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Developing materials for active matter that can efficiently respond to external stimuli with designed multifold mechanical motions remains a major challenge, and overcoming this will greatly propel the advancement of micromachines and microrobots toward unprecedented biomedical, electronic, and particle-separation applications. Here, we propose an innovative working mechanism that allows multifold-translational-motion control of semiconductor microentities by AC dielectrophoresis with simple visible-light stimulation. We study the dielectrophoresis forces on semiconducting particles of various geometries in aqueous suspension by modeling with the consideration of both the Maxwell–Wagner relaxation and the electrical-double-layer-charging effect. With the obtained understanding, we rationally design a manipulation system that can versatilely transport semiconductors and orient them toward desired directions simultaneously by tuning the light intensity in an electric field. This research could provide insights toward developing a new class of micromachines with rarely found control flexibility and precision and offer a new route toward separation and purification of optoelectric microparticles of different geometries. [ABSTRACT FROM AUTHOR]

Negative Poisson's ratio (NPR) foams are usually prepared by the transformation of positive Poisson's ratio (PPR) foams with honeycomb cell structure, which face a challenge for restraining the increase in volume and Poisson's ratio once they are stimulated by high temperature. In addition, they cannot restore to its reentrant structure after large deformation. In this work, a novel method for preparing anisotropic NPR foam with excellent structural stability and shape recovery property is established by synergistically controlling hierarchical pore structures. The obtained NPR silicone rubber/polylactic acid (SR/PLA) composite foam has large-size holes (auxetic structure) with concave hexagonal shape and small-size honeycomb cells, which are generated by 3D printing technology and salt leaching method, respectively. The auxetic structure with the orientation characteristic is directly formed rather than transformed from the honeycomb cell structure. Therefore, the dimension and Poisson's ratio value of the NPR SR/PLA composite foam keep constant after high temperature heating treatment, meaning an excellent structural stability. Furthermore the excellent shape recovery property of the NPR SR/PLA composite foam endows it restore to the initial auxetic structure after large deformation to a large extent. It should be mentioned that the anisotropy of the NPR SR/PLA composite foam further will bring a broad application prospect in the field of human body cushioning materials, such as prosthetic lining sleeve. [Display omitted] • Anisotropic NPR SR/PLA composite foam was prepared by synergistically controlling hierarchical pore structures. • NPR SR/PLA composite foam has excellent structural stability and shape recovery property. • NPR SR/PLA composite foam shows both constant dimension and NPR after high temperature heating treatment. • This work overcomes the difficulty for deformation recovering of traditional NPR foams after large deformation. • Anisotropic NPR SR/PLA composite foam is promising as prosthetic lining sleeve. [ABSTRACT FROM AUTHOR]

The design and fabrication of various types of flexible, portable, and foldable devices have received immense interest owing to the remarkable potential in impacting peoples' lives including real‐time health monitoring, point‐of‐care diagnosis, and athletic training. In this work, the authors present 3D graphite as the key sensing element of polymer composite strain sensors that offers ultrahigh sensitivity and durability in the detection of fine motions. The graphite–polymer sensors in this work provide high bending sensitivities that are reproducible within 3% signal shift after 11 000 bending cycles and exhibit gauge factors of 100 and 52 at tensile strains of 80% and 100%, respectively. The sensing mechanism is modeled, and correlated with experimental studies. The high strain sensitivity compared to graphene based devices is analyzed and understood with respect to levels of defect in materials. Such graphite–polymer sensors are able to detect fine features of human pulses, respiration rates, and throat vibration in real time and are also applied in the detection of posture correctness of musical instrument learners for the first time. [ABSTRACT FROM AUTHOR]

