The photocurrent conversions of transition metal dichalcogenide nanosheets are unprecedentedly impressive, making them great candidates for visible range photodetectors. Here we demonstrate a method ...for fabricating micron-thick, flexible films consisting of a variety of highly separated transition metal dichalcogenide nanosheets for excellent band-selective photodetection. Our method is based on the non-destructive modification of transition metal dichalcogenide sheets with amine-terminated polymers. The universal interaction between amine and transition metal resulted in scalable, stable and high concentration dispersions of a single to a few layers of numerous transition metal dichalcogenides. Our MoSe2 and MoS2 composites are highly photoconductive even at bending radii as low as 200 μm on illumination of near infrared and visible light, respectively. More interestingly, simple solution mixing of MoSe2 and MoS2 gives rise to blended composite films in which the photodetection properties were controllable. The MoS2/MoSe2 (5:5) film showed broad range photodetection suitable for both visible and near infrared spectra.
This paper presents a power-generating sensor array in a flexible and stretchable form. The proposed device is composed of resistive strain sensors, capacitive tactile sensors, and a triboelectric ...energy harvester in a single platform. The device is implemented in a woven textile structure by using proposed functional threads. A single functional thread is composed of a flexible hollow tube coated with silver nanowires on the outer surface and a conductive silver thread inside the tube. The total size of the device is 60 × 60 mm² having a 5 × 5 array of sensor cell. The touch force in the vertical direction can be sensed by measuring the capacitance between the warp and weft functional threads. In addition, because silver nanowire layers provide piezoresistivity, the strain applied in the lateral direction can be detected by measuring the resistance of each thread. Last, with regard to the energy harvester, the maximum power and power density were measured as 201 μW and 0.48 W/m², respectively, when the device was pushed in the vertical direction.
Enhancing the device performance of organic memory devices while providing high optical transparency and mechanical flexibility requires an optimized combination of functional materials and smart ...device architecture design. However, it remains a great challenge to realize fully functional transparent and mechanically durable nonvolatile memory because of the limitations of conventional rigid, opaque metal electrodes. Here, we demonstrate ferroelectric nonvolatile memory devices that use graphene electrodes as the epitaxial growth substrate for crystalline poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) polymer. The strong crystallographic interaction between PVDF-TrFE and graphene results in the orientation of the crystals with distinct symmetry, which is favorable for polarization switching upon the electric field. The epitaxial growth of PVDF-TrFE on a graphene layer thus provides excellent ferroelectric performance with high remnant polarization in metal/ferroelectric polymer/metal devices. Furthermore, a fully transparent and flexible array of ferroelectric field effect transistors was successfully realized by adopting transparent polybis(4-phenyl)(2,4,6-trimethylphenyl)amine semiconducting polymer.
Predicting photolithography performance in silico for a given materials combination is essential for developing better patterning processes. However, it is still an extremely daunting task because of ...the entangled chemistry with multiple reactions among many material components. Herein, we investigated the EUV-induced photochemical reaction mechanism of a model photoacid generator (PAG), triphenylsulfonium cation, using atomiC–Scale materials modeling to elucidate that the acid generation yield strongly depends on two main factors: the lowest unoccupied molecular orbital (LUMO) of PAG cation associated with the electron-trap efficiency ‘before C–S bond dissociation’ and the overall oxidation energy change of rearranged PAG associated with the proton-generation efficiency ‘after C–S bond dissociation’. Furthermore, by considering stepwise reactions accordingly, we developed a two-parameter-based prediction model predicting the exposure dose of the resist, which outperformed the traditional LUMO-based prediction model. Our model suggests that one should not focus only on the LUMO energies but also on the energy change during the rearrangement process of the activated triphenylsulfonium (TPS) species. We also believe that the model is well suited for computational materials screening and/or inverse design of novel PAG materials with high lithographic performances.
A gas‐driven ultrafast adhesion switching of water droplets on palladium‐coated Si nanowire arrays is demonstrated. By regulating the gas‐ambient between the atmosphere and H2, the super‐hydrophobic ...adhesion is repeatedly switched between water‐repellent and water‐adhesive. The capability of modulating the super‐hydrophobic adhesion on a super‐hydrophobic surface with a non‐contact mode could be applicable to novel functional lab‐on‐a‐chip platforms.
A method to fabricate micropatterns of non‐circular droplets of a self‐assembled block copolymer by solvent‐assisted wetting on chemically periodic surface is presented. The block copolymer is ...dewetted on a topographic pre‐pattern to form an array of microdroplets with a sphere‐capped shape and circular contact line. The droplets are then transferred onto a chemically periodic Au line pattern microcontact‐printed with two types of self‐assembled monolayers (SAMs). Solvent vapor application provides sufficient mobility to the block copolymer molecules to induce spreading of the transferred droplets, resulting in two types of non‐circular microdroplet growth. The growth behavior depends on the size of initial droplets relative to periodic line width and on the initial registries of as‐transferred droplets.
