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A N–CNW@CC electrode is designed to boost the performance of TECs by enhancing the specific surface area, transition kinetic, and ion transmission. The highest ηr (13.02%) is achieved by combining this electrode and optimized electrolytes.

Passive daytime radiative cooling, which reflects sunlight and simultaneously emits heat into space to cool surfaces without energy input, is a promising strategy for energy conservation. Integrating radiative cooling with building systems can tremendously alleviate electrical cooling, but manufacturing high-efficient and eco-friendly coatings remains an urgent and challenging task. Here, we present a simple and scale-up strategy for fabricating ultrawhite coatings consisting of porous ethyl cellulose matrix-random BaSO

Recently, wearable and breathable healthcare devices for air filtering and real-time vital signs monitoring have become urgently needed since virus and particulate matter (PM) cause serious health issues. Herein, we present a trap-induced dense monocharged hybrid perfluorinated electret nanofibrous membrane (HPFM) for highly efficient ultrafine PM0.3 removal with an efficiency of 99.712% under low pressure drop (38.1 Pa) and high quality factor of 0.154 Pa-1. Furthermore, a recyclable multifunctional healthcare mask is constructed by integrating the HPFM-based nanogenerator, which realizes efficient PM0.3 filtering and wireless real-time human respiration monitoring simultaneously. More importantly, the performance of this mask is still relatively stable even at 100%RH humidity and 92 °C temperature conditions for 48 h, which infers that it can be reused after disinfection. The strategy of fabricating HPFM provides an approach to obtain charge-rich stable electret materials, and the design of multifunctional masks demonstrates their potential application for future personal protection and health monitoring devices.

Harvesting heat from fire itself to power wireless sensor networks has the potential to realize effective detection and alarm for forest fires. Thermocells based on the thermogalvanic effect offer an inexpensive and scalable way for heat-to-electricity conversion but challenged by their low performance. We demonstrate a boosted thermogalvanic effect by introducing concentration gradients into a thermocell, achieving a one order magnitude enhancement of output up to 45.9 W m−2. Using a heat-triggered membrane as the start switch, a thermocell which can hibernate in peacetime and awaken when fire occurs, is further obtained. A proof-of-concept device integrated from five units successfully detects precombustion and open fire to synchronously generate a high voltage of ∼2 V for driving an alarm. This system shows promise for combating the globally increasing forest fires.

Harvesting environmental thermal energy from a natural evaporation process is a promising method for acquiring renewable and sustainable energy. Here, we present an evaporation-driven water flow nanogenerator based on a piece of flexible carbon nanoparticle film. The open-circuit voltage of one single-piece device can be tuned from − 3 to 3 V by manipulating the surface functional groups on the carbon nanoparticles. The effects of different modification molecules and solution concentrations were also investigated. By combining the modified carbon films with opposite surface charges, we enhanced the output of the generator to a maximum open-circuit voltage of 5 V and a short-circuit current of 1.5 μA with a film size of 5 cm × 5 cm. Furthermore, the device can be easily integrated with carbon nanotube-based supercapacitors (CNT-SCs) to assemble the energy-storing and energy-harvesting devices into a self-sustaining power system. The electrical output of the device can directly power a liquid crystal display in an ambient environment and a blue LED with help of self-charged built-in SCs. This eco-friendly device, with its low cost and simple fabrication, shows great potential for future clean energy utilization and for extending the field of portable electronics.

Emerging thermocells have the commercialized potential for directly harvesting low-grade heat. Although a huge progress in p-type thermocells, their n-type counterpart has seriously lagged, becoming a major bottleneck for practical utilization of their integrated devices. Here, we developed a novel Cu-based thermosensitive crystallization and 3D multi-structured electrodes to synergistically boost the thermodynamic and kinetic characteristics of the n-type thermocell. As a result, the optimized Cu/Cu2+-based system achieved an exceptionally high value for the Seebeck coefficient (1.66 mV K–1) and the power density (3.5 W m–2), accompanied with a much competitive cost-performance metric (~$3.28 W–1), all of which were superior to the p-type benchmark. Furthermore, a high-performance p-n junction of thermocells was demonstrated with a 14.5 times enhancement of output, paving the way for advancing the integrated devices.

