For emerging biocompatible, wearable, and stretchable epidermal electronic devices, it is essential to realize novel stretchable conductors with the attributes of transparency, low‐cost and nontoxic ...components, green‐solvent processbility, self‐healing, and thermal stabililty. Although conducting materials–rubber composites, ionic hydrogels, organogels have been developed, no stretchable material system that meets all the outlined requirements has been reported. Here, a series of P(SPMA‐r‐MMA) polymers with different ratios of ionic side chains is designed and synthesized, and it is demonstrated that the resulting stretchable ionic conductors with glycerol are transparent, water processable, self‐healable, and thermally stable due to the chemically linked ionic side chain, satisfying all of the aforementioned requirements. Among the series of polymer gels, the P(SPMA0.75‐r‐MMA0.25) gel shows optimum conductivity (6.7 × 10−4 S cm−1), stretchability (2636% of break at elongation), and self‐healing (98.3% in 3 h) properties. Accordingly, the transparent and self‐healable P(SPMA0.75‐r‐MMA0.25) gels are used to realize thermally robust actuators up to 100 °C and deformable and self‐healable thermal sensors.
A series of P(SPMA‐r‐MMA) polymers demonstrates that their resulting stretchable ionic conductors with glycerol are transparent, water processable, self‐healable, and thermally stable due to the chemically linked ionic side chain. Accordingly, the transparent and self‐healable gels are introduced to thermally robust actuators up to 100 °C, and for deformable and self‐healable thermal sensors.
Abstract
Soft robots need to be resilient to extend their operation under unpredictable environments. While utilizing elastomers that are tough and healable is promising to achieve this, mechanical ...enhancements often lead to higher stiffness that deteriorates actuation strains. This work introduces liquid metal nanoparticles into carboxyl polyurethane elastomer to sensitize a dielectric elastomer actuator (DEA) with responsiveness to electric fields and NIR light. The nanocomposite can be healed under NIR illumination to retain high toughness (55 MJ m
−3
) and can be recycled at lower temperatures and shorter durations due to nanoparticle-elastomer interactions that minimize energy barriers. During co-stimulation, photothermal effects modulate the elastomer moduli to lower driving electric fields of DEAs. Bilayer configurations display synergistic actuation under co-stimulation to improve energy densities, and enable a DEA crawler to achieve longer strides. This work paves the way for a generation of soft robots that achieves both resilience and high actuation performance.
Abstract
Dielectric elastomer actuators (DEAs) have shown great potential in the field of robotics, energy harvesting, or haptics for wearables. However, existing DEA materials typically require ...prestretching and exhibit time-dependent deformations due to their inherent viscoelastic properties. In this work, we address these issues by designing and synthesizing a polyurethane acrylate (PUA) DEA copolymerized with a polar crosslinker, polyethylene glycol diacrylate (PEGDA), to reduce viscoelastic effects through chemical crosslinking. We realized a buckling-mode actuator that displays out-of-plane deformations triggered by an electric field without the need for prestretching. Copolymerization with PEGDA showed improved dynamic response actuation performances compared to pristine PUA, wherein the former reached 90% of its maximum actuation in <1 s. In addition, precise and stable actuation was achieved, reducing viscoelastic drifts to a negligible amount. Despite the higher elastic modulus of the DEA incurred by the chemical crosslinks, the polar groups present in the PEGDA comonomer effectively increased the dielectric constant. As such, a higher area strain was achieved in comparison to that exhibited by low viscoelastic elastomers such as silicone. By eliminating the need for prestretching, rigid components can be avoided, thereby enabling greater prospects for the integration of fast response and stable DEAs into soft bodies.
The ability to rationally tune and add new end-groups in polymers can lead to transformative advances in emerging self-healing materials. Self-healing networks manipulated by supramolecular ...strategies such as hydrogen bonding and metal coordination have received significant attention in recent years because of their ability to extend materials lifetime, improve safety and ensure sustainability. This review describes the recent advancements in supramolecular polymers self-healing networks based on hydrogen bonding, metal-containing polymers and their nanocomposites. Collectively, the aim of this review is to provide a panoramic overview of the conceptual framework for the interesting nexus between hydrogen bonding and metal–ligand interactions for enabling supramolecular self-healing soft materials networks and nanocomposites. In addition, insights on the current challenges and future perspectives of this field to propel the development of self-healing materials will be provided.
