The ability to sense multidirectional strains is crucial for understanding complex motions. However, conventional uniaxial strain sensors are incapable of detecting movement across multiple directions, restricting their use in advanced sensing applications such as complex human-machine interfaces and real-time monitoring of human kinetics. Herein, flexible biaxial strain sensors utilizing a metamaterial film based on near- zero Poisson's ratio (NZPR) are developed to enable the self-reliant detection of multiaxial strain. When purposely integrating the hierarchical nanostructures and engineered geometric size, the NZPR of a designed film can be varied from negative to positive. Furthermore, the NZPR film retains a steady transverse dimension when subjected to longitudinal strain. The developed biaxial strain sensor demonstrates excellent stretchability exceeding 40 %, and exceptional durability for over 3000 cycles. It also exhibits notable strain-sensing capabilities, achieving maximum gauge factors of 71.5 for strains applied to the film. Their unique applications are showcased by detecting independent biaxial strain sensing joint actions in the human body and an interactive game with this multifunctional system. The prospective uses of the innovative multiaxial sensor design introduced herein may facilitate the future advancement of sophisticated sensors with flexibility for healthcare and soft, flexible electronics.

Wearable strain sensor prepared with ionic conductive hydrogel holds great promises in a variety of engineering fields. In this work, we introduce sodium casein (SC) into a dual network hydrogel system made of polyvinyl alcohol (PVA) and polyacrylamide (PAM), to prepare an ionic hydrogel sensor. Compared to the PAM/PVA dual network hydrogel, the introduction of SC plays a significant synergistic role. Such dual network PAM/PVA/SC hydrogels exhibit excellent mechanical properties (a maximum strain of 719

High-performance wearable sensors that detect complex, multidimensional signals are indispensable in practical applications. Most existing sensors can only detect axial deformations or single stimuli, dramatically limiting their application fields. In this study, anisotropic strain and deformation-insensitive pressure sensors were effectively constructed based on a rigid-flexible synergistic stretchable substrate. Furthermore, we developed a three-dimensional integrated sensor with highly directional selective sensing through reasonable design and assembly. This integrated sensor recognizes the amplitude and direction of strain in the plane with a maximum gauge factor of 635 and an unprecedented selectivity of 13.99. Additionally, this device can also monitor the pressure outside the plane with a sensitivity of 0.277 kPa−1. We further investigated the working mechanism of sensor anisotropy and confirmed the application of the sensor in detecting complex multifreedom human joint movements. This research discovery provides new ideas and methods for developing multidimensional sensors, which is essential for broadening the application field of wearable electronic products.Graphical Abstract

High-performance wearable sensors that detect complex, multidimensional signals are indispensable in practical applications. Most existing sensors can only detect axial deformations or single stimuli, dramatically limiting their application fields. In this study, anisotropic strain and deformation-insensitive pressure sensors were effectively constructed based on a rigid-flexible synergistic stretchable substrate. Furthermore, we developed a three-dimensional integrated sensor with highly directional selective sensing through reasonable design and assembly. This integrated sensor recognizes the amplitude and direction of strain in the plane with a maximum gauge factor of 635 and an unprecedented selectivity of 13.99. Additionally, this device can also monitor the pressure outside the plane with a sensitivity of 0.277 kPa−1. We further investigated the working mechanism of sensor anisotropy and confirmed the application of the sensor in detecting complex multifreedom human joint movements. This research discovery provides new ideas and methods for developing multidimensional sensors, which is essential for broadening the application field of wearable electronic products.

A series of poly(bisphthalazinone ether sulfone ketone)s with pendant phenyl groups (POPESKs) were synthesized via aromatic nucleophilic substitution polycondensation. The thermal degradation mechanism of POPESKs was determined investigated by TG-FTIR. The Tgs of POPESKs range from 296 to 326 degrees C and the storage modulus retention is up to 46.1 % at 290 degrees C. POPESKs have good solubility in dichloroethane, chloroform, tetrachloroethane, N-methyl-2-pyrrolidone and pyridine, and exhibit good film-forming property. The tensile strength, tensile modulus, and tensile elongation of POPESK films are 85-96 MPa, 1.34-1.86 GPa, and 8.9-11.6 %, respectively. Meanwhile, the polymer films exhibit the high light transmittance of up to 83 % at 800 nm and its water contact angle are in the range of 82.3-94.3 degrees. Its superior overall performance shows great potential in aerospace, petrochemical and energy applications.