Low-grade heat (below 373 kelvin) is abundant and ubiquitous but is mostly wasted because present recovery technologies are not cost-effective. The liquid-state thermocell (LTC), an inexpensive and scalable thermoelectric device, may be commercially viable for harvesting low-grade heat energy if its Carnot-relative efficiency (ηr) reaches ~5%, which is a challenging metric to achieve experimentally. We used a thermosensitive crystallization and dissolution process to induce a persistent concentration gradient of redox ions, a highly enhanced Seebeck coefficient (~3.73 millivolts per kelvin), and suppressed thermal conductivity in LTCs. As a result, we achieved a high ηr of 11.1% for LTCs near room temperature. Our device demonstration offers promise for cost-effective low-grade heat harvesting.

Thermogalvanic cells (TGC) are promising devices for directly converting heat into a stable electric output. The practical applications of TGCs are presently significantly hindered by the low voltage (millivolt level) generated from a limited temperature difference. One general strategy for improving the voltage is to alternately connect n-type and p-type redox units in series. However, the number of the possible redox species is limited, hindering the optimization of the series stacking of devices. In this work, we report a novel concept that enables p-n conversion for the iodide/triiodide (I-/I3-) redox couple induced by poly (N-isopropylacrylamide) (PNIPAM) thermo-sensitive nanogels, with the Seebeck coefficient changing from 0.71 mV K−1 to − 1.91 mV K−1. The results prove that the nanogels enable selective capture of I3- at the hot side followed by the release of I3- at the cold side, yielding a concentration gradient of the free I3-, resulting in the p-n inversion. Furthermore, we designed a wearable device consisting of alternating I-/I3- and I-/I3-/nanogels unites in series that generated the open-circuit voltage of approximately 1 V and output power of approximately 9 μW by utilizing body heat. This work developed a new method for inverting the Seebeck effect of redox couples and is highly important for extending the library of possible redox species in TGCs.

In this work, arbitrarily shaped multi-membrane hydrogels were successfully fabricated from gel-core templates using the layer-by-layer (LbL) method. Namely, the first gel membrane layer was formed around a gel-core template when the crosslinker loaded gel-core was soaked in a polysaccharide solution, and it was then ripened in a crosslinker solution, in which the crosslinker was loaded for the fabrication of the following layer. The formation and control of the gel membrane layer were studied in detail. The results indicated that a reasonably rapid crosslinking of the polysaccharide was essential for the successful preparation of a multi-membrane hydrogel, irrespective of chemical or physical crosslinking. The formation of a gel membrane layer was found to be controlled by the diffusion of the crosslinker. The chemically and the physically crosslinked multi-membrane hydrogels were characterized, and the chemically crosslinked chitosan multi-membrane hydrogel exhibited a unique sub-layered microstructure. The chitosan multi-membrane hydrogel which was sensitive to pH was fabricated using terephthalaldehyde as the crosslinker, and the hydrogel displayed LbL disintegration in acidic medium. Chondrocytes were cultivated in the presence of the multi-membrane hydrogel, and they could be easily attached to proliferate quickly. Because of the arbitrary shape, solid or hollow structure, pH sensitivity and biocompatibility, the polysaccharide multi-membrane hydrogels are promising materials for biomedical applications.

