Jie Mao

Increasing the polarity of molecular chains is the key to achieving high energy density in polymers. However, the polarization capability of polymers is not merely an accumulation of monomer dielectric properties. A pressing need arises for a universal design concept to guide the development of all-organic dielectric films, extending from monomer molecular structure to the polymer cross-linking network. In this research, we have developed a flexible dielectric film with a high energy density. The reduction of rotational space hindrance for polar functional groups ensures the polymer's heightened polarity. Additionally, the staggered arrangement of ester groups and benzene rings, combined with cross-linking constraints, alleviates the decrease in insulation performance caused by the planar conjugation of benzene rings. Significantly, the adjustment of the cross-linking network effectively mitigates the high conduction …

Polymer dielectrics, serving as integral components in electrostatic capacitors, must meet the escalating demands for electrical energy storage and conversion in harsh environments. However, the current enhancement of breakdown strength in polymer composite materials often relies on intricate nanostructure designs or inorganic deposition methods, which result in high production costs, slow processing, and hinder industrial scalability. Here, we present an economically efficient and easily implementable surface modification approach. This method induces the self-assembly of high-insulation-performance boron nitride nanosheets (BNNS) on the film surface through electrostatic interactions, thereby enhancing the high-temperature electrical insulation and energy storage performance of polymer dielectrics. At room temperature, the breakdown strength of the BNNS-coated polyetherimide (PEI) significantly …

Many creatures in the nature can quickly deform their shape and change their color under the stimulation of the external environment. Dielectric elastomer as one of the smart materials interests the scientists for developing biomimetic robots. However, the most dielectric elastomers have single functionality. Herein, an intelligent multifunctional dielectric elastomer with color-changing, tunable stiffness, and shape-morphing abilities is present in this work. To accomplish this material system, the thermochromic microcapsules and well-designed bistable dielectric elastomers actuator were blended. When the high temperature is applied, the material could not only change its color but also decrease its stiffness. The maximum actuation strain over 250% can be achieved at an electric field of 30 V/μm at 50 °C, which is one of the largest deformations compared with the reported materials. To demonstrate the application …

This work describes an easy and effective process for preparing a homogeneous polybutadiene (PB) dielectric elastomer with improved actuated strain by utilizing a photochemical thiol‐ene click reaction. The carboxyl groups and various ester groups are used for grafting on the PB. Since the length of the alkyl chains of the ester groups will significantly influence the polarities of the carbonyl groups and hydrogen bonding effect, the influence of polarity and hydrogen bonding effect on the dielectric properties and mechanical properties of the modified polybutadienes is carefully discussed. Very interestingly, it is found that the increment of dielectric constant of PB modified by carboxyl groups is the lowest one compared to other modified PBs with the ester groups. Meanwhile, the modified PBs with the ester groups could achieve pretty low dielectric loss factor, and finally, a high dielectric constant (3.6), low dielectric …

Insects with small and light bodies possess the capability of agile and fast movement in a small space. Inspired by nature, an insect-like soft robot may update the strategies in many scenarios like exploration, rescue, etc. However, the design and mass manufacture of soft robots combining insect size, fast mobility, good robustness, and impact-perception capability still present great engineering challenges. Herein, we report an insect-scale (15 mm body length (BL), 450 mg body weight) and ultrafast (∼4.0 BL s–1) soft robot. The remarkable motion performance is attributed to the high-frequency (760 Hz) operation as well as the long lifetime (>one million cycles) of its artificial muscle, which is a coil dielectric elastomer actuator (DEA) made by multimaterial coaxial three-dimensional printing with well-designed highly elastic materials and 5-inlets nozzle structure. The current robot is not only the smallest and fastest …

Phase separation has been widely exploited for fabricating structured functional materials. Generally, after being fabricated, the phase structure in a hybrid material system has been set at a specific length scale and remains unchanged during the lifespan of the material. Herein, we report a strategy to construct on-demand and reversible phase switches among homogenous, nano- and macro-phase separation states in a composite elastomer during its lifespan. We trigger the nanophase separation by super-saturating an elastomer matrix with a carefully selected small-molecule organic compound (SMOC). The nanoparticles of SMOC that precipitate out upon quenching will stretch the elastomer network, yet remain stably arrested in the elastomer matrix at low temperatures for a long time. However, at elevated temperatures, the nano-phase separation will transform into the macro-one. The elastic recovery will drive …

The oriented actuation of muscles is an important motion form in the locomotion of living beings. Dielectric elastomers (DE) as soft electroactive materials are considered as one of the leading candidates for artificial muscles. However, the electro-actuated deformations of most DE films are uniformly expanded, since synthetic elastomer films are generally mechanically isotropic. Here, we design an elastomer network with reserved double bonds, which allows post-crosslinking in as-prepared isotropic elastomer films with designed crosslinked patterns to spatially modulate the stiffness, and the elastic modulus in the post-crosslinked areas can be continuously increased by an order of magnitude. We reveal that introducing proper numbers of periodic parallel post-crosslinked strips enables the elastomer film to exhibit strong anisotropic mechanical behavior. Furthermore, we simulate and demonstrate the advantage of …

