Gli autori desiderano ringraziare Giuseppe Muskin e Matthew Ragusa presso la University of Illinois a Urbana-Champaign per la fornitura di immagini in sezione trasversale per strutture 3D mostrato in figura 1D.

1. Preparazione della Soluzione Prepolimero <ol><li> Mix poli (etilene glicole) diacrilato (PEG-DA) (peso molecolare medio ~ 575, Sigma-Aldrich) e poli (etilene glicole) (PEG) (peso molecolare medio ~ 200, Sigma-Aldrich) a 1:2 rapporto in peso. </li><li> Aggiungere 0,67% in peso. foto-iniziatore (Phenylbis (2,4,6-trimetilbenzoil) fosfina, Sigma-Aldrich). La soluzione deve essere conservata in ambiente buio da questo punto. </li><li> Aggiungere 0,05% in peso. photo-assorbitore (Sudan I, Sigma-Aldrich). </li><li> Miscelare la soluzione per 24 ore a temperatura ambiente con un agitatore magnetico. </li></ol> 2. Installazione di una stampante desktop 3D Utilizzo di un proiettore di dati digitali <ol><li> Posizionare un proiettore digitale di dati su una posizione piana e stabile, e collegarlo a un computer con installato Microsoft PowerPoint. </li><li> Inserire un diritto convessa di fronte alla lente di uscita del fascio proiettore digitale. Scegli una lente convessa per rendere il piano focale di circa 10 cm di distanza dal proproiettore. (Risoluzione ottica diventa più piccola per un obiettivo con lunghezza focale più corta, ma si ha la necessità di riservare un po &#39;di spazio per componenti ottici.) </li><li> Posizionare uno specchio dopo la lente convessa sul percorso del fascio ad angolo 45 ° per dirigere il raggio verso il basso. </li><li> Posizionare un supporto del campione in corrispondenza del piano focale del fascio proiettato. Il supporto del campione deve essere collegato a una fase lineare che viene controllata la posizione verticale del supporto del campione. </li><li> Inserire un bagno di resina sotto il supporto del campione. </li></ol> 3. Progettazione e fabbricazione di tubi Gel <ol><li> Determinare diametro, spessore, e l&#39;altezza del tubo di gel da fabbricare. </li><li> Disegnare immagini in sezione trasversale per il tubo di gel. Le immagini devono essere in bianco su sfondo nero. Inserire questi immagine in diapositive di Microsoft PowerPoint. </li><li> Avvia la presentazione in Microsoft PowerPoint e proiettare qualsiasi immagine. Posizionare il supporto del campione nel piano focale regolando la posizione verticale usando attdoleva palco. </li><li> Passare a una immagine &quot;fittizia&quot; nero in modo che non ci sarà polimerizzazione indesiderati mettendo soluzione prepolimero. </li><li> Versare la soluzione prepolimero a bagno di resina. Riempire la vasca fino a quando la soluzione copre leggermente il supporto del campione. Ora è pronto per l&#39;oggetto di stampa 3D. </li><li> Passare alla diapositiva contenente la prima sezione trasversale immagine del tubo gel per polimerizzare il primo strato. Tenere proiettando l&#39;immagine per 8 secondi e tornare alla diapositiva &quot;blackout&quot;. </li><li> Ruotare la manopola sul palco lineare da ¼ di giro (~ 160 micron) per abbassare il porta-campioni. Ora resina fresca flussi a coprire il primo strato polimerizzato. </li><li> Proiettare l&#39;immagine in sezione trasversale di nuovo per polimerizzare il secondo strato sopra il procedimento uno. Ripetere i passaggi 3,6-3,8 finché il tubo gel dell&#39;altezza desiderata è fabbricato. </li><li> Una volta che tutti i livelli sono completi, sollevare il supporto del campione dalla soluzione prepolimero, e recuperare il campione fabbricato accuratamente con un rasoio blade. </li><li> Sciacquare il campione in acetone per circa 3 ore, e poi lasciare asciugare per ~ 1 ora. </li></ol> 4. Gonfiore Esperimento per la Formazione modello prescritto dal Instabilità elastica <ol><li> Preparare acqua-olio liquido a doppio strato in un piatto di vetro trasparente. </li><li> Fissare il campione secco su un portacampioni con colla super. </li><li> Capovolgere il supporto del campione in modo che il campione è a testa in giù. Immergere il campione in acqua-olio bagno liquido. Approccio al campione di acqua-olio di interfaccia dalla strato di olio. Il campione inizia a gonfiarsi quando il campione tocca la superficie dell&#39;acqua mentre la parte substrato di base su cui è stato fissato il tubo di gel stati in strato di olio superiore. In questo modo, l&#39;acqua può diffondersi nella parete del tubo permettendo il campione gonfiare prima la base vincolante rilassa bagnatura. Monitorare il cambio modello, come si gonfia tubo di gel utilizzando una fotocamera digitale. </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>

