MPN é grato ao Programa de Bolsas do diretor de apoio financeiro. MPN quer agradecer Yu-Chih Tseng ajuda com o desenvolvimento do protocolo para o processamento de células solares. Este trabalho foi realizado no Centro de Materiais em nanoescala, o Departamento de Energia dos EUA, Escritório de Ciência, Instituto de Recurso de Usuário Básico Energy Sciences sob Contrato n º DE-AC02-06CH11357.

1. Aquisição de sinal <ol class="lalpha"><li> Instale amostra (polímero de célula solar sem catódicos (ITO / PEDOT: PSS/P3HT: PC 61 BM)) em um AFM comercial Multimodo (Veeco, Santa Barbara, CA) equipado com Nanoscope-V controlador. </li><li> Instale condutora AFM sonda em Multimode titular sonda de AFM. </li><li> Criar a ligação eléctrica entre a sonda de AFM, de amostra e uma fonte de tensão. </li><li> Rota de saída do amplificador de corrente (sinal de corrente), a saída de deflexão Multimode AFM (força de sinal), multimodo AFM saída altura da amostra (sinais de distância) em um cartão de aquisição digital (NI-PCI-6115 DAQ). O ganho em Femto DLPCA-200 é um amplificador de corrente nA / V a 50 kHz de largura de banda. </li><li> Aplique viés 6V entre AFM sonda e eletrodo de ITO. </li><li> Executar AFM Multimode em PeakForceTM modo de coleta de sinal de topografia: set point pico de força de 30 nN, uma amplitude de oscilação apoio de 300 nm, uma freqüência de oscilação apoio de 2 kHz, uma taxa de varredura de 1 Hz, e um resolutina de 512 por 512 pixels. </li><li> Coletar sinais listados na seção d por LabView / MATLAB controle simultâneo com a aquisição do sinal de topografia (e passo). </li></ol> 2. Dados Análise Passo 1: Produção de pull-off força, rigidez de contato, e mapas atuais <ol class="lalpha"><li> Leia os sinais do tempo com carimbo de força atual, e da distância em MATLAB. </li><li> Criar 2.000 vigor -, distância e força - curvas de corrente para a linha de primeiro exame. Número de curvas é uma função da freqüência de oscilação apoio e velocidade de varredura. </li><li> A partir de cada força - curva distância, determinar contacto rigidez e força de arrancamento, durante a retirada da sonda de AFM (Figura 1). </li><li> A partir de cada força - curva actual, determinar a corrente média, enquanto a sonda de AFM se encontra em contacto com a superfície durante a retirar (Figura 1). </li><li> Interpolar 2000 rigidez de contato igualmente espaçados, pull-off-força, e os pontos atuais por 512 pontos para combinar com resoluçõesção do sinal de topografia. A primeira linha de exploração para a rigidez de contato, pull-off-força, e mapas atuais é feito. </li><li> Criar contacto rigidez, pull-off-força, e mapas atuais, repetindo os passos de B a E 512 vezes. Os resultados são mostrados na Figura 2. </li></ol> 3. Dados Análise Passo 2: Eliminação da área de contato-Artefatos <ol class="lalpha"><li> Utilizar a equação (1) e (2) para se obter o Módulo de Young (MATERIAL E) e resistência (ρ) do material em cada ponto de verificação: 20 <img alt="Equação 1" fo:content-width="2.853in" fo:src="/files/ftp_upload/50293/50293eq1highres.jpg" src="/files/ftp_upload/50293/50293eq1.jpg" /> F usando ADH = F PULL - 8 nN (adesão devido ao menisco de água entre a AFM e a superfície), 20 de contacto da rigidez (k), e de corrente (I) mapas; tensão sondagem (V), a espessura da película (L), e adesãoenergia (w = γ PROBE + γ L MATERIA - γ PROBE - MATERIAL, onde PROBE γ - energia de superfície do material da sonda, MATERIAL γ - energia de superfície do material de amostra, e γ PROBE MATERIAL - energia interfacial de material de amostra e material de sonda) 20. </li></ol>

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Não há conflitos de interesse declarados.

