In this research work, we present the synthesis and characterization of four different TiO₂ structures, such as nanotubes, nanocavities, nanosheets assembled on nanocavities and nanobowls assembled on nanocavities, prepared by electrochemical anodization using organic electrolytes. After synthesis, the structures were thermally annealed to pass from the amorphous phase to the anatase phase, which is one of the most important crystalline structures of TiO₂ due to its high photocatalytic activity and stability. The unique morphology and topography were studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental composition was determined by energy-dispersive X-ray spectroscopy (EDS). The anatase phase was verified by Raman microscopy and X-ray diffraction (XRD), the band gap energy was calculated by the Kubelka–Munk function, and the main defect states that generate the emission, as well as their lifetime, were determined by photoluminescence spectroscopy and time response photoluminescence (TRPL), respectively. The TiO₂ nanomaterials were tested as catalysts in the photodegradation of a solution of methylene blue using a UV lamp at room temperature. The results showed complex morphologies and different surface roughness areas of these nanomaterials. Furthermore, a relationship between defect states, band gap energy, and photocatalytic activity was established. We found that the catalytic activity was improved as an effect of geometric parameters and oxygen vacancies.

The chemical and morphological properties of thin aluminum oxide film surfaces (Al₂O₃ having 10 nm in thickness) in the as-deposited (dry) and after immersion (in pH buffer solutions) conditions were studied. Careful measurement conditions have been followed in order to determine any possible physical and/or chemical change on the surface of these films (after immersion in pH), so that proper correlation to their high and stable sensitivity to pH is possible. After deposition of thin Al₂O₃ films (by Atomic Layer Deposition, ALD) on chemically oxidized p-type silicon wafers, the resulting Al₂O₃/SiO_X/Si stacked structures were characterized by Fourier-Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscopy (AFM) before and after immersion in pH buffer solutions. Also, the Capacitance-Voltage (C-V) and Current-Voltage (I-V) characteristics were obtained after fabrication of Metal-Insulator-Semiconductor (MIS) devices in order to correlate the good chemical and morphological characteristics of thin Al₂O₃ to its electrical properties. Based on the characterization results, low surface oxidation/dissolution mechanisms are found in ALD aluminum oxide films when immersed in pH buffer solutions during short immersion times (immersion time ≤ 10 minutes); therefore, leading to the characteristic slow degradation of the sensitivity to pH for this dielectric material.

This paper reports the novel design of a touch mode capacitive pressure sensor (TMCPS) system with a wireless approach for a full-range continuous monitoring of ventricular pressure. The system consists of two modules: an implantable set and an external reading device. The implantable set, restricted to a 2 × 2 cm² area, consists of a TMCPS array connected with a dual-layer coil, for making a reliable resonant circuit for communication with the external device. The capacitive array is modelled considering the small deflection regime for achieving a dynamic and full 5–300 mmHg pressure range. In this design, the two inductive-coupled modules are calculated considering proper electromagnetic alignment, based on two planar coils and considering the following: 13.56 MHz frequency to avoid tissue damage and three types of biological tissue as core (skin, fat and muscle). The system was validated with the Comsol Multiphysics and CoventorWare softwares; showing a 90% power transmission efficiency at a 3.5 cm distance between coils. The implantable module includes aluminum- and polyimide-based devices, which allows ergonomic, robust, reproducible, and technologically feasible integrated sensors. In addition, the module shows a simplified and low cost design approach based on PolyMEMS INAOE^® technology, featured by low-temperature processing.