Nessun conflitto di interessi dichiarati.

In rigonfiamento di idrogel tubolare vincolato sul substrato, stabilità dipende solo t / h ed instabilità modalità dipende solo h / D 12. Quattro gruppi di campioni (I-IV) con diversi livelli di spessore normalizzato t / h sono stati realizzati, con il gruppo I di essere più spessa e di gruppo IV di essere più sottile. Ogni gruppo è composto da quattro campioni (I-IV) con diversi livelli di altezza normalizzata h / D, con il campione di essere i più brevi e il campione iv essere più alto. Dimensioni dei campioni fabbricati sono riportati in Tabella 1. Gruppo I e II sono progettati per rimanere stabile durante gonfiore, mentre il gruppo III e IV sono progettati per trasformare su fibbia e gonfiore. Per i campioni di instabilità, Buckling modalità dovrebbe diminuire con l&#39;altezza del campione. Figura 3A mostra risultato sperimentale. Come teoria predice, i campioni del gruppo I e II erano stabili e rimasero circolare sul gonfiore, mentre i campioni del gruppo III e IV, tutto è andato per l&#39;instabilità elastica e deformata. Inoltre, campioni con lo stesso h / D mostrati come modalità di carico di punta. 3B Figura confronta osservati sperimentalmente modi di instabilità di campioni nel gruppo III e IV con previsione teorica. Possiamo vedere che i campioni con lo stesso h / D rappresentano la stessa post-critico modello indipendentemente dallo spessore e che i risultati sperimentali sono in accordo con la teoria. Vi presentiamo come costruire un semplice sistema desktop 3D di stampa facendo uso di un proiettore di dati digitali. L&#39;approccio proposto si basa su fotoindurente di polimero per confermarestruct strutture 3D, e pertanto, eventuali polimeri fotoreticolabili può essere utilizzato anche in generale, per quanto riguarda il fotoiniziatore ha assorbanza appropriata lunghezza d&#39;onda visibile. Notare che molti fotoiniziatori disponibili in commercio sono progettati per ultravioletta (UV) lunghezze d&#39;onda, ma il fotoiniziatore usato qui è relativamente più elevata assorbanza a lunghezze d&#39;onda superiori a 400 nm. Offre un modo facile e rapido per fabbricare oggetti 3D, questo metodo si trovano molte applicazioni in vari campi tra cui la meccanica di materiali morbidi come dimostrato qui.

<table border="1"><tbody><tr><td> Nome del reagente </td><td> Azienda </td><td> Numero di catalogo </td><td> Commenti (opzionale) </td></tr><tr><td> Poli (etilene glicole) diacrilato </td><td> Sigma-Aldrich </td><td> 437441 </td><td> ~ 575 Mw </td></tr><tr><td> Poli (etilene glicole) </td><td> Sigma-Aldrich </td><td> P3015 </td><td> ~ 200 Mw </td></tr><tr><td> phenylbis (2,4,6-trimetilbenzoil) fosfina </td><td> Sigma-Aldrich </td><td> 511447 </td><td> Photo-iniziatore </td></tr><tr><td> Sudan I </td><td> Sigma-Aldrich </td><td> 103624 </td><td> Photo-assorbitore </td></tr><tr><td> Dati digitali proiettore </td><td> Viewsonic </td><td> PJD6221 </td><td></td></tr><tr><td> Convex lente </td><td> Thorlabs </td><td> LA1145 </td><td> f = 75,0 millimetri </td></tr><tr><td> Mirro </td><td></td><td></td><td> 4 &quot;wafer di silicio </td></tr><tr><td> Fase manuale </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