Flexible Zn-based batteries with intrinsic safety, non-toxicity and biocompatibility are promising power sources for wearable electronics. To meet practical applications, they need to be durable, robust and stable. However, inevitable self-discharge and interface delamination between electrodes and hydrogel electrolytes often cause serious capacity fading or even failure for flexible Zn-based batteries. Here, inspired from nature, we report hydrogel diodes with strong and tunable interfacial adhesion by attaching oppositely charged hydrogels together. The high adhesion energy is stemmed from strong coulombic interaction and effectively dissipating energy of hydrogel matrix. The adhesion is facilely tuned by narrowing the depletion region in hydrogel diodes. Subsequently we design Hook&Loop-like Cu-Zn batteries by using hydrogel diodes as electrolytes, which are robust, stable and durable and capable for powering wearable electronics. The batteries can eliminate self-discharge and maintain their capacity by splitted into two half cells during long-term storage and easily reattaching together at working stage. Further, the batteries are ultra-stable during 2000 stretching and bending cycles because of their robust interfacial adhesion. It is believed the hydrogel-electrolyte platforms can be utilized to harness issues including interface contact, stability, durability and safety for flexible power sources.

We report a bio-inspired ionic skin with high stretchability (>1700%), transparency (>80%) and sensitivity (2 kPa−1). It is promising for sensing applications because it works stably in various harsh environments, without dehydration at high temperature (80 °C), swelling or ion leakage in aqueous mediums, or freezing at low temperature (−40 °C).

Piezoelectric polymers hold physical properties, such as high mechanical flexibility and smaller acoustical impedance, that piezoelectric ceramics do not have. Nevertheless, owing to the piezoelectricity originates from the crystalline region, it is still a challenge for most semi-crystalline polymers to generate a high piezoelectric response. Here, we develop a class of piezoelectret with sandwiched polymer structure (electret/dielectric/electret, EDE) which is assembled via simple electrostatic interaction. The transparent and mechanical robust EDE piezoelectrets exhibit the piezoelectric constant (d33) up to ~930 pC N-1, and the corresponding physical model is established to investigate major influence factors to the piezoelectric properties, including the relative permittivity and elastic modulus of the electret and dielectric, and the simulated results are in accord with the experimental data. We demonstrate the strain sensors and acoustic transducers based on the ultrathin and flexible EDE piezoelectret, verifying the feasibility of the electrostatic assembled piezoelectrets in the applications of epidermal and implantable electronics. Moreover, various combinations of polymers in the EDE structure can be employed based on our proposed model to explore other unique applications such as transient electronics.

Chitosan has biocompatibility and biodegradability; however, the practical use of the bulk chitosan materials is hampered by its poor strength, which can not satisfy the mechanical property requirement of organs. Thus, the construction of highly strong chitosan-based materials has attracted much attention. Herein, the high strength nanofibrous hydrogels and films (CS-E) were fabricated from the chitosan solution in LiOH/KOH/urea aqueous system via a mild regenerating process. Under the mild condition (ethanol at low temperature) without the severe fluctuation in the system, the alkaline-urea shell around the chitosan chains was destroyed, and the naked chitosan molecules had sufficient time for the orderly arrangement in parallel manner to form relatively perfect nanofibers. The nanofibers physically cross-linked to form CS-E hydrogels, which could be easily oriented by drawing to achieve a maximum orientation index of 84%, supported by the scanning electron microscopy and two-dimensional wide-angle X-ray diffraction. The dried CS-E films could be bent and folded arbitrarily to various complex patterns and shapes. The oriented CS-E films displayed even ultrahigh tensile strength (282 MPa), which was 5.6× higher than the chitosan films prepared by the traditional acid dissolving method. The CS-E hydrogels possessed hierarchically porous structure, beneficial to the cell adhesion, transportation of nutrients, and removal of metabolic byproducts. The cell assay results demonstrated that the CS-E hydrogels were no cytotoxicity, and osteoblastic cells could adhere, spread, and proliferate well on their surface. Furthermore, the oriented CS-E hydrogels could regulate the directional growth of osteoblastic cells along the orientation direction, on the basis of the filopodia of the cells to extend and adhere on the nanofibers. This work provided a novel approach to construct the oriented high strength chitosan hydrogels and films.

