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The ability of a surface to completely absorb a liquid droplet is an important property that can be controlled by geometrical structure and chemical composition of the surface. Here, using Laplace pressure and Gibbs free energy (GFE) considerations, a capped truncated microcone array geometry is proposed to obtain a near zero degree for contact angle (θ) of a water droplet. Our results showed that two essential conditions must be met to achieve a superabsorbent surface. First, negative Laplace pressure and, second, absence of a relative minimum in the plot of GFE versus contact angle. To investigate the effect of surface tension on the wettability, capped truncated microcone array films were prepared on Si (100) substrate using a lithography method. To validate the proposed geometry as a super water-absorbent surface, we compared theoretical calculations with the experimental results. Our theoretical and experimental studies show that the capped truncated SiO2microcone array film is a superabsorbent surface with nearly zero contact angle. The amount of 130° ± 3 was measured for the water contact angle of the capped truncated Si microcone array in the hydrophobic state, which is very close to the calculated water contact angle using the minimum of GFE (126.1°). Results proved that the predicted water contact angles are in very good agreement with the experimental measurements.

Numerous techniques, including colorimetric, optical and electrical/electrochemical have been employed in biosensing. The employment of electrochemical technologies, particularly the field-effect transistors (FETs), have been embraced because of their many benefits, including simple design, affordability, a lack of expensive testing equipment, and acceptable findings. There are numerous applications for the ion-sensitive FET (ISFETs) in biology and medicine. Hydrogen peroxide (H2O2), a crucial intermediary in many metabolic and regulatory pathways, glucose, cholesterol, acetylcholine, deoxyribonucleic acid (DNA), cells, and other compounds have been measured using ISFET sensors. In the ISFET structure, due to its proximity to the sensor layer and H2O2, the gate terminal has an undeniable impact on the sensitivity and efficiency of the ISFET-based sensors. Here, we will provide a brief overview of the general characteristics of ISFET before discussing the gate terminal. The structure and composition of the gate surface-sensitive layer as the main factor in determining the sensitivity of ISFET-based sensors will be discussed. We will next review, for the first time, the widely used thin film, nanotubes, nanowires and nanorods, as well as 2-D materials like graphene and molybdenum disulfides as sensitive layer materials.

Two-dimensional (2-D) perovskites are gaining significant attention as promising materials for optoelectronic applications due to their unique optical and electrical properties along with their good stability compared to their three-dimensional (3-D) counterparts. In this study, we present the successful fabrication of a photodetector based on the heterojunctions of silicon (Si) and the 2-D Ruddlesden–Popper-phase perovskites of (CH3 (CH2)3NH3)PbI4 and (CH3 (CH2)3NH3)2(CH3NH3)Pb2I7. The vertical junction of 2-D lead iodide perovskite and p-type Si is responsible for photocharge generation in this type of photodetectors. We investigate the effects of active area on the responsivity of the 2-D perovskite/Si-based photodetector. The best performance is achieved for the device with $80\times 80\,\,\mu \text{m}^{{2}}$ active area that is about the crystal grain size in 2-D perovskite. The detector shows high sensitivity as high as 100 A/W in the visible and near infrared (NIR) ranges, which is a noticeably high and competitive responsivity among devices with similar architectures. Although perovskite-based devices suffer from low stability, the fabricated device shows stable performance without needing encapsulation.