MPN est reconnaissant envers le programme de bourses du directeur d&#39;un soutien financier. MPN tient à remercier Yu-Chih Tseng de l&#39;aide au développement du protocole pour le traitement de cellules solaires. Ce travail a été effectué au Centre pour les nanomatériaux, un Département américain de l&#39;énergie, Bureau de la science, Bureau de la Facilité Energie utilisateur sciences fondamentales en vertu du contrat n ° DE-AC02-06CH11357.

1. Acquisition de signaux <ol class="lalpha"><li> Installez échantillon (cellule solaire polymère sans cathode (ITO / PEDOT: PSS/P3HT: PC 61 BM)) dans une publicité AFM multimode (Veeco, Santa Barbara, CA) équipé d&#39;Nanoscope-V contrôleur. </li><li> Installez conducteur AFM sonde dans multimode AFM porte-sonde. </li><li> Créer une connexion électrique entre la sonde AFM, l&#39;échantillon et la source de tension. </li><li> Sortie de l&#39;amplificateur itinéraire actuel (signal de courant), multimode de sortie de déflexion AFM (force du signal), multimode de sortie AFM hauteur de l&#39;échantillon (signal de distance) dans une carte d&#39;acquisition numérique (NI PCI-6115-DAQ). Le gain sur la Femto DLPCA-200 amplificateur de courant est de 1 nA / V à 50 kHz de bande passante. </li><li> Appliquer biais 6V entre l&#39;AFM sonde et l&#39;électrode ITO. </li><li> Exécuter multimode AFM en mode PeakForceTM collecte signal de topographie: pic de point de consigne force de 30 nN, une amplitude d&#39;oscillation soutien de 300 nm, une fréquence d&#39;oscillation de soutien de 2 kHz, une vitesse de balayage de 1 Hz, et une resolutile de 512 par 512 pixels. </li><li> Capter les signaux énumérés à l&#39;article j en LabView / MATLAB commande en même temps l&#39;acquisition du signal topographie (e étape). </li></ol> 2. Étape 1 Analyse des données: Génération de Pull-off Force, rigidité de contact et cartes actuelles <ol class="lalpha"><li> Lire horodatées de signaux de courant, la force et la distance dans MATLAB. </li><li> Créez 2.000 vigueur - la distance et la force - courbes de courant pour la première ligne de balayage. Nombre de courbes est une fonction de la fréquence d&#39;oscillation de support et le taux de balayage. </li><li> A partir de chaque courbe force - distance, de déterminer avec rigidité et l&#39;arrachement de la force lors du retrait de la sonde AFM (Figure 1). </li><li> À partir de chaque courbe force - courant, déterminer le courant moyen pendant la sonde AFM est en contact avec la surface pendant retirer (figure 1). </li><li> Interpoler 2000 rigidité de contact à distance égale, l&#39;arrachement de la force, et les points actuels de 512 points pour correspondre à la résolutiontion du signal de la topographie. La première ligne de balayage pour une rigidité de contact, l&#39;arrachement de la force, et les cartes actuelles est effectuée. </li><li> Créer un contact rigidité, une halte-d&#39;œuvre, et les cartes actuelles en répétant les étapes B à E 512 fois. Les résultats sont présentés dans la figure 2. </li></ol> 3. Étape d&#39;analyse des données 2: Élimination de la région de contact Artefacts <ol class="lalpha"><li> Utiliser l&#39;équation (1) et (2) pour obtenir le module d&#39;Young (E MATERIAU) et la résistance (ρ) du matériau en chaque point de l&#39;analyse: 20 <img alt="L&#39;équation 1" fo:content-width="2.853in" fo:src="/files/ftp_upload/50293/50293eq1highres.jpg" src="/files/ftp_upload/50293/50293eq1.jpg" /> avec F = F ADH PULL - 8 nN (adhérence due à ménisque d&#39;eau entre l&#39;AFM et la surface), 20 raideur de contact (k), et le courant (I) cartes; tension d&#39;évaluation (V), l&#39;épaisseur du film (L), et adhésionl&#39;énergie (w = γ + SONDE L MATERIA γ - γ SONDE - MATERIEL, où SONDE γ - énergie de surface du matériau sonde, MATÉRIEL γ - énergie de surface du matériau de l&#39;échantillon, et γ-SONDE MATÉRIEL - énergie interfaciale du matériau de l&#39;échantillon et le matériau de la sonde) 20. </li></ol>

<ol>
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Aucun conflit d&#39;intérêt déclaré.