This review summarizes recent progress of the robust and smart hydrogels prepared from natural polymers including polysaccharides, proteins, etc. These hydrogels exhibit outstanding mechanical properties due to their nanofibrous aggregated microstructures and special crosslinking networks. Furthermore, these hydrogels show some smart stimuli-responsive behaviors triggered by pH, temperature, light, electricity and magnetism. Hopefully, these hydrogels derived from natural polymers with inherent biodegradation and biocompatibility have great application potential in the fields of biomedicine, tissue engineering, soft robots and bio-machine.

Natural polymers as abundant resource are excellent candidates of adsorbents for wastewater purification due to their inherent advantages such as strong affinity, biodegradability, and non-toxic. In this work, ampholytic polyelectrolyte microspheres were fabricated successfully via emulsification procedure from the homogeneous chitosan/carrageenan solution in LiOH/KOH/urea aqueous system, showing good compatibility and homogeneous network structure. In the chitosan/carrageenan blend solution, chitosan displayed the neutral feature, as a result of the dissolution caused by destruction of the native intermolecular hydrogen bonds rather than protonation of the amino groups, thus no flocculation occurred here. The experimental results demonstrated that the ampholytic microspheres were composed of positively charged chitosan and negatively charged carrageenan, and the magnetic Fe3O4 nanoparticles with a mean diameter of 180 nm were embedded in the composite matrix, showing a sensitive magnetic responsiveness. The ampholytic microspheres exhibited highly efficient adsorption capacity towards both cationic and anionic dyes and heavy metal ions in wastewater, as a result of their strong electrostatic and chelating affinity. The ampholytic chitosan/carrageenan composite matrix in microspheres played a dominant role in the adsorption of pollutants, and the Fe3O4 nanoparticles were mainly contributed to magnetic separation. The effects of ionic strength and pH value on adsorption behaviors indicated that the microspheres were available to be used in a harsh environment. The ampholytic microspheres could also be used as column packing for rapid and efficient dye wastewater purification. Furthermore, the microspheres could be recycled, reused, and biodegraded in soil, showing great potentials in the field of the water decontamination.

Zero liquid discharge (ZLD), which maximizes water recovery and eliminates environmental impact, is an urgent wastewater management strategy for alleviating freshwater shortage. However, because of the high concentration of salts and broad-spectrum foulants in wastewater, a huge challenge for ZLD is lack of a robust membrane-based desalination technology that enables direct wastewater recovery without costly pretreatment processes. Here, a paradigm-shift membrane distillation (MD) strategy is presented, wherein the traditional hydrophobic porous membrane is replaced with a hydrophilic nonporous charge-gradient hydrogel (CGH) membrane that possesses hypersaline tolerance, fouling/scaling-free properties, and negligible vapor transfer resistance inside the membrane, simultaneously. Therefore, the CGH-based MD with high water flux enables direct desalination of hypersaline wastewater (130 g L-1 ) containing broad-spectrum foulants (500 mg L-1 ) during continuous long-term operation (200 h), and this technology paves a promising way to direct ZLD for wastewater management.

Sulfated polysaccharides from marine biomass exhibit various biological activities, however, traditional purification approaches are time and money consuming, particularly involving the usage of toxic chemical reagents. Herein, novel chitosan microspheres cross-linked by genipin (CSGs) were prepared from chitosan solution in an alkali/urea aqueous system as multifunctional adsorbents for deproteinization and decoloration by one step. The compression fracture stress of chitosan hydrogels fabricated from the alkaline solution system was over 10 times that of the hydrogels prepared by a traditional acid method, suggesting a significantly improved mechanical strength. The robust CSGs with mean diameter of 100 μm exhibited mesoporous structure. The adsorption/desorption performance of CSGs for sulfated polysaccharides was investigated by using heparin as a model, showing significantly high adsorption capacity, over 3-fold of that from commercial Q Sepharose Fast Flow. Moreover, CSGs selectively adsorbed hepari...

