A Fast Autonomous Healing Magnetic Elastomer for Instantly Recoverable,Modularly Programmable,and Thermorecyclable Soft Robots

Intrinsically self-healing stretchable polymers have been intensively explored for soft robotic applications due to their mechanical compliance and damage resilience. However, their prevalent use in real-world robotic applications is currently hindered by various limitations such as low mechanical strength, long healing time, and external energy input requirements. Here, a self-healing supramolecular magnetic elastomer (SHSME), featuring a hierarchical dynamic polymer network with abundant reversible bonds, is introduced. The SHSME exhibits high mechanical strength (Young's modulus of 1.2 MPa, similar to silicone rubber) and fast self-healing capability (300% stretch strain after 5 s autonomous repair at ambient temperature). A few SHSME-based robotic demonstrations, namely, rapid amphibious function recovery, modular-assembling-prototyping soft robots with complex geometries and diverse functionalities, as well as a dismembering–navigation–assembly strategy for robotic tasking in confined spaces are showcased. Notably, the SHSME framework supports circular material design, as it is thermoreformable for recycling, demonstrates autorepair for extended lifespan, and is modularizable for customized constructs and functions.     

Transparent High-Performance Supramolecular Plastics Operating in All-Weather Environments

Supramolecular plastics (SMPs) can be made mechanically robust, repairable, and recyclable, rendering themselves promising alternatives to their conventional predecessors to address environmental concerns. However, dense accumulations of noncovalent bonds generally lead to mechanical brittleness as well as intolerance toward heat and moisture. To resolve this issue, a simple strategy of preparing high-performance SMP by constructing highly dense, but irregular hydrogen-bond networks with hierarchical structures is proposed. The resultant SMP exhibits an outstanding combination of good comprehensive mechanical properties (high stiffness, strength, and toughness with ductile failure when fracturing), excellent dynamic behaviors (repairability and recyclability), and high tolerances toward moisture and high temperatures (as high as 90 °C). Additionally, the SMP also shows a high dielectric constant, exhibiting great potential for applications such as healable flexible touch screens and energy storage. Last, through structure characterizations and molecular dynamic simulation, this study provides a fundamental insight into the mechanism behind such high-performances from nano- to micro-scales, which is expected to inspire the design of a wide range of other SMPs that use different chemistries.     

Excellent Specific Mechanical and Electrical Properties of Anisotropic Freeze-Cast Native and Carbonized Bacterial Cellulose-Alginate Foams

Native and carbonized freeze-cast bacterial cellulose-alginate (BC-ALG) foams possess an ice-templated honeycomb-like architecture with remarkable properties. Their unique pore morphology consists of two levels of porosity: 20–50 µm diameter pores between, and 0.01–10 µm diameter pores within the cell-walls. The mechanical properties of the BC-ALG foams, a Young's modulus of up to 646.2 ± 90.4 kPa and a compressive yield strength of up to 37.1 ± 7.9 kPa, are high for their density and scale as predicted by the Gibson–Ashby model for cellular materials. Carbonizing the BC-ALG foams in an inert atmosphere at 1000–1200 °C in a second processing step, both pore morphology and mechanical properties of the BC-ALG remain well preserved with specific mechanical properties that are higher than those reported in the literature for similar foams. Also the electrical conductivity of the BC-ALG foams is high at 1.68 ± 0.04 S cm^?1 at a density of only 0.055 g cm^?3, and is found to increase with density as predicted, and as a function of the degree of carbonization determined by both carbonization temperature and atmosphere. The property profile makes freeze-cast BC-ALG foams and their carbonized foams attractive for energy applications and as a sorbent.     