Les découvertes récentes de l&#39;efficacité de conversion de puissance (PCE) de photovoltaïque organique (OPV) des cellules (10% poussant au niveau cellulaire) 3, de concert avec le respect des procédés de fabrication à haut débit et à faible coût 4 ont mis un coup de projecteur sur la technologie VPO comme un solution possible pour relever le défi de la fabrication bon marché de grande surface des cellules solaires. VPO matériaux sont intrinsèquement inhomogène à l&#39;échelle nanométrique. Inhomogénéité échelle nanométrique de matériaux VPO et les performances des dispositifs photovoltaïques sont intimement liés. Ainsi, la compréhension hétérogénéité de la composition ainsi que les propriétés électriques des matériaux VPO est d&#39;une importance primordiale pour déplacer la technologie VPO avant. Microscopie à force atomique (AFM) a été conçu comme un outil pour les mesures à haute résolution de la topographie de surface depuis 1986. 5 De nos jours, les techniques de propriétés des matériaux (module d&#39;Young, 6-10 fonction de travail, 11 conduitemesures ivité, 12 électromécanique, 13-15, etc) sont d&#39;une attention croissante. Dans le cas de matériaux VPO, la corrélation de composition de la phase locale et les propriétés électriques promet de révéler de mieux comprendre les rouages ​​de cellules solaires organiques. 1, 16-17 AFM à base de techniques sont capables de haute résolution phase d&#39;attribution 8 ainsi comme la cartographie des propriétés électriques des matériaux polymères. Ainsi, en principe, la corrélation de composition de la phase polymère (par des mesures mécaniques) 18 et des propriétés électriques est possible en utilisant des techniques basées sur l&#39;AFM. Beaucoup AFM techniques basées sur des mesures des propriétés mécaniques et électriques des matériaux utiliser l&#39;hypothèse de la région constante de contact entre la sonde et la surface de l&#39;AFM. Cette hypothèse n&#39;est pas souvent, ce qui entraîne une forte corrélation entre la topographie de surface et les propriétés mécaniques / électriques. Récemment, une nouvelle technique basée sur l&#39;AFM pourà haut débit mesures des propriétés mécaniques (PeakForce) 19 a été introduit. THON PeakForce (variante de la méthode PeakForce) fournit une plate-forme pour des mesures simultanées des propriétés mécaniques et électriques de l&#39;échantillon. Cependant, la méthode THON PeakForce produit des cartes de propriétés mécaniques et électriques, qui sont généralement fortement corrélés en raison de la variabilité disparus de contact pendant les mesures. Dans cet article, nous présentons un protocole expérimental pour enlever les corrélations associées à rayon variable de contact tout en maintenant des mesures précises des propriétés mécaniques et électriques par AFM. La mise en œuvre des résultats du protocole de mesures quantitatives de la résistance des matériaux et de module d&#39;Young.

<table border="1"><tbody><tr><td> Nom de réactif / Matériel </td><td> Entreprise </td><td> Numéro de catalogue </td><td> Commentaires </td></tr><tr><td> Encres Plextronics </td><td> Plexcore </td><td> PV 1000 </td><td></td></tr><tr><td> Substrats en verre revêtus d&#39;ITO </td><td> Delta Technologies, Inc </td><td></td><td> 25 ohms / carré </td></tr><tr><td> 30 MHz synthétisé générateur de fonction </td><td> Stanfor recherche sur les systèmes </td><td> DS345 </td><td></td></tr><tr><td> Amplificateur de courant </td><td> Femto </td><td> DLPCA-200 </td><td></td></tr><tr><td> Multimode AFM </td><td> Veeco, Santa Barbara, Californie </td><td></td><td> équipé d&#39;Nanoscope-V contrôleur </td></tr><tr><td> DAQ carte </td><td> National Instruments </td><td> NI PCI-6115- </td><td></td></tr><tr><td> Métal sondes Pt </td><td> RMNano </td><td> 12Pt3008 </td><td></td></tr><tr><td> Logiciel MATLAB </td><td> Mathworks </td><td></td><td></td></tr><tr><td> Logiciel LabView </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

