Improved interfacial adhesion for stable flexible inverted perovskite solar cells

Flexible perovskite solar cells have attracted widespread attention due to their unique advantages in lightweight,high flexibility,and easy deformation,which are suitable for portable electronics.However,the inverted(p-i-n)structured devices suffer from poor stability largely due to the low adhesion at the brittle interface(the hole transport layer/perovskite).Herein,zeolitic imidazolate framework-67(ZIF-67)is applied to inverted structured cells to optimize the interface and prolong the device lifetime.As a result,the flexible devices based on ZIF-67 obtain the champion power conversion efficiency of 20.16%.Over 1000 h under continuous light irradiation,the device retains 96%and 80%of its original efficiency without and with bias,respectively.Notably,devices show mechanical endurance with over 78%efficiency retention after 10,000 cycles of consecutive bending cycles(R=6 mm).The introduction of ZIF-67 suppresses the cracking in device bending,which results in improved environmental stability and bending durability.

Adjusting the interfacial adhesion via surface modification to prepare high-performance fibers

Ultra-high molecular weight polyethylene(UHMWPE)fiber is a new kind of high-performance fiber.Due to its excellent physical and chemical characteristics,it is widely used in various fields.However,the surface UHMWPE fiber is smooth and demonstrates no-polar groups.The weak interfacial adhesion between fiber and resin seri-ously restricts the applications of UHMWPE fiber.Therefore,the surface modification treatments of UHMWPE fiber are used to improve the interfacial adhesion strength.The modified method by adding nanomaterials elu-cidates the easy fabrication,advanced equipment and proper technology.Thus,the progress of UHMWPE nanocomposite fibers prepared via adding various nanofillers are reviewed.Meanwhile,the effects of other various methods on surface modification are also reviewed.This work advances the various design strategies about nano technologies on improving interfacial adhesion performance via treatment methodologies.

Improving Interfacial Adhesion of PLA/Lignin Composites by One-Step Solvent-Free Modification Method

To clarify the effects of lignin as a biodegradable filler added into the PLA matrix,PLA/lignin composites with or without silane coupling agent ofγ-(2,3-epoxypropoxy)propy trimethoxysilane(KH560)were prepared by a one-step solvent-free modification method.The effects of KH560 as a compatibilizer on the morphology,chemical structure,crystallization behavior,thermal degradative behavior as well as mechanical strength of the PLA/lignin composites were analyzed in detail.It was found that,after modification by KH560,the fractured surfaces of composites became smooth,suggested sufficient bonding between the lignin and PLA in the composites with KH560 coupling agent molecules.This result further proved by 1H NMR and ATR spectra of the composites that lignin and PLA formed stable chemical bonds with KH560.Due to the toughening effect of KH560,mainly affect the molecular chain mobility,the thermodynamic properties of LG-KH560/PLA composites were all reduced.When compared to the conventional solution modification method of adding silane coupling agents into PLA/lignin,the composites were synthesized via a single-step reactive extrusion modification procedure in this work showed relatively low tensile strength,which mainly because the existence of the free radicals due to coupling agents result in the composite’s deterioration and subsequent weakening of the tensile properties.

Evaluation of Interfacial Adhesion Property for Thin Hard Films with Fuzzy Method

According to nanoscratch results for the TiN film, an evaluation method for interfacial fracture toughness of thin hard films is presented with fuzzy concepts, which can account for such influential factors in scratch test as surface roughness and material imperfection. Based on configuration changes in scratching curves, the parameters RV and RF are defined as the relative ratios of tip vertical displacement and of friction coefficinet. Fuzzy features of the scratching curves are analyzed carefully. The critical load is deduced from fuzzy logic operations and used to calculate the value of interfacial fracture toughness. With this method, the interfacial fracture toughness of TiN/HSS is evaluated approximately as 4.18 MPam^1/2. Results show that the method is valid and can benefit the interfacial adhesion property investigation for thin hard films.

EFFECTS OF INTERPARTICLE DISTANCE,TEMPERATURE AND INTERFACIAL ADHESION ON BRITTLE-DUCTILE TRANSITION FOR NYLON 6/ABS BLENDS

The toughness of blends composed of nylon 6 and acrylonitrile-butadiene-styrene(ABS) compatibilized by using styrene-maleic anhydride(SMA) as a compatibilizer was measured over a wide temperature region.Results reveal that the combining effects of particle size and volume fraction of ABS on the toughness of nylon 6/ABS/SMA blends can be described through plotting brittle-ductile transition of the impact strength versus the interparticle distance(ID) on the assumption that ABS domains relieve the triaxial te...

