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Hindered gas bubble release and limited electron conducting process represent the major bottlenecks for large scale electrochemical water splitting. Both the desorption of bubbles and continuous electron transport are achievable on the surfaces of biomimetic catalytic materials by designing multiscale structural hierarchy. Inspired by the tubular structures of the deep-sea sponges, we fabricated an exceptionally active and binder-free porous nickel tube arrays (PNTA) decorated with NiFe-Zn

Pseudocapacitance holds great promise for energy density improvement of supercapacitors, but electrode materials show practical capacity far below theoretical values due to limited ion diffusion accessibility and/or low electron transferability. Herein, inducing two kinds of straight ion-movement channels and fast charge storage/delivery for enhanced reaction kinetics is proposed. Very thick electrodes consisting of vertically aligned and ordered arrays of NiCo2S4-nanoflake-covered slender nickel columns (NCs) are achieved via a scalable route. The vertical standing ∼5 nm ultrathin NiCo2S4 flakes build a porous covering with straight ion channels without the "dead volume", leading to thickness-independent capacity. Benefiting from the architecture acting as a "superhighway" for ultrafast ion/electron transport and providing a large surface area, high electrical conductivity, and abundant availability of electrochemical active sites, the NiCo2S4@NC-array electrode achieves a specific capacity up to 486.9 mAh g-1. The electrode even can work with a high specific capacity of 150 mAh g-1 at a very high current density of 100 A g-1. In particular, due to the advanced structure features, the electrode exhibits excellent flexibility with a unexpected improvement of capacity when being largely bent and excellent cycling stability with an obvious resistance decrease after the cycles. An asymmetric pseudocapacitor applying the NiCo2S4@NC-array as a positive electrode achieves an energy density of 66.5 Wh kg-1 at a power density of 400 W kg-1, superior to the most reported values for asymmetric devices with NiCo2S4 electrodes. This work provides a scalable approach with mold-replication-like simplicity toward achieving thickness-independent electrodes with ultrafast ion/electron transport for energy storage.

Nowadays, numerous electrochemical and photoelectrochemical (PEC) methods have been utilized for water splitting hydrogen production. Herein, we designed a novel photocathode based on a TiO2/Au nanoring (AuNR)/Si nanohole (SiNH) heteronanostructure (HN), which can be fabricated in a programmable way. The SiNH arrays substrate was prepared by nanoimprint lithography and then embedded AuNRs were fabricated by sputtering deposition and subsequent ion beam etching to remove the Au layer covering the horizontal Si surface. Cylindrical AuNRs clinging to the side walls of SiNH arrays could maximize the horizontal exposure area of the Si substrate and has little adverse effect on its light absorption. The design is supported by theory simulation and could lead to expectable PEC performance by precisely controlling the geometry and size of the AuNR which will trigger localized surface plasmon resonance (LSPR), bringing about prominent enhancement of light harvesting ability and exciting vast hot electrons under li...

Both poor electron conductivity and low ion diffusion of electrode materials are two main issues limiting the rate performance of pseudocapacitors. The present work reports the design and fabrication of hierarchically nano-architectured electrodes consisting of sulfide vacancies enhanced Ni–Co–S nanoparticle covering bent nickel nano-forest (BNNF). We propose new insight into vastly increased ion-accessible active sites and fast charge storage/delivery enhanced the reaction kinetics. The Ni−Co−S@BNNF electrode exhibits extremely high rate performance with 90.1% capacity retention from 1 to 20 A g−1, and even still remains 83.6% capacity at 40 A g−1, much superior to reported NiCo2S4–based electrodes. The high rate performance is attributed to the unique nano-architecture providing increased ion availability of electrochemically active sites and high conductivity for fast electron transport. Especially the electrode achieves remarkable long-term cycle stability with more than 100% initial capacity value after 5000 cycles at 5 A g−1 and exhibits excellent cycle reversibility even at 20 A g−1. Goog cycle stability should be attributed to the sulfide vacancies in Ni−Co−S nano-branches and the electrode architecture sustaining structural strain during fast redox reactions. An asymmetric pseudocapacitor applying such electrode achieves a high energy density of 99.9 W h kg−1 and exhibits superior cycling stability at a high current density of 20 A g−1. This study underscores the potential importance of developing nanoarrays covered with highly redox-active materials with increasing ions/charge kinetics for energy storage.