Recentes avanços na eficiência de conversão de energia (PCE) de fotovoltaico orgânico (OPV) células (empurrando a 10% no nível da célula) 3 em conjunto com a conformidade com processos de manufatura de alto rendimento e baixo custo 4 trouxe um holofote sobre tecnologia OPV como um solução possível para o desafio de fabricação barata de grande-área de células solares. Materiais OPV são inerentemente heterogênea em escala nanométrica. Heterogeneidade de materiais em nanoescala OPV e desempenho de dispositivos fotovoltaicos estão intimamente ligados. Assim, a falta de homogeneidade na composição compreensão, bem como propriedades elétricas de materiais OPV é de suma importância para a tecnologia de mudança OPV frente. Microscopia de força atômica (AFM) foi desenvolvido como uma ferramenta para medições de alta resolução de topografia da superfície desde 1986. 5 Hoje em dia, as técnicas para materiais de propriedades (módulo de Young, 6-10 função de trabalho, 11 condutamedições ivity, 12 electromecânica, 13-15, etc) estão atraindo cada vez mais atenção. No caso de materiais de OPV, a correlação da composição da fase local e propriedades eléctricas é promissor para revelar melhor compreensão do funcionamento interno de células solares orgânicas. 1, 16-17 AFM baseados em técnicas são capazes de alta resolução de fase atribuição 8, bem como propriedades elétricas de mapeamento em materiais poliméricos. Assim, em princípio, a correlação da composição da fase polímero (através de medições mecânicas) 18 e propriedades eléctricas é possível, utilizando técnicas baseadas em AFM. Muitos AFM baseados em técnicas de medições das propriedades mecânicas e eléctricas dos materiais usar o pressuposto de área constante de contacto entre a sonda de AFM e a superfície. Esta suposição frequentemente falha, o que resulta em uma forte correlação entre a topografia da superfície e as propriedades mecânicas / eléctricas. Recentemente, uma técnica de AFM nova base parahigh-throughput medições das propriedades mecânicas (PeakForce) 19 foi introduzido. PeakForce ATUM (variação do método PeakForce) fornece uma plataforma para medições simultâneas de propriedades mecânicas e elétricas da amostra. No entanto, o método ATUM PeakForce produz mapas de propriedades mecânicas e elétricas, que geralmente são fortemente correlacionados devido à variabilidade desaparecidos de contato durante as medições. Neste artigo, apresentamos um protocolo experimental para a remoção de correlacoes variando raio de contato, mantendo medições precisas das propriedades mecânicas e elétricas utilizando AFM. Aplicação dos resultados do protocolo de medições quantitativas de resistência e materiais &quot;Módulo de Young.