Regulatable interfacial adhesion between stamp and ink for transfer printing

As an emerging processing technology,transfer printing enables the assembly of functional material arrays(called inks)on various substrates with micro/nanoscale resolution and has been widely used in the fabrication of flexible electronics and display systems.The critical steps in transfer printing are the ink pick-up and printing processes governed by the switching of adhesion states at the stamp/ink interface.In this review,we first introduce the history of transfer printing in terms of the transfer methods,transferred materials,and applications.Then,the fundamental characteristics of the transfer printing system and typical strategies for regulating the stamp/ink interfacial adhesion strength are summarized and exemplified.Finally,future challenges and opportunities for developing the novel stamps,inks,and substrates with intelligent adhesion capability are discussed,aiming to inspire the innovation in the design of transfer printing systems.

Protective cleaning of Chinese paper artworks with strong hydrogels: An interfacial adhesion perspective

Up to now, it is always a delicate and challenging task to clean and protect Xuan paper ink painting. Xuan paper is composed of cellulose with a rough surface and easy to absorb dust, which leads to poor cleaning effect and irreversible damage in traditional cleaning process. Hydrogel is one of the most effective tools to clean the artworks. However, in the practice of cleaning Xuan paper, most hydrogels cannot achieve fine cleaning result due to the interfacial adhesion issues. Herein, to protectively and effectively clean Xuan paper, using physical yet strong poly(vinyl alcohol)/poly(N-(2-hydroxyethyl) acrylamide)(PVA/PHEAA)hydrogel with suitable stiffness as the model, the interfacial adhesion between hydrogel and Xuan paper was systematically investigated, and various technologies were used to evaluate the cleaning effect. A critical interfacial adhesive energy(< 4 J/m^(2))is found to achieve the protective and effective cleaning purpose. To the best of our knowledge, this is the first report to estimate the adhesion of hydrogel on the cleaning of paper artwork, which will provide a new viewport in the conservation practice.

Coupling of Adhesion and Anti‑Freezing Properties in Hydrogel Electrolytes for Low‑Temperature Aqueous‑Based Hybrid Capacitors

Solid-state zinc-ion capacitors are emerging as promising candidates for large-scale energy storage owing to improved safety,mechanical and thermal stability and easy-to-direct stacking.Hydrogel electrolytes are appealing solid-state electrolytes because of eco-friendliness,high conductivity and intrinsic flexibility.However,the electrolyte/electrode interfacial contact and anti-freezing properties of current hydrogel electrolytes are still challenging for practical applications of zinc-ion capacitors.Here,we report a class of hydrogel electrolytes that couple high interfacial adhesion and anti-freezing performance.The synergy of tough hydrogel matrix and chemical anchorage enables a well-adhered interface between hydrogel electrolyte and electrode.Meanwhile,the cooperative solvation of ZnCl2 and LiCl hybrid salts renders the hydrogel electrolyte high ionic conductivity and mechanical elasticity simultaneously at low temperatures.More significantly,the Zn||carbon nanotubes hybrid capacitor based on this hydrogel electrolyte exhibits low-temperature capacitive performance,delivering high-energy density of 39 Wh kg^(-1)at-60°C with capacity retention of 98.7%over 10,000 cycles.With the benefits of the well-adhered electrolyte/electrode interface and the anti-freezing hydrogel electrolyte,the Zn/Li hybrid capacitor is able to accommodate dynamic deformations and function well under 1000 tension cycles even at-60°C.This work provides a powerful strategy for enabling stable operation of low-temperature zinc-ion capacitors.