Regulating Intercalation of Layered Compounds for Electrochemical Energy Storage and Electrocatalysis

Layered materials have received extensive attention for widespread applications such as energy storage and conversion, catalysis, and ion transport owing to their fast ion diffusion, exfoliative feature, superior mechanical flexibility, tunable bandgap structure, etc. The presence of large interlayer space between each layer enhances intercalation of the guest ion or molecule, which is beneficial for fast ion diffusion and charge transport along the channels. This intercalation reaction of layered compounds with guest species results in material with improved mechanical and electronic properties for efficient energy storage and conversion, catalysis, ion transport, and other applications. This review extensively discusses the intercalation of guest ionic or molecular species into layered materials used for various types of applications. It assesses the intercalation strategies, mechanism of ionic or molecular intercalation reactions, and highlights recent advancements. The electrochemical performances of several typical intercalated materials in batteries, supercapacitors, and electrocatalytic systems have been thoroughly discussed. Moreover, the challenges in the design and intercalation of layered materials, as well as prospects of future development are highlighted.     

Pulsed DC magnetron sputtering deposition of crystalline photocatalytic titania coatings at elevated process pressures

The use of elevated process pressures is described in the magnetron sputter deposition of titanium dioxide photocatalytic coatings to enable the direct low-temperature formation of the most photoactive titania crystal phase; anatase. Most other works on this subject deal with relatively low ‘conventional’ pressures (0.1–0.5 Pa). However, the present work describes pulsed DC reactive magnetron sputtering deposition of titanium dioxide thin films at process pressures in the range 2–5 Pa in a purpose-built sputtering rig. The influence of the other deposition conditions, such as pulse frequency and duty cycle, is also discussed. Additionally, a series of N-doped titania coatings was produced by using air as the reactive gas. The morphological and compositional properties of the coatings were studied using energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Wettability of the films was studied through measurement of water contact angles under UV light irradiation. Photocatalytic properties of the samples were assessed through the degradation of two model pollutants, methylene blue and stearic acid, under UV light irradiation. The results showed that elevated process pressures (4 Pa and above) allow the direct deposition of anatase titania films, without additional heat treatment, while amorphous titania tends to form at lower process pressures.     

1D/2D Nanomaterials Synergistic,Compressible, and Response Rapidly 3D Graphene Aerogel for Piezoresistive Sensor

Graphene‐based aerogels have been widely studied for their high porosity, good compressibility, and electrical conductivity as piezoresistive sensors. However, the fabrication of graphene aerogel sensors with good mechanical properties and excellent sensing properties simultaneously remains a challenge. Therefore, in this study, a novel nanofiber reinforced graphene aerogel (aPANF/GA) which has a 3D interconnected hierarchical microstructure with surface‐treated PAN nanofiber as a support scaffold throughout the entire graphene network is designed. This 3D interconnected microporous aPANF/GA aerogel combines an excellent compressive stress of 43.50 kPa and a high piezoresistive sensitivity of 28.62 kPa^?1 as well as a wide range (0–14 kPa) linear sensitivity. When aPANF/GA is used as a piezoresistive sensor, the compression resilience is excellent, the response time is fast at about 37 ms at 3 Pa, and the structural stability and sensing durability are good after 2600 cycles. Indeed, the current signal value is 91.57% of the initial signal value at 20% compressive strain. Furthermore, the assembled sensors can monitor the real time movement of throat, wrist pulse, fingers, wrist, and knee joints of the human body at good sensitivity. These excellent features enable potential applications in health detection.     

Ultralow Voltage High-Performance Bioartificial Muscles Based on Ionically Crosslinked Polypyrrole-Coated Functional Carboxylated Bacterial Cellulose for Soft Robots

The development of ultralow voltage high-performance bioartificial muscles with large bending strain, fast response time, and excellent actuation durability is highly desirable for promising applications such as soft robotics, active biomedical devices, flexible haptic displays, and wearable electronics. Herein, a novel high-performance low-priced bioartificial muscle based on functional carboxylated bacterial cellulose (FCBC) and polypyrrole (PPy) nanoparticles is reported, exhibiting a large bending strain of 0.93%, long actuated bending durability (96% retention for 5 h) under an ultralow harmonic input of 0.5 V, broad frequency bandwidth up to 10 Hz, fast response time (≈4 s) in DC responses, high energy density (6.81 KJ m⁻³), and high power density (5.11 KW m⁻³), all of which mainly stem from its high surface area and porosity, large specific capacitance, tuned mechanical properties, and strong ionic interactions of cations and anions in ionic liquid with FCBC and PPy nanoparticles. More importantly, bioinspired applications such as the grapple robot, bionic medical stent, bionic flower, and wings-vibrating have been realized. These successful demonstrations offer a viable means for developing high-performance bioartificial muscles for next-generation soft bioelectronics including bioinspired robotics, biomedical microdevices, and wearable electronics.     