<table border="1"><tbody><tr><td> Nome do reagente / Material </td><td> Companhia </td><td> Número de catálogo </td><td> Comentários </td></tr><tr><td> Tintas Plextronics </td><td> Plexcore </td><td> PV 1000 </td><td></td></tr><tr><td> ITO-substratos de vidro revestidos </td><td> Delta Technologies, Inc </td><td></td><td> 25 Ohms / m² </td></tr><tr><td> 30 MHz sintetizado gerador de função </td><td> Stanfor Research Systems </td><td> DS345 </td><td></td></tr><tr><td> Amplificador de corrente </td><td> Femto </td><td> DLPCA-200 </td><td></td></tr><tr><td> AFM multimodo </td><td> Veeco, Santa Barbara, CA </td><td></td><td> equipado com Nanoscope V-controlador </td></tr><tr><td> DAQ cartão </td><td> National Instruments </td><td> NI-PCI-6115 </td><td></td></tr><tr><td> Sondas de metal Pt </td><td> RMNano </td><td> 12Pt3008 </td><td></td></tr><tr><td> Software MATLAB </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 orgânicos (OPV) materiais são inerentemente heterogênea em escala nanométrica. Heterogeneidade de materiais em nanoescala OPV afeta o desempenho de dispositivos fotovoltaicos. Assim, a compreensão das variações espaciais da composição, bem como propriedades elétricas de materiais OPV é de suma importância para a movimentação tecnologia fotovoltaica para a frente. 1,2 Neste trabalho, nós descrevemos um protocolo de medidas quantitativas de características elétricas e mecânicas de materiais OPV com sub -100 resolução nm. Actualmente, as medições de propriedades dos materiais disponíveis comercialmente realizada utilizando técnicas baseadas em AFM (PeakForce, AFM condutivo) geralmente fornecem apenas informação qualitativa. Os valores de resistência, bem como o módulo de elasticidade medido utilizando o nosso método no protótipo ITO / PEDOT: PSS/P3HT: PC 61 sistema BM correspondem bem com os dados da literatura. O P3HT: PC 61 mistura BM separa no PC 61 BM-ricos e P3HT rica domains. As propriedades mecânicas do PC 61 domínios BM-ricos e P3HT-ricos são diferentes, o que permite a atribuição de domínio sobre a superfície da película. É importante notar que a combinação de dados mecânicos e eléctricos permite a correlação da estrutura do domínio da superfície do filme com variação propriedades eléctrica medida através da espessura da película.

Módulo de Young e resistividade mapas (Figura 3) apresentam resultados típicos das medições descritas acima. Propriedades mecânicas e elétricas do ITO / PEDOT: PSS/P3HT: PC 61 pilha BM foram medidos no negativo (-10 V) e positiva (+6 V) tensões aplicada à sonda de AFM. Artefactos de imagem, associados com a interacção electrostática entre a sonda e a amostra de AFM, são um problema comum para medidas quantitativas de propriedades funcionais utilizando AFM. A semelhança de magnitu...

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 orgânicos (OPV) materiais são inerentemente heterogênea em escala nanométrica. Heterogeneidade de materiais em nanoescala OPV afeta o desempenho de dispositivos fotovoltaicos. Neste trabalho, nós descrevemos um protocolo de medidas quantitativas de características elétricas e mecânicas de materiais OPV com sub-resolução de 100 nm.

Condutividade quantitativa concorrente e Medidas mecânicas de materiais fotovoltaicos orgânicos 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 visualizações.  Argonne National Laboratory. Fotovoltaicos orgânicos (OPV) materiais são inerentemente heterogênea em escala nanométrica. Heterogeneidade de materiais em nanoescala OPV afeta o desempenho de dispositivos fotovoltaicos. Neste trabalho, nós descrevemos um protocolo de medidas quantitativas de características elétricas e mecânicas de materiais OPV com sub-resolução de 100 nm.

Vídeo: 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.

Controlando o tamanho, forma e estabilidade de Polímeros Supramoleculares na Água

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

Engenharia

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 impressão 3D usando um projetor digital e sua aplicação no estudo de Mecânica dos materiais macios

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.

Usando neutron spin echo resolvi a dispersão da incidência de pastagem para investigar materiais orgânicos 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.

Caracterização dos Transportes térmica em materiais sólidos unidimensionais

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.

Usando microondas e amostras macroscópicas de dielétricos sólidos para estudar as propriedades fotônicas de desordenados fotônicos Bandgap Materiais

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.

Preparação e Friction Microscopia de Força Medidas do Insolúvel, opondo-Polymer Brushes

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.

A Plataforma de testes de durabilidade Estudos de Polímeros e reforçado com fibra de polímero Composites, sob estímulo Concurrent Hygrothermo-mecânico

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.

Medição de dureza quantitativa por Instrumented AFM-recuo

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.

Recombinação Dynamics em Thin-film materiais fotovoltaicos via Condutividade Microondas resolvida no tempo

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.

Preparação das redes de cristal líquido para macroscópica movimento oscilatório induzido pela luz

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