Stretchable conductive yarns have received significant consideration in the direction of wearable and flexible electronics. Wearable electronic structures need strong materials to assure stability, durability, and an extensive range of strain to develop their applications. Therefore, manufacturing high-performance yarn-based devices with ultrarobustness and great stretchability with a simple, cost-effective, and scalable method remains a great challenge for wearable electronics. Here, a highly stretchable yarn with high performance is fabricated, which comprises a core TPU nanoyarn, successively decorated with a liquid metal (LM) layer, and a protective outer nanofiber layer. The ultrarobust (40 MPa) and high-strain (548%) conducting yarn presents potential applications in assembling strain sensors. Moreover, such a unique conductive yarn can be used as a highly deformable, stretchable conductor to charge a mobile phone or for data transfer, a sensor to monitor human activities, and as an effective control for a hand robot as well as for smart thermal management textile application. This research gives promising applications in the field of flexible and wearable electronics.

Fiber-based nanostructures are greatly desired for the improvement of wearable/flexible electronics, which are expected to be stretchable, conformable, flexible, and long-term. Herein, an ultra-stretchable, breathable, and highly sensitive flexible capacitive tactile sensor and triboelectric effect core-shell nanofibers are proposed. In particular, core-shell ionic TPU/PVDF-HFP nanofibers are effectively prepared by an electrospinning approach. The core-shell ionic TPU/PVDF-HFP nanofibers exhibit high performance as a capacitive flexible sensor with high sensitivity (0.718 kPa(-1)) in a low linear pressure range (0-1.2 kPa), an ultralow detection limit (7 Pa), a rapid response and recovery time, and excellent stability. Moreover, we assembled a self-powered pressure sensor, which has a sensitivity of 0.071 V kPa(-1) in the high linear pressure range of 90 kPa to 400 kPa. The increase in the inductive charges of the nanofiber layer allows it to work as an energy harvester with a high power density (1.6 W m(-2)) that can light up 100 LEDs instantly. These remarkable results allow the capacitive flexible devices to be applied in various applications, such as spatial pressure mapping, bending angle detection, soft grabbing, and physiological signal monitoring.

Transpiration cooling with liquid coolant phase change in porous matrix is a highly efficient heat dissipation mechanism, but the mathematical model and algorithm to predict precisely the details of coolant flow, absorbing heat and phase change are always bothering investigators up to now. Although the independent equations of separated phase model (SPM) can describe the mass, momentum, and energy conservation of liquid and vapor in two-phase region, the solving process of the SPM is quite complex due to the uncertainty of moving interface and the highly coupled nonlinear equations between different phases. This paper suggests a modified SPM by introducing a coupled pressure equation and a phase equation, so that the solving process can be conducted under the framework of OpenFOAM, and is greatly simplified thereby. The new model and algorithm suggested can provide the investigators of transpiration cooling with a highly efficient tool. Some interesting and important phenomena appearing in the transpiration cooling process are revealed for the first time, and the detailed numerical analyses can help us to understand the special phenomena, including the counter flow of vapor, condensation within the porous matrix, and transient temperature fluctuation.