Study on the effects of pressure and material characterization in thin film and TSV fabricated by supercritical carbon dioxide electrolyte

Supercritical CO₂ (sc-CO₂), post sc-CO₂ and traditional electroplating are used to fabricate Cu metal thin films. The effects of adjusting electroplating pressure over grain size, preferred grain orientation, mechanical properties and sheet resistance are discussed in this work. Additionally, through silicon vias (TSV) with an aspect ratio of 1:4 were fabricated by the three methods presented, and their influence over electrical resistance of the Cu pillar was observed. From the results it was clear that sc-CO₂ process provides the fastest micro-hole filling at 4 h, followed by post sc-CO₂ process at 5 h and lastly, traditional process at 36 h. Moreover, grain size produced by the sc-CO₂ process was smallest, calculated at 20 nm; second smallest was by post sc-CO₂ process at around 27 nm, and the largest was traditional process at around 38 nm. Fabrication process had an evident effect over grain size, hence affecting the mechanical and electrical properties of the structures. It is revealed that thin films produced by sc-CO₂ process have highest hardness, highest internal stresses and lowest roughness at 64–67 Hv, 45–54 MPa, and 0.68–0.85 µm, respectively; traditional process had the lowest values at 57 Hv, 30 MPa and 1.15 µm respectively; and post sc-CO₂ process was intermediate at 58–62 Hv, 33–41 MPa and 0.95–1.10 µm, respectively. In sheet resistance measurements, the trend persists and the highest values were displayed by the sc-CO₂ process at 1.3–1.5 µΩ-cm, the lowest by traditional process at 1.1 µΩ-cm, and post sc-CO₂ process was intermediate at 1.2–1.3 µΩ-cm. For TSV Cu pillars, the sc-CO₂ process displayed the highest electrical resistance at 5 mΩ, second largest was post sc-CO₂ process at 1.5 mΩ and the smallest was traditional process at 1.1 mΩ. Sc-CO₂ electroplating described in this work was performed without any additives, and still produced a high degree of grain refinement and excellent filling capabilities.     

Design Strategies toward High-Performance Hybrid Carbon Bilayer Anode for Improved Ion Transport and Reaction Stability

Compositing carbon-based materials with different properties can significantly improve the energy density of lithium-ion batteries for applications that require high power, such as electric vehicles, owing to their effective current distribution. Nevertheless, the chemical reaction is not uniform throughout the entire depth of conventionally blended electrodes. This study proposes a hybrid patterned bilayer anode that comprises a blended layer of spherical crystalline graphite (SCG) and soft carbon and a single layer of SCG alone, which maintains a stable ionic reaction at the electrode surface and improves ion transport. This bilayer anode has a smaller, more uniform solid electrolyte interphase layer that is more evenly distributed throughout the electrode compared with the blended electrode. The electrode pattern interfaces, which are optimized by controlling the pattern size, ensure excellent mechanical adhesion and low internal resistance. Consequently, the patterned bilayer half-cell achieves a high-capacity retention of 85.9% after 500 charge–discharge cycles at 1 C. The full cell also attains an energy density of 178.7 Wh kg⁻¹ with fast discharging at 10 C, which is 2.3 times higher than that of the single-layer SCG electrode.     

