MPN es agradecido al Programa de Becas del Director por el apoyo financiero. NMP quiere agradecer Yu-Chih Tseng para ayudar con el desarrollo del protocolo para el procesamiento de células solares. Este trabajo se realizó en el Centro de Materiales a Nanoescala, un Departamento de Energía de EE.UU., Oficina de Ciencia, Oficina del Fondo para el usuario Ciencias Básicas de Energía en virtud del Contrato N º DE-AC02-06CH11357.

1. Señal de adquisición <ol class="lalpha"><li> Instale la muestra (células solares de polímeros sin cátodo (ITO / PEDOT: PSS/P3HT: PC 61 BM)) en un comercial de AFM multimodo (Veeco, Santa Barbara, CA) equipado con Nanoscope-V controlador. </li><li> Instale conductor sonda AFM AFM en multimodo soporte de la sonda. </li><li> Crear conexión eléctrica entre la sonda AFM, muestra y fuente de tensión. </li><li> Ruta de salida del amplificador de corriente (señal de intensidad), la salida multimodo desviación AFM (fuerza de la señal), muestra multimodo salida AFM altura (señal de distancia) en una tarjeta de adquisición digital (NI-DAQ PCI-6115). La ganancia por Femto DLPCA-200 amplificador de corriente es de 1 nA / V en el ancho de banda de 50 kHz. </li><li> Aplicar sesgo 6V entre AFM sonda y el electrodo ITO. </li><li> Ejecutar multimodo AFM en modo de recogida de PeakForceTM señal topografía: punto pico de fuerza conjunto 30 nN, una amplitud de oscilación de apoyo de 300 nm, una frecuencia de oscilación de apoyo de 2 kHz, una velocidad de barrido de 1 Hz, y una resolutisobre de 512 por 512 píxeles. </li><li> Recoger señales listadas en la sección d por LabView / MATLAB de control al mismo tiempo que la adquisición de la señal de topografía (etapa e). </li></ol> 2. Datos Análisis Paso 1: Generación de Pull-off de la Fuerza, rigidez de contacto y mapas actuales <ol class="lalpha"><li> Lea con fecha y hora de señales de corriente, la fuerza y ​​la distancia en MATLAB. </li><li> Cree 2.000 fuerza - distancia, y la fuerza - curvas actuales de la línea de exploración en primer lugar. Número de curvas es una función de la frecuencia de oscilación de apoyo y velocidad de exploración. </li><li> De cada fuerza - distancia curva, determinar en contacto con rigidez y pull-off de la fuerza durante la retirada de la sonda de AFM (Figura 1). </li><li> De cada fuerza - curva actual, determinar la corriente media mientras que la sonda AFM está en contacto con la superficie durante la retirada (Figura 1). </li><li> Interpolar 2.000 contactos equidistantes rigidez, pull-off de fuerza, y los puntos actuales de 512 puntos de resolución para que coincida conción de señal de topografía. La línea de primer ciclo de la rigidez de contacto, pull-off de fuerza, y los mapas actuales se hace. </li><li> Crear contacto rigidez, pull-off de fuerza, y los mapas actuales, repitiendo los pasos bae 512 veces. Los resultados se muestran en la Figura 2. </li></ol> 3. Datos Análisis Paso 2: Eliminación de Artefactos área de contacto <ol class="lalpha"><li> Utilizar la ecuación (1) y (2) para obtener el módulo de Young (MATERIAL E) y la resistencia (ρ) del material en cada punto de la exploración: 20 <img alt="Ecuación 1" fo:content-width="2.853in" fo:src="/files/ftp_upload/50293/50293eq1highres.jpg" src="/files/ftp_upload/50293/50293eq1.jpg" /> usando ADH F = F PULL - 8 nN (adhesión debido al menisco de agua entre el AFM y la superficie), la rigidez de contacto 20 (k), y la corriente (I) mapas; voltaje de sondeo (V), espesor de la película (L), y adhesiónenergía (w = γ + γ SONDA DE MATERIA L - SONDA γ - MATERIAL, donde γ SONDA - energía superficial del material de la sonda, MATERIAL γ - energía superficial del material de la muestra, y γ-SONDA DE MATERIAL - energía interfacial del material de la muestra y el material de la sonda) 20. </li></ol>

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No hay conflictos de interés declarado.

