Los autores desean agradecer a José Muskin y Ragusa Mateo en la Universidad de Illinois en Urbana-Champaign para proporcionar imágenes transversales de las estructuras 3D se muestra en la Figura 1D.

1. Preparación de solución de prepolímero <ol><li> Mezcla de poli (etilenglicol) diacrilato (PEG-DA) (peso molecular medio ~ 575, Sigma-Aldrich) y poli (etilenglicol) (PEG) (peso molecular promedio de ~ 200, Sigma-Aldrich) a una relación de peso de 1:2. </li><li> Añadir 0,67% en peso. foto-iniciador (fenilbis (2,4,6-trimetilbenzoil) fosfina, óxido de Sigma-Aldrich). La solución deberá mantenerse en un ambiente oscuro a partir de este punto en adelante. </li><li> Añadir 0,05% en peso. foto-absorbedor (Sudán I, Sigma-Aldrich). </li><li> Mezclar la solución durante 24 horas a temperatura ambiente usando un agitador magnético. </li></ol> 2. Configuración de una impresora de escritorio 3D con un proyector digital de datos <ol><li> Coloque un proyector digital de datos en una posición plana y estable, y conectarlo a un ordenador con Microsoft PowerPoint instalado. </li><li> Colocar una lente convexa derecho en frente de la lente de salida del haz del proyector digital. Elija una lente convexa para hacer que el plano focal de aproximadamente 10 cm de distancia de la proproyector. (Resolución óptica se hace más pequeño para una lente con distancia focal más corta, pero hay que reservar algo de espacio para componentes ópticos.) </li><li> Colocar un espejo después de la lente convexa en el camino del haz en un ángulo de 45 ° para dirigir el haz hacia abajo. </li><li> Colocar un soporte de muestra en el plano focal del haz proyectado. El soporte de la muestra debe estar unido a una fase lineal mediante el cual se controla la posición vertical del soporte de muestra. </li><li> Colocar un baño de resina debajo del portamuestras. </li></ol> 3. Diseño y fabricación de tubos de gel <ol><li> Determinación del diámetro, espesor de pared, y la altura del tubo de gel a ser fabricado. </li><li> Dibujar imágenes en sección transversal para el tubo de gel. Las imágenes deben estar en blanco con fondo negro. Inserte estas imágenes en diapositivas de Microsoft PowerPoint. </li><li> Iniciar la presentación en Microsoft PowerPoint y proyectar cualquier imagen. Colocar el soporte de muestra en el plano focal mediante el ajuste de la posición vertical usando attle dolía el escenario. </li><li> Cambie a una &quot;falsa&quot; imagen negro para que no habrá polimerización, sin dejar de poner solución prepolímero. </li><li> Vierta la solución de prepolímero de baño de resina. Llene la bañera hasta que la solución ligeramente cubre el soporte de la muestra. Ahora está listo para su objeto de impresión 3D. </li><li> Cambiar a la diapositiva que contiene la primera imagen transversal del tubo de gel para polimerizar la primera capa. Sigue la proyección de la imagen durante 8 segundos y volver a &quot;apagón&quot; de diapositivas. </li><li> Gire la perilla en la etapa lineal de ¼ de vuelta (~ 160 m) para bajar el soporte de la muestra. Ahora resina fresca fluye hacia abajo para cubrir la primera capa polimerizada. </li><li> Proyectar la imagen de la sección transversal de nuevo para polimerizar la capa de segundo en la parte superior del procedimiento uno. Repetir los pasos 3.6-3.8 hasta que el tubo de gel de la altura deseada se fabrica. </li><li> Una vez que todas las capas están completas, levante el soporte de la muestra de la solución de prepolímero, y recuperar la muestra fabricada cuidadosamente usando una maquinilla de afeitar blade. </li><li> Lavar la muestra en acetona durante ~ 3 horas, y luego deje que se seque durante aproximadamente 1 hora. </li></ol> 4. Hinchazón Experimento para la Formación pauta prescrita por la inestabilidad elástica <ol><li> Prepare agua-aceite líquido de doble capa en un plato de cristal transparente. </li><li> Coloque la muestra seca en un soporte de muestras utilizando pegamento. </li><li> Dele la vuelta al soporte de la muestra de modo que la muestra está al revés. Sumergir la muestra en el líquido del baño de agua-aceite. Enfoque de la muestra a la interfase agua-aceite de la capa de aceite. La muestra comienza a hincharse cuando la muestra toca la superficie del agua mientras que la parte de sustrato de base sobre la que se fija el tubo de gel se quedó en la capa de aceite superior. De esta manera, el agua puede difundirse en la pared del tubo permitiendo que la muestra se hinchan antes de la base de restricción se relaja por la humectación. Supervisar el cambio de patrón como las olas tubo de gel utilizando una cámara digital. </li></ol>