Metallic nanomesh, one of the emerging transparent conductive film (TCF) materials with both high electrical conductivity and optical transmittance, shows great potential to replace indium tin oxide (ITO) in optoelectronic devices. However, lithography-fabricated metallic nanomeshes suffer from an iridescence problem caused by the optical diffraction of periodic nanostructures, which has negative effects on display performance. In this work, we propose a novel approach to fabricate large-scale metallic nanomesh as TCFs on flexible polyethylene terephthalate (PET) sheets by maskless phase separation lithography of polymer blends in a low-cost and facile process. Polystyrene (PS)/polyphenylsilsequioxane (PPSQ) polymer blend was chosen as resist material for phase separation lithography due to their different etching selectivity under O2 reactive ion etching (RIE). The PS constituent was selectively removed by O2 RIE and the remained PPSQ nanopillars with varying sizes in random distribution were used as masks for further pattern transfer and metal deposition process. Gold (Au) nanomeshes with adjustable nanostructures were achieved after the lift-off step. Au nanomesh exhibited good optoelectronic properties (RS = 41 Ω/sq, T = 71.9%) and non-iridescence, without angle dependence owing to the aperiodic structures of disordered apertures. The results indicate that this Au nanomesh has high potential application in high-performance and broad-viewing-angle optoelectronic devices.

Stimuli-responsive delivery systems hold promise in cancer treatments. However, their application potential has been limited due to undesirable drug leaking during blood circulation and inefficient therapeutic efficacy in tumors, resulting in undesirable therapeutic outcomes. Herein, we have developed a novel redox-sensitive pegylated phospholipid, termed as DOPE-SS-PEG, which can form a glutathione (GSH)-triggered precision explosive system (GPS) for simultaneously improving circulation stability, tumor specificity, and chemosensitivity, leading to explosive anticancer effects. GPS is constructed of liposomal doxorubicin (DOX) functionalized with DOPE-SS-PEG and MnO2 nanoparticles, which can protect liposome structure in the presence of serum GSH (20 pM), whereas converts to cationic liposome in response to intracellular GSH (10 mM), thereby enhancing circulation stability, tumor specificity, endosomal escape, and cytoplasmic delivery. Importantly, GPS can not only generate oxygen to relieve hypoxia and consequently enhance chemosensitivity, but quench GSH antioxidability to elevate the accruement of intracellular reactive oxygen species (ROS), leading to an explosion of oxidative stress induced cell injury. Particularly, in vivo studies show that GPS selectively accumulates in tumor tissues, effectively inhibits tumor growth, exhibits minimal systemic adverse effects, and consequently prolongs the survival time of tumor-bearing mice. Therefore, GPS is a unique stimuli-responsive treatment with programmed and on-demand drug delivery, as well as explosive therapeutic efficacy, and provides an intelligent anticancer treatment.

Pseudocapacitance holds great promise for energy density improvement of supercapacitors, but electrode materials show practical capacity far below theoretical values due to limited ion diffusion accessibility and/or low electron transferability. Herein, inducing two kinds of straight ion-movement channels and fast charge storage/delivery for enhanced reaction kinetics is proposed. Very thick electrodes consisting of vertically aligned and ordered arrays of NiCo

We demonstrated a simple and effective approach to fabricate dense and high aspect ratio sub-50 nm pillars based on phase separation of a polymer blend composed of a cross-linkable polysiloxane and polystyrene (PS). In order to obtain the phase-separated domains with nanoscale size, a liquid prepolymer of cross-linkable polysiloxane was employed as one moiety for increasing the miscibility of the polymer blend. After phase separation via spin-coating, the dispersed domains of liquid polysiloxane with sub-50 nm size could be solidified by UV exposure. The solidified polysiloxane domains took the role of etching mask for formation of high aspect ratio nanopillars by O2 reactive ion etching (RIE). The aspect ratio of the nanopillars could be further amplified by introduction of a polymer transfer layer underneath the polymer blend film. The effects of spin speeds, the weight ratio of the polysiloxane/PS blend, and the concentration of polysiloxane/PS blend in toluene on the characters of the nanopillars were...