Random copolymer membrane coated PBO fibers with significantly improved interfacial adhesion for PBO fibers/cyanate ester composites

Poly(p-phenylene-2,6-benzobisoxazole)(PBO) fibers possess excellent dielectric, mechanical properties and heat resistance. However, the surface of PBO fibers is smooth and highly chemical inert, resulting in poor interfacial compatibility to polymer matrix, which severely limits its wider application in high-performance fiber-reinforced resin matrix composites. In this work, random copolymers(P(S-co-BCB-co-MMA)) containing benzocyclobutene in the side-chain were synthesized by reversible addition-fragmentation chain transfer(RAFT) polymerization, which were then utilized to form dense random copolymer membrane on the surface of PBO fibers by thermally cross-linking at 250 °C(PBO@P fibers). Four kinds of synthesized P(S-co-BCB-co-MMA) with different number-average molar mass(Mn) were well controlled and possessed narrow dispersity.When the Mnwas 32300, the surface roughness of PBO@P fibers was increased from 11 nm(PBO fibers) to 39 nm. In addition, PBO@P fibers presented the optimal interfacial compatibility with bisphenol A cyanate(BADCy) resins. And the single fiber pull-out strength of PBO@P fibers/BADCy micro-composites was 4.5 MPa, increasing by 45.2% in comparison with that of PBO fibers/BADCy micro-composites(3.1 MPa). Meantime, PBO@P fibers still retained excellent tensile strength(about 5.1 GPa). Overall, this work illustrates a simple and efficient surface functionalization method, which would provide a strong theoretical basis and technical support for controlling the surface structure & chemistry of inert substrates.

Stick-and-play system based on interfacial adhesion control enhanced by micro/nanostructures

The evolution of membrane-type electronics has facilitated the development of stick-and-play systems,which confer diverse electrical functions to various planar or arbitrary curvilinear surfaces.The stick-and-play concept is based on the development of thin electronic devices in a printable format and their subsequent transfer to target surfaces.The development of this technology requires control of the interfacial adhesion of the electronic prints for retrieval from a carrier and transfer to the target surface.First,we discuss the transfer printing for membrane-type electronics,starting from an overview of materials available for flexible substrates,transfer printing of electronic prints for retrieval,and assembly for further integration.Second,we explain the stick-and-play concept based on fabricated membrane-type electronics;"stick" and “play"refer to the transfer of electronic devices and the performance of their electronic functions,respectively.In particular,we broadly survey various methods based on micro/nanostructures,including gecko-inspired,interlocking,cephalopod-sucker-inspired,and cilia structures,which can be employed to stick-and-play systems for enhancing interfacial adhesion with complex target surfaces under dynamic and wet conditions.Finally,we highlight the stick-and-play system application of micro/nanostructures for skin-attachable biomedical electronics,e-textiles,and environmental monitoring electronics.

Effects of Different Compatibilizing Agents on the Interfacial Adhesion Properties of Polypropylene/Magnesium Oxysulfate Whisker Composites

The effects of maleic anhydride-grafted polypropylene （PP-g-MAH） and maleic anhydride-grafted polyolefin elastomer （POE-g-MAH） on interracial adhesion properties of the polypropylene/magnesium oxysulfate whiskers （PP/MOSw） composites were investigated via mechanical, thermal, ATR-FTIR and rheological tests. Although significant increases in yield strength and Young＇s modulus were observed in PP-g-MAH treated composites, a sharp decline in these properties was observed in POE-g-MAH treated composites. ATR-FTIR results indicated that esterification occurred between the hydroxyl groups of MOSw and the carbonyls of anhydrides of both compatibilizers but POE-g-MAH was still incompatible with the PP matrix, as verified by the presence of shoulder peaks in DTG curves and numerous voids in SEM micrographs. On the other hand, PP-g-MAH was highly compatible with the PP matrix, as evidenced by the peaks in DTG curves and vague interfaces with wrapped melts on the surface of MOSw. Rheological behaviors also confirmed that introducing PP-g-MAH resulted in a transition from liquid-like to solid-like, which was attributed to the stronger interfacial adhesion between MOSw and the PP matrix. POE-g-MAH treated composites, in contrast to PP-g-MAH, maintained liquid- like rheological behaviors as typical molten polymers. There is likely a MOSw network formed in the PP/15PP-g- MAH/15MOSw composite as suggested by the significant deviation of G＇ versus G＂ plots and the two crossover frequencies observed in plots of tan6versus frequency.