<ol>
	<li>Timoshenko, S. P., Gere, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Theory of Elastic Stability. , (1961).</li><li>Sharon, E., Marder, M., Swinney, H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leaves+Flowers+and+Garbage+Bags:+Making+Waves.">Leaves Flowers and Garbage Bags: Making Waves.</a> American Scientist. 92, 254-261 (2004).</li><li>K&#252;cken, M., Newell, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fingerprint+formation.">Fingerprint formation.</a> Journal of Theoretical Biology. 235, 71-83 (2005).</li><li>Liang, H., Mahadevan, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+shape+of+a+long+leaf.">The shape of a long leaf.</a> Proceedings of the National Academy of Sciences. 106, 22049-22054 (2009).</li><li>Bayer, S. A., Altman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The human brain during the second trimester. , (2005).</li><li>Trujillo, V., Kim, J., Hayward, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Creasing+instability+of+surface-attached+hydrogels.">Creasing instability of surface-attached hydrogels.</a> Soft Matter. 4, 564 (2008).</li><li>Breid, D., Crosby, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+stress+state+on+wrinkle+morphology.">Effect of stress state on wrinkle morphology.</a> Soft Matter. 7, 4490 (2011).</li><li>Mora, T., Boudaoud, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Buckling+of+swelling+gels.">Buckling of swelling gels.</a> The European Physical Journal E. 20, 119-124 (2006).</li><li>DuPont, S. J., Cates, R. S., Stroot, P. G., Toomey, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Swelling-induced+instabilities+in+microscale,+surface-confined+poly(N-isopropylacryamide)+hydrogels.">Swelling-induced instabilities in microscale, surface-confined poly(N-isopropylacryamide) hydrogels.</a> Soft Matter. 6, 3876-3882 (2010).</li><li>Dervaux, J., Couder, Y., Guedeau-Boudeville, M. -. A., Ben Amar, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shape+Transition+in+Artificial+Tumors:+From+Smooth+Buckles+to+Singular+Creases.">Shape Transition in Artificial Tumors: From Smooth Buckles to Singular Creases.</a> Physical Review Letters. 107, 018103 (2011).</li><li>Jang, J. -. H., Koh, C. Y., Bertoldi, K., Boyce, M. C., Thomas, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combining+Pattern+Instability+and+Shape-Memory+Hysteresis+for+Phononic+Switching.">Combining Pattern Instability and Shape-Memory Hysteresis for Phononic Switching.</a> Nano Letters. 9, 2113-2119 (2009).</li><li>Lee, H., Zhang, J., Jiang, H., Fang, N. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prescribed+Pattern+Transformation+in+Swelling+Gel+Tubes+by+Elastic+Instability.">Prescribed Pattern Transformation in Swelling Gel Tubes by Elastic Instability.</a> Physical Review Letters. 108, 214304 (2012).</li><li>Sun, C., Fang, N., Wu, D. M., Zhang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Projection+micro-stereolithography+using+digital+micro-mirror+dynamic+mask.">Projection micro-stereolithography using digital micro-mirror dynamic mask.</a> Sensors and Actuators A: Physical. 121, 113-120 (2005).</li><li>Muskin, J., Ragusa, M., Gelsthorpe, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-Dimensional+Printing+Using+a+Photoinitiated+Polymer.">Three-Dimensional Printing Using a Photoinitiated Polymer.</a> Journal of Chemical Education. 87, 512-514 (2010).</li></ol>

No hay conflictos de interés declarado.

