Agradecemos à Fundação Lindback de apoio financeiro, e Dr. Alexandre Sidorenko e Elza Chu para discussões frutíferas e assistência técnica, eo professor Robert Smith para a assistência com o C. Os ensaios de elegans.

NOTA: Nos procedimentos descritos a seguir, as diretrizes de segurança do laboratório deve ser sempre seguido. De particular importância é a segurança quando se lida com alta voltagem (&gt; 500 V) e de manuseamento de produtos químicos. 1. revestimento de um substrato condutor com vela Fuligem <ol><li> Cobre corte de metal em retângulos (75 x 43 mm, 0,5 mm de espessura). Limpe cada substrato de cobre por imersão em etchant cobre por cerca de 30 segundos, lavar com água corrente por cerca de 20 segundos, e seque com papel. NOTA: Se estiver usando o método 1 a seguir, alterar as dimensões de 75 x 25 mm para caber na máquina. </li><li> Varrer uma vela de parafina iluminada sob o substrato de cobre durante 30-45 segundos, para se obter um revestimento de fuligem aproximadamente uniforme (cerca de 40 um de espessura). Mantenha o substrato em ~ 1 cm para dentro da chama. Não toque na superfície fuligem frágil. </li></ol> 2. Proteger a camada de fuligem com Revestimento NOTA: A camada de fuligem é muito frágil, E devem ser revestidos para protecção. Duas alternativas simples (métodos 1 e 2 abaixo) são sugeridos aqui, mas protocolos mais robustos estão atualmente em desenvolvimento. <ol><li> Método 1 <ol><li> Coloque a amostra para o evaporador de metal ou de sistema de pulverização. Seguindo os procedimentos de funcionamento do sistema, evacuar a câmara, e começar a deposição controlada de ouro sobre a camada de fuligem (150-200 nm). Deixe o dispositivo de arrefecer até à temperatura ambiente. </li><li> Dip-revestir o substrato metalizado em uma solução de 1-dodecanotiol (1% v / v, em etanol a 95%, ACS / grau USP), durante 10 minutos dentro de uma capa química. Então, segurando o aparelho em um ângulo perto de 60 °, lavar cuidadosamente a superfície com várias gotas de etanol só. Deixe os dispositivos seca, durante a noite. </li></ol></li><li> Método 2 <ol><li> Em uma capa de química, imediatamente depois do revestimento do substrato com a fuligem e ao mesmo tempo o substrato ainda está quente da chama da vela, depositar algumas gotas de líquido fluorado sobre um lado dosubstrato, e inclinar o substrato a um ângulo próximo de 90 °. Deposite mais gotas, e deixá-los rolar sobre a superfície inteira fuligem. NOTA: Quando a gota cai em um ponto, a fuligem serão lavados daquela área. Deixe as gotículas de líquido propagação fluorado, tanto quanto possível. </li><li> Asse o substrato sobre uma placa quente (160 ° C durante 15 min) no interior de uma capa química. </li><li> Deixe o substrato se sentar durante a noite à temperatura ambiente antes do uso. Armazenar indefinidamente. </li></ol></li></ol> (12 Adaptado de Abdelgawad et al.) 3. Fabricação de Top Eletrodos <ol><li> Desenhe os eletrodos utilizando software de design gráfico. Cada eletrodo é de 2 mm de comprimento, 0,3 mm de largura, ea diferença entre os eletrodos é de 0,3 mm. A diferença entre contatos (para encaixar no conector, veja abaixo) é de 2,3 mm (Figura 1). </li><li> Apare um laminado de cobre flexível (35 mm de espessura) para o formato Monarch (3,87 x 7,5 polegadas). Use outros tamanhos if compatível com a impressora. Coloque o laminado na bandeja de alimentação manual de uma impressora colorida. </li><li> Certifique-se de usar o &quot;preto rico&quot;, ou &quot;Registro de preto&quot;, ao imprimir na folha de cobre (ver 12 Abdelgawad et al. Para mais detalhes) para permitir que uma camada mais densa de tinta preta sobre o substrato de cobre, protegendo o padrão impresso durante gravura . Deixe o substrato seco impresso completamente, durante