Rational design of robust nano-Si/graphite nanocomposites anodes with strong interfacial adhesion for high-performance lithium-ion batteries

The nano-Si/graphite nanocomposites are the promising anodes candidates for high-energy lithium-ion batteries because of their high theoretical capacities and low volume variations.However,the nano-Si has a severe tendency to separate from the graphite substrate due to the inherently weak bonding between them,thus leading to the deteriorated cycling performance and low Coulombic efficiency.Herein,we design a robust nano-Si/graphite nanocomposite structure with strong interfacial adhesion caused by the Si—Ti and Ti—C covalent bonds.The abundant Si—Ti and Ti—C bonds formed between nano-Si and graphite greatly enhance the interfacial adhesion force,resulting in the highly stabilized and integrated electrode structure during battery cycling.Consequently,the as-obtained nano-Si/graphite anodes deliver a high capacity retention of 90.0% after 420 cycles at 0.5 C with an average Coulombic efficiency of 99.5%;moreover,a high initial Coulombic efficiency of 90.2% is achieved.Significantly,this work provides a novel strategy to address the poor interfacial adhesion between nano-Si and graphite,which can be applied to other nano-Si based composites anodes.

Modification of Interfacial Performance of Fiber Bragg Grating Embedded in the Composite Materials

The interfacial performance of the Fiber Bragg grating（FGB） embedded in the composite was studied and the influence of interface modification on the final profile of the spectra of the FBG sensor was examined. A type of polyamine（Pentaethylenehexamine, PEHA） was proposed to modify the coating of PI on FBG, and the interfacial performance was evaluated by a pull-out test. Sharp improvements of the interfacial shear strength（77%） were obtained by 40 min treatment of PEHA. Compared with untreated specimen, FGB spectra of treated specimen in the tensile tests show improved linearity within the test regime, which proves that the enhanced interface is beneficial for the sensing performance.

Mass transfer techniques for large-scaleand high-density microLED arrays

Inorganic-based micro light-emitting diodes (microLEDs) offer more fascinating properties and unique demands in next-generation displays. However, the small size of the microLED chip (1–100 µm) makes it extremely challenging for high efficiency and low cost to accurately, selectively, integrate millions of microLED chips. Recent impressive technological advances have overcome the drawbacks of traditional pick-and-place techniques when they were utilized in the assembly of microLED display, including the most broadly recognized laser lift-off technique, contact micro-transfer printing (µTP) technique, laser non-contact µTP technique, and self-assembly technique. Herein, we firstly review the key developments in mass transfer technique and highlight their potential value, covering both the state-of-the-art devices and requirements for mass transfer in the assembly of the ultra-large-area display and virtual reality glasses. We begin with the significant challenges and the brief history of mass transfer technique, and expand that mass transfer technique is composed of two major techniques, namely, the epitaxial Lift-off technique and the pick-and-place technique. The basic concept and transfer effects for each representative epitaxial Lift-off and pick-and-place technique in mass transfer are then overviewed separately. Finally, the potential challenges and future research directions of mass transfer are discussed.

Constructing nanocomposites with robust covalent connection between nanoparticles and polymer for high discharged energy density and excellent tensile properties

High discharged energy density and excellent flexible properties in dielectric materials are significantly sought to meet the rapid advancements in the electronics industry. In this study, covalent bonds are constructed between poly(vinylidene fluoride-chlorotrifluoroethylene), which contains olefinic bonds, and thiol-modified BaTiO_(3) at the interface before the nanocomposite films are fabricated. The presence of the covalent bonds is proved to promote the dispersibility of the modified BaTiO_(3) and enhance the interfacial adhesion between the modified BaTiO_(3) and the polymer, followed by a remarkably positive effect in suppressing the dielectric loss(tanδ) and increasing the breakdown strength(Eb) of the nanocomposite films. In addition, the cross-linking treatment in the preparation process is found to be favourable for improving the mechanical properties of the nanocomposite films, which benefits the enhancement of Eb. Furthermore, at 400% elongation, the stretched nanocomposite film doped with 5 vol% modified BaTiO_(3) exhibits an Eb15.6% greater than that of the unstretched film, and the discharged energy density reaches 11.4 J/cm^(3) with a high discharge energy efficiency of 84.5%. This study provides a novel strategy for preparing flexible nanocomposites with powerful interfacial adhesion at high filler content to achieve high discharged energy density.