Biocompatible hydrogels with high strength, high precision patterns, and arbitrary 3D shapes are extremely desired soft platforms in the biomedicine fields. On the basis of the thermal-reversible sol-gel transition of agarose and the formation of nanofibers below 35 °C, a robust and thermoplastic hydrogel (TPG) was fabricated by in situ polymerization of acrylamide in the agarose matrix. The tensile fracture stress/strain values of the TPG were unexpectedly higher than those of both agarose and polyacrylamide hydrogels as a result of the double networks reinforced with nanofibers. The TPG could reversibly soften and harden by heating and cooling treatment, respectively, leading to an excellent mechanical recoverability and reprocessing ability. Thus, arbitrary 3D-shaped hydrogels and micro-patterns embossed on the TPG surface with a high resolution of 1 μm were constructed. The rigid TPG exhibited a remarkable affinity for the adhesion and proliferation of cells. In particular, the TPGs with microgrooves could highly guide the oriented growth of osteoblasts, showing potential applications in the field of tissue engineering.

Solar-driven interfacial water evaporation, which concentrates solar heating at the water surface, has attracted increasing interest in pursuing highly efficient solar desalination. The rapid evaporation of water at the light absorber surface would induce a high concentration comparable with that of brine underlying the interface, which however has been paid much less attention and has never been proposed to produce electricity. Here in this work, we proved that, the theoretical real-time salinity power generated between the surface water and bulk seawater could be 12.5 W m−2 during steam production under one sun illumination. By employing a hybrid system based on a piece of carbon nanotube modified filter paper and a commercial Nafion membrane, we achieved a maximum solar thermal efficiency of up to 75% and derived extra electricity power of ∼1 W m−2 under one sun illumination. These results provide a novel avenue for blue energy utilization, demonstrating the potential for solar desalination and electricity generation under natural sunlight simultaneously.

Following the rapid development of lightweight and flexible smart electronic products, providing energy for these electronics has become a hot research topic. The human body produces considerable mechanical and thermal energy during daily activities, which could be used to power most wearable electronics. In this context, fiber-based energy conversion devices (FBECD) are proposed as candidates for effective conversion of human-body energy into electricity for powering wearable electronics. Herein, functional materials, fiber fabrication techniques, and device design strategies for different classes of FBECD based on piezoelectricity, triboelectricity, electrostaticity, and thermoelectricity are comprehensively reviewed. An overview of fiber-based self-powered systems and sensors according to their superior flexibility and cost-effectiveness is also presented. Finally, the challenges and opportunities in the field of fiber-based energy conversion are discussed.

Wearable pressure sensors, as essential components of flexible wearable electronics, may play important roles in early diagnosis and mortality prevention for cardiovascular healthcare. However, traditional self-powered pressure sensors can hardly obtain both high sensitivity and wide pressure range, which makes perceiving both cardiac and vascular signals in a wearable self-powered way challenging as these physiological signals not only have imperceptible changes but also span a broad pressure range. Here, we develop a flexible hierarchical elastomer tuned self-powered pressure sensor, which achieves both high-sensitivity and wide pressure range, showing a high sensitivity of 7.989 V kPa−1 and wide pressure range of 0.1–60 kPa simultaneously. Fast response (40 ms) and high signal noise ratio (38 db) with good stability are also achieved. We demonstrate that the self-powered pressure sensor can not only sensitively monitor pulse, artery and heart condition but also monitor the wide range blood pressure, which satisfies the diverse needs of wearable cardiovascular healthcare. As most of the pressure related to human interface is less than 50 kPa, we envision the sensor holds great potential in wearable electronics, mobile healthcare and human-machine interaction.