In this work, separation performance of hierarchically porous membranes (HPMs) has been investigated with the combination of experiment and finite element simulation. From the blend of poly (vinylidene fluoride), poly (methyl methacrylate) and sodium chloride (i.e., PVDF/PMMA/NaCl), PVDF HPMs with cubic-large-pores connected through narrow nanopores have been fabricated successfully by etching NaCl and PMMA respectively. In the case of extremely high fill of NaCl, the inorganic fillers distribute all-over the specimen, yielding simultaneously internal and surface cubic-large-pores. Relative to the reference with only nanopores, the attained HPMs exhibit much higher permeability (up to ∼200 times) without any loss of selectivity. Such a significant improvement of separation performance can be attributed to the synergism effect between internal and surface cubic-large-pores. On one hand, the high content of isolated large pores in HPMs corresponds to shorter diffusion length and lower diffusion barrier for fluid; On the other hand, the existence of cubic-large-pores on membrane surface produces not only bigger pores and higher porosity on membrane surface, corresponding to convenient diffusion pathway, but also the enhanced hierarchical roughness including narrow nanopores and cubic-large-pores, providing additional driving force for water/oil separation. [Display omitted] • Simulation results clarify the synergism effect between internal and surface cubic-large-pores. • PVDF HPMs with both internal/surface cubic-large-pores and narrow nanopores have been fabricated successfully. • The attained PVDF HPMs exhibit higher flux without any loss of rejection ratio during separation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Auxetic PU/PDA/GR composite foam with high EMI SE was prepared via simple method. • The relationship between EMI SE and reentrant structure was studied at first time. • The high EMI SE of auxetic foam results from the reentrant structure and high SE A. • The auxetic foam is promising as temperature-regulated EMI shielding material. In this work, two kinds of auxetic composite foams of polyurethane (PU) with polydopamine (PDA) and graphene (GR) (PU/PDA/GR) were prepared by dip-coating and ultrasonic immersing, then followed by triaxial compression-heating process. The electromagnetic interference (EMI) shielding effectiveness (SE) value of the PU/PDA/GR auxetic composite foam with a Poisson's ratio of −2.36 from PU foam with open cellular structure reaches 59.75 dB, which is 8.9 times of the positive Poisson's ratio composite foam with the same GR content. Furthermore, the relationship of the EMI shielding performance of auxetic foam with different forms of reentrant structure was studied for the first time, in which the absolute value of negative Poisson's ratio was used to quantitatively describe the difference of the reentrant structure in the obtained auxetic foam. The larger the absolute value of negative Poisson's ratio is, the better the EMI shielding performance of the composite foam is. The high absorption EMI SE and the existence of reentrant structure are the key factors for the high EMI shielding performance of the auxetic composite foam. In addition, it is found that the EMI SE of the auxetic foam can be adjusted via simple heating treatment, showing that the auxetic composite foam may be used as a temperature-regulated EMI shielding material in the future. [ABSTRACT FROM AUTHOR]

In this work, poly (vinylidene fluoride) (PVDF) hierarchically porous membranes (HPMs) with isolated large pores and continuous narrow nano-pores have been fabricated from its blend with poly (methyl methacrylate) (PMMA) based on the combination of crystallization template with chemical or supercritical CO2 foaming. On the one hand, the decomposition of azodicarbonamide (ADC, chemical foaming agent) or the release of CO2 can produce isolated large pores. On the other hand, PMMA is expelled during the isothermal crystallization of PVDF in their miscible blend, yielding narrow nano-pores upon etching with a selective solvent. In the case of supercritical CO2, the attained PVDF HPMs fail to improve separation performance because of the compact wall of isolated-large-pore and consequent poor connectivity of hierarchical pores. In the case of ADC, the optimal HPM exhibits much higher flux (up to 20 times) without any loss of selectivity compared with the reference only with nano-pores. The enhanced permeability can be attributed to the shorter diffusion length and lower diffusion barrier from isolated large pores, while the comparable selectivity is determined by narrow nano-pores in THE matrix. [ABSTRACT FROM AUTHOR]

Precise delivery of molecular doses of biologically active chemicals to a pre-specified single cell among many, or a specific subcellular location, is still a largely unmet challenge hampering our understanding of cell biology. Overcoming this could allow unprecedented levels of cell manipulation and targeted intervention. Here, we show that gold nanowires conjugated with a cytokine such as tumour-necrosis factor-alpha can be transported along any prescribed trajectory or orientation using electrophoretic and dielectrophoretic forces to a specific location with subcellular resolution. The nanowire, 6 µm long and 300 nm in diameter, delivered the cytokine and activated canonical nuclear factor-kappaB signalling in a single cell. Combined computational modelling and experimentation indicated that cell stimulation was highly localized to the nanowire vicinity. This targeted delivery method has profound implications for controlling signalling events on the single cell level. [ABSTRACT FROM AUTHOR]

Bulk transition metal dichalcogenide (TMDC) nanostructures are regarded as promising material candidates for integrated photonics due to their high refractive index at the near‐infrared wavelengths. In this work, colloidal TMDC waveguides with tailorable dimensions are prepared by a scalable synthetic approach. The optical waveguiding properties of colloidal nanowires are studied by the near‐field nanoimaging technique. In addition to dependence on thickness and wavelength, the excitonic responses and resultant waveguide modes in TMDC nanowires can be modulated by the environmental temperature. With the high‐throughput production and tunable optical properties, colloidal TMDC nanowires highlight the potential for active optical components and integrated photonic devices. [ABSTRACT FROM AUTHOR]

