Electronic textiles capable of sensing, powering, and communication can be used to non-intrusively monitor human health during daily life. However, achieving these functionalities with clothing is ...challenging because of limitations in the electronic performance, flexibility and robustness of the underlying materials, which must endure repeated mechanical, thermal and chemical stresses during daily use. Here, we demonstrate electronic textile systems with functionalities in near-field powering and communication created by digital embroidery of liquid metal fibers. Owing to the unique electrical and mechanical properties of the liquid metal fibers, these electronic textiles can conform to body surfaces and establish robust wireless connectivity with nearby wearable or implantable devices, even during strenuous exercise. By transferring optimized electromagnetic patterns onto clothing in this way, we demonstrate a washable electronic shirt that can be wirelessly powered by a smartphone and continuously monitor axillary temperature without interfering with daily activities.
Networks of sensors placed on the skin can provide continuous measurement of human physiological signals for applications in clinical diagnostics, athletics and human-machine interfaces. Wireless and ...battery-free sensors are particularly desirable for reliable long-term monitoring, but current approaches for achieving this mode of operation rely on near-field technologies that require close proximity (at most a few centimetres) between each sensor and a wireless readout device. Here, we report near-field-enabled clothing capable of establishing wireless power and data connectivity between multiple distant points around the body to create a network of battery-free sensors interconnected by proximity to functional textile patterns. Using computer-controlled embroidery of conductive threads, we integrate clothing with near-field-responsive patterns that are completely fabric-based and free of fragile silicon components. We demonstrate the utility of the networked system for real-time, multi-node measurement of spinal posture as well as continuous sensing of temperature and gait during exercise.
The internal structure of many aero-engines is designed with a dual-rotor system. Up to now, there have been few studies on the influence of aerodynamic excitation on the dual-rotor system. The ...phenomenon of synchronous impact may occur when the frequency of the aerodynamic excitation force of the fan blade is close to the characteristic frequency of the inter-shaft bearing. This paper investigates the dynamic characteristics of a dual-rotor system under the condition of synchronous impact. The system's motion equations are formulated considering the complex nonlinearities of the inter-shaft bearing, such as Hertz contact force of 10/9 exponential function, clearance, and periodic varying compliance. In addition, the inter-shaft bearing with a local defect is considered. The fan blade's aerodynamic excitation force is modeled by synthesizing multiple harmonic excitation forces, the amplitudes of which are obtained by the Fourier series expansion. Numerical simulations are employed to get the dynamic responses of the system. The results show that the dynamic characteristic of the dual-rotor system at the primary resonance caused by the high-pressure (H.P.) rotor is not changed by the aerodynamic excitation force, while the primary resonance caused by the low-pressure (L.P.) rotor increases significantly. However, three aerodynamic resonances of the amplitude-frequency response of the dual-rotor system are emerging in the low-frequency region (124, 146 and 186 rad/s). When the synchronous impact phenomenon occurs, the amplitude of the three resonance peaks will increase twice compared to the original status, leading to a doubled increase in the dynamic load of the inter-shaft bearing. The characteristics of the dual-rotor system affected by the parameters such as initial phase difference of local defect, rotor eccentricity of system, clearance of inter-shaft bearing, and the stiffness and damping of supports are discussed in detail. The results obtained provide a deep insight into the mechanism of synchronous impact.
The harmonic balance method (HBM) is one of the most widely used methods in solving nonlinear vibration problems, and its accuracy and computational efficiency largely depend on the number of the ...harmonics selected. The adaptive harmonic balance (AHB) method is an improved HBM method. This paper presents a modified AHB method with the asymptotic harmonic selection (AHS) procedure. This new harmonic selection procedure selects harmonics from the frequency spectra of nonlinear terms instead of estimating the contribution of each harmonic to the whole nonlinear response, by which the additional calculation is avoided. A modified continuation method is proposed to deal with the variable size of nonlinear algebraic equations at different values of path parameters, and then all solution branches of the amplitude-frequency response are obtained. Numerical experiments are carried out to verify the performance of the AHB-AHS method. Five typical nonlinear dynamic equations with different types of nonlinearities and excitations are chosen as the illustrative examples. Compared with the classical HBM and Runge-Kutta methods, the proposed AHB-AHS method is of higher accuracy and better convergence. The AHB-AHS method proposed in this paper has the potential to investigate the nonlinear vibrations of complex high-dimensional nonlinear systems.
Electronic textiles (e-textiles) are fabrics that can perform electronic functions such as sensing, computation, display, and communication. They can enhance the functionality of clothing in a ...variety of convenient and unobtrusive ways, thus have garnered significant research and commercial interest in applications ranging from fashion to healthcare. Recent advances in materials science and electronics have given rise to variety of e-textile components, including sensors, energy harvesters, batteries, and antennas on flexible and breathable textiles substrates. In this review, we discuss recent advances in the development of e-textiles for energy, sensing, and communication. In addition, we investigate challenges in the integration of components to realize e-textile systems, and highlight opportunities enabled by innovations in materials science, engineering, and data science.
Display omitted
Applied sciences, Signal processing in communications, and Wireless sensor.