Unimolecular dual agonists of the glucagon (GCG) receptor (GCGR) and glucagon-like peptide-1 receptor (GLP-1R) are a new class of drugs that are potentially superior to GLP-1R–specific agonists for ...the management of metabolic disease. The dual-agonist, peptide 15 (P15), is a glutamic acid 16 analog of GCG with GLP-1 peptide substitutions between amino acids 17 and 24 that has potency equivalent to those of the cognate peptide agonists at the GCGR and GLP-1R. Here, we have used cryo-EM to solve the structure of an active P15-GCGR-Gs complex and compared this structure to our recently published structure of the GCGR-Gs complex bound to GCG. This comparison revealed that P15 has a reduced interaction with the first extracellular loop (ECL1) and the top of transmembrane segment 1 (TM1) such that there is increased mobility of the GCGR extracellular domain and at the C terminus of the peptide compared with the GCG-bound receptor. We also observed a distinct conformation of ECL3 and could infer increased mobility of the far N-terminal His-1 residue in the P15-bound structure. These regions of conformational variance in the two peptide-bound GCGR structures were also regions that were distinct between GCGR structures and previously published peptide-bound structures of the GLP-1R, suggesting that greater conformational dynamics may contribute to the increased efficacy of P15 in activation of the GLP-1R compared with GCG. The variable domains in this receptor have previously been implicated in biased agonism at the GLP-1R and could result in altered signaling of P15 at the GCGR compared with GCG.
By incorporating fillers into dielectric elastomers, electromechanical sensitivities can be enhanced to lower the required operating electrical field for actuation. However, existing solid and liquid ...fillers suffer from increased stiffness and filler leakage problems respectively, hindering the actuation performance of dielectric elastomer actuators (DEAs). To address these challenges, a soft, stretchable (∼300%), transparent (∼99%), and solid-state poly(ionic liquid) (PIL) is introduced to DEAs as a compliant filler. The mechanical properties of the PIL can be tuned by controlling the solvent ratio within precursors. When the PIL filler is introduced to a very high bonding elastomer (VHB), the effective dielectric constant increases from 4.7 to 16.4 at 1 kHz and the Young's modulus decreases to 0.21 MPa. The resulting planar DEA could achieve an area strain of 133% at 17 V μm
−1
, exceeding that of most DEAs with fillers. Notably, the PIL achieves adhesion and rapid self-healability, which eliminates filler leakage problems and endows DEAs with recoverability. A unimorph DEA demonstrates a bending angle of 44.7° at 12.6 V μm
1
, two times greater than that exhibited by a DEA without the PIL filler. Simultaneous dynamic motion and light emission are further realized by integrating a unimorph DEA with an electroluminescent layer. Thus, the solid-state PIL filler provides high-performing and safer DEAs for soft robotics, interactive lighting, or wearables.
A soft and solid-state poly(ionic liquid) (PIL) filler is synthesized to increase the dielectric constant and decrease the Young's modulus of composite elastomers, thereby improving the actuation performance and safety of dielectric elastomer actuators (DEAs).
Pressing environmental challenges require focused research on sustainable solutions in the domains of energy, water, food, land, and climate. The pigment eumelanin has recently been positioned as a ...promising candidate for solving issues in health, sensors, and energy storage. However, the low solubility of eumelanin in aqueous solvents, difficult film processibility, and high cost have hindered the material from wide deployment. Here, we propose melanin extracted from the black soldier fly, Hermetia illucens (Mel-BSF), as a sustainable alternative for the preparation of organic electrodes in energy storage applications. Mel-BSF displays pseudocapacitive behaviour with a high potential window, good electrochemical stability, and higher maximum capacity (91.8 mAh g−1) compared to synthetic eumelanin (17.3 mAh g−1) as the working electrode material in zinc-ion hybrid capacitors using an ionic liquid electrolyte. Structural and surface investigations reveal that additional aliphatic compounds, potentially lipids present after Mel-BSF refinement, significantly increase the film stability and redox centre availability.Eumelanin is a promising pigment for use in energy storage applications but has limitations hindering its wide usage. Here, melanin extracted from the black soldier fly is used to prepare electrodes with higher performance than synthetic melanin in zinc-ion hybrid capacitor applications.
