cr-rich particles is monitored by scanning electron microscopy throughout the new tube forming processes. The final microstructures of the newly developed tubes are totally different from those of the EAST project previously chosen tubes and the elongation of Cr-rich precipitates has been substantially suppressed by using the new tube forming protocol. The newly developed tubes show better HIP performance than the EAST previously chosen ones. Since circumferential mechanical properties, especially ductility, are of great importance, a circumferential ductility testing manner for small-diameter tubes, which might be a supplement to longitudinal tensile testing, has been utilized and the preliminary testing results are given. The recrystallization behavior of the newly developed tubes is also investigated.

In the development of EAST actively cooled W/Cu components, the ITER-grade CuCrZr has been chosen as the heat sink material for its good thermomechanics properties. To realize the seal joint of the heat sink, a large number of electron beam welding (EBW) of CuCrZr/CuCrZr or CuCrZr/Inconel625 has been carried out. In the quality control of the W/Cu components, the helium leak detection at thermal condition has been performed on the entire components before delivery. However, in the operation of EAST device some micro leak on the components was detected indicating that the helium leak detection under present standard was unreliable for the quality control. Therefore, the ultrasonic non-destructive testing technique was introduced to exclude the defects. In addition, the welding shrinkage and bending has also been investigated to meet the required tight tolerances for plasma-facing components in vacuum vessel.

A hot isostatic pressing (HIP) route has been developed by the Institute of Plasma Physics of the Chinese Academy of Sciences in collaboration with the Advanced Technology & Materials Co., Ltd. for...

Two forms of axial strain localization of CuCrZr tubes, i.e., cracking and denting, were observed during the manufacturing of ITER-like mono-block W/Cu components for EAST employing hot isostatic pressing (HIP). Microscopic investigations indicate that the occurrence of axial strain localization correlates to the heavily deformed Cu grains and elongated Cr-rich precipitates as well as highly anisotropic microstructures, which impair the circumferential ductility. Annealing the as-received tubes at 600 °C alleviates cracking due to partial recrystallization of Cu grains. However, the annealed tubes are still sensitive to wall thinning (caused by non-uniform polishing or tube bending), which results in denting. Denting may cause bonding flaws at CuCrZr/Cu interfaces and the underlying mechanisms are discussed. To some extent, denting seems do not affect the high heat flux performance of components. In this paper, we demonstrate that testing only the axial mechanical properties is not enough for manufacturers who use HIP or hot radial pressing technologies, especially for those anisotropic tubes.

Recently, the EAST W/Cu divertor components, including the ITER-like monoblock W/Cu units and flat-type W/Cu units, have been developed by Institute of Plasma Physics, Chinese Academy of Sciences (...