Self-Powered Multimodal Temperature and Force Sensor Based-On a Liquid Droplet.

Herein we report a self-powered multimodal temperature and force sensor based on the reverse electrowetting effect and the thermogalvanic effect in a liquid droplet. The deformation of the droplet and the temperature difference across the droplet can induce an alternating pulse voltage and a direct voltage, respectively, which is easy to separate/analyze and can be utilized to sense the external force and temperature simultaneously. In addition, an integral display system that can derive information from external temperature/force concurrently is constructed. Combined with advantages of excellent sensing properties and a simple structure, the droplet sensor has promising applications in a wide range of intelligent electronics.

Induced Potential in Porous Carbon Films through Water Vapor Absorption.

Sustainable electrical potential of tens of millivolts can be induced by water vapor adsorption on a piece of porous carbon film that has two sides with different functional group contents. Integrated experiments, and Monte Carlo and ab initio molecular dynamics simulations reveal that the induced potential originates from the nonhomogeneous distribution of functional groups along the film, especially carboxy groups. Sufficient adsorbed water molecules in porous carbon facilitate the release of protons from the carboxy groups, resulting in a potential drop across the carbon film because of the concentration difference of the released free protons on the two sides. The potential utilization of such a phenomenon is also demonstrated by a self-powered humidity sensor.

Organohydrogel-based transparent terahertz absorber via ionic conduction loss.

The fast-growing terahertz technologies require high-performance terahertz absorber for suppressing electromagnetic interference. Since the dissipation mechanism in terahertz band usually focuses on electronic conduction loss, almost all terahertz absorbers are constructed with electronically conducting materials being opaque, which limits their applications in scenarios requiring high visible transmittance. Here, we demonstrate a transparent terahertz absorber based on permittivity-gradient elastomer-encapsulated-organohydrogel. Our organohydrogel-based terahertz absorber exhibits a high absorbing property (average reflection loss of 49.03 dB) in 0.5-4.5 THz band with a thin thickness of 700 µm and a high average visible transmittance of 85.51%. The terahertz absorbing mechanism mainly derives from the ionic conduction loss of the polar liquid in organohydrogel. Besides, the hydrophobic and adhesive elastomer coating endows this terahertz absorber high absorbing stability and interfacial adhesivity. This work paves a viable way to designing transparent terahertz absorbers.

Physics-guided co-designing flexible thermoelectrics with techno-economic sustainability for low-grade heat harvesting.

Flexible thermoelectric harvesting of omnipresent spatial thermodynamic energy, though promising in low-grade waste heat recovery (<100°C), is still far from industrialization because of its unequivocal cost-ineffectiveness caused by low thermoelectric efficiency and power-cost coupled device topology. Here, we demonstrate unconventional upcycling of low-grade heat via physics-guided rationalized flexible thermoelectrics, without increasing total heat input or tailoring material properties, into electricity with a power-cost ratio (W/US$) enhancement of 25.3% compared to conventional counterparts. The reduced material usage (44%) contributes to device power-cost "decoupling," leading to geometry-dependent optimal electrical matching for output maximization. This offers an energy consumption reduction (19.3%), electricity savings (0.24 kWh W-1), and CO2 emission reduction (0.17 kg W-1) for large-scale industrial production, fundamentally reshaping the R&D route of flexible thermoelectrics for techno-economic sustainable heat harvesting. Our findings highlight a facile yet cost-effective strategy not only for low-grade heat harvesting but also for electronic co-design in heat management/recovery frontiers.

Non-planar dielectrics derived thermal and electrostatic field inhomogeneity for boosted weather-adaptive energy harvesting.