Carico di punta è un tema classico della meccanica. Mentre instabilità è stato a lungo studiato come uno dei principali modi di guasto strutturali 1, ha recentemente attirato l&#39;attenzione come un nuovo meccanismo unico per la trasformazione pattern. La natura è piena di questi esempi in cui un gran numero di modelli esotici si formano per 2-5 instabilità meccanica. Ispirato da questo meccanismo elegante, molti studi hanno dimostrato la creazione e la trasformazione dei modelli che utilizzano materiali morbidi come elastomeri e idrogel 6-11. Gel gonfiore sono di particolare interesse perché possono innescare spontaneamente instabilità meccanica per generare i vari modelli senza bisogno di forza esterna 6-10. Recentemente, abbiamo riportato la dimostrazione di pieno controllo instabilità modello di gel tubolari micro-scala con proiezione micro-stereolitografia (PμSL), a tre dimensioni (3D), la tecnologia di produzione in grado di convertire rapidamente i modelli di 3D generati into degli oggetti fisici ad alta risoluzione 12,13. Qui vi presentiamo un metodo semplice per costruire un sistema semplificato PμSL facendo uso di un proiettore digitale di dati per lo studio gonfiore indotto instabilità instabilità per la trasformazione modello controllato. Una stampante desktop semplice 3D è costruito utilizzando un off-the-shelf dati digitali proiettore e semplici componenti ottici, come una lente convessa e uno specchio 14. Trasversali immagini estratte da un modello solido 3D viene proiettato sulla superficie di resina fotosensibile in sequenza, polimerizzazione resina liquida in una desiderata struttura 3D solida in un layer-by-layer moda. Anche con questa configurazione semplice e processo facile, arbitrari oggetti 3D possono essere facilmente realizzati con sub-risoluzione di 100 micron. Questa stampante desktop 3D rappresenta un potenziale per lo studio della meccanica dei materiali morbidi, offrendo una grande opportunità di esplorare varie geometrie 3D. Usiamo questo sistema per fabricate struttura tubolare a forma di idrogel con dimensioni diverse. Fissato sul fondo al substrato, il gel tubolare sviluppa durante lo stress disomogeneo gonfiore, che dà luogo a instabilità instabilità. Vari motivi ondulati appaiono lungo la circonferenza del tubo quando le strutture gel subiscono deformazioni. Esperimento mostra che la deformazione circonferenziale del modo desiderato può essere creato in modo controllato. Trasformazione del modello tridimensionale gel strutturati tubolari ha implicazioni significative non solo in meccanica e scienza dei materiali, ma anche in molti altri settori emergenti come la matamaterials sintonizzabili.