With the rapid advances in wearable technology, several excellent strain sensors have been developed. Recent strain sensors have met various requirements, such as mechanical applicability, rapid responsiveness, and high sensitivity. Nevertheless, the processing technology, wearing comfort, and safety of strain sensors, which have received inadequate attention, have greatly hindered their commercial development and large-scale use. Through mature electrospinning and screen-printing, a high-performance, safe, comfortable, waterproof, breathable, economical, and reliable wearable strain sensor is simply and quickly prepared. This strain sensor has excellent repeatability and stability with remarkable sensitivity (maximum gauge factor = 520), a broad working strain range (500%), and an ultrafast response time (100 ms). Notably, the mechanical properties of the proposed strain sensor are similar to those of natural skin, making the sensor a good match to the skin. Additionally, the strain sensor has incomparable biofriendly, enabling long-term harmless contact with the skin. To the best of the authors' knowledge, this is the first report on the optimization of flexible electronic equipment in terms of the manufacturing process, sensing performance, and wearing experience. The results of this study have important implications for the development and practical application of flexible electronics.

Flexible electronics as an emerging technology has demonstrated potential for applications in various fields. With the advent of the Internet of Things era, countless flexible electronic systems need to be developed and deployed. However, materials and fabrication technologies are the key factors restricting the development and commercialization of flexible electronics. Here we report a simple, fast, and green flexible electronics preparation technology. The stencil printing method is adopted to pattern liquid metal on the thermoplastic polyurethane membrane prepared by electrospinning. Besides, with layer-by-layer assembly, flexible circuits, resistors, capacitors, inductors, and their composite devices can be prepared parametrically. Furthermore, these devices have good stretchability, air permeability, and stability, while they are multilayered and reconfigurable. As proof, this strategy is used to fabricate flexible displays, flexible sensors, and flexible filters. Finally, flexible electronic devices are also recycled and reconfigured.

Abstract In the severe high-temperature environment caused by aerodynamic heating, the vibrational excitation, dissociation and ionization of gas may successively occur, which are known as real gas effects. Under the real gas effects, the thermodynamic properties of gas vary drastically and significantly influence the performances of the active thermal protection system of hypersonic vehicles, especially in the case with coolant outflow, for example transpiration cooling. This paper numerically investigates the transpiration cooling performance with the consideration of the interaction between coolant outflow and hypersonic flow under the real gas effects. The mathematical models and coupled numerical strategy are firstly validated by experimental data, then the influences of real gas effects on the transpiration cooling of a wedged leading edge (WLE) are studied under a flight Mach number range from 8 to 12 and a flight height of 40 km. The analysis and discussions of the numerical results reveal some important phenomena and demonstrate the need to consider real gas effects.

This paper proposed a numerical strategy which could achieve the coupled modeling and solving of transpiration cooling with external high-temperature gas flow and especially take the radiation effect into account. Based on the numerical strategy, the heat and mass transfer characteristics of the transpiration cooling in a high-temperature gas channel were studied, and the radiation effect and corresponding influence factors were analyzed. The results indicated that the radiative heat flux takes an important role in the heat transfer between the transpiration cooling and external high-temperature gas flow which may reach 40% under the operating condition considered in this work, and the radiation absorption from the coolant is more obvious near the downstream wall. As the wall emissivity increases, the radiation heat transfer in the downstream area of the porous wall is enhanced significantly and thereby the wall temperature there increases, as the result, the uniformity of the temperature distribution on the whole porous wall is improved to some extent.

A novel double layer combined cooling conception is suggested in this paper, i.e., an inner layer with discrete slots to allocate the coolant locally and an outer layer with homogeneous porous matrix to diffuse the coolant extensively. To investigate the cooling performances, mechanisms and improvements of the new structure, an entire-field-coupled numerical approach is established and validated by the experimental data obtained in an arc-heated wind tunnel under the supersonic conditions of Ma = 4.2, T0 = 2310 K and P0 = 1.33 MPa. Using the validated numerical approach, three interesting attempts are conducted: (1) The cooling characteristics of four slot-layouts (S1/S3/S5/S7) are systematically studied and compared at three coolant injection rates (30/40/50 g/s). (2) The comparison indicated that S3 can decrease the peak temperature most greatly even by 66.9% when Mc = 50 g/s, hence it’s chosen as the best design to investigate the cooling mechanisms in the entire region. (3) Based on the mechanism investigation, an improved design with a semi through-slot in the high temperature region is suggested, and the corresponding simulation predicated that this design can further reduce the coolant consumption by 20%. This work aims to provide the designers of future hypersonic vehicles with a valuable reference, to search for an active thermal management approach with high efficiency and low thermal stress.