En hinchazón de hidrogel tubular limitada sobre el sustrato, la estabilidad depende sólo de t / h y el pandeo modo sólo depende de h / D 12. Cuatro grupos de muestras (I-IV) con diferentes niveles de espesor normalizado t / h fueron fabricados, con el grupo I es más grueso y el grupo IV de ser más delgado. Cada grupo consta de cuatro muestras (i-iv) con diferentes niveles de altura normalizada h / d, con la muestra i es más corto y la muestra iv ser más alto. Dimensiones de las muestras fabricadas se presentan en la Tabla 1. Grupo I y II están diseñados para permanecer estable durante el hinchamiento, mientras que los grupos III y IV están diseñados para doblarse y transformar al hincharse. Para las muestras de pandeo, Buckling modo debe disminuir con la altura de la muestra. Figura 3A muestra el resultado experimental. Como predice la teoría, las muestras del grupo I y II se mantuvieron estables y se mantuvo circular en la inflamación, mientras que las muestras del grupo III y IV, todos pasaron por la inestabilidad elástica y cinturón. Además, las muestras con el mismo h / D muestra el modo de pandeo similares. Figura 3B compara observados experimentalmente modos de pandeo de las muestras en el grupo III y IV con la predicción teórica. Podemos ver que las muestras con el mismo h / D presentan el mismo post-pandeo patrón independientemente de su grosor y que los resultados experimentales de acuerdo bien con la teoría. Se presenta cómo construir un sencillo sistema de escritorio 3D de impresión con un disponible en el mercado digital, proyector de datos. El enfoque propuesto se basa en fotocurado de polímero para construct estructuras 3D, y por lo tanto, cualquier polímeros fotocurables puede también ser utilizado en general, por lo que el fotoiniciador tiene absorbancia correspondiente en el rango de longitud de onda visible. Tenga en cuenta que muchos fotoiniciadores comercialmente disponibles están diseñados para ultra-violeta (UV) longitudes de onda, pero el fotoiniciador utilizado aquí tiene absorbancia relativamente mayor a longitudes de onda más largas que 400 nm. Ofrece una manera fácil y rápida de fabricar objetos 3D, este método se encuentra muchas aplicaciones en varios campos, incluyendo la mecánica de materiales blandos como se demuestra aquí.

<table border="1"><tbody><tr><td> Nombre del reactivo </td><td> Empresa </td><td> Número de catálogo </td><td> Comentarios (opcional) </td></tr><tr><td> El poli (etilenglicol) diacrilato </td><td> Sigma-Aldrich </td><td> 437441 </td><td> 575 Mw ~ </td></tr><tr><td> El poli (etilenglicol) </td><td> Sigma-Aldrich </td><td> P3015 </td><td> 200 Mw ~ </td></tr><tr><td> fenilbis (2,4,6-trimetilbenzoil) fosfina </td><td> Sigma-Aldrich </td><td> 511447 </td><td> Foto-iniciador </td></tr><tr><td> Sudán I </td><td> Sigma-Aldrich </td><td> 103624 </td><td> Foto-absorbedor </td></tr><tr><td> Los datos digitales proyector </td><td> Viewsonic </td><td> PJD6221 </td><td></td></tr><tr><td> Lente convexa </td><td> Thorlabs </td><td> LA1145 </td><td> f = 75,0 mm </td></tr><tr><td> Mirro </td><td></td><td></td><td> 4 &quot;oblea de silicio </td></tr><tr><td> Manual etapa </td><td> Velmex </td><td> A2506DE-S2.5 </td><td></td></tr></tbody></table>

micro 3d printing using a digital projector and its application in the study of soft materials mechanics

