Fabian Ambriz-Vargas

La serie animada de Los Supersónicos, lanzada en 1962, presentó la visión de una sociedad futurista llena de automóviles voladores, robots y tecnología inteligente. Aunque nunca se explicó qué tipo de automatización era aquella que permitía que los autos volaran y que los autómatas fueran tan inteligentes, sabemos que muchos de esos aparatos se basarán en el desarrollo de técnicas de almacenamiento de energía avanzadas, como las baterías. Hoy en día, podemos ver cómo algunas de esas tecnologías se están volviendo realidad al generar acumuladores de iones de litio que permiten almacenar energía a gran escala en dispositivos cada vez más pequeños y ligeros. Desde el punto de vista científico, esto se logrará gracias al desarrollo de nuevos materiales que se utilicen en los cátodos, ánodos y electrolitos de las baterías, también con métodos emergentes como las de estado sólido. Aunque aún queden muchas barreras que superar, por ejemplo, el agotamiento de dichos dispositivos durante los ciclos de carga y descarga, mejoras constantes nos están trayendo cada vez más hacia el futuro tecnológico que se nos presentó en Los Supersónicos. Abstract The Jetsons animated series, released in 1962, presented a vision of a futuristic society filled with flying cars, robots, and intelligent technology. While the specific technology enabling flying cars and intelligent robots was never explained, we know that many of these technologies will rely on the development of advanced energy storage technologies, such as batteries. Today, we can see some of these technologies becoming a reality thanks to the development of lithium-ion batteries, which allow for the storage of large amounts of energy in increasingly smaller and lighter devices. From a scientific perspective, this will be achieved through the development of new materials used in battery cathodes, anodes, and electrolytes, as well as emerging technologies like solid-state batteries. Although many barriers remain to be overcome, such as battery depletion during charge and discharge cycles, constant improvements are bringing us ever closer to the technological future envisioned in The Jetsons.

Lithium manganese oxide (LiMn₂O₄) is an effective cathode material for high-capacity lithium-ion (Li-ion) batteries. Therefore, to optimize battery efficiency, it is essential to understand how sputtering deposition conditions affect the quality and performance of LiMn₂O₄. This research examines how argon deposition pressure affects the stoichiometric characteristics and electrochemical performance of LiMn₂O₄. The study finds that changing argon deposition pressures, from a low of 5 mTorr to a high of 30 mTorr, results in the formation of different coating stoichiometries. At low argon deposition pressures, stoichiometric LiMn₂O₄ cathode coatings formed, exhibiting the highest discharge capacity of 115 mAh/g. Conversely, at high argon deposition pressures, non-stoichiometric LiMn₂O₄ with lithium deficiency was produced. These coatings exhibited diminished electrochemical behavior, achieving a discharge capacity of only 70 mAh/g at 5 mTorr. The lack of lithium resulted in a significant reduction in electrochemical performance, indicated by a high surface charge transfer resistance (R₂ = 48,529 Ω), which led to a low discharge capacity of 40 mAh/g.

The electric stimulation (ES) of the cornea is a novel therapeutic approach to the treatment of degenerative visual diseases. Currently, ES is delivered by placing a mono-element electrode on the surface of the cornea that uniformly stimulates the eye along the electrode site. It has been reported that a certain degree of correlation exists between the location of the stimulated retinal area and the position of the electrode. Therefore, in this study, we present the development of a sectioned surface electrode for selective electric stimulation of the human cornea. The proposed device consists of 16 independent microelectrodes, a reference electrode, and 18 contact pads. The microelectrodes have a size of 200 µm × 200 µm, are arranged in a 4 × 4 matrix, and cover a total stimulation area of 16 mm². The proposed fabrication process, based on surface micromachining technology and flexible electronics, uses only three materials: polyimide, aluminum, and titanium, which allow us to obtain a simplified, ergonomic, and reproducible fabrication process. The fabricated prototype was validated to laboratory level by electrical and electrochemical tests, showing a relatively high electrical conductivity and average impedance from 712 kΩ to 1.4 MΩ at the clinically relevant frequency range (from 11 Hz to 30 Hz). Additionally, the biocompatibility of the electrode prototype was demonstrated by performing in vivo tests and by analyzing the polyimide films using Fourier transform infrared spectroscopy (FTIR). The resulting electrode prototype is robust, mechanically flexible, and biocompatible, with a high potential to be used for selective ES of the cornea.

The continued evolution of electronic devices relies on the development of new semiconductor memory technology. Given the high compatibility of the Hf0.5Zr0.5O2 thin films with the CMOS technology, we investigate the charge transport mechanisms that occur in a relative thick Hf0.5Zr0.5O2 thin film (4 to 6 nm-thick) when subjected to electrical stresses. To that end we fabricate Hf0.5Zr0.5O2 heterostructures with a Pt tip as the top electrode and TiN and Pt as bottom electrode by radio-frequency magnetron sputtering. After analyzing the surface morphology of the as-received and as-deposited films by atomic force microscopy, the transfer of the desired chemical stoichiometry from the sputtering target to the substrate surface is studied by Raman spectroscopy. The ferroelectricity of the Hf0.5Zr0.5O2 thin films is confirmed by piezoresponse force microscopy measurements, and a retention of 22 h is obtained, attesting to the non-volatility of the samples. Nano-scale electrical measurements reveal the presence of resistive switching, where the low resistance state (ON state) in both Pt-tip/Hf0.5Zr0.5O2/TiN and Pt-tip/Hf0.5Zr0.5O2/Pt heterostructures can be created by the formation of a conductive filament based on oxygen vacancies.