Wearable optoelectronic devices can interface with the skin for applications in continuous health monitoring and light-based therapy. Measurement of the thermal effect of light on skin is often ...critical to track physiological parameters and control light delivery. However, accurate measurement of light-induced thermal effects is challenging because conventional sensors cannot be placed on the skin without obstructing light delivery. Here, we report a wearable optoelectronic patch integrated with a transparent nanowire sensor that provides light delivery and thermal monitoring at the same location. We achieve fabrication of a transparent silver nanowire network with >92% optical transmission that provides thermoresistive sensing of skin temperature. By integrating the sensor in a wireless optoelectronic patch, we demonstrate closed-loop regulation of light delivery as well as thermal characterization of blood flow. This light delivery and thermal monitoring approach may open opportunities for wearable devices in light-based diagnostics and therapies.
Display omitted
•A wireless optoelectronic patch measures photothermal effects on the skin•A transparent nanowire sensor enables co-located light delivery and thermal monitoring•Experiments demonstrate closed-loop thermal regulation and blood flow monitoring
Health technology; Optoelectronics; Bioelectronics;
One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and ...electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS2) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS2 and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS2‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.
On fiber: A solid‐state, asymmetric supercapacitor is fabricated by using flexible hybridized fibers of MoS2‐rGO/MWCNT and rGO/MWCNT as the anode and cathode, respectively (MWCNT: multi‐walled carbon nanotube; rGO: reduced graphene oxide). This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.
•A modified HB-AFT method is proposed, which can solve high-dimensional differential equations with complex nonlinearities programmatically and efficiently.•All periodic solutions of a ...dual-rotor-bearing-casing system are obtained, the nonlinear dynamics of the system is analyzed.•The nonlinear dynamic behaviors such as vibration jumping, bi-stable and resonance hysteresis are revealed.•The evolution of the inter-shaft bearing’s nonlinear dynamic load is analyzed, jumping phenomena are also found here.
This paper presents a modified harmonic balance-alternating frequency/time domain (HB-AFT) method to analyze the nonlinear dynamics of a dual-rotor-bearing-casing system. The motion equations of a dual-rotor-bearing-casing system subjected to the unbalanced excitations of the two rotors are formulated with 284 degrees of freedom, in which, the complex nonlinear factors of the inter-shaft bearing such as exponential nonlinear restoring force, radial clearance and varying stiffness excitation are taken into consideration. The HB-AFT method is modified by applying the AFT procedure to obtain the harmonic expending coefficients of the harmonic balance residuals rather than that of the nonlinear terms, hence, the Jacobian matrix is calculated programmatically and efficiently, as a result the performance of the HB-AFT method is improved greatly. The primary resonance of the system is analyzed by employing the three-dimensional diagrams of amplitude-frequency responses of each node of the system, including the inner casing and the outer casing. In addition, the amplitude-frequency response curves with separated frequencies and orbits of the two rotors are also discussed. Furthermore, the pseudo-arclength continuation procedure is introduced into the modified HB method, then all periodic solution branches of the system including the unstable solutions are obtained. The results show that there are two resonant peaks in the amplitude-frequency response curves of the system and the vibration of each part of the system, i.e., LPC, LPT, HPC, HPT, inner casing and outer casing, is synchronous. Besides, the nonlinear dynamic behaviors such as vibration jumping, bi-stable and resonance hysteresis are revealed. Accordingly, the dynamic load of the inter-shaft bearing is calculated. The results show that the evolution of the inter-shaft bearing’s dynamic load is associated with the vibration responses of the two rotors. The nonlinear characteristics of the force-frequency responses of the inter-shaft bearing are consistent with that of the two rotors and casings. In addition, with the increase of the inter-shaft bearing clearance, the nonlinear characteristics of the force-frequency responses of the inter-shaft bearing are more significant. In comparison with the Newmark method, the modified HB-AFT method proposed in this paper has a great advantage in computing efficiency, and it can also grasp all solution branches of the system including the unstable solutions. Consequently, it has great potential to deal with high-dimensional systems with complex nonlinearities and multifrequency excitations in practical engineering.
This paper presents a modified incremental harmonic balance (IHB) method to analyze the nonlinear dynamic and thermal coupling characteristics of rotor-bearing systems after thermal balance. The IHB ...method is modified by tensor contraction and fast Fourier transform (FFT) to efficiently calculate the residual vector and Jacobian matrix. Nonlinear dynamic and thermal full coupling is implemented through the nonlinear part of the Jacobian matrix. The presented method achieves the simultaneous and efficient calculation of the motion and heat balance equations in the frequency domain according to the improvement measures. The effectiveness of the presented method is tested using the vibration response and temperature variation analysis for the coupled thermo-mechanical model of a rotor-ball bearing system. Furthermore, the performance comparisons show the good consistency of results between the presented method and the step-by-step (S-S) method, which is a partitioned iterative solution method for dealing with fully coupled problems in the time domain. The presented method has greater computational efficiency, more accurate temperature prediction, and better recognition of nonlinear phenomena in the system rather than the S-S method. Consequently, the presented method has a broad application prospect in solving fully coupled thermo-mechanical problems of more complex and higher dimensional rotor-bearing systems.
•The motion and heat balance equations can be calculated simultaneously.•Greater calculation efficiency is illustrated than the step-by-step method.•Temperature can be predicted more accurately by time-varying nonlinear forces.•Nonlinear phenomenon recognition of coupled thermo-mechanical problems is improved.
PDF
