Os autores gostariam de agradecer a Joseph Muskin e Mateus Ragusa, na Universidade de Illinois em Urbana-Champaign para fornecer imagens transversais de estruturas 3D mostrados na Figura 1D.

1. Preparação da solução de pré-polímero <ol><li> Mistura poli (etileno glicol) diacrilato (PEG-DA) (peso molecular médio ~ 575, Sigma-Aldrich) e poli (etileno glicol) (PEG) (peso molecular médio ~ 200, Sigma-Aldrich) em razão 1:2 em peso. </li><li> Adicionar 0,67% em peso. foto-iniciador (Phenylbis (2,4,6-trimetilbenzoil) fosfina, Sigma-Aldrich). A solução deve ser mantida em ambiente escuro a partir deste ponto. </li><li> Adicionar 0,05% em peso. foto-absorvente (Sudan I, Sigma-Aldrich). </li><li> Misture a solução durante 24 horas à temperatura ambiente usando um agitador magnético. </li></ol> 2. Configurando uma impressora 3D Desktop Usando um projetor digital de dados <ol><li> Coloque um digital projetor de dados em uma posição plana e estável, e conectá-lo a um computador com o Microsoft PowerPoint instalado. </li><li> Coloque uma lente convexa para a direita em frente da lente do feixe de saída do projector digital. Escolha de uma lente convexa para tornar o plano focal de cerca de 10 cm de distância da proprojetor. (Resolução óptica torna-se menor para uma lente com distância focal menor, mas é preciso reservar algum espaço para os componentes ópticos.) </li><li> Colocar um espelho após a lente convexa no caminho do feixe em ângulo de 45 ° para dirigir o feixe para baixo. </li><li> Colocar um suporte de amostra no plano focal do feixe projectado. O suporte de amostra deve ser ligado a uma fase linear, através da qual a posição vertical do suporte da amostra é controlada. </li><li> Colocar num banho de resina de baixo do suporte de amostras. </li></ol> 3. Projeto e fabricação de tubos de gel <ol><li> Determinar o diâmetro, espessura da parede, e a altura do tubo de gel a ser fabricado. </li><li> Desenhar imagens transversais para o tubo de gel. As imagens devem ser em branco com fundo preto. Inseri-las de imagem em slides do Microsoft PowerPoint. </li><li> Iniciar apresentação de slides no Microsoft PowerPoint e projectar qualquer imagem. Colocar o suporte da amostra no plano focal, ajustando a posição vertical, utilizando attdoía palco. </li><li> Mudar para uma imagem &quot;dummy&quot; preto de modo que não haverá polimerização indesejada ao colocar solução de pré-polímero. </li><li> Despeje a solução de pré-polímero banho de resina. Encher o banho até a solução ligeiramente cobre o suporte da amostra. Agora ele está pronto para o objeto 3D de impressão. </li><li> Mudar para a lâmina que contém a imagem da secção transversal do tubo do primeiro gel para polimerizar a primeira camada. Mantenha projetar a imagem para 8 seg e voltar para o &quot;apagão&quot; de slides. </li><li> Gire o botão no palco linear por ¼ de volta (~ 160 pm) para reduzir o suporte da amostra. Agora resina fresca flui para cobrir a camada polimerizada em primeiro lugar. </li><li> Projectar a imagem da secção transversal de novo para polimerizar a segunda camada no topo de um processo. Repita os passos 3,6-3,8 até que o tubo de gel de a altura desejada é fabricado. </li><li> Uma vez que todas as camadas estão completos, levantar o suporte da amostra para fora da solução de pré-polímero, e recuperar a amostra fabricada cuidadosamente usando uma navalha blade. </li><li> Lavar a amostra em acetona para ~ 3 horas, e depois deixe-o secar por ~ 1 hora. </li></ol> 4. Inchaço Experiência de Formação padrões prescritos pela instabilidade elástica <ol><li> Preparar água-óleo líquido de camada dupla em um prato de vidro transparente. </li><li> Fixe a amostra seca em um suporte de amostra usando super cola. </li><li> Virar o suporte de amostras de modo a que a amostra é de cabeça para baixo. Imergir a amostra no banho de água-óleo líquido. Aproximar a amostra a água-óleo de interface da camada de óleo. A amostra começa a inchar quando a amostra atinge a superfície da água, enquanto que a parte do substrato de base no qual o tubo de gel foi fixado esteve no topo da camada de óleo. Deste modo, a água pode difundir-se a parede do tubo permitindo que a amostra incham antes da base restringindo relaxa por molhagem. Monitorar a mudança de padrão, como as ondas de gel tubo com uma câmera 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>

