Multiresponse Liquid Metal Bionic Flexible Actuator.

The flexible actuator has attracted significant interest for its ability to respond flexibly to external stimuli, especially for renewable natural energy sources. However, the flexible actuator faces issues such as inadequate sensitivity and inability to achieve synergistic responses. Therefore, we prepared a highly sensitive flexible actuator by mixing liquid metal (LM) with poly(vinylpyrrolidone) (PVP), graphene oxide (GO), and coating the resulting mixtures onto poly(ethylene terephthalate) (PET) substrate materials using the rod coating process. The flexible actuator responds quickly to near-infrared light and humidity and can be rapidly transformed from flat to curved with a maximum angular change of 540°. By demonstrating the flexible actuator in action, it can be used to create a crawling robot that mimics the movement of an inchworm on a leaf, as well as a gripper capable of lifting objects 5 times its weight, and a crawling robot that moves forward, turns left, and then right. Flexible actuators hold significant promise for applications in emerging fields such as advanced bionics and artificial intelligence.

Application of SWMM 5.1 in flood simulation of sponge airport facilities.

Construction of an airport runway makes the impervious area of the airport high, which leads to the deterioration of the water environment and frequent waterlogging disasters. The selection of sponge airport facilities (e.g., pump, multi-functional storage tanks, green roof) to mitigate airport flooding has been a crucial issue in China. This study aims to develop a conceptual rainwater-runoff simulation model, which can take into account the effects of such facilities of a sponge airport. Taking catchment N1 of Beijing Daxing Airport as a case study, SWMM 5.1 was implemented to develop three sponge airport models (one pump, two pumps, combination of pump and multi-functional storage tanks). A sensitivity analysis was carried out to guarantee the robustness of the developed models. A 1-hour rainfall scenario with a 5-year return period was employed on the three sponge airport models. The results showed that the effect rankings of the control strategies on the water depth, volume and peak inflow of catchment N1 were comparable - combined strategies (combination of pump and multi-functional storage tanks) > one pump and two pumps. The conceptual and hydrological models developed in this study can serve as a simulation tool for implementing a real-time rainwater drainage control system in Beijing Daxing Airport.

Synthesis of Silver Nanowires by Using Tetrabutyl Ammonium Dibromochloride as the Auxiliary for Low-Haze Flexible Transparent Conductive Films.

Silver nanowires (AgNWs) with the diameter down to 16 nm have been synthesized by using tetrabutyl ammonium dibromochloride (TBADBC) as the organic auxiliary. Moderate dosage of TBADBC was proven to be favorable for the in situ growth of Ag pentahedral seeds on the surface of small AgClBr2 particles and have a passivation effect on the Ag{100} crystal facet during the growth of AgNWs, eventually resulting in the formation of thin AgNWs. Furthermore, the transparent conductive film fabricated by using the obtained AgNWs exhibited excellent photoelectric properties, which has a transmittance of 90.60%, a haze of 0.95%, and a sheet resistance of 110.8 Ω/sq, indicating large potential for application in flexible transparent conductors.

In Situ Synthesis of Liquid Metal Conductive Fibers toward Smart Cloth.

To meet the diverse needs of humans, smart cloth has become a potential research hotspot to replace traditional cloth. However, it is challenging to manufacture a flexible fabric with multiple functions. Here, we introduce a smart cloth based on liquid metal (LM) conductive fibers. Ga2O3 nanoparticles are obtained through ultrasonic pretreatment. Furthermore, a coordination bond is formed between thiol groups on the surface of protein fibers and Ga2O3 through a scraping method, allowing Ga2O3 particles to be grafted onto the surface of protein fibers in situ. Finally, LM conductive fibers are encapsulated using a photocuring adhesive. In addition, a wearable smart cloth integrated with multiple sensors has been developed based on LM conductive fibers. Users can not only monitor their movement trajectory and the surrounding environment in real time but also have their data supervised by family members through a client, achieving remote and continuous monitoring. The development of this wearable smart cloth provides strong support for future wearable, flexible electronic devices.

Tough Gelatin Hydrogel for Tissue Engineering.

Tough hydrogel has attracted considerable interest in various fields, however, due to poor biocompatibility, nondegradation, and pronounced compositional differences from natural tissues, it is difficult to be used for tissue regeneration. Here, a gelatin-based tough hydrogel (GBTH) is proposed to fill this gap. Inspired by human exercise to improve muscle strength, the synergistic effect is utilized to generate highly functional crystalline domains for resisting crack propagation. The GBTH exhibits excellent tensile strength of 6.67 MPa (145-fold that after untreated gelation). Furthermore, it is directly sutured to a ruptured tendon of adult rabbits due to its pronounced toughness and biocompatibility, self-degradability in vivo, and similarity to natural tissue components. Ruptured tendons can compensate for mechanotransduction by GBTH and stimulate tendon differentiation to quickly return to the initial state, that is, within eight weeks. This strategy provides a new avenue for preparation of highly biocompatible tough hydrogel for tissue regeneration.

Multifunctionally wearable monitoring with gelatin hydrogel electronics of liquid metals.