a noite. </li><li> Dentro de uma capa química, aquecer (40 ° C) num copo com 50 ml de produto corrosivo de cobre. Mergulhe o laminado impresso no copo e agite-o na solução por cerca de 10 min. Tempo de condicionamento depende da solução de produto corrosivo de cobre. A cada poucos minutos, verifique a corrosão e ver se o padrão está intacta. </li><li> Cuidadosamente lavar o laminado com água, e remover o revestimento com acetona e etanol na capa química. Lavar uma vez, e seca suavemente com a toalha de papel laminado. </li><li> Cuidadosamente anexar o laminado com eletrodos a uma ABLslides ss (75 x 25 mm, ~ 1 mm de espessura), usando fita dupla face. Evite bolsas de ar. </li><li> Anexar um filme de perfluoroalcoxi PFA aos eletrodos utilizando fita. Isso serve para evitar o contato acidental dos eletrodos com a gota, o que prejudica top eletrodos devido a curto-circuito. </li></ol> 4. A interface eletrônica (circuito na Figura 2) <ol><li> Soldar os relés e os capacitores C a uma placa de circuito universal. </li><li> Monte o restante dos 10 pilotos de revezamento em uma placa de ensaio sem solda para circuitos eletrônicos. </li><li> Fio de entrada de cada motorista relé para um canal na placa de controle. </li><li> Tirar com cuidado os melhores eletrodos em um conector (Figura 3). Fio condutor de saída de cada retransmissão a um eléctrodo de topo, como mostrado na figura. Note que existe um contato do conector aterrado entre um par de fios de relés, para minimizar o ruído elétrico. NOTA: O conector fica em uma plataforma ajustável para controlar tele distância (0,1-0,5 mm) entre o substrato superior e inferior (fuligem-revestido). </li><li> Utilizar um programa para controlar a temporização para a aplicação de alta voltagem (HV) (cerca de 0,8 seg) para quatro eléctrodos, ao mesmo tempo, deslocando um eléctrodo na direcção de movimento (ou seja, durante 0,8 seg, accionar 1234; em seguida, 2345, 3456, etc. ., 0,8 segundos para cada grupo, e depois para trás, move-se de forma de gotículas na direcção oposta, como bem). </li></ol> 5. Visualização Gota e Manuseio <ol><li> Para gravar gotícula de movimento, utilizar o sistema de visualização, o qual é composto por uma 24X - montagem de ampliação 96X combinado com uma câmara CCD. Ligue o gravador de vídeo para a câmera usando S-video. </li><li> Pipetar uma gota de 4 ul contendo C. elegans em meios na parte inferior do substrato revestido de fuligem. </li><li> Trazer os melhores eletrodos para ~ 0,3 milímetros acima da gota. A gota deve ser próximo ao centro, logo abaixo do quinto eletrodo, para facilitar a operação. </li><li> Ligue a interface eletrônica e alta tensão (500 V RMS), e ajustar a distância do eléctrodo superior à gota, até que começa a se mover. Não deixe que os melhores eletrodos tocar a gota. </li><li> Recolha de dados de registo do número de transferências de gotículas de sucesso no dispositivo em resposta a impulsos eléctricos. Uma experiência de sucesso é caracterizado por, pelo menos, 700 transferências de gotículas, ou seja, uma transferência após cada pulso eléctrico. </li><li> Recolha de dados continuamente, até que a gotícula não mais mover-se em resposta a 5 a 10 pulsos. NOTA: Quando a superfície começa a degradar-se, o movimento pode ser restaurado, trazendo os melhores eléctrodos mais perto da gotícula. </li></ol>

<ol>
