MPN ist dankbar, des Direktors Fellowship Program für finanzielle Unterstützung. MPN will Yu-Chih Tseng für die Hilfe bei der Entwicklung des Protokolls für Solarzellenprozessierung danken. Diese Arbeit wurde am Center for Nanoscale Materials, ein US-Department of Energy, Office of Science, Office of Basic Energy Sciences User Facility unter Vertrag Nr. DE-AC02-06CH11357 durchgeführt.

Ein. Signalerfassung <ol class="lalpha"><li> Installieren Probe (Polymer-Solarzelle ohne Kathode (ITO / PEDOT: PSS/P3HT: PC 61 BM)) in einem kommerziellen Multimode AFM (Veeco, Santa Barbara, CA) mit Nanoscope-V-Controller ausgestattet. </li><li> Installieren leitenden AFM-Sonde in Multimode AFM Sondenhalter. </li><li> Erstellen elektrische Verbindung zwischen der AFM-Sonde, Proben-und Spannungsquelle. </li><li> Route aktuellen Verstärkerausgang (Stromsignal), Multimode AFM Ablenkung Ausgang (Kraft-Signal), Multimode AFM Probenhöhe Ausgang (Abstandssignal) in einen digitalen Messkarte (NI-PCI-6115 DAQ). Der Gewinn aus Femto DLPCA-200 Stromverstärkers ist 1 nA / V bei 50 kHz Bandbreite. </li><li> Bewerben 6V Vorspannung zwischen AFM-Sonde und ITO-Elektrode. </li><li> Führen Multimode AFM in PeakForceTM Modus Sammeln Topographie Signal: Spitzenkraft Sollwert von 30 nN, einen Träger Schwingungsamplitude von 300 nm, einem Träger Oszillationsfrequenz von 2 kHz, einer Scangeschwindigkeit von 1 Hz und einer resolutiauf der 512 x 512 Pixel. </li><li> Collect-Signale in Abschnitt d durch LabView / MATLAB Kontrolle gleichzeitig mit dem Erwerb der Topographie (Schritt e) aufgeführt. </li></ol> 2. Data Analysis Schritt 1: Erzeugung von Pull-off Force, Kontakt Steifigkeit und aktuellen Karten <ol class="lalpha"><li> Lesen Zeitstempel Strom, Kraft und Distanz Signale in MATLAB. </li><li> Erstellen 2.000 Kraft - Abstand und Kraft - Strom-Kurven für die ersten Scan-Linie. Anzahl der Kurven ist eine Funktion der Unterstützung Oszillationsfrequenz und Scangeschwindigkeit. </li><li> Von jeder Kraft - Abstand Eichkurve kontaktieren Steifigkeit und Pull-off-Kraft beim Herausziehen des AFM-Sonde (Abbildung 1). </li><li> Von jeder Kraft - Stromkurve, den mittleren Strom zu ermitteln, während der AFM-Sonde in Kontakt mit der Oberfläche während zurückzuziehen (Abbildung 1). </li><li> Interpolieren 2.000 gleichem Abstand Kontakt Steifigkeit, Pull-off-Kraft, und aktuelle Punkte 512 Punkte Auflösung entsprechention der Topographie Signal. Die erste Abtastzeile für Berührungssteifigkeit, Abzugshilfeelement Kraft, und aktuellen Karten erfolgt. </li><li> Kontakt erstellen Steifigkeit, Pull-off-Kraft und aktuellen Karten durch Wiederholen der Schritte b bis e 512-mal. Die Ergebnisse sind in Abbildung 2 dargestellt. </li></ol> 3. Data Analysis Schritt 2: Beseitigung von Kontakt-Bereich Artifacts <ol class="lalpha"><li> Verwenden Gleichung (1) und (2) zum Elastizitätsmodul (E MATERIAL) und Widerstand (ρ) des Materials an jedem Punkt des Scans erhalten: 20 <img alt="Gleichung 1" fo:content-width="2.853in" fo:src="/files/ftp_upload/50293/50293eq1highres.jpg" src="/files/ftp_upload/50293/50293eq1.jpg" /> mit F ADH = F PULL - 8 nN (Adhäsion durch Wasser Meniskus zwischen der AFM und der Oberfläche), 20 Kontakt Steifigkeit (k) und Strom (I) Karten; Messspannung (V), Schichtdicke (L), und HaftungEnergie (w = γ PROBE + γ MATERIA L - γ PROBE - MATERIAL, wo γ PROBE - Oberflächenenergie der Sonde Material, γ MATERIAL - Oberflächenenergie von Probenmaterial und γ PROBE-MATERIAL - Grenzflächenenergie von Probenmaterial und Sonde Material) . 20 </li></ol>

<ol>
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Keine Interessenskonflikte erklärt.

