Ingeniería de superficies y monocapas autoensambladas

De forma general, las características de los materiales pueden clasificarse en dos: las que resultan de la naturaleza de su masa y las de su superficie. Algunos ejemplos de las propiedades masivas de un material son resistencia mecánica, magnetismo, densidad, e incluso el precio. Las propiedades que se deben a la superficie son biocompatibilidad, resistencia a la corrosión y, hasta cierto punto, la apariencia estética. Con frecuencia sucede que las propiedades ideales para cierta aplicación no se encuentran en un solo material y la mejor solución es recubrir o modificar su superficie, cuyas propiedades masivas sean ideales para conjuntarse con las de otro material que aporte las propiedades superficiales deseables. La ingeniería de superficies es la rama de la ciencia de los materiales que se encarga de resolver este tipo de problemas. En este artículo se revisan conceptos básicos de esta ciencia con el próposito de comprender cómo puede ayudar al desarrollo de nuevos materiales, modificando su superficie para hacerla funcional

Pelotas y aerodinámica

El uso de pelotas con el propósito de jugar data de la antigüedad y forma parte de muchas culturas. Un objeto rodante atrae no sólo a un bebé humano, también a un gatito o a un cachorro. Las pelotas más antiguas de Eurasia se han descubierto en Karasahr, China, y tienen más de 3 000 años (Gershon, 2020). Estaban hechas de cuero relleno de pelo. Existe una gran cantidad de deportes que evolucionaron de estos juegos y que utilizan pelotas; éstas han adquirido formas, texturas y tamaños muy distintos según el deporte para el que fueron diseñadas. Quienes sean aficionados al fútbol, sin duda, habrán escuchado de algún “tiro con chanfle” para referirse a la trayectoria curva que toma una pelota cuando es pateada con cierta técnica. De la misma manera, los fanáticos del béisbol habrán visto cómo los lanzadores o pitchers pueden lanzar desde la “lomita de las responsabilidades” bolas curvas, rectas, sliders o bolas de nudillos según la trayectoria de la bola en su camino al plato. Al observar las pelotas de los diferentes deportes que las utilizan podemos hacernos varias preguntas: ¿cómo es posible obtener estos efectos?, ¿por qué las pelotas de tenis son peludas? y ¿por qué las pelotas de golf tienen huecos

Metamateriales y el sueño de la invisibilidad

Artículo de divulgación científica sobre metamateriale

Investigation of the thermal and physicochemical behavior of two types of gutta-percha cones for back-filling the root canal

Gutta-percha (Gp) is an inert thermoplastic polymer used as a filling to replace the dental pulp space, which has been reformulated to improve its three-dimensional sealing properties. Therefore, this study aimed to analyze the physical, chemical and thermal properties of two types of gutta-percha filling. As well as measuring the temperature distribution along the cone at the time of cutting through an in-situ test. MATERIAL AND METHODS: Two commercially available brands of gutta-percha point were investigated: Conform Fit TM Gutta-Percha for ProTaper Gold(R) (PTG) (Dentsply Sirona), and Hygenic Gutta-Percha (Coltene whaledent). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were selected for the thermal characterization of materials, and Fourier Transform Infrared Spectroscopy (FT-IR) for the chemical analysis of Gp cones. Regarding temperature distribution, it was evaluated using a thermographic camera (FLIR ONE(R) PRO by MicroUSB P/N 435-0011-01) at 0 to 20 s after the cutting process (n=11/group). RESULTS: Both materials have three fusion endotherms associated with the three crystalline phases of Gp, with similar temperatures but enthalpies that differ by 60%, the fusion enthalpy being higher for Conform Fit. In the chemical characterization, elements such as Zn, C, O, Ba, S and Si were found in both materials but in different proportions. Regarding the content of fillers, the Conform Fit presented around 30% of Gp polymer and 25% for the Hygenic. The morphological characterization shows a microtexturized coating in the form of bars on a micrometric scale for the Conform Fit, which could favor a better three-dimensional seal. In addition to that, in heat transfer studies they showed greater temperature control. CONCLUSIONS: The characterization of the materials allowed us to see the variation in terms of their composition and configuration to the Gp cones of two commercial brands. These variations directly modify the thermal behavior of the material. Key words:Gutta-percha, Conform Fit, Infrared thermography, Differential Scanning Calorimetry, Infrared Spectroscopy

Determination of the Immunoglobulin G Spectrum by Surface-Enhanced Raman Spectroscopy Using Quasispherical Gold Nanoparticles