Monitoring of the hemostasis status is essential for therapeutic anticoagulants, undergoing surgery, cardiovascular diseases, etc. Although the clinical values of conventional blood coagulation tests have been well demonstrated, these devices have limitations such as large and expensive equipment, excessive sample volumes, long turnaround times, and difficulty in miniaturization for point-of-care use. Here, we present a novel strategy to evaluate blood hemostasis using the single-port Love-mode surface acoustic wave (SLSAW) sensor. The SLSAW sensor was designed as a plug-and-play-type unit for disposable use and operated under the harmonic resonant mode to produce frequency response to the blood coagulation cascade. Compared with a quartz crystal microbalance, Lamb wave, and film bulk acoustic resonator, the frequency shift of SLSAW was significantly increased, ranging from approximately 8960 to 10 368 kHz, which indicated enhancement of the signal-to-noise ratio. To demonstrate the feasibility of the SLSAW, studies were carried out to examine the effects of temperature and clotting reagents on coagulation times and kinetics. Activated partial thromboplastin times of plasma were validated by comparing with SYSMEX CA-7000 with the correlation (R-2) as 0.996. In terms of coagulation kinetics, reaction time, clot formation time, maximum frequency shift, and clot formation rate of whole blood correlated well with corresponding parameters of the standard thromboelastography (TEG) analyzer (R-2 = 0.9942, 0.9868, 0.9712, and 0.9939, respectively). The SLSAW sensor, with the advantages of low cost, small size, little sample consumption (1 mu L), disposable use, and simple operation, is a promising tool for point-of-care diagnosis of hemostasis.

Transpiration cooling with coolant phase change provides a wide range of applications in effective thermal protection. Water is usually employed as the coolant and experiences huge temperature and pressure changes during the transpiration cooling process. Mathematical model and numerical approach of transpiration cooling with phase change in consideration of the real variation of water thermodynamic properties are established in this paper, and compared with the constant property model. The IWAPS Industrial Formulation 1997 is used to calculate the thermodynamic properties of water in wide ranges of temperature and pressure. The numerical results obtained indicate some thermodynamic properties vary significantly with temperature and pressure, leading to higher phase change temperature and coolant driving force. With the increase of mass flow rate, the two property models exhibit the similar changing trend in temperature and pressure and there is a lag in the start and end positions of phase change.

Tuning ice recrystallization (IR) has attracted tremendous interest in fundamental research and a variety of practical applications, including food and pharmaceutical engineering, fabrication of anti-icing coating and porous materials, and cryopreservation of biological cells and tissues. Although great efforts have been devoted to modulation of IR for better microstructure control of various materials, it still remains a challenge, especially in cryopreservation, where insufficient suppression of IR during warming is fatal to the cells. Herein, we report an all-in-one platform, combining the external physical fields and the functional materials for both active and passive suppression of IR, where the photo- and magnetothermal dual-modal heating of GO-Fe3O4 nanocomposites (NCs) can be used to suppress IR with both enhanced global warming and microscale thermal disturbance. Moreover, the materials alginate hydrogels and GO-Fe3O4 NCs can act as IR inhibitors for further suppression of the IR effect. As a typical application, we show that this GO-Fe3O4 nanocomposite-alginate hydrogel platform can successfully enable low-cryoprotectant, high-quality vitrification of stem cell-laden hydrogels. We believe that the versatile ice recrystallization inhibition platform will have a profound influence on cryopreservation and tremendously facilitate stem cell-based medicine to meet its ever-increasing demand in clinical settings.

