Ultrathin (4–6 nm) single-crystal Bi2Se3 nanodiscs and nanosheets were synthesized through a simple and quick solution process. The growth mechanism was investigated in detail. Crystal seeds grew via ...2D self-attachment of small nanoparticles followed by epitaxial recrystallization into single crystals. The lateral dimension of the nanodiscs increased and their shape changed from circles to hexagons as the reaction temperature increased. Positively charged polymer surfactants greatly enlarged the lateral dimension to produce nanosheets with uniform thickness.
With the rapidly approaching implementation of wearable electronic devices such as implantable devices, stretchable sensors, and healthcare devices, stretchable power sources have aroused worldwide ...attention as a key component in this emerging field. Among stretchable power sources, batteries, which store electrical energy through redox reactions during charge/discharge processes, are an attractive candidate because of their high energy density, high output voltage, and long‐term stability. In recent years, extensive efforts have been devoted to developing new materials and innovative structural designs for stretchable batteries. This review covers the latest advances in stretchable batteries, focusing on advanced stretchable materials and their design strategies. First, we provide a detailed overview of the materials aspects of components in a stretchable battery, including electrode materials, solid‐state electrolytes, and stretchable separator membranes. Second, we provide an overview on various structural engineering strategies to impart stretchability to batteries (i. e., wavy/buckling structures, island‐bridge structures, and origami/kirigami structures). Third, we summarize recently reported developments in stretchable batteries based on various chemistries, including Li‐based batteries, multivalent‐based batteries, and metal‐air batteries. Finally, we discuss the future perspectives and remaining challenges toward the practical application of stretchable batteries with reliable mechanical robustness and stable electrochemical performance under a physical strain.
Go to the future! This review covers the latest advances in stretchable batteries, focusing on advanced materials and promising structural designs. The recent developments reported for state‐of‐the‐art stretchable batteries are summarized and the future perspectives and remaining challenges toward the practical application of stretchable batteries with reliable mechanical robustness and stable electrochemical performance under physical deformations are discussed.
A hybrid electrode, PEDOT:PSS/Ag NW containing a non-ionic surfactant (Triton X-100), was developed to enhance the mechanical stability of the Ag NW electrode and used for flexible ECL displays. The ...resulting hybrid electrode exhibited an outstanding figure of merit value of 12.3 × 10
Ω
and stable luminescence efficiency under the bending test.
The microdomain orientation in thin films of cylinder- and lamella-forming diblock copolymers, polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA), was investigated as a function of the film ...thickness and the composition of random copolymers composed of styrene (S) and methyl methacrylate (MMA), denoted as P(S-r-MMA), that were anchored to the substrate. Using scanning force microscopy (SFM) and grazing incidence small-angle X-ray scattering (GISAXS), the dependence of the microdomain orientation on film thickness around lattice period (or d-spacing, L 0), where the microdomain orientations normal to the film surface could be achieved, showed that the optimal condition for the balanced interfacial interactions (the so-called neutrality in random copolymer) was 0.64 of PS mole fraction (X PS) for the cylindrical microdomain having narrow compositional range of P(S-r-MMA) from 0.52 to 0.72 of X PS, whereas for the lamella microdomain it was observed at X PS = 0.55 ranging extensively from 0.48 to 0.78.
High-performance organic field-effect transistors (OFETs) based on polyelectrolyte gate dielectric and electrospun poly(3-hexylthiophene) (P3HT) nanofibers were fabricated on a flexible polymer ...substrate. The use of UV-crosslinked hydrogel including ionic liquids for the insulating layer enabled fast and large-area fabrication of transistor arrays. The P3HT nanofibers were directly deposited on the methacrylated polymer substrate. During UV irradiation through a patterned mask, the methacrylate groups formed covalent bonds with the patterned polyelectrolyte dielectric layer, which provides mechanical stability to the devices. The OFETs operate at voltages of less than 2 V. The average field-effect mobility and on/off ratio were ∼2 cm2/(Vs) and 105, respectively.
