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Hydrogel, recognized as a promising biomaterial for tissue engineering, possesses notable characteristics, including high water uptake, an interconnected porous structure, and excellent permeability. However, the intricate task of fabricating a hierarchically macro–micronanoporous structure, essential for providing adequate space for nutrient diffusion and cell growth within hydrogels, remains a formidable challenge. In response to these challenges, this study introduces a sustainable and straightforward three-dimensional (3D) foaming printing strategy to produce hierarchically macro–micronanoporous hydrogels (HPHs) without the utilization of porogens and post-etching process. This method entails the controlled generation of air bubbles within the hydrogels through the application of optimal mechanical stirring rates. Subsequent ultraviolet (UV) cross-linking serves to effectively stabilize the macropores within the HPHs. The resulting hierarchically macro–micronanoporous structures demonstrate a substantial improvement in the viability, adhesion, and proliferation of human umbilical vein endothelial cells (HUVECs) when incubated with the hydrogels. These findings present a significant advancement in the fabrication of hierarchically macro–micronanoporous hydrogels, with potential applications in the fields of tissue engineering and organoid development.

Piezoelectric polymer films are forthcoming choices for self-powered portable flexible electronics due to instant mechanoelectrical transduction, ease of fabrication, and assembly for device integration. However, the low piezoelectricity of polymers in comparison with piezoelectric ceramics precludes their practical applications significantly. Here, we report an interesting method to fabricate piezoelectric poly(vinylidene fluoride) (PVDF) fiber mats with excellent piezoelectricity by collecting electrospun fibers using low-temperature electrolytes. Specifically, fiber collection assisted by liquid electrolytes enables the formation of piezoelectric PVDF crystals with zigzag conformation induced by strong solvent–electrolyte and dipole–ion interactions, as well as the immobilization of aligned dipoles at low temperature. Consequently, compared with conventional PVDF fibers collected by aluminum foils, those fiber mats electrospun using liquid electrolytes can generate an open-circuit voltage of 2.3 V under a pressure of 20 N at 1 Hz for an effective area of 1 cm2, showing a nearly eight-times improvement. In addition, the as-prepared piezoelectric fiber mats enable the conversion of mechanical energy into electricity with an instantaneous output power density of ∼16.2 mW/m2, which allows for self-powered sensing or energy harvesting. Such an electrospinning technology enables simple fabrication of high-performance piezoelectric polymer fiber mats with diverse surface microstructure for self-powered flexible electronics.

• A one-step thermal stretching strategy is developed to fabricate anti-fatigue ionic gels (AIG). • A multimodal wearable respiratory monitoring system (WRMS) is designed based on the AIG. • The WRMS can long-term detect the movement of the chest and abdomen simultaneously. • The WMRS provides four effective parameters for patient-doctor interaction detection. Wearable electronics integrated with stretchable sensors are considered a promising and non-invasive strategy to monitor respiratory status for health assessment. However, long-term and stable monitoring of respiratory abnormality is still a grand challenge. Here, we report a facile one-step thermal stretching strategy to fabricate an anti-fatigue ionic gel (AIG) sensor with high fatigue threshold (Γ 0 = 1130 J m–2), high stability (> 20,000 cycles), high linear sensitivity, and recyclability. A multimodal wearable respiratory monitoring system (WRMS) developed with AIG sensors can continuously measure respiratory abnormality (single-sensor mode) and compliance (multi-sensor mode) by monitoring the movement of the ribcage and abdomen in a long-term manner. For single-sensor mode, the respiratory frequency (F r), respiratory energy (E r), and inspire/expire time (I / E ratio) can be extracted to evaluate the respiratory status during sitting, sporting, and sleeping. Further, the multi-sensors mode is developed to evaluate patient-ventilator asynchrony through validated clinical criteria by monitoring the incongruous movement of the chest and abdomen, which shows great potential for both daily home care and clinical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Wearable strain sensors have huge potential for applications in healthcare, human–machine interfacing, and augmented reality systems. However, the nonlinear response of the resistance signal to strain has caused considerable difficulty and complexity in data processing and signal transformation, thus impeding their practical applications severely. Herein, we propose a simple way to achieve linear and reproducible resistive signals responding to strain in a relatively wide strain range for flexible strain sensors, which is achieved via the fabrication of Janus and heteromodulus elastomeric fiber mats with micropatterns using microimprinting second processing technology. In detail, both isotropic and anisotropic fiber mats can turn into Janus fiber mats with periodical and heteromodulus micropatterns via controlling the fiber fusion and the diffusion of local macromolecular chains of thermoplastic elastomers. The Janus heterogeneous microstructure allows for stress redistribution upon stretching, thus leading to lower strain hysteresis and improved linearity of resistive signal. Moreover, tunable sensing performance can be achieved by tailoring the size of the micropatterns on the fiber mat surface and the fiber anisotropy. The Janus mat strain sensors with high signal linearity and good reproducibility have a very low strain detection limit, enabling potential applications in human–machine interfacing and intelligent control fields if combined with a wireless communication module.