El pandeo es un tema clásico en la mecánica. Mientras pandeo mucho tiempo se ha estudiado como uno de los modos de fallo estructurales principales 1, recientemente ha llamado la atención de nuevo como un mecanismo único para la transformación patrón. La naturaleza está llena de ejemplos donde una gran cantidad de patrones exóticos se forman por 2-5 inestabilidad mecánica. Inspirado por este mecanismo elegante, muchos estudios han demostrado creación y la transformación de los patrones usando materiales blandos tales como elastómeros y los hidrogeles 6-11. Geles de hinchamiento son de particular interés debido a que puede espontáneamente provocar inestabilidad mecánica para crear varios patrones sin la necesidad de una fuerza externa 6-10. Recientemente, se ha reportado la demostración de un control total sobre el pandeo patrón de micro-escala geles tubulares con proyección micro-estereolitografía (PμSL), una de tres dimensiones (3D) de la tecnología de fabricación capaz de convertir rápidamente los modelos 3D generados por ordenador inPara objetos físicos en alta resolución 12,13. Aquí presentamos un método simple para construir un sistema simplificado PμSL usando un proyector digital disponible en datos para estudiar la inflamación inducida por la inestabilidad de pandeo para la transformación patrón controlado. Una impresora de escritorio 3D simple se construye utilizando un off-the-shelf datos digitales proyector y simples componentes ópticos tales como una lente convexa y un espejo 14. Imágenes transversales extraídas de un modelo sólido 3D se proyecta sobre la superficie de la resina fotosensible en secuencia, la polimerización de resina líquida en un sólido deseado estructura 3D de una forma capa por capa. Incluso con esta configuración simple y fácil proceso, arbitrarias objetos 3D se pueden fabricar fácilmente con una resolución de micras sub-100. Esta impresora 3D de escritorio tiene un potencial en el estudio de la mecánica de materiales blandos, ofreciendo una gran oportunidad de explorar diferentes geometrías 3D. Nosotros usamos este sistema para fabricaTE tubular estructura del hidrogel en forma de diferentes dimensiones. Fijada en la parte inferior para el sustrato, el gel tubular desarrolla estrés no homogénea durante la inflamación, lo que da lugar a la inestabilidad de pandeo. Varios patrones ondulados aparecen a lo largo de la circunferencia del tubo cuando las estructuras de gel someterse a pandeo. Experimento muestra que circunferencial pandeo de modo deseado se puede crear de una manera controlada. Transformación de patrones de tres dimensiones estructuradas geles tubulares tiene implicaciones importantes no sólo en la mecánica y ciencia de los materiales, sino también en muchos otros campos emergentes como matamaterials ajustables.