Role of thermal annealing on SiGe thin films fabricated by PECVD

Amorphous Silicon Germanium (a-SiGe) thin films of 500 nm thickness are deposited on silicon substrates using Plasma Enhanced Chemical Vapour Deposition (PECVD). To obtain polycrystalline nature of films, thermal annealing is done at various temperature (450–600 °C) and time (1–10 h). The surface morphology of the pre- and post-annealed films is investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The crystallographic structure of the film is obtained by X-ray diffraction method. Raman spectroscopy is carried out to quantify the Ge concentration and the degree of strain relaxation in the film. Nano-indentation is performed to obtain the mechanical properties of the film. It is found that annealing reduces the surface roughness of the film and increases the Ge concentration in the film. The grain size of the film increases with increase in annealing temperature. The grain size is found to decrease with increase in annealing time up to 5 h and then increased. The results show that 550 °C for 5 h is the critical annealing condition for variation of structural and mechanical properties of the film. Recrystallization starts at this condition and results in finer grains. An increase in hardness value of 7–8 GPa has been observed. Grain growth occurs above this critical annealing condition and degrades the mechanical properties of the film. The strain in the film is only relaxed to about 55% even for 10 h of annealing at 600 °C. Transmission Electron Microscopy (TEM) observations show that the strain relaxation occurs by forming misfit dislocations and these dislocations are confined to the SiGe/Si interface.     

Synthesis and characterization of nanostructured magnetoresistive Ni doped ZnO films

We report a method to produce magnetic nanostructured semiconductor films based in ZnO doped with Nickel to control their magnetic properties. The method is based on a combined diffusion–oxidation process within a controlled atmosphere chamber to produce a uniform distribution of Ni ions in the ZnO films (ZnO:Ni). The synthesis of ZnO:Ni films is reported as well as the magnetoresistive characteristics, the used method yields films with reproducible and homogeneous properties. The films were also characterized structurally by X-Ray Diffraction (XRD) and Raman spectroscopy, and by Hall–van der Pauw measurements. The XRD measurements confirm the nanocrystalline films character. The films resulted of n-type conductivity with electron concentrations of ~10²⁰ cm⁻³ in average and carrier mobilities of 5 cm²/V s. The Magnetoresistance (MR) behavior of the films at 300 K shows negative changes of ΔR~0.5% in accordance with the usual literature reports on samples produced by other methods.     

Versatile Solution-Processed Organic–Inorganic Hybrid Superlattices for Ultraflexible and Transparent High-Performance Optoelectronic Devices

Crystalline or amorphous metal oxides are widely used in various optoelectronic devices as key components, such as transparent conductive electrodes, dielectrics or semiconducting active layers for thin-film transistor (TFT) backplanes in large-area displays, photovoltaics, and light-emitting diodes. Although crystalline inorganic materials demonstrate outstanding optoelectronic performance, owing to their wide bandgaps, large conductivities, and high carrier mobilities, their inherent brittleness makes them vulnerable to mechanical stress, thereby limiting the use of metal-oxide films in emerging flexible electronic applications. In this study, stress-diffusive organic–inorganic hybrid superlattice nanostructures are developed to overcome the mechanical limitation of crystalline oxides and to provide high mechanical stability to metal-oxide semiconductors. In particular, hybrid transparent superlattice electrodes based on crystalline indium–tin oxide exhibit high electrical conductivities of up to 555 S cm^–1 (resistance variation < 3%) and effectively reduce the mechanical stress on the inorganic layer (up to 10 000 bending cycles with a radius of 1 mm). Furthermore, to ensure the viability of the hybrid superlattice flexible electronics, all solution-processed superlattice crystalline indium–gallium-oxide TFTs are implemented on a thin (≈5 µm) polyimide substrate, providing highly robust and excellent electrical performance (average mobility of 7.6 cm² V^–1 s^–1).     