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Em inchaço hidrogel tubular restringida sobre o substrato, estabilidade depende apenas t / h e o modo de deformação depende apenas de h / D 12. Quatro grupos de amostras (I-IV) com níveis diferentes de espessura normalizada t / h foram fabricados, com o grupo I de ser mais espessa e grupo IV sendo mais delgada. Cada grupo é composto por quatro amostras (I-IV) com diferentes níveis de altura normalizada h / D, com a amostra i ser mais curto e a amostra iv ser mais alto. Dimensões das amostras fabricadas são apresentados na Tabela 1. Grupo I e II são concebidos para permanecer estável durante o inchamento, enquanto que o grupo III e IV destinam-se a fivela e transformar mediante inchamento. Para amostras de flambagem, Buckling modo deve diminuir com a altura da amostra. Figura 3A mostra o resultado experimental. Como a teoria prevê, as amostras do grupo I e II eram estáveis ​​e permaneceram circular sobre o inchamento, enquanto que as amostras do grupo III e IV tudo passou por instabilidade elástica e dobraram. Além disso, as amostras com o mesmo h / D exibido o modo de deformação semelhante. Figura 3B compara observados experimentalmente modos de instabilidade de amostras do grupo III e IV, com a previsão teórica. Podemos ver que as amostras com o mesmo h / D representam o padrão de pós-flambagem mesmo, independentemente da espessura e que os resultados experimentais concordam bem com a teoria. Nós apresentamos como construir uma simples área de trabalho do sistema de impressão 3D usando uma disponíveis comercialmente dados digitais projetor. A abordagem proposta baseia-se na fotopolimerização de polímero de construct estruturas 3D, e, portanto, quaisquer polímeros fotocurável podem ser também utilizados, em geral, na medida em que o fotoiniciador tem absorvância apropriado na faixa de comprimento de onda visível. Note-se que muitas fotoiniciadores comercialmente disponíveis são concebidos para ultra-violeta (UV) comprimentos de onda, mas o fotoiniciador utilizado aqui tem absorvância relativamente mais elevada em comprimentos de onda maiores que 400 nm. Oferecendo uma maneira fácil e rápida para fabricar objetos 3D, esse método irá encontrar muitas aplicações em vários campos, incluindo a mecânica materiais macios como demonstrado aqui.

<table border="1"><tbody><tr><td> Nome do reagente </td><td> Companhia </td><td> Número de catálogo </td><td> Comentários (opcional) </td></tr><tr><td> Poli (etileno glicol) diacrilato </td><td> Sigma-Aldrich </td><td> 437441 </td><td> Mw ~ 575 </td></tr><tr><td> Poli (etileno glicol) </td><td> Sigma-Aldrich </td><td> P3015 </td><td> Mw ~ 200 </td></tr><tr><td> phenylbis (2,4,6-trimetilbenzoil) óxido de fosfina </td><td> Sigma-Aldrich </td><td> 511447 </td><td> Foto-iniciador </td></tr><tr><td> Sudan I </td><td> Sigma-Aldrich </td><td> 103624 </td><td> Foto-absorvente </td></tr><tr><td> Digital projetor de dados </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 milímetros </td></tr><tr><td> Mirrou </td><td></td><td></td><td> 4 &quot;bolacha de silício </td></tr><tr><td> Estágio manual </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