Thermal nanoimprint lithography is playing a vital role in fabricating micro/nanostructures on polymer materials by the advantages of low cost, high throughput, and high resolution. However, a typical thermal nanoimprint process usually takes tens of minutes due to the relatively low heating and cooling rate in the thermal imprint cycle. In this study, we developed an induction heating apparatus for the thermal imprint with a mold made of ferromagnetic material, nickel. By applying an external high-frequency alternating magnetic field, heat was generated by the eddy currents and magnetic hysteresis losses of the ferromagnetic nickel mold at high speed. Once the external alternating magnetic field was cut off, the system would cool down fast owe to the small thermal capacity of the nickel mold, thus, providing a high heating and cooling rate for the thermal nanoimprint process. In this paper, nanostructures were successfully replicated onto polymer sheets with the scale of 4-inch diameter within 5 min.

Size-based filtration has been proved an efficient and quick approach to separate circulating tumor cells (CTCs) from other blood cells for cancer diagnosis and therapy monitoring. In this work, we proposed a simple, cost efficient and scalable approach to fabricate microporous polyethylene (PE) membranes for CTC filtration by thermal nanoimprint method. PE was selected as the material for the membrane due to its commercially available films with a thickness as thin as ~ 10 µm, which is matched well with the size of the micropores for CTCs and critical to a successful nanoimprint with a low and uniform residual layer. A thermal imprint process with a nickel mold was applied to fabricate periodic microporous PE membranes with a pitch of 20 µm and diameter of 10 µm. The perforated micropores were obtained by a short time O2 plasma-etching to remove the imprint residual layer. This PE membrane microfilter achieved 84% average capture efficiency for lung cancer cells spiked in blood samples.

In this Article, two readily available polymers that contain silicon and have different surface tensions, polydimethylsiloxane (PDMS) and polyphenylsilsequioxane (PPSQ), were used to produce polymer blends with polystyrene (PS). Spin-coated thin films of the polymer blends were treated by O2 reactive-ion etching (RIE). The PS constituent was selectively removed by O2 RIE, whereas the silicon-containing phase remained because of the high etching resistance of silicon. This selective removal of PS substantially enhanced the contrast of the phase separation morphologies for better scanning electron microscope (SEM) and atomic force microscope (AFM) measurements. We investigated the effects of the silicon-containing constituents, polymer blend composition, concentration of the polymer blend solution, surface tension of the substrate, and the spin-coating speed on the ultimate morphologies of phase separation. The average domain size, ranging from 100 nm to 10 μm, was tuned through an interplay of these factors. In addition, the polymer blend film was formed on a pure organic layer, through which the aspect ratio of the phase separation morphologies was further amplified by a selective etching process. The formed nanostructures are compatible with existing nanofabrication techniques for pattern transfer onto substrates.

In this paper, we demonstrate the fabrication of metallic patterns on both planar and highly curved substrates via nanoimprint lithography in association with an etch-in process. First, the resist pattern is fabricated on the surface of a metal coated substrate via UV-curing nanoimprint lithography using a hybrid soft nanoimprint mold and the double transfer method. After the resist pattern was etched through by reactive ion etching (RIE), the sample is immersed in an etchant to fabricate metallic patterns using the resist pattern as the etching mask. An ammonium cerium nitrate/acetic acid system is used as the etchant to fabricate Cr patterns and the Fe3+/thiourea etching system is used to fabricate Au patterns. High quality 70 nm deep Cr gratings and 80 nm deep Au gratings with 550 nm pitch and 275 nm linewidth are obtained. Additionally, the linewidth of Cr patterns can be tuned from 275 nm to 95 nm by changing the etching time. Furthermore, a 550 nm pitch Cr grating is patterned on the cylindrical surface of a 125 μm-diameter optical fiber and a surface relief fiber Bragg grating with a groove depth of 330 nm is fabricated via RIE using the Cr mask. This method is universally used for fabricating metallic patterns on different substrates and it greatly widens the process window compared to the lift-off process.