Effects of gate dielectric surface modification on phototransistors with polymer-blended benzothieno[2,3-b]benzothiophene semiconductor thin films

In the present work, we investigated effects of the dielectric/semiconductor interface modification on the photoelectrical properties of phototransistors comprising a UV responsive semiconductor blend 2,7-dipentyl-[1]benzothieno[2,3-b][1]benzothiophene (C5-BTBT) and a linear unsaturated polyester (L-upe). Using various self-assembly monolayers with different end-groups at the dielectric/semiconductor interface we modulated the drain photocurrent and response times under the UV light illumination of phototransistors. Treatment of the SiO₂ dielectric surface with organosilanes led to the variation of the max mobility in the dark 0.10–0.18 cm² V⁻¹ s⁻¹ and under UV light 0.08–0.50 cm² V⁻¹ s⁻¹. Interestingly, detailed crystal structure analysis using 2D X-ray diffraction and photoelectrical characterization revealed that mobility in the dark predominantly depends on the alignment of C5-BTBT crystallites at the interface. Under UV light, the mobility increased with the electron withdrawing/donating nature of the SAM end-functional group. Additionally, chemical modification of the SiO₂ dielectric surface increased photocurrent relaxation/decay times upon UV light removal while retaining fast response times when exposed to UV light, which enhanced memory properties of fabricated phototransistors (fast UV response = writing and long relaxation = long data storage).     

A Biologically Muscle-Inspired Polyurethane with Super-Tough,Thermal Reparable and Self-Healing Capabilities for Stretchable Electronics

Polymeric elastomers play an increasingly important role in the development of stretchable electronics. A highly demanded elastic matrix is preferred to own not only excellent mechanical properties, but also additional features like high toughness and fast self-healing. Here, a polyurethane (DA-PU) is synthesized with donor and acceptor groups alternately distributed along the main chain to achieve both intra-chain and inter-chain donor-acceptor self-assembly, which endow the polyurethane with toughness, self-healing, and, more interestingly, thermal repair, like human muscle. In detail, DA-PU exhibits an amazing mechanical performance with elongation at break of 1900% and toughness of 175.9 MJ m⁻³. Moreover, it shows remarkable anti-fatigue and anti-stress relaxation properties as manifested by cyclic tensile and stress relaxation tests, respectively. Even in case of large strain deformation or long-time stretch, it can almost completely restore to original length by thermal repair at 60 °C in 60 s. The self-healing speed of DA-PU is gradually enhanced with the increasing temperature, and can be 1.0–6.15 µm min⁻¹ from 60 to 80 °C. At last, a stretchable and self-healable capacitive sensor is constructed and evaluated to prove that DA-PU matrix can ensure the stability of electronics even after critical deformation and cut off.     

The characterization of electrically conductive silver ink patterns on flexible substrates

Electrically conductive silver ink patterns were produced by the screen printing method. Paper, fabrics and plastics were used as the substrate materials. The electrical properties of the samples were characterized by sheet resistance measurement as a function of curing temperature and curing time. The mechanical properties of the samples were characterized by cross hatch adhesion test, bending test and tensile test. Depending on the process parameters and materials, the sheet resistance of the printed conductive patterns varied between 0.04 Ω/□ and 0.13 Ω/□. The curing temperature appeared to have a significant effect on the sheet resistance. In all cases sheet resistance decreased as a function of curing temperature. Adhesion between the substrates and the conductive patterns appeared to be good. The result of the bending test indicated that the resistivity of the silver ink patterns increased as a function of the bending cycle process. The results of the tensile and electrical tests showed that with the screen printing method it is possible to produce highly stretchable electrically conductive patterns for practical applications.     

Industry-Scale and Environmentally Stable Ti3C2Tx MXene Based Film for Flexible Energy Storage Devices

MXenes, 2D transition metal carbides, and nitrides have attracted tremendous interest because of their metallic conductivity, solution processability, and excellent merits in energy storage and other applications. However, the pristine MXene films often suffer from poor ambient stability and mechanical properties that stem from their polar terminal groups and weak interlayer interactions. Here, a heteroatom doping strategy is developed to tailor the surface functionalities of MXene, followed by the addition of large-sized reduced graphene oxide (rGO) as conductive additives to achieve a scalable production of S, N-MXene/rGO (SNMG-40) hybrid film with high mechanical strength ( ≈ 45 MPa) and energy storage properties (698.5 F cm⁻³). Notably, the SNMG-40 film also demonstrates long-term cycling stability ( ≈ 98% capacitance retention after 30 000 cycles), which can be maintained under ambient condition or immersed in H₂SO₄ electrolyte for more than 100 days. The asymmetric supercapacitor (aMGSC) based on SNMG-40 film shows an ultrahigh energy density of 22.3 Wh kg⁻¹, which is much higher than those previously reported MXene-based materials. Moreover, the aMGSC also provides excellent mechanical durability under different deformation conditions. Thus, this strategy makes MXene materials more competitive for real-world applications such as flexible electronics and electromagnetic interference shielding.     