Un sistema simple PμSL utilizando un off-the-shelf digital de datos del proyector se muestra en la figura 1. Una lente convexa con una longitud focal de 75 mm se concentra el haz de iluminación en el área pequeña de 2 cm por 2 cm. Resultando en avión resolución óptica es de unos 45 m. La resolución vertical se determina por el nivel de precisión de la etapa lineal. Espesor de capa de las estructuras hechas para este estudio es de 160 micras. Cada capa se polimeriza para el 8 de iluminación de luz seg. Una estructura 3D representante fabricado por el sistema se muestra en la Figura 1D. Estos objetos se compone de 58 capas de PEGDA. Hemos preparado fotocurable hidrogel PEGDA. Reticulación bajo, por lo tanto, gran hinchazón, de hidrogel PEGDA se logró mediante la adición de PEG no reticulante en la solución de prepolímero. En sentido longitudinal de la relación de hinchamiento del hidrogel resultante PEGDA es 1,5, lo que corresponde a la expansión volumétrica superior a 300%. &gt; Un conjunto de tubos de hidrogel PEGDA se han diseñado y fabricado sobre la base de nuestra teoría 12. Colocamos una muestra al revés y poner en la bañera con agua cubierta con una capa de aceite en la parte superior como se ilustra en la Figura 2A. Dependiendo de los parámetros dimensionales, tubos circulares permanecido estable o transformados en un patrón ondulado como se muestra en la Figura 2B. La amplia variedad de hinchazón patrón de las diferentes muestras fue capturada por una cámara digital y se presenta en la Figura 3A. <img alt="Figura 1" src="/files/ftp_upload/4457/4457fig1.jpg" /> Figura 1. Una proyección desktop micro-sistema de estereolitografía (a) Representación esquemática (b) El sistema actual (c) vista cercana de los componentes (d) Representante de estructuras 3D. <a href="http://www.jove.com/files/ftp_upload/4457/4457fig1large.jpg" target="_blank">Haga clic aquí para ampliar la cifra</a> . tienda &quot;fo: keep-together.within-page =&quot; always &quot;&gt; <img alt="Figura 2" src="/files/ftp_upload/4457/4457fig2.jpg" /> Figura 2. (A) Montaje experimental para el tubo de hidrogel hinchazón (b) Tubo limitado hidrogel se transforma en diferentes patrones. Barra de escala indica 5 mm. <img alt="Figura 3" src="/files/ftp_upload/4457/4457fig3.jpg" /> Figura 3. (A) Los patrones formados en la hinchazón experimento. El eje vertical indica t / h (por lo tanto la estabilidad), y el eje horizontal indica h / D (por lo tanto el modo de pandeo). Barra de escala indica 5 mm. (B) el modo de pandeo depende sólo de h / D. Resultado experimental concuerda bien con la predicción teórica. <a href="http://www.jove.com/files/ftp_upload/4457/4457fig3large.jpg" target="_blank">Haga clic aquí para ampliar la cifra</a> . <table border="1"><tbody><tr><td colspan="2"> Ejemplo &lt;/ Strong&gt; </td><td> D (m) </td><td> t (micras) </td><td> h (m) </td></tr><tr><td rowspan="4"> Yo </td><td> yo </td><td> 9300 ± 420 </td><td> 760 ± 40 </td><td> 840 ± 40 </td></tr><tr><td> ii </td><td> 9700 ± 420 </td><td> 1040 ± 40 </td><td> 1060 ± 40 </td></tr><tr><td> iii </td><td> 9700 ± 420 </td><td> 1210 ± 40 </td><td> 1340 ± 40 </td></tr><tr><td> iv </td><td> 9700 ± 420 </td><td> 1660 ± 40 </td><td> 1680 ± 40 </td></tr><tr><td rowspan="4"> II </td><td> yo </td><td> 9000 ± 420 </td><td> 480 ± 40 </td><td> 880 ± 40 </td></tr><tr><td> ii </td><td> 9000 ± 420 </td><td&gt; 660 ± 40 </td><td> 1060 ± 40 </td></tr><tr><td> iii </td><td> 9500 ± 420 </td><td> 740 ± 40 </td><td> 1350 ± 40 </td></tr><tr><td> iv </td><td> 9200 ± 420 </td><td> 970 ± 40 </td><td> 1650 ± 40 </td></tr><tr><td rowspan="4"> III </td><td> yo </td><td> 8900 ± 420 </td><td> 160 ± 40 </td><td> 790 ± 40 </td></tr><tr><td> ii </td><td> 8900 ± 420 </td><td> 300 ± 40 </td><td> 1020 ± 40 </td></tr><tr><td> iii </td><td> 9100 ± 420 </td><td> 380 ± 40 </td><td> 1330 ± 40 </td></tr><tr><td> iv </td><td> 9000 ± 420 </td><td> 490 ± 40 </td><td> 1630 ± 40 </td></tr><tr><td rowspan="4"> IV </td><td> yo </td><td> 8900 ± 420 </td><td> 140 ± 40 </td><td> 780 ± 40 </td></tr><tr><td> ii </td><td> 8800 ± 420 </td><td> 190 ± 40 </td><td> 1010 ± 40 </td></tr><tr><td> iii </td><td> 9300 ± 420 </td><td> 230 ± 40 </td><td> 1340 ± 40 </td></tr><tr><td> iv </td><td> 8900 ± 420 </td><td> 290 ± 40 </td><td> 1650 ± 40 </td></tr></tbody></table> Tabla 1. Dimensiones de la muestra medido a través del microscopio óptico. Los errores indican incertidumbre de medición.

Watch this Scientific Journal Video about Micro 3D Printing Using a Digital Projector and its Application in the Study of Soft Materials Mechanics at JoVE.com

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

Demostramos transformación patrón controlado de tubos de gel de inflamación por la inestabilidad elástica. Una proyección simple micro estéreo-litografía de instalación se construye utilizando un off-the-shelf proyector digital de datos para fabricar estructuras tridimensionales poliméricos en forma de capa por capa. Hinchazón tubos de hidrogel de bajo restricción mecánica mostrar varios modos de pandeo circunferenciales según dimensión.

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

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

micro-3d-printing-using-digital-projector-its-application-study-soft

Research

Education

JoVE Journal

JoVE Core

Physics

Engineering

Unit 1

Equilibrium and Elasticity

SCIENTISTS IN ACTION

25.1K vistas.  Massachusetts Institute of Technology. Demostramos transformación patrón controlado de tubos de gel de inflamación por la inestabilidad elástica. Una proyección simple micro estéreo-litografía de instalación se construye utilizando un off-the-shelf proyector digital de datos para fabricar estructuras tridimensionales poliméricos en forma de capa por capa. Hinchazón tubos de hidrogel de bajo restricción mecánica mostrar varios modos de pandeo circunferenciales según dimensión.