In the applications of transpiration cooling, water acting as a liquid coolant shows excellent cooling performances due to its huge heat capacity and latent enthalpy. However, the fluidity of liquid water could cause extra difficulties on occasions where unexpected interferences to the system balance should be avoided. To overcome the above issue, we propose a new transpiration cooling pattern, in which the liquid water is solidified and stored as hydrogels. In this work, the hydrogel was prepared from the superabsorbent polymer (SAP) and thermogravimetric analysis was conducted to test the water release property and upper critical temperature. Respectively using water and hydrogels as coolant, transpiration cooling experiments on a homemade porous plate were carried out to explore the feasibility and cooling performance of the new transpiration cooling pattern. The results implied that the transpiration cooling with hydrogels and water can both slow down the temperature rising of the structure. The hydrogel can provide considerable cooling effect and is superior for prolonging service time.

Oocyte quality plays a crucial role in the early development and implantation of the embryos, and consequently has a profound impact on the accomplishment of assisted reproductive technology (ART). A simple and efficient method for detecting high-quality human oocytes is urgently needed. However, the clinically used morphological method is time-consuming, subjective, and inaccurate. To this end, we propose a practical and effective approach for detecting high-quality oocytes via on-chip measurement of the oocyte membrane permeability. We found that oocytes can be divided into two subpopulations (high-quality versus poor-quality oocytes) according to their membrane permeability differences, and as was further confirmed by subsequent in vitro fertilization (IVF) and development experiments (the blastocyst rates of high-quality and poor-quality oocytes were 60% and 0%, respectively). This approach shows great potentials in improving the success of ART, including both the fertilization and development rates, and thus it may have wide applications in the clinic.

Constructs of magnetic nanocomposite hydrogels microencapsulated with stem cells are of great interest as smart materials for tissue engineering and regenerative medicine. Due to the short shelf life of such biocomposites at an ambient temperature, their long-term storage and banking at cryogenic temperatures are essential for the "off-the-shelf" availability of such biocomposites for widespread clinical applications. However, high-quality cryogenic recovery of stem cell-nanocomposite hydrogel constructs has not yet been achieved due to the damage to cells and/or microstructures of hydrogel constructs caused by ice formation, particularly during warming from cryogenic temperatures. Herein, stem cell-magnetic nanocomposite hydrogel constructs, which have an inherent magnetothermal property provided by embedded magnetic nanoparticles, are explored to achieve ultra-rapid cryogenic warming. The binding of water molecules by the hydrogel combined with the magnetothermal heating greatly suppressed ice formation during both cryogenic cooling and warming. Thus, the cryogenic recovery of nanocomposite hydrogel constructs with intact microstructures and fully functional stem cells from ultra-low temperatures was successfully achieved. We further demonstrated that magnetic nanocomposite hydrogels microencapsulated with stem cells could be conveniently manipulated for a self-assembled 3D culture. Together, we have developed a highly efficient and easy-to-perform approach for the cryogenic recovery of stem cell-encapsulated magnetic nanocomposite hydrogel constructs. Our results will facilitate the applications of such stem cell-magnetic nanocomposite hydrogels in regenerative medicine and tissue engineering.

Two-dimensional (2D) graphene oxide (GO) and molybdenum disulfide (MoS2) nanosheets (NSs) have been widely used as photothermal agents and as potential carriers of antitumor drugs. Their spatial thermal effects have been extensively explored for use at physiological and hyperthermic temperatures (37 to 46 °C). Furthermore, the modulation of the spatial thermal distributions with these NSs may have even more profound applications in the microstructural control of biomaterials at cryogenic temperatures (-196 to 37 °C). These applications include bioinspired microfabrication via freezing, food and drug freeze-drying, and biomaterial cryopreservation. However, such thermal effects of NSs and their applications at cryogenic temperatures had never been fully explored. Therefore, in this study, we have utilized the near-infrared laser induced photothermal effects of GO and MoS2 NSs to suppress the ice nucleation and ice crystal growth during warming of the biosamples. Using this approach, biological cells subjected to fast cooling to a deeply frozen state (-196 °C) were successfully recovered with high survival rates and full biological functionality. Thus, we provide a NS based effective approach to control the crystallization behaviors of water during warming at cryogenic temperatures, as NSs may have wide applications in both materials science and bioengineering.