Hydrogels totally from inorganic nanosheets and water with mechanical robustness,self-healing,controlled lubrication and anticorrosion

Synthetic hydrogels with attractive mechanical strength and self-healing are particular appealing,in light of their significance and prospects in industrial,engineering and biomimetic fields.Fabricating various mechanically robust and self-healable hydrogels have achieved some successes in using strong covalently bonded organic polymers as building blocks.However,creation of such soft materials entirely building on rigid inorganic components remains greatly challenging,because inorganic materials are usually poorly flexible and processable.In this study,mechanical robustness and self-recovery are successfully integrated into a single-component colloidal hydrogel system of aluminium hydroxide nanosheets(AHNSs).The inorganic colloidal hydrogel gains an excellent elasticity and stiffness,as indicated by its elastic modulus>10 MPa,due to the use of tough AHNS gelator and the formation of long-range ordered lamellar architectures consisting of self-assembled side-to-side or interlaced-stacking NS superstructures.The metastability in internal gel network endows the hydrogel a self-healing efficiency of larger than 100%.The AHNS hydrogel has been demonstrated to be effectively lubricative and anti-corrosive.Its mechanical,tribological and anticorrosion properties can be optimized by tuning its internal NS configuration and salt content.Our study may be a potent replenishment to the scope of materials science and may provide new insights into nanotechnology,colloidal chemistry,green tribology and mechanical engineering.

Efficient concentration of trace analyte with ordered hotspot construction for a robust and sensitive SERS platform

Surface-enhanced Raman scattering(SERS)platform,which enables trace analyte detection,has important application prospects.By structuring/modifying the surface of the SERSsubstrate,analyte in highly diluted solutions can be concentrated into localized active areas for highly sensitive detection.However,subject to the difficulty of the fabrication process,itremains challenging to balance hot-spot construction and the concentration capacity of analyte simultaneously.Therefore,preparing SERS substrates with densely ordered hot spots andefficient concentration capacity is of great significance for highly sensitive detection.Herein,we propose an Ag and fluoroalkyl-modified hierarchical armour substrate(Ag/F-HA),which has a double-layer stacking design to combine analyte concentration with hotspot construction.The microarmour structure is fabricated by femtosecond-laser processing to serve as asuperhydrophobic and low-adhesive surface to concentrate analyte,while the anodic aluminium oxide(AAO)template creates a nanopillar array serving as dense and ordered hot spots.Under the synergistic action of hot spots and analyte concentration,Ag/F-HA achieves a detectionlimit down to 10^(-7)M doxorubicin(DOX)molecules with a RSD of 7.69%.Additionally,Ag/F-HA exhibits excellent robustness to resist external disturbances such as liquid splash or abrasion.Based on our strategy,SERS substrates with directional analyte concentrations are further explored by patterning microcone arrays with defects.This work opens a way to the realistic implementation of SERS in diverse scenarios.

Printable and stable all-polymer solar cells based on non-conjugated polymer acceptors with excellent mechanical robustness

All-polymer solar cells(all-PSCs)trigger enormous commercial applications,and great progress has been made in recent years.However,from small-area devices to large-area modules,the poor adaption of the materials for printing methods and the large efficiency loss are still great challenges.Herein,three novel non-conjugated polymer acceptors(PTH-Y,PTClm-Yand PTClo-Y)are developed for all-PSCs.It can be found that non-conjugated polymer acceptors can effectively minimize the technique and efficiency gaps between small-area spin-coating and large-area blade-printing method,which can facilitate the preparation of large-area flexible device.By directly inheriting the spin-coating condition,the blade-coating processed device based on PTCloY achieves an impressive power conversion efficiency(PCE)of 12.42%,comparable to the spin-coating processed one(12.74%).Such a non-conjugated polymer system also can well tolerate large-scale preparation and flexible substrate.Notable PCE of 11.94%for large-area rigid device and 11.56%for large-area flexible device are obtained,which is the highest value for large-area flexible all-PSCs fabricated by blade-coating.In addition,the non-conjugated PTClo-Y-based devices show excellent thermal stability and mechanical robustness.These results demonstrate that the non-conjugated polymer acceptors are potential candidates for the fabrication of highly-efficient,large-area and robust flexible all-PSCs by printing methods.

