physical/chemical functionalization is capable of optimization of mechanical properties, [7] interfacial adhesion, [8] and self-healing ability of hydrogels. [9] These protocols normally introduced functional elements or structures that elicited physical/chemical interactions for the performance improvements of hydrogels. For example, polymeric nanoparticles from crystallization-driven self-assembly enabled mechanical improvements on hydrogel by physical hybridization with matrix. [10] Grafting silica nanoparticles to a double-network polymer also improved the hydrogel mechanical performances. [11] Construction of electrostatic interaction between carboxyl groups and various surfaces resulted in a catechol-chemistrybased hydrogel for the long-term adhesiveness. [12] Treatment by metal ions resulted in a hydrophobic surface that promoted formation of a water-resistant molecular bridge between the hydrogel surface and hydrophobic domains on the substrates, endowing the hydrogels prominent underwater-adhesion capability. [13] Similar adhesive hydrogel could also be achieved by dopamine-modified clay nanosheets. [14] An effective molecular structure design based on acid-ether hydrogen bonding and imine bonds was capable of accelerating hydrogel healing time to 30 min. [15] A dynamic borate bond in network enabled 100% cure of hydrogel in air. [16] Reversible metal-ligand coordination bonding interaction could also be used to construct self-healing hydrogel. [17] These protocols are efficient for the construction of functional hydrogels, yet still challenging to synchronously improve the mechanical strength, self-healing, and interfacial adhesion of a hydrogel, and especially, hard to endow the hydrogel with modular sensitivity to external pressure. Therefore, the development of a new class of protocol is still essential.Herein, we proposed an electrochemistry functionalization protocol, in which the functional improvements on hydrogels were achieved by the electrode reactions, and electrochemistrytriggered ionic and molecular migration. This protocol was capable of enabling the function improvements of the hydrogel in mechanical strength, interfacial adhesion, and self-healing. In the meantime, it allowed generation of various patterns on the hydrogel surface, and endowed the hydrogel modular sensitivity to external pressure. The functional improvements Hydrogels have demonstrated great potential in biomedical and engineering areas. To improve the physical performance, development of efficient physical/chemical protocols is essential. Herein, an electrochemistry functionalization strategy that is capable of enabling the functional improvements of hydrogel is reported. The electrochemistry functionalization is demonstrated on a hydrogel model of polyacrylamide (PAAm)@κ-carrageenan. The electrochemistry reaction generates metal ions (Fe 3+ ) that migrate and coordinate with the sulfate groups of κ-carrageenan resulting in the prominent function improvements. In comparison with untreated PAAm@κcarrageenan hydrogel, it c...

The formation of complete and well-functioning endothelium is critical for the success of tissue-engineered vascular grafts yet remaining a fundamental challenge. Endothelium remodeling onto the lumen of tissue-engineered vascular grafts is affected by their topographical, mechanical, and biochemical characteristics. For meeting multiple requirements, composite strategies have recently emerged for fabricating hybrid scaffolds, where the integrated properties are tuned by varying their compositions. However, the underlying principle how the integrated properties of hybrid scaffolds regulate vascular endothelium remodeling remains unclear. To uncover the regulation effects of hybrid scaffolds on vascular endothelium remodeling, we prepared different biomimetic hybrid scaffolds using gelatin methacrylamide (GelMA) and poly-ε-caprolactone (PCL) and then investigated vascular endothelial cell responses on them. GelMA and PCL, respectively, conferred the resulting scaffolds with biomimetic bioactivity and mechanical properties, which were tuned by varying GelMA/PCL mass ratios (3:1, 1:1, or 1:3). On different GelMA/PCL hybrid scaffolds, distinct vascular endothelial cell responses were observed. Firm cell-scaffold/cell-cell interactions were rapidly established on the hybrid scaffolds with the highest mass ratio of bioactive GelMA. However, they were mechanically insufficient as vascular grafts. On the contrary, the scaffolds with the highest mass ratio of PCL showed significantly reinforced mechanical properties but poor biological performance. Between the two extremes, the scaffolds with the same GelMA/PCL mass ratio balanced the pros and cons of two materials. Therefore, they could meet the mechanical requirements of vascular grafts and support the early-stage vascular endothelial cell remodeling by appropriate biological signaling and mechanotransduction. This investigation experimentally proves that scaffold bioactivity is the dominant factor affecting vascular endothelial cell adhesion and remodeling, whereas mechanical properties are crucial factors for the integrity of endothelium. This work offers a universal design strategy for desirable vascular grafts for improved endothelium remodeling.