Los recientes avances en la eficiencia de conversión de energía (PCE) de la fotovoltaica orgánica (OPV) células (empujando un 10% a nivel celular) 3 de común acuerdo con el cumplimiento de los procesos de fabricación de alto rendimiento y bajo costo-4 han puesto de relieve en la tecnología de la VPO como posible solución para el desafío de la fabricación económica de gran superficie de células solares. Materiales OPV son inherentemente no homogénea a escala nanométrica. Falta de homogeneidad de los materiales a nanoescala OPV y el rendimiento de los dispositivos fotovoltaicos están íntimamente conectados. Por lo tanto, la falta de homogeneidad en la composición de la comprensión, así como las propiedades eléctricas de los materiales de la OPV es de suma importancia para mover hacia delante la tecnología OPV. Microscopía de fuerza atómica (AFM) se ha desarrollado como una herramienta para mediciones de alta resolución de la topografía de la superficie desde 1986. 5 En la actualidad, las técnicas de propiedades de los materiales (módulo de Young, 6-10 función de trabajo, 11 conductamediciones ividad, 12 electromecánica, 13-15, etc) están atrayendo cada vez más atención. En el caso de materiales de la OPV, la correlación de la composición de fase local y propiedades eléctricas es una promesa para revelar una mejor comprensión de los mecanismos internos de las células solares orgánicas. 1, 16-17 AFM basados ​​en técnicas son capaces de alta resolución de fase de atribución 8, así como las propiedades eléctricas de cartografía en materiales poliméricos. Así, en principio, la correlación de la composición de fase de polímero (a través de mediciones mecánicas) 18 y las propiedades eléctricas es posible utilizando técnicas basadas en AFM. Muchos AFM basados ​​en técnicas para mediciones de las propiedades mecánicas y eléctricas de los materiales de utilizar el supuesto de área constante de contacto entre la sonda AFM y la superficie. Esta suposición falla a menudo, lo que resulta en una fuerte correlación entre topografía de la superficie y las propiedades mecánicas / eléctricas. Recientemente, un nuevo AFM basado en la técnica parade alto rendimiento de las mediciones de propiedades mecánicas (PeakForce) 19 fue introducido. TUNA PeakForce (variación del método PeakForce) proporciona una plataforma para mediciones simultáneas de propiedades mecánicas y eléctricas de la muestra. Sin embargo, el método TUNA PeakForce produce mapas de propiedades mecánicas y eléctricas, que por lo general están fuertemente correlacionados debido a la variabilidad no contabilizada de contacto durante las mediciones. En este trabajo, presentamos un protocolo experimental para la eliminación de las correlaciones asociadas con diferentes radio de contacto, manteniendo las medidas exactas de las propiedades mecánicas y eléctricas usando AFM. Aplicación de los resultados del protocolo en las mediciones cuantitativas de la resistencia de los materiales &#39;y módulo de Young.

<table border="1"><tbody><tr><td> Nombre del reactivo / material </td><td> Empresa </td><td> Número de Catálogo </td><td> Comentarios </td></tr><tr><td> Plextronics tintas </td><td> Plexcore </td><td> PV 1000 </td><td></td></tr><tr><td> ITO recubiertos con sustratos de vidrio </td><td> Delta Technologies, Inc </td><td></td><td> 25 Ohms / sq </td></tr><tr><td> 30 MHz sintetizado generador de funciones </td><td> Stanfor Investigación de Sistemas </td><td> DS345 </td><td></td></tr><tr><td> Amplificador de intensidad </td><td> Femto </td><td> DLPCA-200 </td><td></td></tr><tr><td> Multimodo AFM </td><td> Veeco, Santa Barbara, CA </td><td></td><td> equipado con un controlador Nanoscope-V </td></tr><tr><td> DAQ tarjeta </td><td> National Instruments </td><td> NI PCI-6115 </td><td></td></tr><tr><td> Pt metálico sondas </td><td> RMNano </td><td> 12Pt3008 </td><td></td></tr><tr><td> MATLAB software </td><td> Mathworks </td><td></td><td></td></tr><tr><td> LabView software </td><td> National Instruments </td><td></td><td></td></tr></tbody></table>

concurrent quantitative conductivity and mechanical properties measurements of organic photovoltaic materials using afm