Effects of Flexible Conjugation-Break Spacers of Non-Conjugated Polymer Acceptors on Photovoltaic and Mechanical Properties of All-Polymer Solar Cells

All-polymer solar cells(all-PSCs)possess attractive merits including superior thermal stability and mechanical flexibility for large-area roll-to-roll processing.Introducing flexible conjugation-break spacers(FCBSs)into backbones of polymer donor(P_(D))or polymer acceptor(P_(A))has been demonstrated as an efficient approach to enhance both the photovoltaic(PV)and mechanical properties of the all-PSCs.However,length dependency of FCBS on certain all-PSC related properties has not been systematically explored.In this regard,we report a series of new non-conjugated P_(A)s by incorporating FCBS with various lengths(2,4,and 8 carbon atoms in thioalkyl segments).Unlike com-mon studies on so-called side-chain engineering,where longer side chains would lead to better solubility of those resulting polymers,in this work,we observe that the solubilities and the resulting photovoltaic/mechanical properties are optimized by a proper FCBS length(i.e.,C2)in P_(A) named PYTS-C2.Its all-PSC achieves a high efficiency of 11.37%,and excellent mechanical robustness with a crack onset strain of 12.39%,significantly superior to those of the other P_(A)s.These results firstly demonstrate the effects of FCBS lengths on the PV performance and mechanical properties of the all-PSCs,providing an effective strategy to fine-tune the structures of P_(A)s for highly efficient and mechanically robust PSCs.

Mechanical robust and self-healing flexible perovskite solar cells with efficiency exceeding 23%

Flexible perovskite solar cells(f-PSCs) have experienced rapid advancements due to the light-weight, flexibility, and solution processability of the perovskite materials, which prompted the power conversion efficiency(PCE) to 24.08%. However, f-PSCs still face challenges in terms of mechanical and environmental stability. This is primarily due to their inherent brittleness, the presence of residual tensile strain, and the high density of defects along the boundaries of perovskite grains. To this end, we carefully developed a cross-linkable elastomers 3-[(3-acrylamidopropyl)dimethylammonium] propanoate(ADP) with electrostatic dynamic bond, which could be in-situ cross-linked and coordinate with [Pb I6]4-to regulate the crystallization process of perovskite. The cross-linked elastomers attached to the perovskite grain boundaries could release the remaining tensile strains and mechanical stresses, leading to enhanced stability and flexibility of the f-PSCs. More importantly, the electrostatic interaction between positive and negative groups of cross-linked elastomers and hydrogen bond formation between N–H and C=O accelerate the cross-linking of ADP, endowing the flexible perovskite films with self-healing ability under mild treating conditions(60 °C for 30 min). As a result, the device achieves a remarkable PCE of 23.53%(certified 23.16%). Additionally, the device exhibits impressive mechanical sustainability and durability, retaining over 90% of initial PCE even after undergoing8,000 bending cycles.

Polysaccharides Based Random and Unidirectional Aerogels for Thermal and Mechanical Stability

Owing to the increasing energy demands and the environmental constraints,the need for bio-based materials has been on the rise due to their variety of favorable properties like biocompatibility,cost-effectiveness,large specific surface area,high porosity,and non-toxicity.Thermal stability and mechanical strength of aerogels are highly dependent on their micro-porous structures.A three-dimensional structure based on cellulose nanofiber/chitosan(CNF/CS)aerogels was built using two different freezing methodologies,namely random freezing,and unidirectional freezing techniques,by changing mold shapes.The unidirectional aerogels ultimately resulted in high-temperature stability and mechanical strength.The results show that the unidirectional CNF/CS(u-CNF/CS)aerogels contain controlled micro porous orientation relative to random-CNF/CS(r-CNF/CS)aerogels with the disordered porous distribution.The high-temperature stability with an increase of glass transition temperature T_(g) from 275℃(CNF)to 283℃(CNF/CS),the ultra-low thermal conductivity of 0.030 W/(m·K),and mechanical robustness of u-CNF/CS aerogels make them quite favorable for practical applications.