Background. Immunoglobulins (Ig) are glycoprotein molecules produced by plasma cells in response to antigenic stimuli involved in various physiological and pathological conditions. Intravenous immunoglobulin (IVIG) is a compound whose composition corresponds to Ig concentrations in human plasma, predominantly IgG. It is used as a replacement treatment in immunodeficiencies and as an immunomodulator in inflammatory and autoimmune diseases. The determination of IgG concentrations is useful in the diagnosis of these immunodeficiencies. Surface-enhanced Raman spectroscopy (SERS) is a technique that allows protein quantification in a fast and straightforward way. Objective. This study is aimed at determining the Raman spectrum of IgG at physiological concentrations using quasispherical gold nanoparticles as a SERS substrate. Methods. We initially determined the Raman spectrum of IVIG at 5%. Subsequently, for SERS’ characterization, decreasing dilutions of the protein were made by adding deionized water and an equal volume of the 5 nm gold quasispherical nanoparticle colloid. For each protein concentration, the Raman spectrum was determined using a 10x objective; we focused the 532 and 785 nm laser on the sample surface, in a range of 500-1800 cm-1, with five acquisitions and an acquisition time of 30 seconds. Results. We obtained the IVIG spectrum using SERS up to a concentration of 75 mg/dl. The Raman bands correspond to aromatic amino acid side chains and the characteristic beta-sheet structure of IgG. Conclusion. The use of 5 nm quasispherical gold nanoparticles as a SERS substrate allows for detecting the Raman spectrum of IVIG at physiological concentrations

An automated method for the evaluation of breast cancer using infrared thermography

Breast cancer is one of the major causes of death for women. Temperature measurement is advantageous because it is non-invasive, non-destructive, and cost-effective. Temperature measurement through infrared thermography is useful to detect changes in blood perfusion that can occur due to inflammation, angiogenesis, or other pathological causes. In this work, we analyzed 206 thermograms of patients with suspected breast cancer, using a classification method, in which thermal asymmetries were computed, the most vascularized areas of each breast were extracted and compared; then these two metrics were added to yield a thermal score, indicative of thermal anomalies. The classification method based on this thermal score allowed us to obtain the test sensitivity of 100 %, specificity of 68.68 %; a positive predictive value of 11.42 % and negative predictive value of 100 %. These results highlight the potential of thermography imaging as adjunctive tool to mammography in breast cancer screening

Design and Fabrication of Interdigital Nanocapacitors Coated with HfO2

In this article nickel interdigital capacitors were fabricated on top of silicon substrates. The capacitance of the interdigital capacitor was optimized by coating the electrodes with a 60 nm layer of HfO2. An analytical solution of the capacitance was compared to electromagnetic simulations using COMSOL and with experimental measurements. Results show that modeling interdigital capacitors using Finite Element Method software such as COMSOL is effective in the design and electrical characterization of these transducers

Development and validation of an algorithm to predict the treatment modality of burn wounds using thermographic scans: Prospective cohort study.

BACKGROUND:The clinical evaluation of a burn wound alone may not be adequate to predict the severity of the injury nor to guide clinical decision making. Infrared thermography provides information about soft tissue viability and has previously been used to assess burn depth. The objective of this study was to determine if temperature differences in burns assessed by infrared thermography could be used predict the treatment modality of either healing by re-epithelization, requiring skin grafts, or requiring amputations, and to validate the clinical predication algorithm in an independent cohort. METHODS AND FINDINGS:Temperature difference (ΔT) between injured and healthy skin were recorded within the first three days after injury in previously healthy burn patients. After discharge, the treatment modality was categorized as re-epithelization, skin graft or amputation. Potential confounding factors were assessed through multiple linear regression models, and a prediction algorithm based on the ΔT was developed using a predictive model using a recursive partitioning Random Forest machine learning algorithm. Finally, the prediction accuracy of the algorithm was compared in the development cohort and an independent validation cohort. Significant differences were found in the ΔT between treatment modality groups. The developed algorithm correctly predicts into which treatment category the patient will fall with 85.35% accuracy. Agreement between predicted and actual treatment for both cohorts was weighted kappa 90%. CONCLUSION:Infrared thermograms obtained at first contact with a wounded patient can be used to accurately predict the definitive treatment modality for burn patients. This method can be used to rationalize treatment and streamline early wound closure

Dynamic infrared thermography of nanoheaters embedded in skin-equivalent phantoms

"Nanoheaters are promising tools for localized photothermal therapy (PTT) of malignant cells. The anisotropic AuNPs present tunable surface plasmon resonances (SPR) with ideal NIR optical response to be applied as theranostic agents. To this purpose, nanoparticles with branches are suitable because of the electromagnetic field concentrated at their vertices. We standardized a protocol to synthesize multibranched gold nanoparticles (MB-AuNPs) by the seed-growth method and found a size-seed dependence tunability on the hierarchy of branching. Once the optical response is evaluated, we tested the temporal stability as nanoheaters of the MB-AuNPs immersed in skin-equivalent phantoms by dynamic infrared thermography (DIRT). The most suited sample presents a concentration of 5.2 x 10(8) MB-AuNPs/mL showing good thermal stability with Delta T = 4.5 degrees C, during 3 cycles of 10 min at 785 nm laser irradiation with power of 0.15 W. According to these results, the MB-AuNPs are suitable nanoheaters to be tested for PTT in more complex models.