Electro-generated chemiluminescence (ECL) has attracted increasing attention as a new platform for light-emitting devices; in particular, the use of mechanically stretchable ECL gels opens up the ...opportunity to achieve deformable displays. The movements of radical ions under an external electric field include short-range diffusion near the electrodes and long-distance migration between the electrodes. So far, only the diffusion of radical ions has been considered as the operating principle behind ECL. In this study, electrochemical and optical analysis was performed systematically to investigate the role of ion migration in ECL devices. This study reveals that long-distance migration of radical ions can be a key variable in ECL at low frequencies and that this effect depends on the type of ion species and the operating conditions (
voltage and frequency). We also report that the emissions from the two electrodes are not identical, and the emission behaviors are different in the optimal operating conditions for the red, green, and blue ECL emissions.
In spite of the recent successes in transistors and solar cells utilizing poly(3-hexylthiophene) (P3HT) nanofibrils, systematic analysis on the growth kinetics has not been reported due to the lack ...of analytical tools. This study proposed a simple spectroscopic method to obtain the crystallinity of P3HT in solutions. On the basis of the analytical approach, we found that the crystallinity hysteresis upon temperature is a simple function of the solubility parameter difference (Δδ) between the P3HT and the solvents. When Δδ ≥ 0.7, a cooling (−20 °C)-and-heating (25 °C) process allowed the preparation of solutions including 1D crystal seeds dispersed in the solution. Simple coating of the seeded solutions completed the growth of the seeds into long nanofibrils at the early stage of the coating and thereby achieved almost 100% crystallinity in the resulting films without any postannealing process. The existence of PCBM for bulk-heterojunction (BHJ) solar cells did not affect the nucleation and growth of the nanofibrils during the cooling-and-heating process. The solar cells prepared from the solutions with Δδ ≥ 0.7 had solar conversion efficiencies higher than the conventional thermally annealed cells.
Although ion gels are attractive sensing materials for deformable epidermal sensors or implantable devices, their sensing performances are highly affected by environmental humidity change, so that ...their sensing reliability cannot be secured. This study proposes a new concept of maintaining the high‐precision temperature sensing performance of highly deformable ion gel sensors. In this approach, a hydrophobic ion gel sensing layer is kept water‐saturated by attaching a hydrogel layer, rather than attempting to completely block water penetration. This study performs experimental and theoretical investigation on water concentration in the ion gel, using the analysis of mass transportation at the interface of the ion gel and the hydrogel. By using the charge relaxation time of the ionic molecules, the temperature sensor is not affected by environmental humidity in the extreme range of humidity (30%–100%). This study demonstrates a highly deformable on‐skin temperature sensor which shows the same performance either in water or dry state and while exercising with large strains (ε = 50%).
A highly deformable ion gel‐based temperature sensor that is not affected by environmental humidity change is fabricated by keeping a hydrophobic ion gel sensing layer to be water saturated. The sensor shows identical high‐precision temperature sensing performance either in water or dry conditions, additionally in a stretched state when attached to the elbow.
Piezoelectric self‐powered sensors are promising platforms for wearable portable devices. Poly(vinylidene fluoride) (PVDF) and its copolymer derivatives are extensively explored as a soft ...piezoelectric material owing to their high piezoelectric coefficient, chemical thermal stability, biocompatibility, lightweight, and excellent flexibility. It is proved that the dominance of the electroactive (EA) β‐phase crystals versus the non‐electroactive α‐phase crystals is one of the key parameters to obtaining high piezoelectric performance of PVDF. Conventional methods, such as mechanical stretching, electrical poling, and high‐temperature annealing, are investigated to enhance the fraction of the β‐phase. Recently, embedding nanoscale fillers in the PVDF matrix has been investigated to further increase the β‐phase fraction and achieved considerable advances. The introduction of nanofillers is also advantageous in terms of improving the electrical conductivity and dielectric properties of PVDF, which are not readily obtained through conventional methods. This review introduces the principles of EA phase transformation in the presence of nanofillers and summarizes recent advances achieved by introducing various fillers, such as perovskites, oxide semiconductors, and 2D chalcogenides. The potential sensor applications of the PVDF nanocomposites responding to temperature, light, acoustic, and mechanical stimuli are reviewed. This review ends with the outlook of this new approach.
Nanoparticles could effectively increase the electroactive phase of poly(vinylidene fluoride) (PVDF), which further improves its piezoelectric response. Herein, the mechanism of the electroactive phase transformation in PVDF through the incorporation of various nanofillers and its correlation with the improved sensing performance for various external stimuli (mechanical, acoustic, optical, and thermal changes) are reviewed.
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