Flambagem é um tema clássico em mecânica. Enquanto flambagem tem sido estudado como um dos principais modos de falhas estruturais 1, apresentou recentemente um novo chamado a atenção como um mecanismo único para transformação padrão. A natureza é cheia de exemplos onde uma grande variedade de padrões exóticos são formados por 2-5 instabilidade mecânica. Inspirado por este mecanismo elegante, muitos estudos têm demonstrado criação e transformação de padrões usando materiais suaves, como elastômeros e hidrogéis 6-11. Géis inchamento são de interesse particular porque podem provocar instabilidade mecânica espontaneamente para criar vários padrões, sem a necessidade de uma força externa 6-10. Recentemente, relatou demonstração de controle total sobre flambagem padrão de micro-escala géis tubulares usando projeção micro-estereolitografia (PμSL), uma imagem tridimensional da tecnologia de fabricação (3D) capaz de converter rapidamente gerados por computador modelos 3D into objetos físicos em alta resolução 12,13. Aqui apresentamos um método simples para construir um sistema simplificado PμSL utilizar um produto digital, projetor de dados para estudar inchaço induzido por instabilidade flambagem para a transformação padrão controlado. Uma impressora de mesa 3D simples é construído usando um off-the-shelf digital, projetor de dados e simples componentes ópticos, como uma lente convexa e um espelho de 14. Imagens transversais extraídos a partir de um modelo 3D sólido é projectado sobre a superfície da resina fotossensível em sequência, a polimerização de resina líquida a uma desejada estrutura 3D de uma forma sólida de camada por camada. Mesmo com essa configuração simples e processo fácil, arbitrárias objetos 3D podem ser facilmente fabricados com sub-resolução de 100 m. Esta impressora desktop 3D tem um potencial no estudo da mecânica material macio, oferecendo uma grande oportunidade para explorar várias geometrias 3D. Usamos este sistema para fabricate tubular em forma de hidrogel estrutura com dimensões diferentes. Fixada na parte inferior do substrato, o gel tubular desenvolve o stress não homogéneo durante o inchaço, o que dá origem a instabilidade de flambagem. Vários padrões ondulados aparecem ao longo da circunferência do tubo, quando as estruturas de gel sofrer flambagem. Experimento mostra que circunferencial encurvadura de modo desejado, pode ser criado de forma controlada. Transformação padrão de tridimensionalmente estruturados géis tubulares tem implicação importante não só em mecânica e ciência dos materiais, mas também em muitos outros campos emergentes, como matamaterials ajustáveis.