Traditional devices, including conventional rigid electronics and machines, as well as emerging wearable electronics and soft robotics, almost all have a single mechanical state for particular service purposes. Nonetheless, dynamic materials with interchangeable mechanical states, which enable more diverse and versatile applications, are urgently necessary for intelligent and adaptive application cases in the future electronic and robot fields. Here, we report a gel-like material composed of a crosslinking polymer network impregnated with a phase changing molten liquid, which undergoes an exceptional stiffness transition in response to a thermal stimulus. Vice versa, the material switches from a soft gel state to a rigid solid state with a dramatic stiffness change of 105times (601 MPa versus4.5 kPa) benefiting from the liquid–solid phase change of the crystalline polymer once cooled. Such reversibility of the phase and mechanical transition upon thermal stimuli enables the dynamic gel mechanical transformation, demonstrating potential applications in an adhesive thermal interface gasket (TIG) to facilitate thermal transport, a high-temperature warning sensor and an intelligent gripper. Overall, this dynamic gel with a tunable stiffness change paves a new way to design and fabricate adaptive smart materials toward intelligent control of versatile devices.

An increasing utilization of flexible healthcare electronics and biomedicine-related therapeutic materials urges the development of multifunctional wearable/flexible smart fabrics for personal therapy and health management. However, it is currently a challenge to fabricate multifunctional and on-body healthcare electronic devices with reliable mechanical flexibility, excellent breathability, and self-controllable joule heating effects. Here, we fabricate a multifunctional MXene-based smart fabric by depositing 2D Ti3C2Txnanosheets onto cellulose fiber nonwoven fabric viaspecial MXene–cellulose fiber interactions. Such multifunctional fabrics exhibit sensitive and reversible humidity response upon H2O-induced swelling/contraction of channels between the MXene interlayers, enabling wearable respiration monitoring application. Besides, it can also serve as a low-voltage thermotherapy platform due to its fast and stable electro-thermal response. Interestingly, water molecular extraction induces electrical response upon heating, i.e., functioning as a temperature alarm, which allows for real-time temperature monitoring for thermotherapy platform without low-temperature burn risk. Furthermore, metal-like conductivity of MXene renders the fabric an excellent Joule heating effect, which can moderately kill bacteria surrounding the wound in bacteria-infected wound healing therapy. This work introduces a multifunctional smart flexible fabric suitable for next-generation wearable electronic devices for mobile healthcare and personal medical therapy.

Hydrogel bioelectronics as one of the next-generation wearable and implantable electronics ensures excellent biocompatibility and softness to link the human body and electronics. However, volatile, opaque, and fragile features of hydrogels due to the sparse and microscale three-dimensional network seriously limit their practical applications. Here, we report a type of smart and robust nanofibrillar poly(vinyl alcohol) (PVA) organohydrogels fabricated via one-step physical cross-linking. The nanofibrillar network cross-linked by numerous PVA nanocrystallites enables the formation of organohydrogels with high transparency (90%), drying resistance, high toughness (3.2 MJ/m3), and tensile strength (1.4 MPa). For strain sensor application, the PVA ionic organohydrogel after soaking in NaCl solution shows excellent linear sensitivity (GF = 1.56, R2> 0.998) owing to the homogeneous nanofibrillar PVA network. We demonstrate the potential applications of the nanofibrillar PVA-based organohydrogel in smart contact lens and emotion recognition. Such a strategy paves an effective way to fabricate strong, tough, biocompatible, and ionically conductive organohydrogels, shedding light on multifunctional sensing applications in next-generation flexible bioelectronics.

Solar energy triggered steam generation has emerged as a green and sustainable strategy that can potentially address the long-standing global freshwater scarcity issue. However, given that there is inadequate light illumination early in the morning or late afternoon or cloudy days, it is continuous steam generation in all weather that is a great challenge for the state-of-the-art solar-driven steam generators. Here, we present an all-weather-available steam generation system, which is capable of harvesting solar energy to continuously generate steam based on the alternative photo-thermal and electro-thermal conversion of crosslinked MXene aerogels (CMAs) in the day time and at night. In virtue of the strong light absorption and excellent electrical conductivity of the CMA, the constructed steam generation system can not only convert sunlight into heat for steam generation on sunny days but persistently achieve heat generation by utilization of electricity in low-light or dark circumstances. Furthermore, the ingenious introduction of solar cells-battery components makes full use of the daytime sunlight to further power the steam generation system for heating up the CMA at night, avoiding extra electrical energy input and loss. This work offers new insights into developing continuous steam generation technologies applicable to day–night alternation and complex environments.

Solar-driven interfacial water evaporation is regarded as an effective, renewable, and environment-friendly technology for clean water production. However, biofouling caused by the nonspecific interaction between the steam generator and biofoulants generally hinders the efficient application of wastewater treatment. Herein, this work reports a facile strategy to fabricate flexible anti-biofouling fibrous photothermal membrane consisting of a MXene-coated cellulose membrane for highly efficient solar-driven water steam evaporation toward water purification applications. The as-prepared MXene/cellulose photothermal membrane exhibits light absorption efficiency as high as ∼94% in a wide solar spectrum range and a water evaporation rate up to 1.44 kg m–2h–1under one solar illumination. Also, the MXene/cellulose membrane shows very high antibacterial efficiency (above 99.9%) owing to the MXene coating as a highly effective bacteriostatic agent. Such a flexible, anti-biofouling, and high-efficiency photothermal membrane sheds light on practical applications in long-term wastewater treatments.