As thermal nanoimprint lithography offers promising potential in industrial manufacture, it is more and more desirable to obtain a suitable mold with good anti-adhesive property. In this study, we developed a new fabrication route of nickel mold based on the commonly used electroplating process. Utilizing titanium as the seed layer material and surface modification basis, perfluoroalkyl trichlorosilane was simply and firmly bonded to the surface of the titanium-nickel composite mold, offering a low surface energy state and a good anti-adhesive property. The availability of high-quality anti-adhesive coatings makes titanium-nickel composite molds well suitable for thermal nanoimprint lithography.

We report a new method to fabricate stretching-tunable metal gratings on elastomeric substrates by combining nanoimprint lithography and metal transfer using a patterned sacrificial layer. Fabrication of metal lines with a period of 550 nm and a linewidth of 270 nm was demonstrated on polydimethylsiloxane (PDMS) membranes using this process. Optical diffraction characterization was used to measure the period of stretched gratings on the PDMS membrane and demonstrates tuning of the grating period by deforming the carrying PDMS substrate. The pattern transfer process using a water-soluble sacrificial layer can also be applied to fabrication of other deformable micro- and nano-devices.

A thin and uniform residual layer, especially zero-residual layer, is highly desired in the nanoimprint lithography, because it is critical to the succeeding pattern transfer process. In this study, a partial cavity filling method was applied on UV-curable resins instead of thermal plastic polymer to realize zero-residual layer based on a hybrid nanoimprint technique. The initial thickness of the UV-curable resin on the substrate was precisely quantified less than the cavity volume of the imprint mold by adjusting the resin concentration and spin coating speed. A near-zero-residual layer was successfully achieved under an extremely low imprint pressure by the control of the viscosity, surface tension and thickness of the UV-curable resist.

Ferroelectric polymers are among the most promising materials for flexible electronic devices. Highly ordered arrays of the defect-modified ferroelectric polymer P(VDF-TrFE-CFE) (poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)) are fabricated by nanoimprint lithography for nonvolatile memory application. The defective CFE units reduce the coercive field to one-fifth of that of the un-modified P(VDF-TrFE), which can help minimize the energy consumption and extend the lifespan of the device. The nanoimprint process leads to preferable orientation of polymer chains and delicately controlled distribution of the defects, and thus a bi-stable polarization that makes the memory nonvolatile, as revealed by the pulsed polarization experiment.

We demonstrated the fabrication of dense hexagonal arrays of Ag nanodots over a large area using a novel nanoimprint-based fabrication technique for surface-enhanced Raman spectroscopy. Flexible imprint molds with sub-10 nm features were duplicated from AAO templates using a novel hybrid mold technique. This method solves the nonflatness-induced defect issue in the conventional thermal nanoimprint technique, and allows high-quality duplications of nanometer features from rigid nonflat templates. Moreover, with the help of the excellent tunability of the size of nanoholes on AAO templates, we were able to tune the size of Ag nanodots, and consequently to tailor the resonance frequency of the Ag nanodot arrays. Finally, surface-enhanced Raman scattering of Rhodamine-123 on Ag nanodot arrays was measured, and large signal enhancement was observed on the 70 nm Ag nanodots. We numerically simulated the optical properties of those Ag nanodot arrays, and excellent agreement was found with the experimental results.

In this work, the liquid acrylated materials were transferred onto the nanostructured surfaces by a transfer printing method. Further, they were frozen (solidified) by UV-light exposure. The morphology of the solidified liquid reflects the original liquid-state profile because the UV-curing shrinkage of the acrylated material was only a few percent in volume so that it would not largely alter the liquid morphology. The cured samples were then examined with high resolution SEM or AFM measurement. This proposed method allows for the observation of liquid behavior down to sub-20 nm scale with more subtle details such as nano-menisci between nanogrooves, and liquid bridges covering nanostructures. The wetting behavior of the liquid strongly depends on the surface properties and geometries of the underlying nanostructures. Experimental results agree with the prediction of a simple surface energy variation model. They indicate that macroscopic wetting behaviors of liquids are preserved as dimensions go down to 100 nm.