Fotovoltaicos orgánicos (OPV) materiales son inherentemente no homogénea a escala nanométrica. Falta de homogeneidad de escala nanométrica de materiales OPV afecta al rendimiento de los dispositivos fotovoltaicos. Por lo tanto, la comprensión de las variaciones espaciales en la composición, así como las propiedades eléctricas de los materiales de la OPV es de suma importancia para mover hacia delante la tecnología fotovoltaica. 1,2 En este artículo, se describe un protocolo para mediciones cuantitativas de las propiedades eléctricas y mecánicas de los materiales de la OPV con sub -100 nm resolución. En la actualidad, propiedades de los materiales mediciones realizadas utilizando comercialmente disponibles basados ​​en técnicas de AFM (PeakForce, conductora AFM) por lo general sólo proporcionan información cualitativa. Los valores de la resistencia así como el módulo de Young medido utilizando nuestro método en el prototipo de ITO / PEDOT: PSS/P3HT: PC 61 del sistema BM corresponden bien con datos de la literatura. El P3HT: PC 61 BM mezcla se separa en el PC 61 y BM-rico-rico P3HT Domains. Las propiedades mecánicas de PC 61 dominios ricos y BM-P3HT ricos son diferentes, lo que permite la atribución de dominio en la superficie de la película. Es importante destacar que, combinando los datos mecánicos y eléctricos permite la correlación de la estructura del dominio en la superficie de la película con la variación de propiedades eléctricas medidas a través del espesor de la película.

Módulo de Young y mapas de resistividad (Figura 3) presentan resultados típicos de las mediciones descritas anteriormente. Las propiedades mecánicas y eléctricas de la ITO / PEDOT: PSS/P3HT: PC 61 pila BM se midieron a negativo (-10 V) y positivo (+6 V) tensiones aplicadas a la sonda AFM. Artefactos de imagen, asociados a la interacción electrostática entre la sonda de AFM y la muestra, son un problema común para las mediciones cuantitativas de las propiedades funcionales utilizando AF...

Watch this Scientific Journal Video about Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM at JoVE.com

Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Fotovoltaicos orgánicos (OPV) materiales son inherentemente no homogénea a escala nanométrica. Falta de homogeneidad de escala nanométrica de materiales OPV afecta al rendimiento de los dispositivos fotovoltaicos. En este trabajo se describe un protocolo para las mediciones cuantitativas de las propiedades eléctricas y mecánicas de los materiales de la OPV con resolución sub-100 nm.

Conductividad concurrente cuantitativa y Medidas propiedades mecánicas de los materiales fotovoltaicos orgánicos utilizando AFM

Organic photovoltaic  (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale  inhomogeneity of OPV materials affects performance ...

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Engineering

11.6K vistas.  Argonne National Laboratory. Fotovoltaicos orgánicos (OPV) materiales son inherentemente no homogénea a escala nanométrica. Falta de homogeneidad de escala nanométrica de materiales OPV afecta al rendimiento de los dispositivos fotovoltaicos. En este trabajo se describe un protocolo para las mediciones cuantitativas de las propiedades eléctricas y mecánicas de los materiales de la OPV con resolución sub-100 nm.

Video: Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult1. At the same time, the ability to do so is highly important in view of a number of applications in functional soft matter including electronics, biomedical engineering, and sensors. In the past, successful strategies to control the size and shape of supramolecular polymers typically focused on the use of templates2,3, end cappers4 or selective solvent techniques5. 
Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing electrostatic repulsive interactions on the hydrophilic rim and attractive non-covalent forces within the hydrophobic core of the polymerizing building block, we manage to create small and discrete spherical objects6,7. Increasing the salt concentration to screen the charges induces a sphere-to-rod transition. Intriguingly, this transition is expressed in an increase of cooperativity in the temperature-dependent self-assembly mechanism, and more stable aggregates are obtained. 
For our study we select a benzene-1,3,5-tricarboxamide (BTA) core connected to a hydrophilic metal chelate via a hydrophobic, fluorinated L-phenylalanine based spacer (Scheme 1). The metal chelate selected is a Gd(III)-DTPA complex that contains two overall remaining charges per complex and necessarily two counter ions. The one-dimensional growth of the aggregate is directed by &pi;-&pi; stacking and intermolecular hydrogen bonding. However, the electrostatic, repulsive forces that arise from the charges on the Gd(III)-DTPA complex start limiting the one-dimensional growth of the BTA-based discotic once a certain size is reached. At millimolar concentrations the formed aggregate has a spherical shape and a diameter of around 5 nm as inferred from 1H-NMR spectroscopy, small angle X-ray scattering, and cryogenic transmission electron microscopy (cryo-TEM). The strength of the electrostatic repulsive interactions between molecules can be reduced by increasing the salt concentration of the buffered solutions. This screening of the charges induces a transition from spherical aggregates into elongated rods with a length &gt; 25 nm. Cryo-TEM allows to visualise the changes in shape and size. In addition, CD spectroscopy permits to derive the mechanistic details of the self-assembly processes before and after the addition of salt. Importantly, the cooperativity -a key feature that dictates the physical properties of the produced supramolecular polymers- increases dramatically upon screening the electrostatic interactions. This increase in cooperativity results in a significant increase in the molecular weight of the formed supramolecular polymers in water.