Mechanically robust antifouling coating with dual-functional antifouling strategy by infiltrating PDMS into plasma-sprayed porous Al_(2)O_(3)-Cu coating

Marine biofouling is a worldwide challenge that needs to be solved urgently.Poly(dimethylsiloxane)(PDMS)-based fouling release coatings with low surface free energy(SFE)could effectively inhibit bio-fouling.Nevertheless,their poor mechanical durability,adhesive strength,and antifouling performance under static conditions significantly limit their applications.Herein,a novel mechanically robust Al_(2)O_(3)-PDMS-Cu composite coating with strong adhesive strength and remarkable antifouling performance was developed.The Al_(2)O_(3)-PDMS-Cu coating loaded with a small amount of Cu was fabricated by infiltrating PDMS into plasma-sprayed micro/nano-scaled porous Al_(2)O_(3)-Cu coating.Results showed that the fabri-cation of this Al_(2)O_(3)-PDMS-Cu coating did not alter the surface hydrophobicity and SFE of PDMS signif-icantly,thus presenting little influence on its inherent fouling release property.After rigorous abrasion test,the Al_(2)O_(3)-PDMS-Cu coating presented remarkably improved surface hydrophobicity due to the ex-posure of micro/nano structure,rather than falling offas that of PDMS coating.The combination of excel-lent abrasion resistance and one order of magnitude higher adhesive strength and hardness than PDMS coating contributed to the outstanding mechanical robustness of Al_(2)O_(3)-PDMS-Cu coating.Additionally,the antifouling assays against marine bacteria adhesion(95%reduction rate for Escherichia coli.(E.coli))and algae attachment(96%and 94%reduction rates for Chlorella and Phaeodactylum tricornutum(P.tricor-nutum),respectively after 21 days of incubation)demonstrated the superior antifouling performance of the Al_(2)O_(3)-PDMS-Cu coating.Thus,a high-performance Al_(2)O_(3)-PDMS-Cu antifouling coating with excellent mechanical robustness and long-term antifouling performance was achieved via the combination of me-chanical durability of Al_(2)O_(3)skeleton and the dual-functional antifouling strategy,i.e.,the fouling release property of PDMS and fouling resistance of Cu.

Semi-template based,biomimetic-architectured,and mechanically robust ceramic nanofibrous aerogels for thermal insulation

Energy efficient buildings require novel thermal insulators accompanied by lightweight,mechanically robust,fire resistant,and low thermal conductivity.Ceramic fibrous aerogels have emerged as promising candidates,however it’s difficult for these materials to achieve exceptional mechanical and thermal insulation performance simultaneously.Here,we demonstrate a unique semi-template method to fabricate biomimetic-architectured silica/carbon dual-fibrous aerogel with robust mechanical performance.Specifically,aerogels with honeycomb-like cellular and nanofiber/nanonet cell wall were constructed by freezedrying the homogeneous dispersion of SiO_(2)nanofibers and cellulose nanofibers co-suspensions.It is worth noting that the biomimetic structure has been perfectly inherited even subjected to high-temperature carbonization.As a result,the excellent structural stability brought by the novel structure enables the aerogel to completely recover under large compression and buckling strain of 80%,and exhibit robust fatigue resistance over 200,000 cycles.More importantly,the aerogels exhibit ultralow thermal conductivity(0.023 W·m^(−1)·K^(−1)),superior flame retardancy,together with excellent thermal insulation performance over a wide temperature ranging from−196 to 350°C.The fabrication of such materials may provide new ideas for the development of next-generation thermal insulators for harsh conditions.