Soft robots, sensors, and energy harvesters require materials that are capable of converting external stimuli to visible deformations, especially when shape-programmable deformations are desired. Herein, we develop a polymer film that can reversibly respond to humidity, heating, and acetone vapors with the generation of shape-programmable large deformations. Poly(vinylidene fluoride) film, capable of providing acetone responsiveness, is designed with microchannel patterns created on its one side by using templates, and the microchannels-patterned side is then treated with hygroscopic 3-aminopropyltriethoxysilane (APTES) to give humidity/heating-responsive elements. The APTES-modified microchannels lead to anisotropic flexural modulus and hygroscopicity in the film, resulting in the shape-programmed kinematics depending on the orientations of surface microchannels. As the microchannels align at oblique/right angles with respect to the long axis of the film strips, the coiling/curling motions can be generated in response to the stimuli, and the better motion performances are found in humidity- and heating-driven systems. This material utilized in self-adaptive soft robots exhibits prominent toughness, powerful strength, and long endurance for converting humidity and heat to mechanical works including transportation of lightweight objects, automatic sensing cap, and mimicking crawling in nature. We thus believe that this material with shape-programmable multisensing capability might be suitable for soft machines and robotics.

An improved protocol is proposed for preparation of a humiditysensitive soft actuator through the layer-by-layer assembling of weight-ratio-variable composites of sodium alginate (SA) and poly(vinyl alcohol) (PVA) into laminated structures. The design induces nonuniform hygroscopicity in the thickness direction and gives rise to strong interfacial interaction between layers, making the actuator have directional motility. A mathematical model reveals that the directional motion is driven by the chemical potential of humidity, and its energy conversion efficiency from humidity to mechanical work reaches 81.2% at 25 °C. By coating with CoCl 2 , the composite film of SA@PVA/CoCl 2 can act as a warning sign that provides reminder information to prevent people from slipping or falling by a conspicuous red sign during a high-humidity environment. When the film is involved in a bidirectional switch, it is capable of turning on/off light-emitting diodes by humidity, showing promising potential in control over humidity-dependent devices.

Hollow hydrogel tubes that are capable of maintaining their flexibility and structural stability in extreme temperature conditions have potential for use in biomedical scaffolds, carriers, and soft robotics over a wide temperature range. However, the preparation of hollow hydrogel tubes still remains challenging because it normally requires templates or complex devices and it is hard to endow the hollow tubes with antifreezing heat-resistant capabilities. We report a protocol that does not require a template or complex devices, in which sodium alginate film strips are immersed in an aqueous mixture of CaCO3, CaCl2, NaHCO3, and HCl, which results in the manufacture of hollow tubes in 30 min. These hollow tubes are functionalized by glycerol and poly­(ethylene glycol), which provides the tubes with antifreezing heat-resistant performances and enables them to keep their flexibility and hollow structures from −70 to 120 °C. This is the first report on antifreezing heat-resistant hollow hydrogel tubes, to the best of our knowledge. Such hollow tubes as carriers can control the sublimation of a mothball at a rate of 1.1 mg/h, which is one-tenth of the sublimating rate of an unloaded mothball. This sublimating rate reduces the hazard to environments along with maintaining the repellent effects. As the tube is a honey carrier, it enables the sustainable release of the honey over 800 min with a high efficacy for tricking and capturing ants. The simple applications demonstrate that the antifreezing heat-resistant hollow tubes might be feasible as carriers for the controlled release in extremely cold/hot environments.

Freezing and dehydration together with interfacial failure are capable of causing the functional reduction of hydrogels for sensing applications. Herein, we develop a multifunctional bilayer that consists of a mussel-inspired adhesive layer and a functionally ionic layer that is composed of sodium p-styrene sulfonate (SSS) and an ionic liquid of [BMIM]­Cl. The adhesive layer enables the strong adhesion of the bilayer to the surface of the skin. The introduction of ionic elements of SSS-[BMIM]Cl not only provides the bilayer with sensing adaptability in a wide temperature range of −25 to 75 °C, but also endows it with elastic, stretchable, self-healing, and conductive features. These mechanical properties are utilized to assemble a wearable sensor that has unprecedented sensitivity and reusability in monitoring human motions, including stretching, pulsing, frowning, and speaking. It is thus expected that the concept in this work would provide a promising route to design soft sensing devices that can work in a wide temperature range.

We reported a controlled synthesis method to obtained carbon spheres with tunable geometry under low ZnCl 2 aqueous solution conditions using polytriazine as a precursor. The polytriazine precursor was polymerized by mixing/reaction of 2,6diaminopyridine and formaldehyde in the presence of a diluted ZnCl 2 aqueous system. The obtained nanospheres were then decomposed to adulterate nitrogen porous carbon nanospheres (N-PCNSs) by the decomposition and blistering process at high temperature by degrees. ZnCl 2 worked as a solid-template and played the role of a stabilizing and foaming agent in the reaction. The as-prepared N-PCNSs with controllable spherical geometry, large micro-/mesoporous volume and high nitrogen content (∼8.5 wt %) were employed in electric double-layer capacitors that have a good specific capacitance (636 F/g at 1 A/g) and are long lasting. Besides, the N-PCNS delivered a high energy density of 22.1 Wh/Kg at a power density of 500 W/kg.

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