Weather-adaptive energy harvesting of omnipresent waste heat and rain droplets, though promising in the field of environmental energy sustainability, is still far from practice due to its low electrical output owing to dielectric structure irrationality and unscalability. Here we present atypical upcycling of ambient heat and raindrop energy via an all-in-one non-planar energy harvester, simultaneously increasing solar pyroelectricity and droplet-based triboelectricity by two-fold, in contrast to conventional counterparts. The delivered non-planar dielectric with high transmittance confines the solar irradiance onto a focal hotspot, offering transverse thermal field propagation towards boosted inhomogeneous polarization with a generated power density of 6.1 mW m-2 at 0.2 sun. Moreover, the enlarged lateral surface area of curved architecture promotes droplet spreading/separation, thus travelling the electrostatic field towards increased triboelectricity. These enhanced pyroelectric and triboelectric outputs, upgraded with advanced manufacturing, demonstrate applicability in adaptive sustainable energy harvesting on sunny, cloudy, night, and rainy days. Our findings highlight a facile yet efficient strategy, not only for weather-adaptive environmental energy recovery but also in providing key insights for spatial thermal/electrostatic field manipulation in thermoelectrics and ferroelectrics.

Giant polarization ripple in transverse pyroelectricity.

Pyroelectricity originates from spontaneous polarization variation, promising in omnipresent non-static thermodynamic energy harvesting. Particularly, changing spontaneous polarization via out-of-plane uniform heat perturbations has been shown in solar pyroelectrics. However, these approaches present unequivocal inefficiency due to spatially coupled low temperature change and duration along the longitudinal direction. Here we demonstrate unconventional giant polarization ripples in transverse pyroelectrics, without increasing the total energy input, into electricity with an efficiency of 5-fold of conventional longitudinal counterparts. The non-uniform graded temperature variation arises from decoupled heat localization and propagation, leading to anomalous in-plane heat perturbation (29-fold) and enhanced thermal disequilibrium effects. This in turn triggers an augmented polarization ripple, fundamentally enabling unprecedented electricity generation performance. Notably, the device generates a power density of 38 mW m-2 at 1 sun illumination, which is competitive with solar thermoelectrics and ferrophotovoltaics. Our findings provide a viable paradigm, not only for universal practical pyroelectric heat harvesting but for flexible manipulation of transverse heat transfer towards sustainable energy harvesting and management.

Paper-based supercapacitors for self-powered nanosystems.

Energy storage on paper: paper-based, all-solid-state, and flexible supercapacitors were fabricated, which can be charged by a piezoelectric generator or solar cells and then discharged to power a strain sensor or a blue-light-emitting diode, demonstrating its efficient energy management in self-powered nanosystems.

An Elastic and Damage-Tolerant Dry Epidermal Patch with Robust Skin Adhesion for Bioelectronic Interfacing.

On-skin patches that record biopotential and biomechanical signals are essential for wearable healthcare monitoring, clinical treatment, and human-machine interaction. To acquire wearing comfort and high-quality signals, patches with tissue-like softness, elastic recovery, damage tolerance, and robust bioelectronic interface are highly desired yet challenging to achieve. Here, we report a dry epidermal patch made from a supramolecular polymer (SESA) and an in situ transferred carbon nanotubes' percolation network. The polymer possesses a hybrid structure of copolymerized permanent scaffold permeated by multiple dynamic interactions, which imparts a desired mechanical response transition from elastic recoil to energy dissipation with increased elongation. Such SESA-based patches are soft (Young's modulus ∼0.1 MPa) and elastic within physiologically relevant strain levels (97% elastic recovery at 50% tensile strain), intrinsically mechanical-electrical damage-resilient (∼90% restoration from damage after 5 min), and interference-immune in dynamic signal acquisition (stretch, underwater, sweat). We demonstrate its versatile physiological sensing applications, including electrocardiogram recording under various disturbances, machine-learning-enabled hand-gesture recognition through electromyogram measurement, subtle radial artery pulse, and drastic knee kinematics sensing. This epidermal patch offers a promising noninvasive, long-duration, and ambulant bioelectronic interfacing with anti-interference robustness.

High-temperature stability in air of Ti3C2Tx MXene-based composite with extracted bentonite.