Manufacturing tolerant topology optimization

In this paper we present an extension of the topology optimization method to include uncertainties during the fabrication of macro, micro and nano structures. More specifically, we consider devices that are manufactured using processes which may result in （uniformly） too thin （eroded） or too thick （dilated） structures compared to the intended topology. Examples are MEMS devices manufactured using etching processes, nano-devices manufactured using e-beam lithography or laser micro-machining and macro structures manufactured using milling processes. In the suggested robust topology optimization approach, under- and over-etching is modelled by image processing-based ＂erode＂ and ＂dilate＂ operators and the optimization problem is formulated as a worst case design problem. Applications of the method to the design of macro structures for minimum compliance and micro compliant mechanisms show that the method provides manufacturing tolerant designs with little decrease in performance. As a positive side effect the robust design formulation also eliminates the longstanding problem of one-node connected hinges in compliant mechanism design using topology optimization.

Mechanically robust antireflective coatings

Mechanical strength is an essential parameter that influences and limits the lifetime performance of antireflective （AR） coatings in optical devices. Speciflcally, amphiphobic AR coatings with reduced reflectance are of great significance as they considerably enlarge the range of fundamental applications. Herein, we describe the design and fabrication of amphiphobic AR coatings with reduced reflectance and enhanced mechanical resilience. Introducing a thin polytetrafluoroethylene （PTFE） layer on top of the bilayer SiOz coating via vapor deposition method makes it highly liquid repellent. We achieved reduced reflectance （〈 1%） over the entire visible wavelength range, as well as tunability according to the desired wavelength region. The fabricated film showed better thermal stability （up to 300℃） with stable AR efficiency, when an ultrathin dense coat of Al2O3 was deposited via atomic layer deposition （ALD） on the polymer-based bilayer SiO2 antireflective coating （P-BSAR）. The experimental results prove that the omnidirectional AR coating in this study exhibits multifunctional properties and should be suitable for the production of protective optical equipment and biocompatible polymer films for the displays of portable electronic devices.

Energy-saving windows derived from transparent

Energy-saving windows play a crucial role in sustainable development of green buildings.Integrating super-insulating aerogels with glasses is an attractive method to minimize the energy loss through building windows.However,achieving energy-saving windows with high transparency,super insulation,mechanical robustness,low cost,and scalable aerogels remains a challenge.In a recent study published in Nature Energy,Smalyukh and coworkers synthesized a highly transparent silanized cellulose aerogel for energy-saving windows,overcoming the challenges.This work promotes the practical application of aerogel-based glazing and provides an effective way to save energy of buildings.

Silicone/graphene oxide co-cross-linked aerogels with wide-temperature mechanical flexibility,super-hydrophobicity and flame resistance for exceptional thermal insulation and oil/water separation

Development of multifunctional and high-performance silicone aerogel is highly required for various promising applications.However,unstable cross-linking structure and poor thermal stability of silicone network as well as complicated processing restrict the practical use significantly.Herein,we report a facile and versatile ambient drying strategy to fabricate lightweight,wide-temperature flexible,super-hydrophobic and flame retardant silicone composite aerogels modified with low-content functionalized graphene oxide(FGO).After optimizing silane molecules,incorporation ofγ-aminopropyltriethoxysilane functionalization is found to promote the dispersion stability of GO during the hydrolysis-polymerization process and thus produce the formation of unique strip-like co-cross-linked network.Consequently,the aerogels containing∼2.0 wt%FGO not only possess good cyclic compressive stability under strain of 70%for 100 cycles and outstanding mechanical reliability in wide temperature range(from liquid nitrogen to 350℃),but also display excellent flame resistance and super-hydrophobicity.Further,the optimized silicone/FGO aerogels display exceptional thermal insulating performance superior to pure aerogel and hydrocarbon polymer foams,and they also show efficient oil absorption and separation capacity for var-ious solvents and oil from water.Clearly,this work provides a new route for the rational design and development of advanced silicone composite aerogels for multifunctional applications.