	<li>Fair, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Digital+microfluidics:+is+a+true+lab-on-a-chip+possible.">Digital microfluidics: is a true lab-on-a-chip possible.</a> Microfluid Nanofluid. 3 (3), 245-281 (2007).</li><li>Gupta, S., Alargova, R. G., Kilpatrick, P. K., Velev, O. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On-Chip+Dielectrophoretic+Coassembly+of+Live+Cells+and+Particles+into+Responsive+Biomaterials.">On-Chip Dielectrophoretic Coassembly of Live Cells and Particles into Responsive Biomaterials.</a> Langmuir. 26 (5), 3441-3452 (2009).</li><li>Shih, S. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dried+blood+spot+analysis+by+digital+microfluidics+coupled+to+nanoelectrospray+ionization+mass+spectrometry.">Dried blood spot analysis by digital microfluidics coupled to nanoelectrospray ionization mass spectrometry.</a> Anal Chem. 84 (8), 3731-3738 (2012).</li><li>Gorbatsova, J., Borissova, M., Kaljurand, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrowetting-on-dielectric+actuation+of+droplets+with+capillary+electrophoretic+zones+for+off-line+mass+spectrometric+analysis.">Electrowetting-on-dielectric actuation of droplets with capillary electrophoretic zones for off-line mass spectrometric analysis.</a> J Chromatogr. 1234, 9-15 (2012).</li><li>Qin, J., Wheeler, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maze+exploration+and+learning+in+C.+elegans.">Maze exploration and learning in C. elegans.</a> Lab Chip. 7 (2), 186-192 (2007).</li><li>Koc, Y., de Mello, A. J., McHale, G., Newton, M. I., Roach, P., Shirtcliffe, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nano-scale+superhydrophobicity:+suppression+of+protein+adsorption+and+promotion+of+flow-induced+detachment.">Nano-scale superhydrophobicity: suppression of protein adsorption and promotion of flow-induced detachment.</a> Lab Chip. 8 (4), 582-586 (2008).</li><li>Perry, G., Thomy, V., Das, M. R., Coffinier, Y., Boukherroub, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibiting+protein+biofouling+using+graphene+oxide+in+droplet-based+microfluidic+microsystems.">Inhibiting protein biofouling using graphene oxide in droplet-based microfluidic microsystems.</a> Lab Chip. 12 (9), 1601-1604 (2012).</li><li>Kumari, N., Garimella, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrowetting-Induced+Dewetting+Transitions+on+Superhydrophobic+Surfaces.">Electrowetting-Induced Dewetting Transitions on Superhydrophobic Surfaces.</a> Langmuir. 27 (17), 10342-10346 (2011).</li><li>Freire, S. L. S., Tanner, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Additive-Free+Digital+Microfluidics.">Additive-Free Digital Microfluidics.</a> Langmuir. 29 (28), 9024-9030 (2013).</li><li>Deng, X., Mammen, L., Butt, H. -. J., Vollmer, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Candle+Soot+as+a+Template+for+a+Transparent+Robust+Superamphiphobic+Coating.">Candle Soot as a Template for a Transparent Robust Superamphiphobic Coating.</a> Science. 335, 67-70 (2011).</li><li>Kang, K. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+Electrostatic+Fields+Change+Contact+Angle+in+Electrowetting.">How Electrostatic Fields Change Contact Angle in Electrowetting.</a> Langmuir. 18 (26), 10318-10322 (2002).</li><li>Abdelgawad, M., Watson, M. W. L., Young, E. W. K., Mudrik, J. M., Ungrin, M. D., Wheeler, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Soft+lithography:+masters+on+demand.">Soft lithography: masters on demand.</a> Lab Chip. 8 (8), 1379-1385 (2008).</li><li>Barbulovic-Nad, I., Yang, H., Park, P. S., Wheeler, A. 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The authors declare that they have no competing financial interests.

A etapa mais crítica do protocolo é a proteção da camada de fuligem, diretamente associado ao sucesso em gotas em movimento. Metalização da camada de fuligem (método 1 acima) permite que perto de 100% de sucesso de fabricação. No entanto, o tempo máximo de operação é de cerca de 10 min; possivelmente, fracções de gotículas são molhar a fuligem através de furos na camada de metal. Revestimento da camada de fuligem com o líquido fluorado é a alternativa mais fácil e rápida, e exige o mínimo de recur...