Although Ti3C2Tx MXene is a promising material for many applications such as catalysis, energy storage, electromagnetic interference shielding due to its metallic conductivity and high processability, it's poor resistance to oxidation at high temperatures makes its application under harsh environments challenging. Here, we report an air-stable Ti3C2Tx based composite with extracted bentonite (EB) nanosheets. In this case, oxygen molecules are shown to be preferentially adsorbed on EB. The saturated adsorption of oxygen on EB further inhibits more oxygen molecules to be adsorbed on the surface of Ti3C2Tx due to the weakened p-d orbital hybridization between adsorbed O2 and Ti3C2Tx, which is induced by the Ti3C2Tx/EB interface coupling. As a result, the composite is capable of tolerating high annealing temperatures (above 400 °C for several hours) both in air or humid environment, indicating highly improved antioxidation properties in harsh condition. The above finding is shown to be independent on the termination ratio of Ti3C2Tx obtained through different synthesis routes. Utilized as terahertz shielding materials, the composite retains its shielding ability after high-temperature treatment even up to 600 °C, while pristine Ti3C2Tx is completely oxidized with no terahertz shielding ability. Joule heating and thermal cycling performance are also demonstrated.

Macromolecule conformational shaping for extreme mechanical programming of polymorphic hydrogel fibers.

Mechanical properties of hydrogels are crucial to emerging devices and machines for wearables, robotics and energy harvesters. Various polymer network architectures and interactions have been explored for achieving specific mechanical characteristics, however, extreme mechanical property tuning of single-composition hydrogel material and deployment in integrated devices remain challenging. Here, we introduce a macromolecule conformational shaping strategy that enables mechanical programming of polymorphic hydrogel fiber based devices. Conformation of the single-composition polyelectrolyte macromolecule is controlled to evolve from coiling to extending states via a pH-dependent antisolvent phase separation process. The resulting structured hydrogel microfibers reveal extreme mechanical integrity, including modulus spanning four orders of magnitude, brittleness to ultrastretchability, and plasticity to anelasticity and elasticity. Our approach yields hydrogel microfibers of varied macromolecule conformations that can be built-in layered formats, enabling the translation of extraordinary, realistic hydrogel electronic applications, i.e., large strain (1000%) and ultrafast responsive (~30 ms) fiber sensors in a robotic bird, large deformations (6000%) and antifreezing helical electronic conductors, and large strain (700%) capable Janus springs energy harvesters in wearables.

Dynamic thermal trapping enables cross-species smart nanoparticle swarms.

Bioinspired nano/microswarm enables fascinating collective controllability beyond the abilities of the constituent individuals, yet almost invariably, the composed units are of single species. Advancing such swarm technologies poses a grand challenge in synchronous mass manipulation of multimaterials that hold different physiochemical identities. Here, we present a dynamic thermal trapping strategy using thermoresponsive-based magnetic smart nanoparticles as host species to reversibly trap and couple given nonmagnetic entities in aqueous surroundings, enabling cross-species smart nanoparticle swarms (SMARS). Such trapping process endows unaddressable nonmagnetic species with efficient thermo-switchable magnetic response, which determines SMARS' cross-species synchronized maneuverability. Benefiting from collective merits of hybrid components, SMARS can be configured into specific smart modules spanning from chain, vesicle, droplet, to ionic module, which can implement localized or distributed functions that are single-species unachievable. Our methodology allows dynamic multimaterials integration despite the odds of their intrinsic identities to conceive distinctive structures and functions.

Scalable thermoelectric fibers for multifunctional textile-electronics.

Textile electronics are poised to revolutionize future wearable applications due to their wearing comfort and programmable nature. Many promising thermoelectric wearables have been extensively investigated for green energy harvesting and pervasive sensors connectivity. However, the practical applications of the TE textile are still hindered by the current laborious p/n junctions assembly of limited scale and mechanical compliance. Here we develop a gelation extrusion strategy that demonstrates the viability of digitalized manufacturing of continuous p/n TE fibers at high scalability and process efficiency. With such alternating p/n-type TE fibers, multifunctional textiles are successfully woven to realize energy harvesting on curved surface, multi-pixel touch panel for writing and communication. Moreover, modularized TE garments are worn on a robotic arm to fulfill diverse active and localized tasks. Such scalable TE fiber fabrication not only brings new inspiration for flexible devices, but also sets the stage for a wide implementation of multifunctional textile-electronics.

Somatosensory, Light-Driven, Thin-Film Robots Capable of Integrated Perception and Motility.