The goal of this experiment is to determine and control the size, shape and stability of self-assembled discotic amphiphiles in water. For aqueous based supramolecular polymers such level of control is very difficult. We apply a strategy using both repulsive and attractive interactions. The experimental techniques applied to characterize this system are broadly applicable.

Controlar el tamaño, forma y estabilidad de los polímeros supramoleculares en el agua

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult1. At the same time, the ability to do ...

Investigación

Ingeniería

Micro 3D Printing Using a Digital Projector and its Application in the Study of Soft Materials Mechanics

Buckling is a classical topic in mechanics. While buckling has long been studied as one of the major structural failure modes1, it has recently drawn new attention as a unique mechanism for pattern transformation. Nature is full of such examples where a wealth of exotic patterns are formed through mechanical instability2-5. Inspired by this elegant mechanism, many studies have demonstrated creation and transformation of patterns using soft materials such as elastomers and hydrogels6-11. Swelling gels are of particular interest because they can spontaneously trigger mechanical instability to create various patterns without the need of external force6-10. Recently, we have reported demonstration of full control over buckling pattern of micro-scaled tubular gels using projection micro-stereolithography (P&mu;SL), a three-dimensional (3D) manufacturing technology capable of rapidly converting computer generated 3D models into physical objects at high resolution12,13. Here we present a simple method to build up a simplified P&mu;SL system using a commercially available digital data projector to study swelling-induced buckling instability for controlled pattern transformation.
A simple desktop 3D printer is built using an off-the-shelf digital data projector and simple optical components such as a convex lens and a mirror14. Cross-sectional images extracted from a 3D solid model is projected on the photosensitive resin surface in sequence, polymerizing liquid resin into a desired 3D solid structure in a layer-by-layer fashion. Even with this simple configuration and easy process, arbitrary 3D objects can be readily fabricated with sub-100 &mu;m resolution.
This desktop 3D printer holds potential in the study of soft material mechanics by offering a great opportunity to explore various 3D geometries. We use this system to fabricate tubular shaped hydrogel structure with different dimensions. Fixed on the bottom to the substrate, the tubular gel develops inhomogeneous stress during swelling, which gives rise to buckling instability. Various wavy patterns appear along the circumference of the tube when the gel structures undergo buckling. Experiment shows that circumferential buckling of desired mode can be created in a controlled manner. Pattern transformation of three-dimensionally structured tubular gels has significant implication not only in mechanics and material science, but also in many other emerging fields such as tunable matamaterials.

We demonstrate controlled pattern transformation of swelling gel tubes by elastic instability. A simple projection micro stereo-lithography setup is built using an off-the-shelf digital data projector to fabricate three-dimensional polymeric structures in a layer-by-layer fashion. Swelling hydrogel tubes under mechanical constraint display various circumferential buckling modes depending on dimension.

Micro 3D Impresión con un proyector digital y su aplicación en el estudio de la mecánica de materiales blandos

Buckling is a classical topic in mechanics. While buckling has long been studied as one of the major structural failure modes1, it has recently drawn new ...

