Stroke and spinal cord or brain injury often result in cavity formation. Stem cell transplantation in combination with tissue engineering has the potential to fill such a cavity and replace lost neurons. Several hydrogels containing unique features particularly suitable for the delicate nervous system were tested by determining whether these materials were compatible with fetal human neural stem cells (hNSCs) in terms of toxicity and ability to support stem cell differentiation in vitro. The hydrogels examined were pluronic F127 (PF127), Matrigel and PuraMatrix. We found that PF127, in a gelated (30%) form, was toxic to hNSCs, and Matrigel, in a gelated (1-50%) form, prevented hNSCs' normal capacity for neuronal differentiation. In contrast, PuraMatrix was the most optimal hydrogel for hNSCs, since it showed low toxicity when gelated (0.25%) and retained several crucial properties of hNSCs, including migration and neuronal differentiation. Further optimization and characterization of PuraMatrix is warranted to explore its full potential in assisting neural regeneration in vivo.

Electromagnetic interference (EMI) shielding materials for electronic devices in aviation and aerospace not only need lightweight and high shielding effectiveness, but also should withstand harsh environments. Traditional EMI shielding materials often show heavy weight, poor thermal stability, short lifetime, poor tolerance to chemicals, and are hard-to-manufacture. Searching for high-efficiency EMI shielding materials overcoming the above weaknesses is still a great challenge. Herein, inspired by the unique structure of natural wood, lightweight and highly anisotropic wood-derived carbon composite EMI shielding materials have been prepared which possess not only high EMI shielding performance and mechanical stable characteristics, but also possess thermally stable properties, outperforming those metals, conductive polymers, and their composites. The newly developed low-cost materials are promising for specific applications in aerospace electronic devices, especially regarding extreme temperatures.

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Electrical stimulation of shape-memory polymers (SMPs) has many advantages over thermal methods; creating an efficient conductive path through the bulk polymers is essential for developing high performance electroactive systems. Here, we show that a three-dimensional (3D) porous carbon nanotube sponge can serve as a built-in integral conductive network to provide internal, homogeneous, in situ Joule heating for shape-memory polymers, thus significantly improving the mechanical and thermal behavior of SMPs. As a result, the 3D nanocomposites show a fast response and produce large exerting forces (with a maximum flexural stress of 14.6 MPa) during shape recovery. We further studied the construction of a double-layer composite structure for bidirectional actuation, in which the shape change is dominated by the temperature-dependent exerting force from the top and bottom layer, alternately. An inchworm-type robot is demonstrated whose locomotion is realized by such bidirectional shape memory. Our large stroke shape-memory nanocomposites have promising applications in many areas including artificial muscles and bionic robots.

Three-dimensional carbon nanotube (CNT) networks with high porosity and electrical conductivity have many potential applications in energy and environmental areas, but the network structure is not very stable due to weak inter-CNT interactions. Here, we coat a thin polyaniline (PANI) layer on as-synthesized CNT sponge to obtain a mechanically and electrically stable network, and enable multifunctional applications. The resulting CNT/PANI network serves as stable strain sensors, highly compressible supercapacitor electrode with enhanced volume-normalized capacitance (632 F/cm), and reinforced nanocomposites with the PANI as intermediate layer between the CNT fillers and polymeric matrix. Our results provide a simple and controllable method for achieving high-stability porous networks composed of CNTs, graphene, or other nanostructures.

Lightweight, high-performance, thermally insulating, and antifrosting porous materials are in increasing demand to improve energy efficiency in many fields, such as aerospace and wearable devices. However, traditional thermally insulating materials (porous ceramics, polymer-based sponges) could not simultaneously meet these demands. Here, we propose a hierarchical assembly strategy for producing nanocomposite foams with lightweight, mechanically flexible, superinsulating, and antifrosting properties. The nanocomposite foams consist of a highly anisotropic reduced graphene oxide/polyimide (abbreviated as rGO/PI) network and hollow graphene oxide microspheres. The hierarchical nanocomposite foams are ultralight (density of 9.2 mg·cm) and exhibit ultralow thermal conductivity of 9 mW·m·K, which is about a third that of traditional polymer-based insulating materials. Meanwhile, the nanocomposite foams show excellent icephobic performance. Our results show that hierarchical nanocomposite foams have promising applications in aerospace, wearable devices, refrigerators, and liquid nitrogen/oxygen transportation.

Graphene-enhanced polymer matrix nanocomposites are attracting ever increasing attention in the electromagnetic (EM) interference (EMI) shielding field because of their improved electrical property. Normally, the graphene is introduced into the matrix by chemical functionalization strategy. Unfortunately, the electrical conductivity of the nanocomposite is weak because the graphene nanosheets are not interconnected. As a result, the electromagnetic interference shielding effectiveness of the nanocomposite is not as excellent as expected. Interconnected graphene network shows very good electrical conduction property, thus demonstrates excellent electromagnetic interference shielding effectiveness. However, its brittleness greatly limits its real application. Here, we propose to directly infiltrate flexible poly(dimethylsiloxane) (PDMS) into interconnected reduced graphene network and form nanocomposite. The nanocomposite is superflexible, light weight, enhanced mechanical and improved electrical conductive. The nanocomposite is so superflexible that it could be tied as spring-like sucker. Only 1.07 wt % graphene significantly increases the tensile strengths by 64% as compared to neat PDMS. When the graphene weight percent is 3.07 wt %, the nanocomposite has the more excellent electrical conductivity up to 103 S/m, thus more outstanding EMI shielding effectiveness of around 54 dB in the X-band are achieved, which means that 99.999% EM has been shielded by this nanocomposite. Bluetooth communication testing with and without our nanocomposite confirms that our flexible nanocomposite has very excellent shielding effect. This flexible nanocomposite is very promising in the application of wearable devices, as electromagnetic interference shielding shelter.

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