lithography process, using the increase in the T g of the photoresist particles caused by UV-induced crosslinking. Subsequent deposition of silica through the patterned-colloidal mask yielded ordered domains of nanoscale-hole arrays on a micrometer length scale. The present technique produces a spatially organized mask with multiple length scales for colloidal lithography. As such, various functional materials can be deposited through these multiscale colloidal masks, fabricating nanopatterned substrates, which are of practical significance in a wide range of applications from biosensors to optoelectronic devices. ExperimentalSynthesis of Photoresist Particles: MMA (Aldrich, > 99 %) and GMA (Aldrich, > 95 %) were used as supplied. Potassium persulfate (KPS) was used as an initiator for emulsion polymerization. A 100 mL two-necked round-bottom flask was filled with KPS dissolved in 50 mL of distilled water, and a monomer mixture of MMA and GMA. The content of KPS was fixed at 1 wt.-%. The content of GMA was varied in the range 5-30 wt.-% of the total monomer content, which was fixed at 10 wt.-%. The system was kept under a nitrogen atmosphere and the reaction mixture was stirred magnetically at 300 rpm. When the KPS was dissolved completely, the mixture was heated to 75°C using an oil bath. After 12 h, the mixture was separated by centrifugation and was purified with distilled water several times. The size of the particles, measured by SEM, ranged from 360 to 420 nm. Later, the cationic photoinitiator, Irgacure 250, was introduced to the photoresist particles by spin-coating.Measurement of T g : The glass-transition temperatures of the UV-exposed and UV-screened poly(MMA-co-GMA) particles were determined using a differential scanning calorimeter (DSC, TA Instruments, Q1000) under a nitrogen atmosphere at a heating rate of 10°C min -1 . To measure the T g of UV-exposed particles, the particles were fully baked at 150°C for 2 h after UV exposure, because the crosslinking reaction could proceed during the DSC measurement. Therefore, the measured T g could be higher than the T g of the UV-exposed particles in the patterning. Meanwhile, T g of the UV-screened particles was compared with that estimated using the rule-of-mixtures theory where T g = 115°C for polyMMA and T g = 75°C for polyGMA [19].Deposition of Silica: Silica was deposited in a batch reactor under atmospheric pressure at room temperature. The sample was sequentially exposed to water vapor for 30 min, dried in argon gas for purging the reactor, and then SiCl 4 vapor for 20 min. The reactant vapors were carried by argon gas under atmospheric pressure. The concentration of SiCl 4 was 0.05 vol.-% in moisture-free argon gas and the relative humidity of water vapor was 50 %. (Caution: silicon tetrachloride is a very corrosive liquid. Use it only with adequate ventilation, and wear protective clothing and safety goggles.) The thickness of the silica layer was controlled by the exposure time to the precursor vapor and around 50 nm for 30 min exposure was obtained.
Periodic wrinkling across different scales has received considerable attention because it not only represents structure failure but also finds wide applications. How to prevent wrinkling or create desired wrinkling patterns is non-trivial because the dynamic evolution of wrinkles is a highly nonlinear problem. Herein, we report a simple yet powerful method to dynamically tune and/or erase wrinkling patterns with visible light. The light-induced photoisomerization of azobenzene units in azopolymer films leads to stress release and consequently to the erasure of the wrinkles. The wrinkles in unexposed regions are also affected and oriented perpendicular to the exposed boundary during the stress reorganization. Theoretical models were developed to understand the dynamics of the reversible photoisomerization-induced wrinkle evolution. This method can be applied for designing functional materials/devices, for example, for the reversible optical writing/erasure of information as demonstrated here.
The controlled synthesis of Cu(OH)2 nanowires and nanoribbons in a solution phase has been realized with high yield at low cost by simply dropping KOH and ammonia solutions into an aqueous solution of CuSO4 at ambient temperature. It is demonstrated that the morphology of nanostructured Cu(OH)2 is significantly influenced by the feeding manner of the alkaline solutions. A rational mechanism based on coordination self-assembly and oriented attachment is proposed for the selective formation of the polycrystalline Cu(OH)2 nanowires and single-crystalline Cu(OH)2 nanoribbons. In the presence of a polymeric additive, poly(acrylic acid) (PAA), ordered assemblies of Cu(OH)2 nanorods can be readily obtained. Furthermore, well-defined CuO nanostructures, such as CuO nanoplatelets, nanoleaflets, and nanowires, were produced by thermal dehydration of the as-prepared Cu(OH)2 nanostructures in solution or in the solid state. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the products.
A simple, novel, and completely lithography-free assembly strategy is reported for directed colloidal crystal assembly on optically transparent substrates. The templates are stable, wellcontrolled relaxation-wrinkles of ultrathin multilayer films in a non-stretched state, which are fabricated by layer-by-layer self-assembly of polymeric films on soft elastomeric substrates followed by uniaxial plastic deformations. The results show that the wrinkles can be used efficiently to topographically direct colloidal crystal assembly in dip coating. Remarkably highly regular 1-and 2-dimensional patterned colloidal crystals with controlled structures have been obtained. Furthermore, the concept is rather universal and applicable to various particle types provided surface interactions between particles and template are suitable.
Coaxial fiber-shaped supercapacitors with short charge carrier diffusion paths are highly desirable as high-performance energy storage devices for wearable electronics. However, the traditional approaches based on the multistep fabrication processes for constructing the fiber-shaped energy device still encounter persistent restrictions in fabrication procedure, scalability, and mechanical durability. To overcome this critical challenge, an all-in-one coaxial fiber-shaped asymmetric supercapacitor (FASC) device is realized by a direct coherent multi-ink writing three-dimensional printing technology via designing the internal structure of the coaxial needles and regulating the rheological property and the feed rates of the multi-ink. Benefitting from the compact coaxial structure, the FASC device delivers a superior areal energy/power density at a high mass loading, and outstanding mechanical stability. As a conceptual exhibition for system integration, the FASC device is integrated with mechanical units and pressure sensor to realize high-performance self-powered mechanical devices and monitoring systems, respectively.
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