Flexible pressure sensors possess promising applications in artificial electronic skin, intelligence robot, wearable health monitoring, flexible physiological signal sensing, etc. Herein, we design a flexible pressure sensor with robust stability, high sensitivity, and large linear pressure region on the basis of tetrafluoroethylene-hexafluoropropylene-vinylide (THV)/cyclic olefin copolymer (COC) piezoelectret nanogenerator. According to the theoretical analysis for piezoelectret nanogenerators with imbalanced charge distribution, THV and COC are utilized to promote the electric field inside the piezoelectret for output voltage enhancement. Meanwhile, the compression property of the piezoelectret nanogenerator is facilely tuned. Owing to high inner electric field and optimized compression property, the THV/COC piezoelectret nanogenerator exhibits a high sensitivity of 30 mV/kPa, which is 10 times higher than that of the traditional cellular polypropylene piezoelectret. Simultaneously, the linear pressure region reaches 150 kPa with excellent linearity ( R2 = 0.99963). The device is demonstrated to realize wearable pressure sensing with a wide pressure range from finger typing to fist hammering. This study presents a fabrication strategy for piezoelectret nanogenerators with high sensitivity and large linear pressure region, paving the way for development of wearable and flexible pressure sensing networks.

The aim of the present work was to develop novel bio-based polymer composite films with improved tensile and thermal properties. In this work, cellulose and spent tea leaf powder (STLP) were used as the matrix and filler respectively in the preparation of biocomposite films. To make cellulose solution, cotton linters were dissolved in pre-cooled aqueous solution of 8 wt.% Lithium hydroxide and 15 wt.% urea. Tea is an important beverage of household and hotels and spent tea leaves form a conjugal solid waste. STLP was added to cellulose solution in 5–25 wt.% of weight of cellulose. The cellulose and cellulose/STLP composite films were prepared by regeneration method using ethyl alcohol coagulation bath. The dry films were characterized by optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and tensile tests. The effect of STLP loading on the properties of the cellulose/STLP composite films was studied. The results indicated that the composite films had higher tensile properties and thermal stability than the cellulose matrix. The dye adsorption ability of cellulose and cellulose/STLP composites in wet form was also studied. It was observed that the composite wet films had higher dye adsorption capacity than the matrix. Results of this study indicated STLP to be a promising green filler for polymer matrices.

Breaking the limitation of traditional acid dissolving methods for chitosan by creating an alkali/urea hydrogen-bonded chitosan complex, a new solvent (4.5 wt % LiOH/7 wt % KOH/8 wt % urea aqueous solution) was used to successfully dissolve chitosan via the freezing–thawing process, for the first time. Subsequently, high strength hydrogels with unique nanofibrous architecture were constructed from the chitosan alkaline solution. The results from 13C NMR, laser light scattering, atomic force microscopy, transmission electron microscopy, and scanning electron microscopy confirmed that chitosan easily aggregated in the solution and could self-assemble in parallel to form perfect regenerated nanofibers induced by heating. At elevated temperature and concentration, the regenerated chitosan nanofibers could entangle and cross-link with each other through hydrogen bonds to form hydrogels. The novel chitosan hydrogels exhibited homogeneous architecture and high strength as a result of the strong networks woven wi...

Energy harvesting and storage are two distinct processes that are generally achieved using two separated parts based on different physical and chemical principles. Here we report a self-charging electrokinetic supercapacitor that directly couples the energy harvesting and storage processes into one device. The device consists of two identical carbon nanotube/titanium electrodes, separated by a piece of anodic aluminum oxide nanochannels membrane. Pressure-driven electrolyte flow through the nanochannels generates streaming potential, which can be used to charge the capacitive electrodes, accomplishing simultaneous energy generation and storage. The device stores electric charge density of 0.4 mC cm–2 after fully charging under pressure of 2.5 bar. This work may offer a train of thought for the development of a new type of energy unit for self-powered systems.