A non-fluorinated mechanochemically robust volumetric superhydrophobic nanocomposite

The widespread use of water-repellent superhydrophobic surfaces is limited by the inherent fragility of their micro-and nanoscale roughness, which is prone to damage and degradation. Here, we report a non-fluorinated volumetric superhydrophobic nanocomposites that demonstrate mechanochemical robustness. The nanocomposites are produced through the addition of microscale diatomaceous earth and nanoscale fumed silica particles to high-temperature vulcanized silicone rubber. The water-repellency of the surface and bulk of nanocomposites having 120 phr of filler was determined based on the water contact angle and contact angle hysteresis. We compared the water-repellency of nanocomposites of differing diatomaceous earth to fumed silica mass ratios. Increasing the amount of diatomaceous earth enhanced the water-repellency of the nanocomposite surface, whereas an increased amount of fumed silica improved the water-repellency of the bulk material. Moreover, increasing the diatomaceous earth/fumed silica mass ratio improved the cross-linking density and hardness values of the nanocomposite.Despite being subjected to a range of mechanical durability tests, including sandpaper abrasion,knife scratching, tape peeling, water jet impact, and sandblasting, the nanocomposite maintained a water contact angle of 163. and contact angle hysteresis of 2°. When the water-repellency of the prepared nanocomposites eventually deteriorated, we restored their superhydrophobicity by removing the upper surface of the nanocomposite. This extraordinary robustness stems from the embedded low surface energy micro/nanostructures distributed throughout the nanocomposite. We also demonstrated the chemical stability, UV resistance, and self-cleaning abilities of the nanocomposite to illustrate the potential for real-life applications of this material.

Nanonet-/fiber-structured flexible ceramic membrane enabling dielectric energy storage

Ceramics are considered intrinsically brittle at macro scale due to the lack of slip mechanism and pre-existing defects,which greatly limits their potential applications in emerging fields including wearable electronic devices and flexible display.In this contribution,we developed BiFeO_(3)/SiO_(2) dual-networks with exceptional flexibility through a coupled electronetting/electrospun method.The hybrid nanostructured networks endow the material with high tensile strength(2.7 MPa),excellent flexibility(80%recoverable deformation),and robust fatigue resistance performance(maintain flexibility after a 1000-cyclic compress test).After in-situ compounded with dielectric polymer via a layer-by-layer solution casting method,the resultant three-dimensional(3D)composite film exhibits a twice higher dielectric constant(εr)than polyether imide(PEI)film.More importantly,the breakdown strength of the 3D composite film is almost the same as that of the PEI film,resulting in an enhanced energy density of~6.0 J/cm^(3) and a high efficiency of 80%at 4.58 MV/cm.The unique structure,combined with the excellent balance between mechanical and dielectric properties in flexible structures,is of critical significance to the design of flexible functional ceramics and broadening their applications in wearable electric devices.

A Passive Anti-icing Strategy Based on a Superhydrophobic Mesh with Extremely Low Ice Adhesion Strength

Although superhydrophobic materials have attracted much research interest in anti-icing,some controversy still exists.In this research,we report a cost-effective method used to verify the contribution of area fraction to ice adhesion strength.We tried to partially-embed siliea nanopnarticles into microscale fabrics of a commercial polyamide mesh.Then,the area fraction could be determined by altering the mesh size.Generally,the ice adhesion strength decreases as the area fraction decreases.An ice adhesion strength of~1.9 kPa and a delayed freezing time of~1048 s can be obtained.We attribute the low ice adhesion strength to the combination of superhydro-phobicity and stress concentration.The superhydrophobicity prohibits the water from penetrating into the voids of the meshes,and the small actual contact area leads to stress concentration which promotes interfacial crack propagation.Moreover,our superhydrophobic mesh simultaneously exhibis a micro-nano hierarchical structure and a partally-cmbedded structure.Therefore,the as-prepared superhydrophobic mesh retained the ieephobicity after 20 icingldeicing cycles,and maintained its superhydrophobicity even afier 60 sandpaper-abrasion cycles and a 220"C thermal treatment.