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

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

La cuantificación de las concentraciones de hidrógeno en superficies e interfaces de capas y materiales a granel a través de perfiles de profundidad con el análisis de Reacción nuclear

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

Investigación

Ingeniería

Wicking Tests for Unidirectional Fabrics: Measurements of Capillary Parameters to Evaluate Capillary Pressure in Liquid Composite Molding Processes

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify their influence on void formation in composite parts. Wicking in a fibrous medium described by the Washburn equation was considered equivalent to a flow under the effect of capillary pressure according to the Darcy law. Experimental tests for the characterization of wicking were conducted with both carbon and flax fiber reinforcement. Quasi-unidirectional fabrics were then tested by means of a tensiometer to determine the morphological and wetting parameters along the fiber direction. The procedure was shown to be promising when the morphology of the fabric is unchanged during capillary wicking. In the case of carbon fabrics, the capillary pressure can be calculated. Flax fibers are sensitive to moisture sorption and swell in water. This phenomenon has to be taken into account to assess the wetting parameters. In order to make fibers less sensitive to water sorption, a thermal treatment was carried out on flax reinforcements. This treatment enhances fiber morphological stability and prevents swelling in water. It was shown that treated fabrics have a linear wicking trend similar to those found in carbon fabrics, allowing for the determination of capillary pressure.

An experimental method to measure geometrical parameters and the apparent advancing contact angles describing capillary wicking in unidirectional synthetic and natural fabrics is proposed. These parameters are mandatory for the determination of the capillary pressures that must be taken into account for liquid composite molding (LCM) applications.

Las pruebas de mecha para unidireccionales Tejidos: Las mediciones de parámetros para evaluar capilar capilar de presión en los procesos de líquido compuesto de moldeo

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify ...

Challenges in Rheological Characterization of Highly Concentrated Suspensions &#8212; A Case Study for Screen-printing Silver Pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching.
The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. 
Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. 
A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

Challenges in Rheological Characterization of Highly Concentrated Suspensions &amp;#8212; A Case Study for Screen-printing Silver Pastes

A protocol for a robust and application relevant rheological characterization of highly concentrated suspensions is presented. Silver pastes used for screen-printing application in solar cell production are employed as model systems.

Desafíos en reológico caracterización de suspensiones de alta concentración - Un estudio de caso para pastas de plata serigrafía

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the ...

A Soft Tooling Process Chain for Injection Molding of a 3D Component with Micro Pillars

The purpose of this paper is to present the method of a soft tooling process chain employing Additive Manufacturing (AM) for fabrication of injection molding inserts with micro surface features. The Soft Tooling inserts are manufactured by Digital Light Processing (vat photo polymerization) using a photopolymer that can withstand relatively high temperaturea. The part manufactured here has four tines with an angle of 60&#176;. Micro pillars (&#216;200 &#181;m, aspect ratio of 1) are arranged on the surfaces by two rows. Polyethylene (PE) injection molding with the soft tooling inserts is used to fabricate the final parts. This method demonstrates that it is feasible to obtain injection-molded parts with microstructures on complex geometry by additive manufactured inserts. The machining time and cost is reduced significantly compared to conventional tooling processes based on computer numerical control (CNC) machining. The dimensions of the micro features are influenced by the applied additive manufacturing process. The lifetime of the inserts determines that this process is more suitable for pilot production. The precision of the inserts production is limited by the additive manufacturing process as well.

A protocol for fabricating injection molding inserts for complex geometry with micro features on surfaces employing Additive Manufacturing (AM) is presented.

Pilares de una cadena de proceso de mecanizado suave para el moldeo de un componente 3D con Micro

The purpose of this paper is to present the method of a soft tooling process chain employing Additive Manufacturing (AM) for fabrication of injection ...