Solar-enabled steam generation has attracted increasing interest in recent years because of its potential applications in power generation, desalination, and wastewater treatment, among others. Recent studies have reported many strategies for promoting the efficiency of steam generation by employing absorbers based on carbon materials or plasmonic metal nanoparticles with well-defined pores. In this work, we report that natural wood can be utilized as an ideal solar absorber after a simple flame treatment. With ultrahigh solar absorbance (∼99%), low thermal conductivity (0.33 W m-1 K-1), and good hydrophilicity, the flame-treated wood can localize the solar heating at the evaporation surface and enable a solar-thermal efficiency of ∼72% under a solar intensity of 1 kW m-2, and it thus represents a renewable, scalable, low-cost, and robust material for solar steam applications.

Wearable electronics have attracted attention for their potential use in constructing a human-centered intelligent world. As one of the most promising materials for constructing high-performance self-powered wearable electronics, piezoelectrets possess the advantages of high flexibility, light weight, biocompatibility and high piezoelectric performance. Herein, recent advances in this area are reviewed. First, the mechanism, theoretical progress, and manufacturing techniques of piezoelectrets are presented. Then, devices based on different piezoelectret materials as human-body mechanical energy harvesters are introduced in sequence, and their major applications are demonstrated, including self-powered acoustic transducers, flexible pressure sensors and wearable physiological monitors. At the end of this review, the perspectives and challenges of piezoelectrets are discussed. We anticipate that traditional piezoelectrets with unique designs will play important roles in wearable energy harvesting and human physiological signal monitoring in the near future.

Novel onion-like and multi-layered tubular cellulose hydrogels were constructed, for the first time, from the cellulose solution in a 7% NaOH/12% urea aqueous solvent by changing the shape of the gel cores. In our findings, the contacting of the cellulose solution with the surface of the agarose gel rod or sphere loaded with acetic acid led to the close chain packing to form immediately a gel layer, as a result of the destruction of the cellulose inclusion complex by acid through inducing the cellulose self-aggregation. Subsequently, multi-layered cellulose hydrogels were fabricated via a multi-step interrupted gelation process. The size, layer thickness and inter-layer space of the multi-layered hydrogels could be controlled by adjusting the cellulose concentrations, the gel core diameter and the contacting time of the solid-liquid interface. The multi-layered cellulose hydrogels displayed good architectural stability and solvent resistance. Moreover, the hydrogels exhibited high compressive strength and excellent biocompatibility. L929 cells could adhere and proliferate on the surface of the layers and in interior space, showing great potential as tissue engineering scaffolds and cell culture carrier. This work opens up a new avenue for the construction of the high strength multi-layered cellulose hydrogels formed from inner to outside via a fast contact of solid-liquid interface.

An ultra-stretchable and force-sensitive hydrogel with surface self-wrinkling microstructure is demonstrated by in situ synthesizing polyacrylamide (PAAm) and polyaniline (PANI) in closely packed swollen chitosan microspheres, exhibiting ultra-stretchability (>600%), high sensitivity (0.35 kPa-1 ) for subtle pressures (

National Basic Research Program of China (973 Program) [2010CB732203]; Fundamental Research Funds for the Central Universities of China [2010121055]; Scientific and Technological Innovation Platform of Fujian Province of China [2009J1009]

National Basic Research Program of China (973 Program) [2010CB732203]; Fundamental Research Funds for the Central Universities of China [2010121055]; Scientific and Technological Innovation Platform of Fujian Province of China [2009J1009]

We have reported an interesting method, named reverse breath figure, for the preparation of polymeric microsphere patterns. By the same procedure as breath figure, instead of under a humid atmosphere, linear and star-shaped poly(styrene-block-butadiene) copolymers dissolved in solvents such as toluene, trichloroform, and dichloromethane were cast onto the surface of a glass substrate in methanol or ethanol vapor. After the complete evaporation of the solvent, microspheres with the diameters ranging from hundreds of nanometers to several micrometers were prepared. The microsphere patterns are the reverse of the honeycomb porous structure of breath figure. The mechanism of the microsphere formation has been studied to show that when the surface tension of the polymer solution is 1.5 mN/m higher than that of the condensed liquid, microsphere patterns can be prepared, whereas a honeycomb porous film of breath figure can be obtained when the surface tension of the polymer solution is lower than that of the con...