Solid‐state black electrochromic devices (ECDs) are promising for smart window applications, particularly when privacy protection and low leakage are required. Herein, a Ni–Cu salts/poly(vinyl ...alcohol) based organohydrogel electrolyte is developed with superior visible‐light transparency (83.8%), ionic conductivity (0.11 mS cm−1), and mechanical properties (tensile strength: 11.1 kPa, breaking strain: 242.6%). Due to the high viscosity of the organohydrogel electrolyte, a homogeneous Ni–Cu alloy film with a surface roughness of around 11.2 nm can be electrodeposited under −3 V for 5 min, and the resulting black color can be retained for over 350 min with a transmittance increase of only 5% at the voltage‐off state. The solid‐state rigid ECD exhibits an outstanding optical contrast between the transparent and colored states (visible light transmittance: 70.8% vs 0.085%), excellent cycling stability with over 90% retention of optical contrast after 2000 cycles. Finally, a flexible ECD is fabricated with the organohydrogel electrolyte and annealed indium tin oxide (ITO)‐coated polyethylene naphthalate (PEN) films as flexible and durable electrodes. It exhibits good mechanical flexibility with transmittance modulation degradation of 10% after 800 bending cycles and switching stability for 400 cycles with up to 43% optical contrast.
The black electrochromic device that consists of two electrodes and electrolyte functions via reversible Ni–Cu electrodeposition and dissolution. To enhance the electrochromic performance and sealability of the rigid device, a solid‐like electrolyte is prepared and employed. Flexible electrochromic device is also fabricated using the solid electrolyte and upgraded flexible conductive electrodes. It achieves acceptable cycling stability and good flexibility.
Soft electrical actuators driven by low voltages are promising for interactive human–machine interfaces (iHMI) applications including executing orders to complete various tasks and communicating with ...humans. The attractive features of low‐voltage soft electrical actuators include their good safety, low power consumption, small system size, and nonrigid or deformable characteristics. This review covers three typical classes of electrical actuators, namely, electrochemical, electrothermal, and other electrical (dielectric, electrostatic, ferroelectric, and plasticized gel) actuators according to their mechanism and working potential range. For each kind of actuators, the advantages, working principle, device configuration/design, materials selection, recent progress, and potential applications for iHMI are summarized, with the strategies for enhancing the actuation performance under low voltages being highlighted. Finally, the challenges for those soft actuators and possible solutions are discussed.
Soft electrical actuators play an important role for interactive human–machine interfaces in intelligent systems. Recent advances in low‐voltage actuators based on different mechanisms are comprehensively reviewed with emphasis on the materials selection, component fabrication, and device design. The current challenges and potential solutions for developing high‐performance low‐voltage soft actuators are also presented.
Enhancing fracture toughness and self‐healing within soft elastomers is crucial to prolonging the operational lifetimes of soft devices. Herein, it is revealed that tuning the polymer chain ...mobilities of carboxylated‐functionalized polyurethane through incorporating plasticizers or thermal treatment can enhance these properties. Self‐healing is promoted as polymer chains gain greater mobility toward the broken interface to reassociate their bonds. Raising the temperature from 80 to 120 °C, the recovered work of fracture is increased from 2.86 to 123.7 MJ m−3. Improved fracture toughness is realized through two effects. First, strong carboxyl hydrogen bonds dissipate large energies when broken. Second, chain mobilities enable the redistribution of localized stress concentrations to allow crack blunting, enlarging the size of dissipation zones. At optimal conditions of plasticizers (3 wt.%) or temperature (40 °C) to promote chain mobilities, fracture toughness improves from 16.3 to 19.9 and 25.6 kJ m−2, respectively. Insights of fracture properties at healed soft interfaces are revealed through double cantilever beam tests. These measurements indicate that fracture mechanics play a critical role in delaying complete failure at partial self‐healing. By imparting optimal polymer chain mobilities within tough and self‐healing elastomers, effective prevention against damage and better recovery are realized.
This study demonstrates that tuning the polymer chain mobilities of carboxylated‐functionalized polyurethane can improve both self‐healing abilities and fracture toughness. Higher mobilities facilitate enhanced reassociation of bonds at the damaged interface and enable redistribution of localized stress concentrations, increasing crack blunting. Healed soft interfaces are investigated, emphasizing the impact of fracture mechanics in delaying complete failure at partial self‐healing.
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