Dynamic acoustic wavefront control is essential for many acoustic applications, including biomedical imaging and particle manipulation. Conventional methods are either static or in the case of phased transducer arrays are limited to a few elements and hence limited control. Here, a dynamic acoustic wavefront control method based on light patterns that locally trigger the generation of microbubbles is introduced. As a small gas bubble can effectively stop ultrasound transmission in a liquid, the optical images are used to drive a short electrolysis and form microbubble patterns. The generation of microbubbles is controlled by structured light projection at a low intensity of 65 mW cm–2 and only requires about 100 ms. The bubble pattern is thus able to modify the wavefront of acoustic waves from a single transducer. The method is employed to realize an acoustic projector that can generate various acoustic images and patterns, including multiple foci and acoustic phase gradients. Hydrophone scans show that the acoustic field after the modulation by the microbubble pattern forms according to the prediction. It is believed that combining a versatile optical projector to realize an ultrasound projector is a general scheme, which can benefit a multitude of applications based on dynamic acoustic fields. [ABSTRACT FROM AUTHOR]

The performances of porous graphitic foams in flexible electronic, electrochemical, and thermal management devices can be enhanced by increasing the interfacial charge or heat transport between the 3D graphitic network and the functional materials filled into the pore space. Herein, an investigation of the effects of chemical vapor deposition (CVD) conditions on the structure and thermal conductivities of both graphitic foams grown from reticular Ni foams and dendritic graphitic foams (DGFs) synthesized from electrodeposited dendritic Ni foams is reported. A room‐temperature solid thermal conductivity (κs) up to 800 W m−1 K−1 is obtained from the graphitic foams (GF) with less than 1% volume fraction. In comparison, the DGFs, which provide a large increase of the specific surface area for enhanced interfacial heat transfer, achieve an effective thermal conductivity of 2.5 ± 0.2 W m−1 K−1 because of an enhanced volume fraction to about 5% despite a compromised κs around 200 W m−1 K−1 due to the increased defect density. Through systematical variations of the catalyst template morphology and CVD conditions, this work reveals the distinct roles of catalyst surface curvature and graphitic strut thickness in controlling the properties of GFs and DGFs for thermal management. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of NIPU by using cardanol as starting material. A cardanol formaldehyde oligomer was first prepared through the reaction of cardanol and formaldehyde, catalyzed by citric acid. The resulting oligomer was then subjected to epoxidation with m-chloroperbenzoic acid to obtain an epoxide compound, which was subsequently used to fix carbon dioxide (CO2) and form a cyclic carbonate. Using this cyclic carbonate, along with an amine, cardanol-based isocyanate polyurethane (NIPU) was prepared. Different characterization methods, such as Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA), were used to confirm the synthesis of the four intermediate products and NIPU in the reaction process. This study highlights the promise of bio-based NIPU as a sustainable alternative in a number of applications while offering insightful information on the synthesis and characterization of the material. [ABSTRACT FROM AUTHOR]

It is highly desirable to precisely tune the molecule release rate from the surfaces of nanoparticles (NPs) that are relevant to cancer therapy and single-cell biology. An innovative mechanism is reported to actively tune the biochemical release rate by rotation of NPs. Plasmonic nanomotors were assembled from NPs and applied in multiplex biochemical release and detection. Both single and multiplex biosignals can be released in a tunable fashion by controlling the rotation speed of the nanomotors. The chemistry and release rate of individual chemicals can be revealed by Raman spectroscopy. The fundamental mechanism was modeled quantitatively and attributed to the fluidic boundary-layer reduction owing to the liquid convection. This work, which explored the synergistic attributes of surface enhanced Raman scattering and nanoelectromechanical systems, could inspire new sensors that are potentially interesting for various bio-applications. [ABSTRACT FROM AUTHOR]

It is highly desirable to precisely tune the molecule release rate from the surfaces of nanoparticles (NPs) that are relevant to cancer therapy and single-cell biology. An innovative mechanism is reported to actively tune the biochemical release rate by rotation of NPs. Plasmonic nanomotors were assembled from NPs and applied in multiplex biochemical release and detection. Both single and multiplex biosignals can be released in a tunable fashion by controlling the rotation speed of the nanomotors. The chemistry and release rate of individual chemicals can be revealed by Raman spectroscopy. The fundamental mechanism was modeled quantitatively and attributed to the fluidic boundary-layer reduction owing to the liquid convection. This work, which explored the synergistic attributes of surface enhanced Raman scattering and nanoelectromechanical systems, could inspire new sensors that are potentially interesting for various bio-applications. [ABSTRACT FROM AUTHOR]