Arrays of sphere‐capped microdroplets of a PS‐b ‐PEO block copolymer are transferred from a PDMS mold to SAM‐treated Au substrates containing periodic hydrophilic and hydrophobic lines, followed by the solvent annealing. This gives rise to a micropattern of non‐circular droplets of the copolymer with hierarchically ordered self‐assembled block copolymer nanostructures.
A triboelectric nanogenerator (TENG) is of tremendous interest owing to its high energy efficiency with a simple device architecture and applicability to various materials. Most previous topological ...surface modifications introduced for further improving the performance of a TENG are detrimental because they require expensive and/or harsh (e.g., high temperature and acidity) postetching processes, which limit the material choice and design of its components. Herein, we demonstrate an one-step route for developing rapid wet-processable surface-conformal triboelectric nanoporous films (STENFs). Our method is based on a simple supramolecular assembly of a ternary polymer blend suitable for various conventional solution processes such as spin-, bar-, spray-, and dip-coating. The one-step wet process of a ternary solution produces thin large-area films in which self-assembled, ordered nanopores of approximately 33 nm in diameter are developed even without an additional etching process. The study reveals that the small amount of amine-terminated poly(ethylene oxide) added to the binary blend of sulfonic-acid-terminated poly(styrene) and poly(2-vinylpyridine) efficiently activates the formation of spontaneous nanopores as a pore-generating agent. Our STENF significantly enhances the open-circuit voltage up to 1.5 times higher than that of a planar one, leading to an improved power density of approximately 77 μW/cm2. The suitability for diverse conventional coating processes offers a convenient approach for fabricating high-performance STENFs not only on flat substrates such as metals, polymers, and oxides but also on topological ones including wrinkled, roughened surfaces, textile fibers, natural leaves, and fabrics over a large area.
Self-powered energy harvesters utilizing triboelectric effect and electrostatic induction have been widely studied, leading in the materials viewpoint to numerous material pairs for facile charge ...separation upon repetitive contacts with elaborate topological structures. Here, we present a simple but robust triboelectric platform based on a molecularly engineered surface triboelectric nanogenerator by self-assembled monolayers (METS). Triboelectric surface charge density of a substrate was readily controlled by the variation of end-functional groups of self-assembled monolayers (SAMs). In particular, by employing fluorine terminated SAMs, we are able to develop a METS with the maximum open circuit voltage and short circuit current of 105 V and 27 μA, respectively, under relatively gentle mechanical contacts with the 3N vertical force at 1.25 Hz. The power density of the device was 1.8 W/m2 at the load resistance of 10 MΩ more than 60 times greater than that of an unmodified dielectric/Al device. Moreover, our approach with SAMs was extended to various types of surfaces including fabrics of silk, cotton, and poly(ethylene terephthalate) (PET) and a PET film, and the results of single-friction-surface triboelectric nanogenerators with these materials offers a facile and universal guideline for designing triboelectic materials.
A triboelectric nanogenerators (TENG) are of great interest as emerging power harvesters because of their simple device architecture with unprecedented high efficiency. Despite the substantial ...development of new constituent materials and device architectures, a TENG with a switchable surface on a single device, which allows for facile control of the triboelectric output performance, remains a challenge. Here, a supramolecular route for fabricating a novel TENG based on an alkali‐metal‐bound porous film, where the alkali metal ions are readily switched among one another is demonstrated. The soft nanoporous TENG contains numerous SO3− groups on the surface of nanopores prepared from the supramolecular assembly of sulfonic‐acid‐terminated polystyrene and poly(2‐vinylpyridine) (P2VP), followed by soft etching of P2VP. Selective binding of alkali metal ions, including Li+, Na+, K+, and Cs+, with SO3− groups enables the development of mechanically robust alkali‐metal‐ion‐decorated TENGs. The triboelectric output performance of the devices strongly depends on the alkali metal ion species, and the output power ranges from 11.5 to 256.5 µW. This wide‐range triboelectric tuning can be achieved simply by a conventional ion exchange process in a reversible manner, thereby allowing reversible control of the output performance in a single device platform.
A supramolecular route for the fabrication of surface‐tunable triboelectric nanogenerators is developed. The method is based on a nanoporous surface capable of binding with alkali metal ions, which are readily switchable among one another, via a conventional ion exchange process. This allows for the repeated and reversible switching of the triboelectric properties in a single device platform.
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