Hierarchical metal oxide spheres (HMOS) have various applications that stem from their special architectures. Here a novel template-free method is developed for mass fabrication of HMOS at room temperature. It is only composed of the facile processes of PEG modification and self-assembly (PMSA). Its powerful fabrication capability is demonstrated by fabricating HMOS of TiO2, Fe2O3, ZrO2 and their mixtures with high quality. The related mechanism is investigated and the peculiar PEG configuration on the surface of the nanoparticle is believed to be the origin of the HMOS formation. Several possible applications of HOMS are also exhibited, such as the superhydrophobic properties, the enhanced light scattering ability and the improved solar cell performance. Considering the unique fabrication abilities and industrial mass production potentials, this method may be used as a powerful tool for the synthesis of HMOS with extended applications.

Surface functionalization is closely associated with the light harvesting and the charge separation, transfer, and injection efficiencies of water-splitting photoelectrode. Here, a dual-phase photoetching template with hierarchical structure, polyphenylsilsequioxane nanopillars and bicontinuous polyphenylsilsequioxane + polystyrene network layer, is patterned on the Si photoanode via a spinodal phase separation mechanism. Controllably photoetching the polymer template allows us to physically deposit functional layers with tunable nanostructures from net to dispersed dot. As a demonstration, the broken Ni/NiOx net modified Si photoanode exhibits a low onset potential of 0.93 VRHE, a high saturated photocurrent density of 40 mA cm−2 and a stability of 50 h in 1.0 M K-borate under AM1.5 G illumination, resulting from the inhomogeneous barrier height driven efficient charge extraction and low light loss by the dispersed surface modification. The proposed dual-phase lithographic template may open a new avenue to easily assemble functional layers on photoelectrodes for efficient solar energy conversion.

We report a method to tune the nanogratings’ period using mechanical stretching and transfer the tuned gratings using a UV-curing nanoimprint process. A hybrid mold with nanogratings was stretched perpendicularly or parallel to the grating lines. The perpendicular stretching caused a continuous enlargement of the grating period, and the parallel stretching led to a continuous shrinkage of the period. As a demonstration, we tuned a grating pattern with a period of 550 nm to a wide range of periods from 450 to 750 nm. The stretched hybrid mold was used to perform a UV-curing imprint process and to transfer the tuned grating structures onto a substrate in combination with a reactive ion etching process. A larger tuning range was achieved by repeating the grating stretching and pattern transfer steps. A grating pattern with a smaller period of 140 nm was also successfully shrunk to 125 nm using this method.

A phase separation lithography (PSL) based on polymer blend provides an extremely simple, low-cost, and high-throughput way to fabricate wafer-scale disordered nanopatterns. This method was introduced to fabricate nanopatterned sapphire substrates (NPSSs) for GaN-based light-emitting diodes (LEDs). The PSL process only involved in spin-coating of polystyrene (PS)/polyethylene glycol (PEG) polymer blend on sapphire substrate and followed by a development with deionized water to remove PEG moiety. The PS nanoporous network was facilely obtained, and the structural parameters could be effectively tuned by controlling the PS/PEG weight ratio of the spin-coating solution. 2-in. wafer-scale NPSSs were conveniently achieved through the PS nanoporous network in combination with traditional nanofabrication methods, such as O2 reactive ion etching (RIE), e-beam evaporation deposition, liftoff, and chlorine-based RIE. In order to investigate the performance of such NPSSs, typical blue LEDs with emission wavelengths of ~450 nm were grown on the NPSS and a flat sapphire substrate (FSS) by metal–organic chemical vapor deposition, respectively. The integral photoluminescence (PL) intensity of the NPSS LED was enhanced by 32.3 % compared to that of the FSS-LED. The low relative standard deviation of 4.7 % for PL mappings of NPSS LED indicated the high uniformity of PL data across the whole 2-in. wafer. Extremely simple, low cost, and high throughput of the process and the ability to fabricate at the wafer scale make PSL a potential method for production of nanopatterned sapphire substrates.