Hydrogel-based flexible electronics have been of widespread interest in recent years. However, current hydrogel electronics have limitations, such as poor biocompatibility, non-reusability, low electrical response to deformation and being single-function. GelMA is a gelatin-based hydrogel that has been widely used in the biological field, such as in tissue repair and drug delivery. Could it be a good choice for high biocompatibility wearable electronics? Here, by controlling the replacement rate of amine and hydroxy functionalities, we made the common brittle GelMA into a highly stretchable hydrogel. And we report for the first time GelMA hydrogel electronics with liquid metals (LMGE), which could be fabricated by simply injecting liquid metals into the internal microchannels of the GelMA hydrogels (GelMA-30). With the unique biocompatibility, outstanding air and ion permeability, and great mechanical properties of GelMA-30, as well as the low toxicity, high conductivity and high rheology of liquid metals, LMGE can not only monitor movement changes and even the heartbeat of rats, but can also be used as a wireless monitor to supervise secretions produced during human exercise. The design of LMGE provides a general strategy for the manufacture of bio-flexible hydrogel electronics, which opens the way for the development of multi-functional biomimetic materials for integrated monitoring and repair for biomedical applications.

Morphology-controlled silver nanowire synthesis using a cocamidopropyl betaine-based polyol process for flexible and stretchable electronics.

Silver nanowire (AgNW) based transparent conductive films (TCFs) are promising building blocks for flexible and stretchable electronics to replace brittle metal oxides. Ultra-long AgNWs are preferred for enabling TCFs with excellent photoelectric properties and mechanical flexibility. Herein, a novel polyol process is proposed for the synthesis of ultra-long AgNWs, with the new finding that the addition cocamidopropyl betaine (CAB) to polyol synthesis allows the rapid production of AgNWs with an average length of ∼120 µm in a high yield of ∼90%. Also, a cocamidopropyl betaine assisted polyol method for the synthesis of ultra-long AgNWs is demonstrated with a possible mechanistic explanation. The prepared AgNWs are coated on a polyethylene glycol terephthalate (PET) substrate to fabricate a flexible transparent conductive film, which exhibits a low sheet resistance of ∼200 Ω sq-1 at 88.74% transmittance with a negligible change of sheet resistance after bending. In addition, flexible TCFs based on the resulting AgNWs reveal excellent mechanical flexibility and high cyclic stability after 300 cycles of bending. The new polyol process in this work will provide a greater possibility for the practical application of long AgNWs towards flexible and wearable optoelectronic devices.

Ascorbic Acid-Assisted One-Step Chemical Reaction To Design an Ultralong Silver Nanowire Structure for a Highly Transparent Flexible Conducting Film.

Increasing the length of silver nanowires (AgNWs) has been demonstrated as an effective measure to enhance their optoelectronic properties by reducing light attenuation. Herein, we report a unique modified polyol synthesis of AgNWs with average length as long as ∼270 µm in a high yield of ∼90%. The synthesis of ultralong AgNWs involves the employment of ascorbic acid in the polyol approach. The strong reducing action of ascorbic acid allows the reduction of silver precursors to occur at a relatively low temperature, wherein the lateral growth of AgNWs is restrained because of efficient surface passivation via the dual function of poly-vinylpyrrolidone and ascorbic acid. The photoelectric properties of the as-synthesized ∼270 µm AgNW film show a noteworthy transmittance of 92.61% with a low haze of 1.35% at a sheet resistance of ∼322 Ω sq-1. In addition, the AgNW film shows distinguished mechanical property and relatively high electrical stability. The breakthrough in the length confinement of AgNWs is a highly expected step to prepare AgNW films with excellent performance.

One-Step Synthesis of Silver Nanowires with Ultra-Long Length and Thin Diameter to Make Flexible Transparent Conductive Films.

High aspect ratio silver nanowires (AgNWs) with ultra-long length and thin diameter were synthesized through bromine ion (Br-)-assisted one-step synthesis method. The bromine ions were used as pivotal passivating agent. When the molar ratio of Br-/Cl- was 1:4, the average diameter of AgNWs was as low as ~40 nm, the average length was as high as ~120 µm, and the aspect ratio reached 2500. Networks of AgNWs were fabricated using as-prepared high-quality AgNWs as conducting material and hydroxyethyl cellulose (HEC) as the adhesive polymer. As a result, a low sheet resistance down to ~3.5 Ω sq-1 was achieved with a concomitant transmittance of 88.20% and a haze of 4.12%. The ultra-low sheet resistance of conductive film was attributed to the long and thin AgNWs being able to form a more effective network. The adhesion of the AgNWs to the substrate was 0/5B (ISO/ASTM). The insights given in this paper provide the key guidelines for bromine ion-assisted synthesis of long and thin AgNWs, and further designing low-resistance AgNW-based conductive film for optoelectronic devices.

A novel synthesis of silver nanowires by using 6-chlorohexylzinc bromide as an additive for low haze transparent conductive films.

High-quality silver nanowires (AgNWs) with a small diameter of ∼20 nm and a length of ∼40 µm were prepared by using a novel organic 6-chlorohexylzinc bromide as an assistant additive. The diameter of as-synthesized AgNWs was confirmed to be strongly dependent on the dosage of 6-chlorohexylzinc bromide. Moreover, a two-dimensional (2D) transparent conductive film (TCF) with an excellent optical performance was fabricated by as-synthesized AgNWs, which has a 90.3% transmittance and low haze value of <1.0% at a sheet resistance of 48.7 Ω sq-1.