Dielectric elastomer is a kind of attractive artificial muscle with fast and reversible deformation excited by applied voltages. Typical dielectric elastomers suffer from low dielectric breakdown strength, which limits the achievable electro-actuation performance. We report that the introduction of surface-modified ZrO2 nanoparticles in dielectric elastomer (poly(styrene-b-butyl acrylate-b-styrene)) can significantly increase the dielectric breakdown strength. We highlight that the surface modifier molecules for ZrO2 nanoparticles should be designed to have an oligomeric chain compatible with the elastomer matrix to relieve the entropy loss of the elastomer chains. Thus, good dispersion of the nanoparticles can be achieved and the modulus is mildly increased. As a result, the maximum electro-actuation area strain is increased by a factor of 2.0 (from 19.1% to 37.8%), and the maximum energy density by a factor of 9.2 (from 5 …

Light production in natural fireflies represents an effective and unique method for communication and mating. Inspired by bioluminescence, we develop a 650 mg aerial robot powered by four electroluminescent (EL) dielectric elastomer actuators (DEAs) that have distinct colors and patterns. To enable simultaneous actuation and light emission, we embed EL particles in a DEA that has highly transparent electrodes. During robot flight, a strong ( 40 V/ m) and high frequency (400 Hz) electric field is generated within the DEA, exciting the EL particles to emit light. Compared to a regular DEA, our new design and fabrication methods require small additional weight (2.4%) and actuation power (3.2%) without adversely impacting the DEA’s output power or lifetime. We further develop a position and attitude tracking method using vision-based color detection. We demonstrate a series of closed-loop flights and compare …

Biological muscles are composed of aligned actuatable fiber units to generate directional linear output, inspiring the design of microstructures in artificial muscles. However, synthetic soft elastomers generally possess isotropic mechanical properties; therefore, a promising artificial muscle (dielectric elastomer actuator) generally outputs nondirectional force or deformation. In this work, we report a muscle-mimetic anisotropic dielectric elastomer fiber with directional output driven by electric field. The millimeter-in-diameter fibers are fabricated by rolling elastomeric ultrathin films of triblock copolymer that are pretreated to generate aligned nanostructures and network strands. We theoretically and experimentally reveal that a moderate orthogonal modulus ratio of radial to axial directions (2.8) leads to highly directional actuation, enhancing linear axial strain by 100%. Assembling the anisotropic fine fibers into bundles is …

Structurally colored materials can switch colors in response to external stimuli, which makes them potentially useful as colorimetric sensors, dynamic displays, and camouflage. However, their applications are limited by the angular dependence, slow response, and absence of synchronous control in time and space. In addition, out-of-plane deformation from shape instability easily occurs in photonic films, leading to inhomogeneous colors in photonic-crystal materials. To address these challenges, we combine structurally colored photonic glasses and dielectric elastomer actuators. We use an external voltage signal to tune color changes quickly (much less than 0.1 s). The photonic glassses produce colors with low angular dependence, so that their colors are homogeneous even when they become curved due to voltage-triggered instabilities (buckling or wrinkling). As proof of concept, we present a pixelated display …

Dielectric elastomer actuators (DEAs) are promising soft electromechanical transducers for soft robotics. Fabricating a high‐performance DEA actuated by sub‐kV voltage remains challenging. Here, a facile method not only to fabricate ultrathin dielectric elastomer films of triblock copolymers but also to enhance the dielectric breakdown strength and thus enhance the electromechanical performance is reported. A thick thermoplastic elastomer film of poly(styrene‐b‐butyl acrylate‐b‐styrene) from solution blading is symmetrically pre‐stretched and relaxed at 120 °C to fabricate a freestanding ultrathin DE film. Compared with the pristine DE film of the same thickness (12 µm), the thermally‐relaxed DE film with equally biaxial pre‐stretch ratio 3.5 × 3.5 exhibits increased electrical breakdown strength by a factor of 1.9 (from 43 to 82 V µm−1), maximum actuation area strain by a factor of 1.9 (from 11.7% to 22.4%), and …

In the current work, the polypropylene composites filled with a M-T-ZnOw@Ag filler with antibacterial and antistatic properties was firstly synthesized. The composites and the fabricated nanocomposites were characterized using SEM, TEM, XRD, FTIR and XPS techniques. With the addition of M-T-ZnOw@Ag, the antibacterial and antistatic properties of composite materials are greatly improved by the synergistic effect of AgNPs and T-ZnOw. When the filler content is 10 wt%, the antibacterial activity of the composite material against Gram negative (Escherichia coli) and Gram positive (Staphylococcus aureus) bacterial were 100%. And the surface resistivity was reduced to 5.5 × 1010 Ω, fell by nearly 7 orders of magnitude compare with the neat PP. Furthermore, the composites showed better mechanical properties. The maximum impact strength of the composites is 56.3% higher than the neat PP. We believe the …

