Omnidirectionally stretchable photodetectors are limited by difficulties in designing material and fabrication processes that enable stretchability in multiaxial directions. Here, we propose a new approach involving an organic-inorganic p-n heterojunction photodetector comprised of free-standing ZnO nanorods grown on a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate transport layer coated on a three-dimensional micropatterned stretchable substrate containing bumps and valleys. This structure allows for efficient absorption of stretching strain. This approach allows the device to accommodate large tensile strain in all of the directions. The device behaves as a photogated p-n heterojunction photodetector in which current modulation was obtained by sensing the mechanisms that rely on photovoltage and photogating effects. The device exhibits a high photoresponse to UV light and reliable electrical performance under applied stretching in uniaxial and omniaxial directions. Furthermore, the device can be easily and conformally attached to a human wrist. This allowed us to investigate the response of the device to UV light during human activity.

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A new feed structure with a loop-type radiator is proposed for achieving a wide bandwidth characteristic. The method for achieving a wide impedance bandwidth characteristic is to control the input impedance of the feed structure using a parallel capacitor and inductor. The size of the ground plane is 50 3 20 mm 2 , which is usually used as the ground for USB dongle applications. The size of the rectangular ground clearance for the loop-type antenna is 8 3 4 mm 2 . The proposed antenna was designed and measured using HFSS and a 3D CTIA OTA chamber. The center frequency is 2.45 GHz and the impedance bandwidth under VSWR 5 2:1 is 550 MHz (2.18-2.73 GHz), which is adequate for long term evolution bands (7, 30, 40) and Wi-Fi applications.

The water splitting properties of InGaN photoanodes equipped with ZnO nanowires were examined in this study. Over the solar spectrum range, the absorbance exhibited a remarkable increase due to the enhanced light absorption caused by the ZnO nanowires. By varying the ZnO nanowires length, the photo-to-current density of photoanodes was increased from 0.017 to 0.205 mA/cm2 at 1.23 V versus reversible hydrogen electrode. Consequently, the incident-photon-to-current efficiency was increased by a factor of 5.5 as the ZnO nanowires growth time increased from 2 to 4 h. The results of this research demonstrate the importance of light absorbance and the surface reaction sites of photoanodes on energy harvesting.

In this paper, the effect of coupling between the antenna and ground characteristic mode is investigated by comparing the radiation performance of antennas located inside and outside the ground plane. In general, it is understood that an antenna occupying a larger space has better radiation performance. However, in this paper, it is shown that coupling between the antenna and ground is important for radiation performance, rather than the size occupied by the antenna. The antenna is strongly coupled with the ground characteristic mode when located inside the ground; the −10 dB bandwidth is 130 MHz at 2.45 GHz, and the measured realized efficiency is −0.64 dB in the 2.4-2.5 GHz band. When the antenna protrudes from the ground plane, the coupling between the antenna and the ground characteristic mode is weak, achieving a narrower −10 dB bandwidth of 50 MHz at 2.45 GHz, and lower measured realized efficiency of −2.20 dB in the 2.4-2.5 GHz band. In other words, the radiation performance of the same antenna is significantly influenced by the coupling with the ground. K E Y W O R D S bluetooth antenna, ground characteristic mode, ground radiation antenna, mobile antenna, radiation performance