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

Uso de neutron spin echo resuelto grazing incidencia dispersión para investigar materiales orgánicos de células solares

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

Characterization of Thermal Transport in One-dimensional Solid Materials

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including conductive, semi-conductive or nonconductive one-dimensional structures. This technique broadens the measurement scope of materials (conductive and nonconductive) and improves the accuracy and stability. If the sample (especially biomaterials, such as human head hair, spider silk, and silkworm silk) is not conductive, it will be coated with a gold layer to make it electronically conductive. The effect of parasitic conduction and radiative losses on the thermal diffusivity can be subtracted during data processing. Then the real thermal conductivity can be calculated with the given value of volume-based specific heat (&#961;cp), which can be obtained from calibration, noncontact photo-thermal technique or measuring the density and specific heat separately. In this work, human head hair samples are used to show how to set up the experiment, process the experimental data, and subtract the effect of parasitic conduction and radiative losses.

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials.

Caracterización de Transporte térmica en materiales sólidos unidimensionales

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including ...

Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). In this article we will describe the methods for constructing and characterizing macroscopic disordered photonic structures using microwaves. The microwave regime offers the most convenient experimental sample size to build and test PBG media. Easily manipulated dielectric lattice components extend flexibility in building various 2D structures on top of pre-printed plastic templates. Once built, the structures could be quickly modified with point and line defects to make freeform waveguides and filters. Testing is done using a widely available Vector Network Analyzer and pairs of microwave horn antennas. Due to the scale invariance property of electromagnetic fields, the results we obtained in the microwave region can be directly applied to infrared and optical regions. Our approach is simple but delivers exciting new insight into the nature of light and disordered matter interaction.

Our representative results include the first experimental demonstration of the existence of a complete and isotropic PBG in a two-dimensional (2D) hyperuniform disordered dielectric structure. Additionally we demonstrate experimentally the ability of this novel photonic structure to guide electromagnetic waves (EM) through freeform waveguides of arbitrary shape.

Disordered structures offer new mechanisms for forming photonic bandgaps and unprecedented freedom in functional-defect designs. To circumvent the computational challenges of disordered systems, we construct modular macroscopic samples of the new class of PBG materials and use microwaves to characterize their scale-invariant photonic properties, in an easy and inexpensive manner.

El uso de microondas y muestras macroscópicas de dieléctricos sólidos para estudiar las propiedades fotónicas de desordenados Fotónicas materiales de banda prohibida

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). ...

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

Preparación y Fricción Fuerza Microscopía mediciones de inmiscibles, opuestos polímero Cepillos

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

The durability of polymers and fiber-reinforced polymer composites in service is a critical aspect for their designs and condition-based maintenance. We present a novel low-cost laboratory testing platform for the investigation of the influence of concurrent mechanical and environmental loadings, and may help design more efficient yet safer composite structures.

Una plataforma de pruebas de Estudios de durabilidad de Polímeros y reforzados con fibra de polímero composites bajo estímulos Concurrente Hygrothermo-mecánica

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs ...

Quantitative Hardness Measurement by Instrumented AFM-indentation

In this work, a combination of amplitude-modulated non-contact atomic force microscopy and atomic force spectroscopy is applied for instrumented hardness measurements on an Au(111) surface with atomistic resolution of single plasticity events. A careful experimental procedure is described that includes the force sensor selection, its calibration, the calibration of the cantilever deflection detection system, and the minimization of instrumental drift for accurate and reproducible force-distance measurements. Also, a method for the data analysis is presented that allows the extraction of force-penetration curves from recorded force-distance curves. A typical curve displays a clear elastic deformation regime up to the first plasticity event, or pop-in, with a length in the range of one to two Burger's vectors. Later plasticity events exhibit the same magnitude. The work of plasticity is further extracted from the measurements. Finally, the hardness is determined in combination with the indentation curve using non-contact atomic force microscopy images of the remaining indents.

This experimental protocol describes how atomic force microscopy can be used to measure hardness at the true nanometer scale and to detect single atomistic plasticity events.

Cuantitativa de la dureza de medición por instrumentado AFM-muesca

In this work, a combination of amplitude-modulated non-contact atomic force microscopy and atomic force spectroscopy is applied for instrumented hardness ...

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

La recombinación Dinámica de capa fina en materiales fotovoltaicos a través de conductividad de microondas resuelta en el tiempo

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

Preparación de redes de cristal líquido para macroscópico movimiento oscilatoria inducida por luz

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...