Um sistema simples PμSL usando um off-the-shelf projector de dados digital é mostrado na Figura 1. Uma lente convexa com uma distância focal de 75 mm concentra o feixe de iluminação para a área pequena de 2 cm por 2 cm. Resultando em avião resolução óptica é de aproximadamente 45 m. Resolução vertical é determinado pelo nível de precisão de fase linear. Espessura da camada das estruturas feitas para este estudo é de 160 ^ m. Cada camada foi polimerizada para iluminação de luz 8 seg. A estrutura 3D representativa fabricada pelo sistema é mostrado na Figura 1D. Este objeto consiste de 58 camadas de PEGDA. Preparamos fotocurável hidrogel PEGDA. Reticulação baixa, inchaço, portanto, de grande porte, de hidrogel PEGDA foi conseguido pela adição de PEG não reticulado em solução de pré-polímero. Longitudinalmente relação inchamento do hidrogel PEGDA resultante é 1,5, o que corresponde a 300% maior do que a expansão volumétrica. &gt; Um conjunto de tubos de hidrogel PEGDA foram concebidos e fabricados com base na nossa teoria 12. Colocámos uma amostra de cabeça para baixo e colocado no banho de água coberto com uma camada de óleo no topo, como ilustrado na Figura 2A. Dependendo dos parâmetros dimensionais, tubos circulares permaneceu estável ou transformados em um padrão ondulado como ilustrado na Figura 2B. A grande variedade de inchaço padrão de amostras diferentes foi capturada por uma câmara digital e apresentadas na Figura 3A. <img alt="Figura 1" src="/files/ftp_upload/4457/4457fig1.jpg" /> Figura 1. Uma área de trabalho sistema de projeção micro-estereolitografia (a) representação esquemática (b) sistema real (c) close-up de componentes (d) representante estruturas 3D. <a href="http://www.jove.com/files/ftp_upload/4457/4457fig1large.jpg" target="_blank">Clique aqui para ver maior figura</a> . tenda &quot;fo: manter-together.within-page =&quot; always &quot;&gt; <img alt="Figura 2" src="/files/ftp_upload/4457/4457fig2.jpg" /> Figura 2. (A) a instalação experimental para o tubo de hidrogel inchaço (b) Tubo de hidrogel constrangido transforma em padrões diferentes. Barra de escala indica 5 mm. <img alt="Figura 3" src="/files/ftp_upload/4457/4457fig3.jpg" /> Figura 3. (A) Patterns formada em inchaço experimento. Eixo vertical indica t / h (assim a estabilidade) e, em eixo horizontal indica h / D (assim flambagem modo). Barra de escala indica 5 mm. (B) Flambagem modo depende apenas de h / D. Resultado experimental está de acordo com a previsão teórica. <a href="http://www.jove.com/files/ftp_upload/4457/4457fig3large.jpg" target="_blank">Clique aqui para ver maior figura</a> . <table border="1"><tbody><tr><td colspan="2"> Amostra &lt;/ Strong&gt; </td><td> D (mm) </td><td> t (mm) </td><td> h (mm) </td></tr><tr><td rowspan="4"> Eu </td><td> Eu </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> Eu </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> Eu </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> Eu </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> As dimensões da tabela 1. Amostra medida através de microscópio óptico. Erros indicam incerteza de medição.

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

Demonstramos transformação padrão controlado de tubos de gel de inchamento pela instabilidade elástica. Um simples projecção de configuração estéreo-litografia micro é construído usando um off-the-shelf projector de dados digitais para o fabrico de estruturas tridimensionais poliméricas de uma forma de camada por camada. Inchaço tubos de hidrogel sob constrangimento mecânico exibir vários modos de instabilidade circunferenciais, dependendo da dimensão.

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 ...

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Unit 1

Equilibrium and Elasticity

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25.1K visualizações.  Massachusetts Institute of Technology. Demonstramos transformação padrão controlado de tubos de gel de inchamento pela instabilidade elástica. Um simples projecção de configuração estéreo-litografia micro é construído usando um off-the-shelf projector de dados digitais para o fabrico de estruturas tridimensionais poliméricas de uma forma de camada por camada. Inchaço tubos de hidrogel sob constrangimento mecânico exibir vários modos de instabilidade circunferenciais, dependendo da dimensão.

Vídeo: 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.

Quantificação de concentrações de hidrogénio nas camadas superficiais e interface e materiais a granel através de perfis de profundidade com Análise reação 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 ...

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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.

Wicking testes para unidirecionais Tecidos: Medidas de capilar parâmetros para avaliar a pressão capilar em Processos Líquido Composite Moldagem

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.

Desafios na reológico Caracterização de suspensões altamente concentrado - um estudo de caso para-impressão da tela de prata Cola

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.

Uma cadeia de processo de ferramental macio para moldagem por injeção de um componente 3D com Micro pilares

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.

Estudar a resposta de grande Amplitude oscilatória de materiais macios

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.

Impressão 3D multimodal de fantasmas para simular tecido 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.

In Situ Transmission Electron Microscopy with Biasing and Fabrication ofAssimetric Crossbars Based on Mix-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 ...

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).

Impressão 3D - Avaliando emissões de partículas de uma caneta de impressão 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 pneumática para concentração 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.