Fabrication strategies that pursue "simplicity" for the production process and "functionality" for a device, in general, are mutually exclusive. Therefore, strategies that are less expensive, less equipment-intensive, and consequently, more accessible to researchers for the realization of omnipresent electronics are required. Here, this study presents a conceptually different approach that utilizes the inartificial design of the surface roughness of paper to realize a capacitive pressure sensor with high performance compared with sensors produced using costly microfabrication processes. This study utilizes a writing activity with a pencil and paper, which enables the construction of a fundamental capacitor that can be used as a flexible capacitive pressure sensor with high pressure sensitivity and short response time and that it can be inexpensively fabricated over large areas. Furthermore, the paper-based pressure sensors are integrated into a fully functional 3D touch-pad device, which is a step toward the realization of omnipresent electronics.
A thermochromic-based interactive sensor that can generate local color switching and pressure mapping is developed using a 2D array of resistive pressure sensor switch. This thermochromic-based interactive sensor will enable the visualization of localized information in arbitrary shapes with dynamic responses in the context of serial/parallel pressure mapping and quantifying capability without optoelectronic arrays.
Quantum beats, periodic oscillations arising from coherent superposition states, have enabled exploration of novel coherent phenomena. Originating from strong Coulomb interactions and reduced dielectric screening, two-dimensional transition metal dichalcogenides exhibit strongly bound excitons either in a single structure or hetero-counterpart; however, quantum coherence between excitons is barely known to date. Here we observe exciton quantum beats in atomically thin ReS2 and further modulate the intensity of the quantum beats signal. Surprisingly, linearly polarized excitons behave like a coherently coupled three-level system exhibiting quantum beats, even though they exhibit anisotropic exciton orientations and optical selection rules. Theoretical studies are also provided to clarify that the observed quantum beats originate from pure quantum coherence, not from classical interference. Furthermore, we modulate on/off quantum beats only by laser polarization. This work provides an ideal laboratory toward polarization-controlled exciton quantum beats in two-dimensional materials.
Semiconductor sensors
equipped with Pd catalysts are promising
candidates as low-powered and miniaturized surveillance devices that
are used to detect flammable hydrogen (H2) gas. However,
the following issues remain unresolved: (i) a sluggish sensing speed
at room temperature and (ii) deterioration of sensing performance
caused by interfering gases, particularly, carbon monoxide (CO). Herein,
a bilayer comprising poly(methyl methacrylate) (PMMA) and zeolitic
imidazolate framework-8 (ZIF-8) is utilized as a molecular sieve for
diode-type H2 sensors based on a Pd-decorated indium-gallium-zinc
oxide film on a p-type silicon substrate. While the PMMA effectively
blocks the penetration of CO gas molecules into the sensing entity,
the ZIF-8 improves sensing performances by modifying the catalytic
activity of Pd, which is preferable for splitting H2 and
O2 molecules. Consequently, the bilayer-covered sensor
achieves outstanding CO tolerance with superior sensing figures of
merit (response/recovery times of <10 s and sensing response of
>5000% at 1% H2).
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