Soft biological tissues and muscles composed of semiflexible networks exhibit rapid strain-hardening behaviors to protect them from accidental rupture. In contrast, synthetic soft elastomers, usually featuring flexible networks, lack such behaviors, leading to a notorious issue when applying them to a promising artificial muscle technology (dielectric elastomer, DE), that is electromechanical instability (EMI) induced premature breakdown. We report that a facile thermomechanical training method can adaptively reconstruct the network of a soft triblock copolymer elastomer to transform its flexible network strands into semiflexible ones without extra chemical modifications and additives so that the electro-actuation performance is significantly enhanced by avoiding EMI. The free-standing actuators of trained elastomers exhibit a large stable electro-actuation strain and a high theoretical energy density (133%, 307 kJ m−3 …

Different crystal planes of nanocrystalline often displayed diverse physical and chemical properties. In this paper, the effects of nano-ZnO with two kinds of crystal planes on crystallization, thermal stability and mechanical properties of PLLA were investigated. The results show that the (1010) planes with no-polar and low surface energy increased the chain mobility of PLLA chain, showed a plasticizing effect; the glass transition temperature, melt and cold crystallization temperature decreased by 12 °C, 10 °C and 12 °C, respectively. The size of spherulites increased and the number of spherulites decreased, the crystal form changed from mixed crystal form α, α′ to unique α crystal form. However, the (0002) planes with polar and high surface energy has highly nucleating effective for PLLA, the crystallization temperature increased to 106.41 °C, the cold crystallization peak disappear. The size of spherulites …

The end group modification of hydrogen bonding units has a significant effect on physical properties of covalent linked polymers. In this study, telechelic poly(ethylene glycol)s (PEG) with various molecular weights were functionalized by thymine (Thy), which was able to form self‐complementary double hydrogen bonding. The physical properties of Thy‐functionalized PEGs, including viscosity in solution or melt state, crystallization behavior, crystalline structure as well as lamellar structure were systemically investigated by comparison with hydroxyl‐terminated PEGs. Crystallinity and melting temperature of linked PEG chains were decreased by the presence of Thy groups and the depression effects were strengthened by increase of Thy content. Crystallization rate and temperatures at which crystallization occurred were more complicated. Lower crystallization rate was obtained for Thy‐functionalized PEGs with …

The nanocrystalline with different crystal planes often displayed diverse physical and chemical properties. However, the effects of crystal planes of inorganic nano-particle have been few focused on. Here, two kinds of nano-crystal ZnO with different crystal planes were used to explore their effect on the crystallization nucleation, crystal morphologies, thermal and thermal-oxidation stability of iPP. The results shown that the (1010) and (0002) planes possessed different effects for iPP. The (1010) planes with non-polar and low surface energy has highly nucleating effective for iPP, the crystallization temperature increased by 11 °C, the size of spherulites decreased, the number of spherulites increased, the nucleation efficiency and crystallization rate up to 57.81% and 1.27 min−1, the thermal and thermal oxidation stability (TG, OIT, OOT) of iPP improved by 6 °C, 6 min and 12 °C. In contrast, the (0002) planes …

Active soft materials that change shape on demand are of interest for a myriad of applications, including soft robotics, biomedical devices, and adaptive systems. Despite recent advances, the ability to rapidly design and fabricate active matter in complex, reconfigurable layouts remains challenging. Here, the 3D printing of core‐sheath‐shell dielectric elastomer fibers (DEF) and fiber bundles with programmable actuation is reported. Complex shape morphing responses are achieved by printing individually addressable fibers within 3D architectures, including vertical coils and fiber bundles. These DEF devices exhibit resonance frequencies up to 700 Hz and lifetimes exceeding 2.6 million cycles. The multimaterial, multicore‐shell 3D printing method opens new avenues for creating active soft matter with fast programable actuation.

Dielectric elastomers (DEs) are promising electroactive artificial muscles for use in soft machines. However, achieving anisotropy and sub-kV actuation voltage remains a great challenge for DE actuators. Herein, we report a facile method to fabricate ultrathin anisotropic DE films of an amorphous triblock copolymer poly(styrene-b-butyl acrylate-b-styrene) (SBAS) for soft actuators. The modulus of anisotropic SBAS in one direction can be modulated from 0.3 MPa to 10.5 MPa, and the modulus in the orthogonal direction remains the same as that of the pristine film (0.3 MPa). The anisotropy endows soft DE actuators with the directional-preferred response to an applied electric field and programmable multiple actuation morphs. These anisotropic SBAS films allowed us to fabricate compact soft robotics with high maneuverability, including soft grippers for object manipulation and crawling robots with reversible moving …