Studying Large Amplitude Oscillatory Shear Response of Soft Materials

We investigate the sequence of physical processes exhibited during large amplitude oscillatory shearing (LAOS) of polyethylene oxide (PEO) in dimethyl sulfoxide (DMSO) and xanthan gum in water &#8212; two concentrated polymer solutions used as viscosifiers in foods, enhanced oil recovery, and soil remediation. Understanding the nonlinear rheological behavior of soft materials is important in the design and controlled manufacturing of many consumer products. It is shown how the response to LAOS of these polymer solutions can be interpreted in terms of a clear transition from linear viscoelasticity to viscoplastic deformation and back again during a period. The LAOS results are analyzed via the fully quantitative Sequence of Physical Processes (SPP) technique, using free MATLAB-based software. A detailed protocol of performing a LAOS measurement with a commercial rheometer, analyzing nonlinear stress responses with the freeware, and interpreting physical processes under LAOS is presented. It is further shown that, within the SPP framework, a LAOS response contains information regarding the linear viscoelasticity, the transient flow curves, and the critical strain responsible for the onset of nonlinearity.

We present a detailed protocol outlining how to perform nonlinear oscillatory shear rheology on soft materials, and how to run the SPP-LAOS analysis to understand the responses as a sequence of physical processes.

Estudio de respuesta de cizalla oscilatoria de amplitud grande de materiales blandos

We investigate the sequence of physical processes exhibited during large amplitude oscillatory shearing (LAOS) of polyethylene oxide (PEO) in dimethyl ...

Multimodal 3D Printing of Phantoms to Simulate Biological Tissue

Biomedical optical imaging is playing an important role in diagnosis and treatment of various diseases. However, the accuracy and the reproducibility of an optical imaging device are greatly affected by the performance characteristics of its components, the test environment, and the operations. Therefore, it is necessary to calibrate these devices by traceable phantom standards. However, most of the currently available phantoms are homogeneous phantoms that cannot simulate multimodal and dynamic characteristics of biological tissue. Here, we show the fabrication of heterogeneous tissue-simulating phantoms using a production line integrating a spin coating module, a polyjet module, a fused deposition modeling (FDM) module, and an automatic control framework. The structural information and the optical parameters of a &#34;digital optical phantom&#34; are defined in a prototype file, imported to the production line, and fabricated layer-by-layer with sequential switch between different printing modalities. Technical capability of such a production line is exemplified by the automatic printing of skin-simulating phantoms that comprise the epidermis, dermis, subcutaneous tissue, and an embedded tumor.

Spin coating, polyjet printing, and fused deposition modeling are integrated to produce multilayered heterogeneous phantoms that simulate structural and functional properties of biological tissue.

Impresión 3D multimodal de fantasmas para simular tejido biológico

Biomedical optical imaging is playing an important role in diagnosis and treatment of various diseases. However, the accuracy and the reproducibility of ...

In Situ Transmission Electron Microscopy with Biasing and Fabrication of Asymmetric Crossbars Based on Mixed-Phased a-VOx

Resistive switching crossbar architecture is highly desired in the field of digital memories due to low cost and high-density benefits. Different materials show variability in resistive switching properties due to the intrinsic nature of the material used, leading to discrepancies in the field because of underlying operation mechanisms. This highlights a need for a reliable technique to understand mechanisms using nanostructural observations. This protocol explains a detailed process and methodology of in&#160;situ nanostructural analysis as a result of electrical biasing using transmission electron microscopy (TEM). It provides visual and reliable evidence of underlying nanostructural changes in real time memory operations. Also included is the methodology of fabrication and electrical characterizations for asymmetric crossbar structures incorporating amorphous vanadium oxide. The protocol explained here for vanadium oxide films can be easily extended to any other materials in a metal-dielectric-metal sandwiched structure. Resistive switching crossbars are predicted to serve the programmable logic and neuromorphic circuits for next-generation memory devices, given the understanding of the operation mechanisms. This protocol reveals the switching mechanism in a reliable, timely, and cost-effective way in any type of resistive switching materials, and thereby predicts the device&#39;s applicability.

In Situ Transmission Electron Microscopy with Biasing and Fabrication of Asymmetric Crossbars Based on Mixed-Phased a-VOx

Presented here is a protocol for analyzing nanostructural changes during in&#160;situ biasing with transmission electron microscopy (TEM) for a stacked metal-insulator-metal structure. It has significant applications in resistive switching crossbars for the next generation of programmable logic circuits and neuromimicking hardware, to reveal their underlying operation mechanisms and practical applicability.

Microscopía electrónica de transmisión in situ con sesgo y fabricación de travesaños asimétricos basados en fase mixta a-VOx

Resistive switching crossbar architecture is highly desired in the field of digital memories due to low cost and high-density benefits. Different ...