Carbon Nanotube/Hygroscopic Salt Nanocomposites with Dual-Functionality of Effective Cooling and Fire Resistance for Safe and Ultrahigh-Rate Operation of Practical Lithium-Ion Batteries

Fire and explosion accidents and reduced energy utilization due to poor cycling stability of lithium-ion batteries (LIBs) caused by inevitable internal temperature rise during high-rate operations have become a growing concern. Herein, a dual-functional carbon nanotube/hygroscopic salt (DFCNT/HS) film with effective passive cooling performance and fire insulation for the safe usage of practical LIBs under extremely fast discharging conditions is reported. The DFCNT/HS film based on the cooling mechanism of self-adaptive moisture absorption/desorption delivers a high cooling power of 32.9 W m⁻² K⁻¹, which can reduce the maximum temperature of a 18650–3.6 V/2.0 Ah LIB by 11.2 and 17.4 °C at discharging rates of 10 and 15 C, respectively. Covering the cooling film, the battery discharges 23.6 Ah more total capacity at 10 within 500 cycles. What is challenging, almost three-fold extended lifetime of 425 cycles is achieved at 15 C with an extra total capacity of 467.2 Ah. Meanwhile, the developed film also shows an excellent high-temperature resistance up to 540 °C, which can alleviate the devastating fire propagation. The fast heat dissipation and excellent fire insulation as well as the mechanical flexibility and manufacturing scalability make this new material promising for safe usage of high-rate LIBs with zero energy consumption.     

Crack-Induced Superelastic,Strength-Tunable Carbon Nanotube Sponges

Lightweight strong aerogels have many applications, but they suffer from the trade-off between key mechanical properties, and it remains challenging to realize superelastic aerogels simultaneously possessing high strength and excellent structural recovery. Herein, a strategy to overcome such a problem by designing a carbon nanotube (CNT)-based aerogel consisting of flexible-rigid core-shell structure, which achieve a combination of excellent properties including superelasticity (complete recovery at 90%), high strength (over 12 MPa at 90%) and wide tunability (from 101 kPa to 4.5 MPa at 50% strain), is presented. It is found that the outer rigid but brittle amorphous carbon shells crosslink the CNT cores and crack into orderly distributed segments during the first compression cycle, while the flexible CNT cores ensure the integrity of the overall skeleton and tolerance to large deformation. This designed CNT composite sponges exhibit overall superior mechanical properties than previously reported foams/aerogels, and due to such unique crack-induced superelasticity mechanism, potential applications such as pressure sensors with wide-range tailored sensitivity and high-performance energy absorbers have been developed. This flexible-rigid core-shell synergia may provide further insight for tunable high-strength aerogel design and innovative applications.     

Effect of Microstructural Development on Mechanical and Electrical Properties of Inkjet-Printed Ag Films

The microstructural characterization of inkjet-printed Ag films sintered at various conditions was carried out to analyze the effect of microstructure on mechanical and electrical properties. As expected, the films became denser with grain growth with increasing sintering time and temperature, which resulted in improvement in mechanical properties. However, the resistivity of the films reached a minimum value of 3.0 μΩ cm before full densification. In order to improve the mechanical properties, pressure-assisted sintering was introduced. As a result, inkjet-printed Ag films sintered at 250°C under 5 MPa showed a tensile strength of 550 MPa, elongation of 2.4%, Young’s modulus of 55 GPa, and resistivity of ~3.0 μΩ cm.