Increasingly serious electromagnetic radiation pollution puts higher demands on wearable devices. Electronic sensor skin capable of shielding electromagnetic radiation can provide extra protection in emerging fields such as electronic skins, robotics, and artificial intelligence, but combining the sensation and electromagnetic shielding performance together remains a great challenge. Here, inspired by the structure and functions of the human skin, a multifunctional electronic skin (M-E-skin) with both tactile sensing and electromagnetic radiation shielding functions is proposed. The tactile sensing of human skin is mimicked with irregular dermislike rough surfaces, and the electromagnetic shielding performance not available on natural skin is introduced by mimicking the ultraviolet electromagnetic radiation absorption of melanin in epidermis. The M-E-skin shows superior sensitivity (9.8 × 104kPa–1for the pressure range 0–0.2 kPa and 3.5 × 103kPa–1within 0.2–20 kPa), broad operating range (0–20 kPa), fast response and relaxation times (<62.5 ms), great pressuring-relaxing stability (10 kPa, 1000 cycles), low operating voltage (0.1 V), low power consumption (1.5 nW), and low detection limit (5 Pa). Besides, a broad range of electromagnetic wave (0.5–7.5 GHz) is shielded more than 99.66% by the M-E-skin. This work holds great potential to enlarge the application scope of current electronic skins.

Continuous monitoring of physical signals such as stress and strain plays a crucial role in Internet of Thing and artificial intelligence, thus flexible mechanical sensors gain increasing attention due to their enormous application potential in wearable electronics, soft robots, human-machine interfaces, etc. Recently, significant progress has been made in mechanical sensors for trading off high sensitivity and wide range for low dimensional strain/force sensors, yet it is still of significant challenge to discriminate complicated three-dimensional (3D) mechanical signals in practical applications. Herein, a novel wearable film sensor capable of sensing multi-directional mechanical stimuli is developed by coating MXene onto low-entropy structured piezoelectric poly(vinylene fluoride-trifluoroethylene) (PVDF-TrFE) mat composed of aligned nanofibers. The resultant functional fiber mats give rise to an anisotropic in-plane conductive network for 2D in-plane strain sensing, and oriented ferroelectric crystals in nanofibers with piezoelectricity allow for out-of-plane dynamic pressure detection. Besides, the all-in-one flexible anisotropic sensor shows linear sensing properties and high sensitivities both in the plane strain and out of the plane pressure due to piezoresistive and piezoelectric mechanisms, respectively. Such sensors can effectively distinguish multi-directional mechanical stimuli for potential applications in human machine interfaces, healthcare, entertainment and other systems.

Solar water purification is a promising technology with a strong potential for producing fresh water without effluent discharge. For energy-intensive interfacial vapor generation, energy loss to air via heat radiation and convection occurs commonly but is normally ignored, which severely limits the energy efficiency. Therefore, it is necessary to precisely regulate the interfacial thermal energy for interfacial vapor generation. Here, we developed a hierarchically porous radiation-absorbing hydrogel film (hp-RAH) through an in situgelation strategy and employed this hp-RAH on various existing solar evaporator surfaces. The hydrogel film efficiently absorbs and reutilizes the thermal radiation energy emitted by the photothermal layer and eradicates thermal convection of the photothermal layer into air. In this way, an evaporation efficiency up to 95% is obtained, and the heat radiation and convection losses are reduced from 6.6% to 0.39% under 1 sun. This strategy demonstrates a promising membrane evaporation prototype based on the evaporation surface thermal utilization.

Wearable flexible electronics are experiencing rapid development for smart life assistance, rehabilitation, and even human enhancement. Owing to the complexity and diversity of wearable and implantable applications, strain sensors with customizable sensing ranges and sensitivities have aroused great interest, while it is still challenging to simultaneously achieve high sensitivity and stretchability. In this work, we report a novel crack design strategy to fabricate sensors for targeted detections via formation of nanocrystal titanium oxide (TiO2) by means of Ti3C2TxMXene surface oxidation and typical micro- and through-crack pattern sensors for stable large and accurate subtle motion detections are fabricated, respectively. An efficient crack pattern control strategy based on strain localization induced fracture mechanism is proposed. Two typical sensors with a stable sensitivity in a wide sensing range (GF = 1.3 for 0–100% strain) and high sensitivities in small sensing ranges (GF = 530, 3380, 4650, and 75000 in the strain ranges of 0–0.175%, 0.175%–0.45%, 0.45%–3.6%, and 3.6%–5%, respectively) are obtained for large and subtle human motion detection, respectively. This work introduces a new way to fabricate and combinedly use customizable strain sensors for full-range human motion monitoring, addressing the sensitivity-stretchability contradiction issues for conventionally fabricated and solely used strain sensors via strain localization dominated crack control strategy.