Effects of EVA Latex on the Properties of Glass-fiber/Magnesium-oxychloride Cement Composites

The effects of Ethylene-Vinyl Acetate copolymer （EVA） latex as an additive or a glass fiber surface modifier on the properties of Glass-Fiber （ GF ）/ Magnesium Oxychloride Cement （MOC） composites was studied. The mechanical properties, water resistance aud aging resistance of the cured GF/ MOC composites were estimated and chemical ingredients analysis and morphological study of the GF/ MOC composites were also performed. It is found that EVA added to the MOC matrix could substantially improve the interfacial adhesion, water resistance aud aging resistance of GF/ MOC composites. EVA treatment on glass fibers resulted in decreasing initial flexural strength of GF/ MOC composites while enhancing the soft coefficients. In addition, the drying time and dilution of the EVA treatment on glass fibers also had an otwioas effect on the properties of GF/ MOC composites. However, excessive EVA interfered with the growth of the 5 Mg（ OH）2· MgCl2 ·8H2O crystal and the properties of GF / MOC composites.

Reactive Compatibilization of Short-Fiber Reinforced Poly(lactic acid)Biocomposites

Poor interfacial adhesion between biobased thermoplastics and natural fibers is recognized as a major drawback for biocomposites.To be applicable for the large-scale production,a simple method to handle is of importance.This work presented poly(lactic acid)(PLA)reinforced with short-fiber and three reactive agents including anhydride and epoxide groups were selected as compatibilizers.Biocomposites were prepared by one-step meltmixing methods.The influence of reactive agents on mechanical,dynamic mechanical properties and morphology of PLA biocomposites were investigated.Tensile strength and storage modulus of PLA biocomposites incorporated with epoxide-based reactive agent was increased 13.9%and 37.4%compared to non-compatibilized PLA biocomposite,which was higher than adding anhydride-based reactive agent.SEM micrographs and Molau test exhibited an improvement of interfacial fiber-matrix adhesion in the PLA biocomposites incorporated with epoxide-based reactive agent.FTIR revealed the chemical reaction between the fiber and PLA with the presence of epoxide-based reactive agents.

Aggregates of fluorescent gels assembled by interfacial dynamic bonds

Life,defined as the specific form of substance,is an integration of aggregates at various scales,ranging from single molecules to tissues.However,these building blocks of common aggregates are usually recognized as confining at the microscopic level,while there are few studies focusing on macroscopic building blocks for aggregates.Fluorescent gels,as the important macroscopic building blocks,are drawing researchers’attention on account of their extraordinary fluorescence as well as soft material properties.Inspired by nature,fluorescent gels can be aggregated through interfacial adhesion.According to the driving forces for interfacial adhesion,a series of aggregates of fluorescent gels(AFGs)was summarized,including H-bond,metal coordinations,host-guest interactions,hydrophobic interactions,electrostatic interactions,dynamic covalent bonds as well as multiple driving forces.These AFGs own dynamic assembled behaviors and rich stimuli responsiveness,which could be applied to information storage,sensing,biomedical systems,and so on.The authors anticipate this review can accelerate the development of aggregate science,especially based on macroscopic building blocks.

Adhesive hydrogel interface for enhanced epidermal signal

This paper presents a discussion on the method,mechanism,and application of adhesive hydrogel in enhancing epidermal signal,focusing on the interface between hydrogel and skin.Due to its excellent conductivity and high adaptability to the skin,the hydrogel is exceptionally suitable for detecting human-machine interfaces,particularly epidermal electromyographic signals.However,the detection of the high epidermal signal is hindered by the gap and low adhesion between hydrogel and skin.This paper addresses these challenges by introducing approaches to reduce the interface gap and increase interface adhesion,thereby enabling the development of hydrogel-based epidermal signal detection arrays with enhanced resolution and detection performance.

High precision patternable liquid metal based conductor and adhesive substrate enabled stretchable hybrid systems

Stretchable hybrid systems have been attracting tremendous attention for their essential role in soft robotics,on-skin electronics,and implantable devices.Both rigid and soft functional modules are typically required in those devices.Consequently,ensuring stable electrical contact between rigid and soft modules is a vital part.Here,we propose a simple,universal,and scalable strategy for the stretchable hybrid system through a highly precise printable liquid metal particle-based conductor and adhesive fluorine rubber substrate.The properties of liquid metal particle-based conductors could be easily tuned to realize high-precision patterning,large-scale printing,and the ability to print on various substrates.Additionally,the fluorine rubber substrate could form strong interfacial adhesion with various components and materials through simply pressing and heating,hence enabling stable electrical contact.Furthermore,we prepared a stretchable hybrid light-emitting diode(LED)display system and employed it in on-skin visualization of pressure levels,which perfectly combined rigid and soft modules,thus demonstrating the promising potential applications in complex multifunctional stretchable hybrid systems for emerging technologies.