Neueste Innovationen in Leistungswandlungseffizienz (PCE) von organischen Photovoltaik (OPV)-Zellen (stossend 10% auf Zellebene) 3 in Absprache mit der Einhaltung High-Throughput-und Low-Cost Fertigungsprozesse 4 haben ein Schlaglicht auf die OPV-Technologie gebracht, wie ein mögliche Lösung für die Herausforderung, kostengünstige Herstellung von großflächigen Solarzellen. OPV Materialien sind von Natur aus inhomogenen auf der Nanometerskala. Nanoscale Inhomogenität der OPV-Materialien und die Leistung von Photovoltaik-Geräte sind eng miteinander verbunden. Daher ist das Verständnis Inhomogenität in der Zusammensetzung als auch elektrischen Eigenschaften der OPV-Materialien von größter Bedeutung für die Bewegung OPV-Technologie voran. Atomic Force Microscopy (AFM) wurde als ein Werkzeug für hochauflösende Messungen der Oberflächentopographie seit 1986 entwickelt. 5 Heute, Techniken für Materialien Eigenschaften (Elastizitätsmodul, 6-10 Austrittsarbeit, 11 Verhaltenduktivität, 12 Elektromechanik, 13-15 etc.) Messungen gewinnt zunehmend an Aufmerksamkeit. Im Fall von OPV-Materialien hält Korrelation von lokalen Phase Zusammensetzung und elektrischen Eigenschaften Versprechen für die Entdeckung ein besseres Verständnis der inneren Abläufe von organischen Solarzellen. 1, 16-17 AFM-basierte Techniken in der Lage hochauflösende Phase Zurechnung 8 sowie Als elektrische Eigenschaften Abbilden in polymeren Stoffen. Somit ist prinzipiell Korrelation der Polymerphase Zusammensetzung (durch mechanische Messungen) 18 und elektrischen Eigenschaften möglich mittels AFM-basierte Techniken. Viele AFM-basierte Techniken zur Messung von mechanischen und elektrischen Eigenschaften der Materialien verwenden Annahme konstanter Fläche des Kontakts zwischen der AFM-Sonde und der Oberfläche. Diese Annahme scheitert oft, was zu starken Korrelation zwischen Oberflächentopographie und mechanische / elektrische Eigenschaften. Kürzlich wurde eine neue AFM-Technik zumHigh-Throughput-Messungen der mechanischen Eigenschaften (PeakForce) 19 eingeführt wurde. PeakForce TUNA (Variation des PeakForce Methode) bietet eine Plattform für die gleichzeitige Messung von mechanischen und elektrischen Eigenschaften der Probe. Jedoch erzeugt die PeakForce TUNA Verfahren mechanische und elektrische Eigenschaft Karten, die in der Regel wegen der stark nachgewiesenes Variabilität der Kontakt während Messungen korreliert. In diesem Beitrag stellen wir ein experimentelles Protokoll für das Entfernen Korrelationen mit unterschiedlichem Kontakt Radius unter Beibehaltung genaue Messungen der mechanischen und elektrischen Eigenschaften mittels AFM assoziiert. Umsetzung des Protokolls in quantitativen Messungen der Materialien &quot;Widerstand und Elastizitätsmodul.

<table border="1"><tbody><tr><td> Name des Reagenz / Material </td><td> Firma </td><td> Catalog Number </td><td> Kommentare </td></tr><tr><td> Plextronics Tinten </td><td> Plexcore </td><td> PV 1000 </td><td></td></tr><tr><td> ITO-beschichtete Glassubstrate </td><td> Delta Technologies, Inc </td><td></td><td> 25 Ohm / sq </td></tr><tr><td> 30 MHz synthetisiert Funktionsgenerator </td><td> Stanfor Research Systems </td><td> DS345 </td><td></td></tr><tr><td> Stromverstärker </td><td> Femto </td><td> DLPCA-200 </td><td></td></tr><tr><td> Multimode AFM </td><td> Veeco, Santa Barbara, CA </td><td></td><td> ausgestattet mit Nanoscope-V-Controller </td></tr><tr><td> Messkarte </td><td> National Instruments </td><td> NI-PCI-6115 </td><td></td></tr><tr><td> Metall Pt Sonden </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