Blend films from cellulose and konjac glucomannan (KGM) in room temperature ionic liquid 1-allyl-3-methylimidazolium chloride were satisfactorily prepared by coagulating with water. The composition of the blend films was gravimetrically analyzed, and the compatibility of the two natural polymers was characterized by Fourier transform infrared spectroscopy and wide-angle X-ray diffraction. The results indicate good compatibility and strong interactions between cellulose and KGM, resulting in almost no loss of the water-soluble KGM from the blend films even after the water coagulating and washing. However, microstructure analyses portrayed phase separations in the blend films, namely, egg-like new phase particles were embedded in a continuous matrix base (MB). Phase diagram analysis and differential scanning calorimetry of the phase inversion coagulation process suggest that relative low molecular mass part of both cellulose and KGM formed the continuous MB, whereas the egg-like new phase particles were super patterns of relative high molecular mass of both polymers, which played an important role in strengthening the blend material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1686–1694, 2009

Novel cellulose–chitosan nanocomposite particles with spherical shape were successfully prepared via mixing of aqueous biopolymer solutions in three different ways. Macroparticles with diameters in the millimeter range were produced by dripping cellulose dissolved in cold LiOH/urea into acidic chitosan solutions, inducing instant co-regeneration of the biopolymers. Two types of microspheres, chemically crosslinked and non-crosslinked, were prepared by first mixing cellulose and chitosan solutions obtained from freeze thawing in LiOH/KOH/urea. Thereafter epichlorohydrin was applied as crosslinking agent for one of the samples, followed by water-in-oil (W/O) emulsification, heat induced sol–gel transition, solvent exchange, washing and freeze-drying. Characterization by X-ray photoelectron spectroscopy, total elemental analysis, and Fourier transform infrared spectroscopy confirmed the prepared particles as being true cellulose–chitosan nanocomposites with different distribution of chitosan from the surface to the core of the particles depending on the preparation method. Field emission scanning electron microscopy and laser diffraction was performed to study the morphology and size distribution of the prepared particles. The morphology was found to vary due to different preparation routes, revealing a core shell structure for macroparticles prepared by dripping, and homogenous nanoporous structure for the microspheres. The non-crosslinked microparticles exhibited a somewhat denser structure than the crosslinked ones, which indicated that crosslinking restricts packing of the chains before and under regeneration. From the obtained volume-weighted size distributions it was found that the crosslinked microspheres had the highest median diameter. The results demonstrate that not only the mixing ratio and distribution of the two biopolymers, but also the morphology and nanocomposite particle diameters are tunable by choosing between the different routes of preparation. First Online: 05 August 2016

We have demonstrated a solution-based synthesis of novel waxberry-like hierarchical ZnO microparticles in the presence casein micelles under mild conditions. The microstructures of the sub-micrometer-sized hierarchical microparticles were characterized, and the synthesis conditions were optimized. The formation mechanism of the hierarchical microparticle was analyzed through control experiments. The hierarchical ZnO microparticles are found to be super-assemblies of 30–70 nm ZnO nanoparticles, which are thought to be based on casein micelle induction followed by Ostwald ripening. In the same manner, copper-based hierarchical microparticles with a similar morphology have also been successfully synthesized. By controlling the synthetic time or temperature, solid or hollow microparticles can be fabricated. The narrowly distributed ZnO microparticles have a high specific surface area, exhibiting great potential application in fields such as photocatalytic and energy conversion. Our findings may meanwhile open a new bottom-up strategy in order to construct structurally sophisticated nanomaterials.