We invented a dual-curable transfer layer to enhance adhesion of the UV-curable nanoimprint resist to the substrate. Based on this transfer layer, we developed bilayer resist and trilayer resist UV-curable nanoimprint lithography processes, which were used for etching and lift-off processes, respectively. The dual-curable transfer layer combined at least two different types of reactive functions based on different polymerization mechanisms. It formed strong chemical bonds with both the underneath material and the nanoimprint resist layer in two curing steps. It helped improve the adhesion of the low surface energy resist film to the substrate substantially, and, more importantly, made high-resolution patterning much more reliable. Moreover, low aspect ratio imprinted patterns were amplified into high aspect ratio patterns through the transfer layer via a selective etching process.

InN films with electron concentration ranging from n similar to 10(17) to 10(20) cm(-3) grown by metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were investigated by variable-temperature photoluminescence and absorption measurements. The energy positions of absorption edge as well as photoluminescence peak of these InN samples with electron concentration above 10(18) cm(-3) show a distinct S-shape temperature dependence. With a model of potential fluctuations caused by electron-impurity interactions, the behavior can be quantitatively explained in terms of exciton freeze-out in local potential minima at sufficiently low temperatures, followed by thermal redistribution of the localized excitons when the band gap shrinks with increasing temperature. The exciton localization energy sigma (loc) is found to follow the n (5/12) power relation, which testifies to the observed strong localization effects in InN with high electron concentrations.

Water-soluble polyphenol-graft-poly(ethylene oxide) (PPH-g-PEO) copolymers were prepared using grafting-through methodology. Polyphenol chains were synthesized via enzymatic polymerization of phenols, and the graft chains were synthesized via living anionic polymerization of ethylene oxides. The polymers were characterized using gel permeation chromatography, static light scattering and 1H NMR, infrared and ultraviolet spectroscopies. The PPH-g-PEO graft copolymers are soluble in several common solvents, such as water, ethanol, N,N-dimethylformamide, tetrahydrofuran and methylene dichloride. The solubility of the PPH-g-PEO graft copolymers is improved significantly compared with that of polyphenol. Copyright © 2009 Society of Chemical Industry

Polyphenols containing Schiff base pendent groups, poly(4-[benzylidene-amino]-phenol) (PBP), and poly(4-[(anthracen-9-ylmethylene)-amino]-phenol) (PAP) have been synthesized through the combination of Schiff base reaction and enzymatic polymerization using horseradish peroxidase (HRP) as catalyst. The polymers were characterized by GPC, FTIR, 1H NMR, and UV spectroscopy. It shows that PBP and PAP are composed of polyphenol main chains bearing Schiff base pendent side groups. The PBP exhibits better solubility than PAP in some common solvents. The PAP has a large red-shift of 86 nm compared with polyphenols, indicating the Schiff base pendent groups remarkably increase the conjugation lengths of polyphenols.

An approach was presented to fabricate wafer-scale nanoring structures based on nanopillar array templates fabricated by nanoimprint lithography. This fabrication method combined UV-curing nanolithography technology, metal deposition, and an etching process, which made it possible to tune the geometric properties of nanorings: height, diameter, and linewidth for various materials, such as Au and Ni. Nanoring arrays showed potential applications in many fields, including memory storage, biosensing, and optical devices. The optical measurement of Au nanorings (d=380 nm) showed its strong transmission resonances at the wavelength of 2.1 μm. A modified version of this fabrication method by depositing Ni in a controlled angle as a sacrificial layer was also utilized to create nanocrescent arrays. This modified method could easily tune the width of crescents through the nickel deposition angles and nanopillar template heights. The large-area gold nanocrescent arrays showed strong polarization-dependent transmission bands. Plasmonic crescent structures were expected to apply in infrared metamaterial and chemical sensing.