3D Printing - Evaluating Particle Emissions of a 3D Printing Pen

Three-dimensional (3D) printing as a type of additive manufacturing shows continuing increase in application and consumer popularity. The fused filament fabrication (FFF) is an inexpensive method used most frequently by consumers. Studies with 3D printers have shown that during the printing process particulate and volatile substances are released. Handheld 3D printing pens also use the FFF method but the consumer&#8217;s proximity to the 3D pens gives reason to higher exposure compared to a 3D printer. At the same time, 3D printing pens are often marketed for children who could be more sensitive to the printing emission. The aim of this study was to implement a low cost method to analyze the emissions of 3D printing pens. Polylactide (PLA) and acrylonitrile butadiene styrene (ABS) filaments of different colors were tested. In addition, filaments containing metal and carbon nanotubes (CNTs) were analyzed. An 18.5 L chamber and sampling close to the emission source was used to characterize emissions and concentrations near the breathing zone of the user.
Particle emissions and particle size distributions were measured and the potential release of metal particles and CNTs investigated. Particle number concentrations were found in a range of 105 - 106 particles/cm3, which is comparable to previous reports from 3D printers. Transmission electron microscopy (TEM) analysis showed nanoparticles of the different thermoplastic materials as well as of metal particles and CNTs. High contents of metal were observed by inductively coupled plasma mass spectrometry (ICP-MS).
These results call for a cautious use of 3D pens due to potential risk to the consumers.

This protocol presents a method to analyze the emission of 3D printing pens. Particle concentration and particle size distribution of the released particle is measured. Released particles are further analyzed with transmission electron microscopy (TEM). Metal content in filaments is quantified by inductively coupled plasma mass spectrometry (ICP-MS).

Impresión 3D - Evaluación de las emisiones de partículas de una pluma de impresión 3D

Three-dimensional (3D) printing as a type of additive manufacturing shows continuing increase in application and consumer popularity. The fused filament ...

Pneumatically Driven Microfluidic Platform for Micro-Particle Concentration

The present article introduces a method for fabricating and operating a pneumatic valve to control particle concentration using a microfluidic platform. This platform has a three-dimensional (3D) network with curved fluid channels and three pneumatic valves, which create networks, channels, and spaces through duplex replication with polydimethylsiloxane (PDMS). The device operates based on the transient response of a fluid flow rate controlled by a pneumatic valve in the following order: (1) sample loading, (2) sample blocking, (3) sample concentration, and (4) sample release. The particles are blocked by thin diaphragm layer deformation of the sieve valve (Vs) plate and accumulate in the curved microfluidic channel. The working fluid is discharged by the actuation of two on/off valves. As a result of the operation, all particles of various magnifications were successfully intercepted and disengaged. When this technology is applied, the operating pressure, the time required for concentration, and the concentration rate may vary depending on the device dimensions and particle size magnification.

The present protocol describes a pneumatic microfluidic platform that can be used for efficient microparticle concentration.

Plataforma microfluídica accionada neumáticamente para la concentración de micropartículas

The present article introduces a method for fabricating and operating a pneumatic valve to control particle concentration using a microfluidic platform. ...

Microfluidic Acoustophoresis for Flowthrough Separation of Gram-Negative Bacteria using Aptamer Affinity Beads

This article describes the fabrication and operation of microfluidic acoustophoretic chips using a microfluidic acoustophoresis technique and aptamer-modified microbeads that can be used for the fast, efficient isolation of Gram-negative bacteria from a medium. This method enhances the separation efficiency using a mix of long, square microchannels. In this system, the sample and buffer are injected into the inlet port through a flow controller. For bead centering and sample separation, AC power is applied to the piezoelectric transducer via a function generator with a power amplifier to generate acoustic radiation force in the microchannel. There is a bifurcated channel at both the inlet and outlet, enabling simultaneous separation, purification, and concentration. The device has a recovery rate of &gt;98% and purity of 97.8% up to a 10x dose concentration. This study has demonstrated a recovery rate and purity higher than the existing methods for separating bacteria, suggesting that the device can separate bacteria efficiently.

This paper describesthe fabrication and operation of microfluidic acoustophoretic chips using the microfluidic acoustophoresis technique and aptamer-modified microbeads that can be used for fast, efficient isolation of Gram-negative bacteria from a medium.