Organische Photovoltaik (OPV) Materialien sind von Natur aus inhomogenen auf der Nanometerskala. Nanoscale Inhomogenität der OPV-Materialien beeinflusst die Leistung von Photovoltaik-Geräte. So, das Verständnis der räumlichen Variationen in der Zusammensetzung als auch elektrischen Eigenschaften der OPV-Materialien ist von größter Bedeutung für die Bewegung PV-Technologie voran. 1,2 In diesem Papier beschreiben wir ein Protokoll für quantitative Messungen der elektrischen und mechanischen Eigenschaften der OPV Materialien mit sub -100 nm Auflösung. Derzeit durchgeführt Materialeigenschaften Messungen mit handelsüblichen AFM-Techniken (PeakForce, leitenden AFM) in der Regel lediglich qualitative Informationen. Die Werte für den Widerstand als auch Elastizitätsmodul gemessen mit unserer Methode auf der prototypischen ITO / PEDOT: PSS/P3HT: PC 61 BM-System gut mit Daten aus der Literatur. Die P3HT: PC 61 BM Mischung trennt sich auf dem PC 61 BM-reich und P3HT-reiche domains. Mechanische Eigenschaften von BM-PC 61 reichen und P3HT-reiche Domänen unterschiedlich sind, das es ermöglicht, honorarfrei Domäne auf der Oberfläche des Films. Wichtig ist, dass die Kombination von mechanischen und elektrischen Daten können zur Korrelation der Domäne Struktur auf der Oberfläche der Folie mit elektrischen Eigenschaften Schwankungen durch die Dicke des Films gemessen.

Elastizitätsmodul und Widerstandsfähigkeit Karten (Abbildung 3) derzeit typischen Ergebnisse der Messungen beschrieben. Mechanische und elektrische Eigenschaften der ITO / PEDOT: PSS/P3HT: PC 61 BM Stapel wurden bei negativen (-10 V) und positive (+6 V) Spannungen, die an der AFM-Sonde gemessen. Imaging Artefakte, mit elektrostatischen Wechselwirkung zwischen der AFM-Sonde und der Probe verbunden sind, sind ein häufiges Problem für quantitative Messungen der funktionellen Eigenschaften mi...

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

Organische Photovoltaik (OPV) Materialien sind von Natur aus inhomogenen auf der Nanometerskala. Nanoscale Inhomogenität der OPV-Materialien beeinflusst die Leistung von Photovoltaik-Geräte. In diesem Papier beschreiben wir ein Protokoll für quantitative Messungen der elektrischen und mechanischen Eigenschaften der OPV Materialien mit sub-100 nm Auflösung.

Concurrent Quantitative Leitfähigkeit und mechanische Eigenschaften Measurements of Organic Photovoltaic Materials mittels 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 Aufrufe.  Argonne National Laboratory. Organische Photovoltaik (OPV) Materialien sind von Natur aus inhomogenen auf der Nanometerskala. Nanoscale Inhomogenität der OPV-Materialien beeinflusst die Leistung von Photovoltaik-Geräte. In diesem Papier beschreiben wir ein Protokoll für quantitative Messungen der elektrischen und mechanischen Eigenschaften der OPV Materialien mit sub-100 nm Auflösung.

Serie: 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.

Steuern der Größe, Form und Stabilität der supramolekularen Polymeren in Wasser

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

Forschung

Ingenieurwesen

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-Druck mit einem digitalen Projektor und ihre Anwendung in der Studie von Soft Werkstoffmechanik

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.

Mit Neutron Spin Echo Gelöste Grazing Incidence Scattering zur Untersuchung organischer Solarzellenmaterialien

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.

Thermische Charakterisierung von Transport-in-One-dimensional Solide Materialien

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.

Mit Mikrowelle und makroskopischen Proben der Dielektrische Festkörper, um die photonischen Eigenschaften ungeordneter photonische Bandlückenmaterialien Studieren

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.

Vorbereitung und Reibungskraftmikroskopie Messungen mischbar, Entgegenpolymerbürsten

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.

Eine Testplattform in Haltbarkeit Studien von Polymeren und faserverstärkten Polymerverbundwerkstoffe unter Concurrent Hygrothermogeber mechanischen Stimuli

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.

Quantitative Härtemessung durch Instrumented AFM-Einzug

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.

Rekombinationsdynamik in Dünnschicht-Photovoltaik-Materialien über zeitaufgelöste Mikrowellenleitfähigkeit

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.

Vorbereitung der Flüssigkristall-Netzwerke für makroskopische oszillierende Bewegung, die durch Licht induzierten

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