Living organisms are capable of sensing and responding to their environment through reflex-driven pathways. The grand challenge for mimicking such natural intelligence in miniature robots lies in achieving highly integrated body functionality, actuation, and sensing mechanisms. Here, somatosensory light-driven robots (SLiRs) based on a smart thin-film composite tightly integrating actuation and multisensing are presented. The SLiR subsumes pyro/piezoelectric responses and piezoresistive strain sensation under a photoactuator transducer, enabling simultaneous yet non-interfering perception of its body temperature and actuation deformation states. The compact thin film, when combined with kirigami, facilitates rapid customization of low-profile structures for morphable, mobile, and multiple robotic functionality. For example, an SLiR walker can move forward on different surfaces, while providing feedback on its detailed locomotive gaits and subtle terrain textures, and an SLiR anthropomorphic hand shows bodily senses arising from concerted mechanoreception, thermoreception, proprioception, and photoreception. Untethered operation with an SLiR centipede is also demonstrated, which can execute distinct, localized body functions from directional motility, multisensing, to wireless human and environment interactions. This SLiR, which is capable of integrated perception and motility, offers new opportunities for developing diverse intelligent behaviors in soft robots.

Direct-Ink-Write 3D Printing of Hydrogels into Biomimetic Soft Robots.

Hydrogels are promising starting materials for biomimetic soft robots as they are intrinsically soft and hold properties analogous to nature's organic parts. However, the restrictive mold-casting and post-assembly fabrication alongside mechanical fragility impedes the development of hydrogel-based soft robots. Herein, we harness biocompatible alginate as a rheological modifier to manufacture 3D freeform architectures of both chemically and physically cross-linked hydrogels using the direct-ink-write (DIW) printing. The intrinsically hydrophilic polymer network of alginate allows the preservation of the targeted functions of the host hydrogels, accompanied by enhanced mechanical toughness. The integration of free structures and available functionalities from diversified hydrogel family renders an enriched design platform for bioinspired fluidic and stimulus-activated robotic prototypes from an artificial mobile tentacle, a bioengineered robotic heart with beating-transporting functions, and an artificial tendril with phototropic motion. The design strategy expands the capabilities of hydrogels in realizing geometrical versatility, mechanical tunability, and actuation complexity for biocompatible soft robots.

Robust and Low-Cost Flame-Treated Wood for High-Performance Solar Steam Generation.

Solar-enabled steam generation has attracted increasing interest in recent years because of its potential applications in power generation, desalination, and wastewater treatment, among others. Recent studies have reported many strategies for promoting the efficiency of steam generation by employing absorbers based on carbon materials or plasmonic metal nanoparticles with well-defined pores. In this work, we report that natural wood can be utilized as an ideal solar absorber after a simple flame treatment. With ultrahigh solar absorbance (∼99%), low thermal conductivity (0.33 W m-1 K-1), and good hydrophilicity, the flame-treated wood can localize the solar heating at the evaporation surface and enable a solar-thermal efficiency of ∼72% under a solar intensity of 1 kW m-2, and it thus represents a renewable, scalable, low-cost, and robust material for solar steam applications.

Water-evaporation-induced electricity with nanostructured carbon materials.

Water evaporation is a ubiquitous natural process that harvests thermal energy from the ambient environment. It has previously been utilized in a number of applications including the synthesis of nanostructures and the creation of energy-harvesting devices. Here, we show that water evaporation from the surface of a variety of nanostructured carbon materials can be used to generate electricity. We find that evaporation from centimetre-sized carbon black sheets can reliably generate sustained voltages of up to 1 V under ambient conditions. The interaction between the water molecules and the carbon layers and moreover evaporation-induced water flow within the porous carbon sheets are thought to be key to the voltage generation. This approach to electricity generation is related to the traditional streaming potential, which relies on driving ionic solutions through narrow gaps, and the recently reported method of moving ionic solutions across graphene surfaces, but as it exploits the natural process of evaporation and uses cheap carbon black it could offer advantages in the development of practical devices.

High-strain sensors based on ZnO nanowire/polystyrene hybridized flexible films.

A type of strain sensor with high tolerable strain based on a ZnO nanowires/polystyrene nanofibers hybrid structure on a polydimethylsiloxane film is reported. The novel strain sensor can measure and withstand high strain and demonstrates good performance on rapid human-motion measurements. In addition, the device could be driven by solar cells. The results indicate that the device has potential applications as an outdoor sensor system.