Advanced Materials Technologies最新文献

Low-melting-point metals, especially those that are liquid at room temperature, are being explored for an increasing number of applications. Like solid-phase metals, liquid metals have high electrical and thermal conductivity. However, liquid metals are also conformal, flexible, and stretchable, even when using thick films and large volumes. The shapes and structures that can be achieved with liquid metals span a variety of geometries and scales, ranging from thin films to 3D structures, and from nanoscale to macroscale feature sizes. Furthermore, liquid metals based on alloys of gallium have been shown to have low toxicity, making them suitable for biomedical devices and wearable electronics. These unique properties of low-melting-point metals make them useful materials in a variety of applications such as soft electronics, catalysis, and microfluidics.

This Special Section is a collection of ten research articles and one review article, contributed by experts in applications that utilize low-melting-point metals. The articles can be broadly sorted into three themes: 1) liquid metals for stretchable electronics, 2) liquid metals for energy storage devices and recyclable devices, and 3) fabrication processes enabled by or tailored to the use of low-melting-point metals. The topics covered by this special section illustrate the wide applicability of low-melting-point metals, and the utility of this class of materials in important and trending research areas.

Liquid metals are inherently suitable for stretchable electronics, as they can be used to realize deformable electrically conductive materials. In addition, repeated cycles of stretching and bending can result in fatigue of solid materials, but liquid–metal components are unaffected. Furthermore, the low toxicity of gallium-based liquid metals makes them suitable for wearable electronics.

In this special section, Liu and co-workers demonstrate a wearable sensor that uses a spiral structure of liquid metal to measure a variety of human motion (article number 2300896). Du and co-workers have reviewed the broader field of stretchable and flexible sensors that employ liquid metals (article number 2300431). Lim and co-workers describe a method of fabricating electrodes that use liquid metal in a sponge-like structure, and demonstrate stretchable sensors and flexible electronic breadboards using these “sponge electrodes” (article number 2301589). Malakooti and co-workers have also created stretchable conductors but with a different approach: printing elastomers impregnated with liquid–metal microdroplets (article number 2301324). Under strain, the microdroplets become electrically connected, and remain conductive after the strain is released. Bae and co-workers also used the direct printing of conductive material, but in their work liquid metal was used as an ink to create a stretchable thermoelectric device (article number 2301171). As seen in these papers, not all of the compo

Clutches are integral components in robotic systems, enabling programming of system stiffness and precise control over a wide range of motion types. While different types of clutches exist, electroadhesive (EA) clutches present several key advantages, such as flexibility, low mass, low power consumption, simplicity, and fast response. Achieving high EA stress in EA clutches has remained a challenge, however, necessitating high voltage input or a large contact area to achieve the desired force. In this work, an EA clutch is proposed with a high EA stress achieved by taking fracture mechanics into account and using a high dielectric composite layer while still maintaining a comparable high switching speed to other dielectric-based EA clutches. The maximum EA stress is observed to be 108.8 N cm⁻², which is four times larger than what has been reported previously among dielectric-based EA clutches at room temperature. This high EA stress clutch can facilitate miniaturization and lower the operating voltage as well as extend to high load capacity applications. The proposed approach holds promise for advancements in various domains, including haptics (both kinesthetic and cutaneous), exoskeletons, walking robots, and other systems that require compliance, low mass, and precise force control.

Mechanochemistry has developed rapidly in recent years for efficient chemicals and materials synthesis. Twin screw extrusion (TSE) is a particularly promising technique in this regard because of its continuous and scalable nature. A key aspect of TSE is that it provides high shear and mixing. Because of the high shear, it potentially also offers a way to delaminate 2-D materials. Indeed, the synthesis of 2-D materials in a scalable and continuous manor remains a challenge in their industrialization. Here, as a proof-of-principle, the automated, continuous mechanochemical exfoliation of graphite to give multi-layer graphene (MLG, ≈6 layers) by TSE is demonstrated. To achieve this, a solid-and-liquid-assisted extrusion (SLAE) process is developed in which organic additives such as pyrene are rendered liquid due to the high temperatures used, to assist with the exfoliation, and simultaneously solid sodium chloride is used as a grinding aid. This gave MLG in high yield (25 wt%) with a short residence time (8 min) and notably with negligible evidence for structural deterioration (defects or oxidation).