Un sistema semplice PμSL utilizzando un off-the-shelf dati digitali proiettore è mostrato in Figura 1. Una lente convessa con una lunghezza focale di 75 mm concentra il fascio in piccola area di illuminazione di 2 cm x 2 cm. Con conseguente piano risoluzione ottica è di circa 45 micron. Risoluzione verticale è determinata dal livello di precisione della fase lineare. Spessore dello strato delle strutture realizzate per questo studio è di 160 micron. Ogni strato è stato polimerizzato per 8 illuminazione luce sec. Una struttura 3D rappresentante fabbricata dal sistema è mostrato in figura 1D. Questi oggetti consiste di 58 strati di PEGDA. Abbiamo preparato fotoinduribile idrogel PEGDA. Reticolazione bassa, gonfiore quindi grande, di idrogel PEGDA è stata ottenuta aggiungendo non reticolazione PEG in soluzione di prepolimero. Nel senso della lunghezza del rapporto di rigonfiamento dell&#39;idrogel risultante PEGDA è 1,5, che corrisponde a volumetrica superiore al 300% di espansione. &gt; Una serie di tubi di idrogel PEGDA sono stati progettati e realizzati sulla base delle nostre 12 teoria. Abbiamo posto un campione capovolto e messo nella vasca con acqua coperto con strato di olio sopra come illustrato nella Figura 2A. A seconda dei parametri dimensionali, tubi circolari sia rimasta stabile o trasformato in un disegno ondulato come mostrato nella figura 2B. La varietà di gonfiore modello di diversi campioni è stata catturata da una telecamera digitale e presentata in Figura 3A. <img alt="Figura 1" src="/files/ftp_upload/4457/4457fig1.jpg" /> Figura 1. Un desktop proiezione micro-sistema di stereolitografia (a) rappresentazione schematica (b) sistema attuale (c) vista ravvicinata dei componenti (d) rappresentative strutture 3D. <a href="http://www.jove.com/files/ftp_upload/4457/4457fig1large.jpg" target="_blank">Clicca qui per ingrandire la figura</a> . tenda &quot;fo: keep-together.within-page =&quot; always &quot;&gt; <img alt="Figura 2" src="/files/ftp_upload/4457/4457fig2.jpg" /> Figura 2. (A) Apparato sperimentale per tubo idrogel gonfiore (b) tubo di idrogel vincolato trasforma in diversi modelli. Barra della scala indica 5 mm. <img alt="Figura 3" src="/files/ftp_upload/4457/4457fig3.jpg" /> Figura 3. (A) Patterns formata in gonfiore esperimento. Asse verticale indica t / h (così la stabilità), e l&#39;asse orizzontale indica h / D (quindi buckling mode). Barra della scala indica 5 mm. (B) modalità di carico di punta dipende solo h / D. Risultato sperimentale ben si accorda con previsione teorica. <a href="http://www.jove.com/files/ftp_upload/4457/4457fig3large.jpg" target="_blank">Clicca qui per ingrandire la figura</a> . <table border="1"><tbody><tr><td colspan="2"> Esempio &lt;/ Strong&gt; </td><td> D (pm) </td><td> t (um) </td><td> h (um) </td></tr><tr><td rowspan="4"> Io </td><td> Io </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> Io </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> Io </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> Io </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> Tabella 1. Dimensioni del campione misurato con microscopio ottico. Gli errori indicano incertezza di misura.

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

Dimostriamo trasformazione controllata modello di tubi gel gonfiore da instabilità elastica. Una semplice proiezione micro stereo-litografia di installazione è costruita con un off-the-shelf dati digitali proiettore per fabbricare strutture polimeriche tridimensionali in uno strato per strato moda. Gonfiore tubi idrogel sotto vincolo meccanico visualizzare varie modalità circonferenziali instabilità seconda dimensione.

Micro 3D Stampa con un proiettore digitale e la sua applicazione nello studio della meccanica dei materiali morbidi

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 Views.  Massachusetts Institute of Technology. Dimostriamo trasformazione controllata modello di tubi gel gonfiore da instabilità elastica. Una semplice proiezione micro stereo-litografia di installazione è costruita con un off-the-shelf dati digitali proiettore per fabbricare strutture polimeriche tridimensionali in uno strato per strato moda. Gonfiore tubi idrogel sotto vincolo meccanico visualizzare varie modalità circonferenziali instabilità seconda dimensione.

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 quantificazione delle concentrazioni di idrogeno in superficie e di interfaccia Livelli e materiale sfuso attraverso profili di profondità con l&#39;analisi reazione nucleare

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

Ricerca

Ingegneria

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 Test per unidirezionali Tessuti: Misure di capillare parametri per valutare capillare pressione nei Processi Liquid Composite Molding

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.

Le sfide in reologico Caratterizzazione di sospensioni altamente concentrato - un caso di studio per la serigrafia paste d&#39;argento

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.

Una catena di processo utensili morbido per lo stampaggio di un componente 3D con Micro pilastri

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.

Studiare la risposta di Shear oscillatorio di grande ampiezza di materiali morbidi

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.

Stampa 3D multimodale di fantasmi per simulare il tessuto biologico

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.

Microscopia elettronica a trasmissione in situ con distorsione e fabbricazione di traverse asimmetriche basate su a -VO x afasemista

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).

Stampa 3D - Valutazione delle emissioni di particelle di una penna da stampa 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.

Piattaforma microfluidica pneumatica per la concentrazione di microparticelle

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.