As a powerful spectroscopy technique, surface-enhanced Raman scattering (SERS) can provide non-destructive and sensitive characterization down to a single molecular level. Aiming to the main challenges of high-performance SERS-active substrates for their real-world applications involving the ultra-sensitive and reproducible signals detection and signal uniformity with large-area, herein, a facile and reliable strategy based on combination of thermal imprinting polycarbonate (PC) film with porous anodic aluminum oxide (AAO) mold and E-beam evaporation of gold is provided to fabricate a high-quality SERS-active substrate consisting of ultra-dense hot-spots with large-area uniformity. Two kinds of sub-10 nm gaps were obtained, including the nanogaps between the neighboring gold coated PC-nanopillars and those between gold on the top of the nanopillars and that on the base, which actually build up a three-dimensional (3D) hot-spot network for high-performance SERS detection. The effect of structural parameters on SERS enhancement was investigated numerically and experimentally, and by optimizing the structural parameters, a remarkable average SERS enhancement factor up to of 1.4×108 is achieved and it shows an excellent reproducibility with a relative standard deviation of 18%, which allows for enhanced practicability in the application of quantitative biochemical detection.

Polydimethylsiloxane-graft-poly(ethylene oxide) (PDMS-g-PEO) copolymers form micelles in water with PDMS as the core and PEO as the corona. The introduction of poly(acrylic acid)-block-polyacrylonitrile (PAA-b-PAN) block copolymers in water leads to the formation of micellar complexes due to the hydrogen bonding between carboxyl groups and ether oxygens among the PAA and PEO chains in the corona of the micelles. The effects of pH, molar ratios (r) of PAA/PEO, and the standing time on the directly mixing these two micelles in water have been investigated using laser light scattering (LLS) and transmission electron microscopy (TEM). Our results showed that the complexation between PAA and PEO in the corona was greatly enhanced at a pH below 3.5. For a fixed pH value, the interactions between these two micelles in water were governed by the value of r. At r∼0.6, mixing the two micelles in water resulted in a large floccule because the smaller PAA-b-PAN micelles act as physical cross-links, which are absorbed onto one PDMS-g-PEO micelle and simultaneously bonded to PEO chains on the other micelles, forming bridges and causing flocculation. At ∼0.6r∼1.2, the mixing led to stable micellar complexes with a layer of PAA-b-PAN micelles absorbed onto the initial PDMS-g-PEO micelles. At r∼1.2, the resultant micellar complexes first remained stable, but they precipitated from solution after a long time standing.

Soft nanoimprint lithography has been developed to overcome the disadvantages of conventional nanoimprint lithography based on rigid molds. Hybrid nanoimprint-soft lithography mold is an efficient strategy to improve the resolution of soft nanoimprint because a rigid UV-curable material is used as the structural layer. In this paper, the authors design a novel UV-curable material for hybrid soft mold fabrication, which is degradable under mild acidic conditions and insensitive to oxygen during photopolymerization. The material comprises an acid-degradable cross-linker, 2,10-diacryloyloxymethyl-1,4,9,12-tetraoxaspiro[4.2.4.2] tetradecane, and an acyrlated polysiloxane, poly[(mercaptopropyl)methylsiloxane]. Oxygen sensitivity of acrylate groups during UV curing is avoided due to the cross-linking mechanism based on thiol-ene chemistry. The cured material can be decomposed into linear chains through the cleavage of acid-labile ketal links and dissolved in organic solvent when heated in an acidic solution. The material possesses necessary properties for mold fabrication and imprinting, including low shrinkage (about 5%), high modulus (1.4 GPa), high thermal stability, high UV transparency and stability in normal environment. Furthermore, since the cured material is degradable in acidic media, the stained master can be renewed in a mild condition. Various nanoscaled patterns are fabricated on planar and curved substrates via UV-nanoimprint when the same material is used as a patterning layer.