Integrating photonic crystals (PCs) into the design of a photocatalyst can significantly enhance its light-harvesting capability. PCs can manipulate the propagation of light uniquely within a material and reduce its group velocity, thereby enhancing the absorption factor for photocatalysts. However, the slow photon effect in photoactive films with chiral nematic structures has not been reported yet, especially at the blue edge of the photonic bandgap. This work proposes a straightforward one-pot method to fabricate various photonic films with chiral nematic, namely g-C₃N₄/SiO₂, TiO₂/SiO₂, and g-C₃N₄/TiO₂/SiO₂. The sol-gel biotemplating formulation using cellulose nanocrystals successfully leads to the elaboration of films exhibiting variable iridescent colors with photonic bandgap from UV to visible range. The tunable wavelength of the Bragg peak reflection offers the opportunity to access a region with a slow photonic effect, which directly impacts the light-harvesting properties of the photoactive material. It is demonstrated that the H₂ generation is significantly enhanced when the blue edge of the photonic bandgap position overlapped with the absorbance band of the photocatalyst. These results offer the opportunity to design photonic materials with chiral nematic structure and optimize the photocatalytic performance for energy application.

Capacitorless two-transistor (2T0C) dynamic random-access memory (DRAM) cells comprising oxide thin-film transistors (TFTs) show potential as low-power and high-density DRAM cells; however, the multiply–accumulate (MAC) operation using these cells is not yet realized. In this study, 2T0C DRAM cells comprising amorphous indium–tin–gallium–zinc oxide TFTs are fabricated for MAC operations. In a 2T0C DRAM cell, one transistor acts as a write transistor and the other as a read transistor, whose gate capacitance corresponds to the data storage capacitance. The cells have a long retention time of 1000 s, which is 10⁴ times longer than that of conventional DRAM cells, owing to the extremely low leakage current of the TFTs (1.11 × 10⁻¹⁸ A µm⁻¹). These cells satisfy the original condition for synaptic devices, in which a proportional relationship exists between the input and output. The MAC operation is performed using two cells. This study demonstrates the usefulness of oxide TFTs in artificial neural networks.

In traditional food industry, the assessment of mushy materials plays an important role in high-quality food production, which still relies heavily on human tactile perception. In this work, to address this issue for enhancing food production efficiency, a flexible electret tactile sensor that can mimic expert touch is developed. The sensor consists of a pair of electrodes, a microstructural spacer, and a pre-charged electret. Benefiting from the electrostatic induction-based working mechanism, the sensor attains high sensitivity and is ideal for precise sensing in actions similar to those of skilled Baijiu distillers. Due to its hermetic and electromagnetic interference-resistant encapsulation with polypropylene/aluminum/parylene films, the sensor remained durable in vinasse in the real distillery, with its high water and alcohol content, for over 21 days. This demonstrates its long-term stability in harsh environment. Based on the proposed flexible electret tactile sensor, an automated and intelligent vinasse identification system is built, mimicking the actions of Baijiu distillers in vinasse assessment. Combining tactile sensing data with machine learning, the system can distinguish 8 kinds of vinasses with different ingredient ratios, achieving an accuracy of 98%. This work significantly demonstrates the practical potential of the sensor in the food industry.

Electrostrictive materials exhibit a strain that is proportional to the square of the induced polarization. In linear dielectrics where the permittivity is constant, this electromechanical strain is also proportional to the square of the electric field. However, under increasing amplitudes of the driving field, the electromechanical strain sometimes saturates; the electrostrictive coefficients therefore appear to depend on the amplitude of the electric field used to measure them. Here, a methodology showing that this apparent field dependence is a consequence of neglecting higher-order electromechanical phenomena is presented. When these are taken into account, not only do the electrostrictive coefficients remain constant but the signs of the high-order coefficients enable the prediction of the saturation behavior from a single measurement. This approach is illustrated on both classical and non-classical (so-called “giant”) electrostrictors.

The logic circuit is the main component of an integrated circuit chip that dictates the operation and performance of the chip. The logic circuit based on a memristor can improve the integration and operation speed of the existing integrated circuit and reduce the chip size and the number of devices used by a single logic circuit. However, most of the research on logic circuits based on memristors has focused only on simulations, and research on the realization of logic circuits by hardware using actual memristors is limited. In this paper, a memristor based on graphene oxide with stable complementary resistive switching characteristics is fabricated, a logic circuit is built by using this device, and the logic functions of “IMP,” “AND,” and “NOR” are successfully realized. The complementary resistive switching device can alleviate the severe power loss caused by the memory separation of the von Neumann architecture. Moreover, its unique structure enables it to realize material logic independently without the use of multiple memristors and resistors, providing a new scheme for the physical realization of logic circuits. It also opens up a new path for integrated chips to break through von Neumann architecture.