Spectral cytopathology (SCP) is a promising label-free technique for diagnosing diseases and monitoring therapeutic outcomes using FTIR spectroscopy. In most cases, cells must be immobilized on a substrate prior to spectroscopic interrogation. This creates significant limitations for high throughput phenotypic whole-cell analysis, especially for the non-adherent cells. Here we demonstrate how metasurface-enhanced infrared reflection spectroscopy (MEIRS) can be applied to a continuous flow of live cell solution by applying AC voltage to metallic metasurfaces. By integrating metasurfaces with microfluidic delivery channels and attracting the cells to the metasurface via dielectrophoretic (DEP) force, we collect the infrared spectra of cells in real time within a minute, and correlate the spectra with simultaneously acquired images of the attracted cells. The resulting DEP-MEIRS technique paves the way for rapid SCP of complex cell-containing body fluids with low cell concentrations, and for the development of a wide range of label-free liquid biopsies. [ABSTRACT FROM AUTHOR]

Abstract The fixation stage of cellular structure during polymer foaming process is difficult to control due to difficult removing of internal heat, especially for crystalline polymers such as polypropylene (PP). In order to control cellular structure in the fixation stage, we established an universal method by introducing water as an in-situ internal cooling agent during the foaming process of PP. Particularly, hydrophilic fillers were added into the high melt flow index polypropylene (HMI-PP) with poor foaming ability to study the effect of adsorbed water on the foaming process of PP/filler composites during sc-CO 2 batch foaming process. Compared to pure HMI-PP, HMI-PP/hydrophilic filler composites showed increased adsorption amount for water and melt viscosity. The water within the composites played a key role in the foaming process, which not only served as a physical foaming agent to increase the volume expansion ratio of PP composite foam, but also showed the function of rapid cooling foam proved by thermal imaging technology. As a result, the presence of some hydrophilic fillers within HMI-PP matrix significantly improved the foaming properties of HMI-PP, including preventing internal bubble collapse and significantly increasing the volume expansion ratio of the foam. The applicability of this method was validated using other PP materials besides HMI-PP, including high molecular weight PP (HMW-PP), high melt strength PP (HMS-PP). Graphical abstract Image Highlights • The presence of hydrophilic fillers enhanced adsorption amount of water in PP/filler composites. • Adsorbed water served as both in-situ cooling agent and foaming co-agent during CO 2 batch foaming process. • The in-situ cooling effect of adsorbed water in PP composites provides an efficient method to control cellular structure. [ABSTRACT FROM AUTHOR]

Abstract: The practical applications of wearable electronics rely on the successful development of flexible and integrable energy devices with small footprints. This work reports a completely new type of graphite foam made of strategically created superstructures with covalently attached diverging microtubes, and their applications as electrode supports for binder‐free and additive‐free flexible supercapacitors. Because of the enhanced volumetric surface areas compared to conventional graphite foams, a high loading of pseudocapacitive materials (Mn3O4, 3.91 mg cm−2, 78 wt%) is achieved. The supercapacitors provide areal capacitances as high as 820 mF cm−2 at 1 mV s−1, while still maintaining high rate capability and 88% retention of capacitance after 3000 continuous charging and discharging cycles. When assembled as all‐solid‐state flexible symmetric supercapacitors, they offer one of the highest full‐cell capacitances (191 mF cm−2) among similar manganese oxide/graphene foams, and retain 80% capacitance after 1000 mechanical cycles. The potential of such flexible supercapacitors is also manifested by directly powering electric nanomotors that can trace along letters “U” and T,” which is the first demonstration of flexible supercapacitors for wireless/portable nanomanipulation systems. This work could inspire a new paradigm in designing and creating 3D porous micro/nanosuperstructures for an array of self‐powered electronic and nanomechanical applications. [ABSTRACT FROM AUTHOR]