High temperature ceramic thermal insulation material

Flexible and lightweight thermal insulation materials with hierarchical microstructures are ubiquitous in thermal management and protection systems.Ceramic aerogels promise high-temperature thermal insulation but lack mechanical robustness,while the fibrous materials with excellent mechanical elasticity display modest thermal insulation.Here we describe flexible hierarchical superhydrophobic ceramic insulation nanocomposites through the densified architectured hierarchical nanostructures,radiative insulation coating,and interfacial cross-linking among composites.The lightweight flexible ceramic nanocomposites exhibit a density of 0.13 g/cm^(3),high-temperature fire resistance with thermal conductivity of 0.024 W/(m·K),and super-hydrophobicity with the water contact angle of 152°.The mechanical robustness and high-temperature thermal insulation of ceramic nanocomposites,together with its soundproof performance,shed light on the low-cost flexible insulation materials manufacturing with scalability for high-temperature thermal insulation applications under high mechanical loading conditions.

Highly flexible ceramic nanofibrous membranes for superior thermal insulation and fire retardancy

Ceramic membranes are attractive for thermal management applications due to its lightweight and ultralow thermal conductivity,while it is indispensable to address the long-standing obstacle of its poor mechanical stability and degradation under thermal shock.In this work,a series of the organic polymer template-modulated yttria doped zirconia(YDZ)nanofibrous membranes with lightweight,superior mechanical and thermal stability are developed through a cost-effective,scalable sol-gel electrospinning and subsequent calcination method.The YDZ membranes demonstrate excellent flexibility and foldability,which can be attributed to the tetragonal phase and small crystallite size of the YDZ fibers due to the presence of yttria.Besides,the fibrous size,grain size,mechanical and thermal stability of YDZ nanofibrous membranes could be tailored by varying the species and molecular weight of polymer template.The remarkable performances are obtained through the poly(vinyl pyrrolidone)(PVP)template YDZ nanofibrous membranes,featuring the superior tensile strength up to~4.82 MPa,excellent flexibility with bending rigidity~26 mN,robust thermal stability up to 1,200℃,ultra-low thermal conductivity of 0.008–0.023 W·m^(−1)·K^(−1)(25–1,000℃),and excellent flame retardancy with tolerance of flame up to 1,000℃.The remarkable properties can be attributed to the smaller fibrous size,and higher grain size resulting from PVP template.This robust material system is ideal for thermal superinsulation with a wide range of uses from energy saving building applications to spacecraft.

Problems and solutions regarding generalized functional safety in cyberspace

The common endogenous security problems in cyberspace and related attack threats have posed subversive challenges to conventional theories and methods of functional safety.In the current design of the cyber physical system(CPS),functional safety and cyber security are increasingly intertwined and inseparable,which evolve into the generalized functional safety(S&S)problem.The conventional reliability and cybersecurity technologies are unable to provide security assurance with quanti able design and veri cation metrics in response to the cyberattacks in hardware and software with common endogenous security problems,and the functional safety of CPS facilities or device has become a frightening ghost.The dynamic heterogeneity redundancy(DHR)architecture and coding channel theory(CCT)proposed by the cyberspace endogenous security paradigm could handle random failures and uncertain network attacks in an integrated manner,and its generalized robust control mechanism can solve the universal problem of quantitative design for functional safety under probability or improbability perturbation.As a generalized functional safety enabling structure,DHR opens up a new direction to solve the common endogenous security problems in the cross-disciplinary elds of cyberspace.