Photovoltaïques organiques (OPV) des matériaux sont intrinsèquement inhomogène à l&#39;échelle nanométrique. Inhomogénéité échelle nanométrique de matériaux VPO affecte les performances des dispositifs photovoltaïques. Ainsi, la compréhension des variations spatiales de la composition ainsi que les propriétés électriques des matériaux VPO est d&#39;une importance primordiale pour le déplacement en avant la technologie photovoltaïque. 1,2 Dans cet article, nous décrivons un protocole pour les mesures quantitatives des propriétés électriques et mécaniques des matériaux avec le VPO sous 100 nm résolution. Actuellement, les propriétés des matériaux mesures effectuées par l&#39;AFM disponibles dans le commerce à base de techniques (PeakForce, conducteur AFM) fournissent généralement que des informations qualitatives. Les valeurs de la résistance ainsi que le module d&#39;Young mesuré à l&#39;aide de notre méthode sur le prototype ITO / PEDOT: PSS/P3HT: 61 Système PC BM correspondent bien aux données de la littérature. Le P3HT: PC 61 mélange BM sépare sur le PC 61 BM-riche et P3HT riche domains. Les propriétés mécaniques des PC 61 domaines BM-riches et P3HT-riches sont différents, ce qui permet l&#39;attribution de domaine sur la surface du film. Surtout, la combinaison de données mécaniques et électriques permettant la corrélation de la structure de domaine sur la surface du film avec des variations des propriétés électriques mesurées à travers l&#39;épaisseur du film.

Le module de Young et de la résistivité des cartes (figure 3) présente des résultats typiques des mesures décrites ci-dessus. Propriétés mécaniques et électriques de l&#39;ITO / PEDOT: PSS/P3HT: PC 61 pile BM ont été mesurées à une valeur négative (-10 V) et positive (+6 V) Tensions appliquée à la sonde AFM. Artefacts d&#39;imagerie, associés à l&#39;interaction électrostatique entre la sonde AFM et l&#39;échantillon, sont un problème courant pour les mesures quantitative...

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

Photovoltaïques organiques (OPV) des matériaux sont intrinsèquement inhomogène à l&#39;échelle nanométrique. Inhomogénéité échelle nanométrique de matériaux VPO affecte les performances des dispositifs photovoltaïques. Dans cet article, nous décrivons un protocole pour les mesures quantitatives des propriétés électriques et mécaniques des matériaux avec une résolution de VPO nm sous-100.

Parallèlement conductivité quantitatives et mesures mécaniques Propriétés des matériaux organiques photovoltaïques par AFM

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

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11.6K vues.  Argonne National Laboratory. Photovoltaïques organiques (OPV) des matériaux sont intrinsèquement inhomogène à l'échelle nanométrique. Inhomogénéité échelle nanométrique de matériaux VPO affecte les performances des dispositifs photovoltaïques. Dans cet article, nous décrivons un protocole pour les mesures quantitatives des propriétés électriques et mécaniques des matériaux avec une résolution de VPO nm sous-100.

Vidéo: 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.

Contrôle de la taille, la forme et la stabilité des polymères supramoléculaires dans l&#39;eau

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

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Ingénierie

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 Impression à l&#39;aide d&#39;un projecteur numérique et son application dans l&#39;étude de la mécanique des matériaux souples

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.

Utilisation de la diffusion de l’incidence de broutage résolue par écho de spin neutronique pour étudier les matériaux des cellules solaires organiques

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.

Caractérisation des Transports thermique dans des matériaux solides unidimensionnels

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.

Utilisation de micro-ondes et d&#39;échantillons macroscopiques des diélectriques solides pour étudier les propriétés photoniques désordonnés de bande interdite photonique Matériaux

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.

Mesures de préparation et de friction Microscopie à force de polymères non miscibles, Opposing Brosses

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.

Une plate-forme d&#39;essais pour une durabilité études de polymères renforcés de fibres et polymères Composites sous stimuli Concurrent Hygrothermo-mécanique

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.

Dureté mesure quantitative par instrumenté AFM-indentation

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.

Recombinaison Dynamics photovoltaïques en couches minces de matériaux par résolution temporelle Micro-ondes Conductivity

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.

Préparation des réseaux de cristaux liquides pour macroscopique mouvement oscillatoire induite par la lumière

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