In this paper, we design and synthesize a degradable polycyclic diacrylate cross-linker, 2,10-diacryloyloxymethyl-1,4,9,12-tetraoxaspiro[4.2.4.2] tetradecane (DAMTT), from easily available starting materials by bis-ketalization of 1,4-cyclohexanedione with glycerol, followed by esterification with acryloyl choride. The chemical structure of the degradable cross-linker is characterized by FTIR, 1H NMR and GC-MS. A UV-NIL resist based on DAMTT has a very low shrinkage (about 2.5%) and a high Young's modulus of 1.89 GPa after UV-curing, and is soluble in acidic media. Patterns with sub-10 nm resolution are faithfully imprinted into the DAMTT film. The degradable cross-linker is incorporated with a multifunctional acrylated siloxane to increase O2 RIE resistance as an etch barrier for high aspect ratio pattern transfer. The cross-linked film of the UV-curable resist remains soluble in acidic media even though its formulation contains acrylated siloxane up to 50% (w/w). Moreover, in contrast to most UV-NIL resists which are insoluble in solvents after curing, the DAMTT resist can independently achieve a lift-off process without the assistance of a thermoplastic polymer layer. That makes it possible to fabricate metal nanostructures on highly curved surfaces via a hybrid UV-curing nanoimprint technique. For example, metal gratings are successfully fabricated on the cylindrical surface of an optical fiber via a lift-off process.

In this paper, we report the highly efficient reinforcement of dynamically cross-linked silane-modified phenol formaldehyde resin (SMPF) in ethylene-propylene diene terpolymer rubber (EPDM). Only 5 phr of SMPF is able to greatly improve the tensile strength of EPDM from 5 MPa to 28 MPa, which is 55% higher than that of EPDM filled with 30 phr of carbon black N330, and it still retains a high elongation of more than 600%. The scanning electron microscopy and X-ray diffraction results reveal the reinforcement mechanism of EPDM. SMPF is uniformly dispersed in the EPDM matrix by a conventional Banbury mixer and is dynamically cross-linked to form a greatly expanded hard phase comprising the interpenetrating polymer networks of EPDM and SMPF during the mixing process, which leads to a high modulus. The high tensile strength is attributed to the strain-induced crystallization of EPDM at high strain according to the X-ray diffraction patterns of the stretched EPDM–SMPF composites. These results reveal the high efficient reinforcement of the thermoset resin in rubber, demonstrate a new mechanism of rubber reinforcement and suggest a new direction for rubber reinforcement.

A challenge in the fabrication of nanostructures into non-planar substrates is to form a thin, uniform resist film on non-planar surfaces. This is critical to the fabrication of nanostructures via a lithographic technique due to the subsequent pattern transfer process. Here we report a new double transfer UV-curing nanoimprint technique that can create a nanopatterned thin film with a uniform residual layer not only on flat substrates but also on highly curved surfaces. Surface relief gratings with pitches down to 200 nm are successfully imprinted on the cylindrical surface of optical fibers, and further transferred into a SiO2 matrix using reactive ion etching (RIE), demonstrating that our technique is applicable for fabricating high-resolution nanostructures on non-planar substrates.

Vinylidene fluoride-trifluoroethylene-chlorofluoroethylene terpolymer, P(VDF-TrFE-CFE), with small amount of CFE is utilized for thin-film nonvolatile memory. Polarization switching voltage for a 50 nm-thick film can be as low as 1 V, and is well suited for integrated driving electronics. The writing-erasing procedure is completely reversible. High signal-to-noise and high capability for data storage are observed in this memory system. Polarization state of the terpolymer is rather stable, making it applicable for memory devices. Polarization switching behavior in the terpolymer can be ascribed to reduced polar domain size with respect to the P(VDF-TrFE) copolymer, and energy cost of domain wall motion during electrically polarization switching decreases.

We report a crack-free controlled wrinkling method based on a bilayer film system. A liquid UV-curable film is solidified on a uniaxially pre-stretched PDMS elastic sheet by UV-exposure. Subsequently, the sheet is released back to its initial non-stretched state, which results in spontaneous formation of grating wrinkles perpendicular to the stretching direction. An interface of gradient interpenetrating polymer networks (IPN) is considered to be formed between the stiff UV-cured film and the elastic support, which is practically beneficial for preventing crack formation and film delamination during the strain relaxation process. The periodicity of the gratings is tuned by controlling the thickness of the UV-cured polymer film and the amplitude of pre-strain of the elastic sheet. The imprinting results demonstrate that these self-formed wrinkles can serve as a mold to duplicate gratings by nanoimprint lithography. Furthermore, metal gratings are successfully fabricated from the wrinkling molds.