Flexible energy storage devices play a pivotal role in realizing the full potential of flexible electronics. This work presents high-performance, all-solid-state, flexible supercapacitors by employing an innovative multilevel porous graphite foam (MPG). MPGs exhibit superior properties, such as large specific surface area, high electric conductivity, low mass density, high loading efficiency of pseudocapacitive materials, and controlled corrugations for accommodating mechanical strains. When loaded with pseudocapacitive manganese oxide (Mn3O4), the MPG/Mn3O4 (MPGM) composites achieve a specific capacitance of 538 F g−1 (1 mV s−1) and 260 F g−1 (1 mV s−1) based on the mass of pure Mn3O4 and entire electrode composite, respectively. Both are among the best of Mn3O4-based supercapacitors. The MPGM is mechanically robust and can go through 1000 mechanical bending cycles with only 1.5% change in electric resistance. When integrated as all-solid-state symmetric supercapacitors, they offer a full cell specific capacitance as high as 53 F g−1 based on the entire electrode and retain 80% of capacitance after 1000 continuous mechanical bending cycles. Furthermore, the all-solid-state flexible supercapacitors are incorporated with strain sensors into self-powered flexible devices for detection of both coarse and fine motions on human skins, i.e., those from finger bending and heart beating. [ABSTRACT FROM AUTHOR]

As one of the most prospective candidates for next-generation rechargeable batteries, lithium-sulfur (Li-S) batteries currently still encounter great challenges associated with the low conductivity, severe shuttle effects, and sluggish redox kinetics. Herein, a self-supported sulfur host is fabricated by an in-situ growth of MoO 2 /MoS 2 nano-sheets on a carbon cloth (CC). First, carbon cloth serves as a good template for the morphology-controlled synthesis of nanostructured materials, which not only alleviates the agglomeration of MoO 2 /MoS 2 , but also enhances the flexibility and mechanical strengthen of the hybrid architecture as a free-standing host. Second, the polysulfide-trapping ability can be greatly enhanced by both physical and chemical adsorption from the MoO 2 /MoS 2 -anchored carbon cloth. Moreover, the partially sulfurized MoO 2 /MoS 2 nano-sheets integrate the benefits of conductive MoO 2 and sulfiphilic MoS 2 , thus facilitating fast charge transfer and redox kinetics of polysulfide conversion. As a result, these attributes enable the host to hold a high sulfur loading (up to 7.6 mg cm−2), which exceeds most of the reported carbon cloth-related cathode work in the literature. Additionally, the Li-S cells can achieve a high peak capacity of 1350 mA h g−1, excellent rate capability (C/20 - 2C rate), impressive areal capacity (up to 6.3 mA h cm−2), and a high capacity retention of 85% after 100 cycles. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Solar steam generation, a sustainable water‐purification technology, holds substantial promise in resolving the global issue of shortage of drinkable water. Here, the design, fabrication, and high‐performance of an innovative 3D solar steamer, offering synergistic high‐efficiency steaming and heavy metal removal functions are reported. The device is made of synthesized carbon‐molybdenum‐disulfide microbeads electrostatically assembled on a 3D polyurethane sponge. The mesoporous composite sponge also serves as a freestanding water reservoir that avoids one‐side contact to bulk water, effectively suppressing the commonly observed parasitic heat loss, and offering a high energy efficiency of 88%. When being sculpted into a 3D spoke‐like structure, the composite sponge achieves one of the highest evaporation rates of 1.95 kg m−2 h−1 at 1 sun. The solar steamer is demonstrated for water treatment, i.e., decontamination of metal ions, disinfection, and reducing alkalinity and hardness of river water. Particularly, the strong mercury adsorption of MoS2 reduces mercury levels from 200 to 1 ppb, meeting the stringent standard set by the Environmental Protection Agency, which is the first demonstration of mercury‐removal powered by solar energy. The unique design, fabrication, water‐handling strategy, and mercury‐removal function of this high‐performance solar steamer can inspire new paradigms of water treatment technologies. Dually functional solar steamers made of molybdenum‐disulfide/amorphous carbon microbeads assembled on 3‐D polymer sponges are strategically designed and fabricated for high‐efficiency solar steaming and synergistic mercury removal. The device offers an evaporation rate up to 1.95 kg m‐2 h‐2 and an energy conversion efficiency as high as 88% under 1 sun. In one steaming operation, mercury can be removed from water, meeting stringent drinking standards. [ABSTRACT FROM AUTHOR]

All‐solid‐state flexible supercapacitors based on strategically created three‐dimensional hierarchically porous graphite foams are reported by Donglei Fan and co‐workers in article number 1702738. The supercapacitors exhibit ultrahigh specific capacitances based on the entire electrode weight and retain 80% of capacitance after 1000 continuous bending cycles. They can be seamlessly integrated with strain sensors for self‐powered detections of strains from skins, including carotid artery pulses and finger bending. [ABSTRACT FROM AUTHOR]