A miniaturização dos dispositivos que funcionam com líquidos é de suma importância para o desenvolvimento de plataformas &quot;lab-on-a-chip&quot;. Nesse sentido, as duas últimas décadas têm testemunhado um progresso significativo na área da microfluídica, com uma variedade de aplicações. 1-5 Contrastando com o transporte de fluidos em canais fechados (canal microfluídicos), DMF manipula gotas em matrizes de eletrodos. Um dos méritos mais atraentes desta técnica é a ausência de partes móveis para o transporte de fluidos, e movimento é imediatamente interrompida ao desligar sinais elétricos. No entanto, o movimento das gotículas é dependente de conteúdos das gotículas, certamente uma característica indesejável para uma plataforma universal &quot;lab-on-a-chip&quot;. Gotículas contendo proteínas e outros analitos aderir a superfícies do dispositivo, tornando-se inabalável. Indiscutivelmente, esta tem sido a principal limitação para o alargamento do âmbito de aplicações DMF; 6-8alternativas para minimizar a proliferação indesejada superfície envolvem a adição de espécies químicas extras para a gota ou seus arredores, o que poderia afetar o conteúdo da gota. Anteriormente, o nosso grupo desenvolveu um dispositivo para permitir o transporte de células e proteínas em DMF, sem aditivos adicionais (dispositivos Campo-DW). 9 Isto foi conseguido através da combinação de uma superfície com base na fuligem vela, 10 com uma geometria do dispositivo que favorece a gotícula de rolamento e leva a uma força ascendente sobre a gotícula, diminuindo ainda mais a interacção gotícula-superfície. Nesta abordagem, gota movimento não está associado a molhar a superfície 11. O objectivo do método descrito abaixo é detalhado para produzir um dispositivo de DMF capaz de transportar gotas contendo proteínas, células e organismos inteiros, sem aditivos adicionais. Os dispositivos de campo-DW pavimentar o caminho para as plataformas totalmente controlados que trabalham em grande parte de forma independente da gota de químicory. Aqui, nós também apresentam simulações mostra que, apesar da alta tensão necessária para o funcionamento do dispositivo, a queda de tensão através da gotícula é uma pequena fracção da tensão aplicada, indicando efeitos insignificantes sobre bioanalytes no interior da gotícula. Na verdade, os testes preliminares com Caenorhabditis elegans (C. elegans), um nemátodo usado para uma variedade de estudos em biologia, mostram que os vermes nadar sem perturbações como as tensões são aplicadas.

<table border="0" cellpadding="0" cellspacing="0" width="1230">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Name of Material/ Equipment</td>
			<td style="width:119px;">Company</td>
			<td style="width:161px;">Catalog Number</td>
			<td style="width:720px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Paraffin candle</td>
			<td style="width:119px;"></td>
			<td style="width:161px;"></td>
			<td>Any paraffin candle</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Sputtering system</td>
			<td style="width:119px;">Denton Vacuum, Moorestown, NJ</td>
			<td style="width:161px;"></td>
			<td>Sputter coater Desk V HP equipped with an Au target.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">1-dodecanethiol</td>
			<td style="width:119px;">Sigma-Aldrich</td>
			<td align="right" style="width:161px;">471364</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Teflon</td>
			<td style="width:119px;">Dupont</td>
			<td style="width:161px;">AF-1600</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Fluorinert FC-40</td>
			<td style="width:119px;">Sigma-Aldrich</td>
			<td style="width:161px;">F9755</td>
			<td>Fluorinated liquid: Prepare Teflon-AF resin in Fluorinert FC-40, 1:100 (w/w), to create the hydrophobic coating.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Graphic design software -Adobe Illustrator</td>
			<td style="width:119px;">Adobe Systems</td>
			<td style="width:161px;"></td>
			<td>Other softwares might be used as well.</td>
		</tr>
		<tr height="18">
			<td height="18" style="height:18px;width:231px;">Copper laminate</td>
			<td style="width:119px;">Dupont</td>
			<td style="width:161px;">LF9110</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:231px;">Laser Printer</td>
			<td style="width:119px;">Xerox</td>
			<td style="width:161px;">Phaser 6360 or similar</td>
			<td>Check for the compatibility with &#34;rich black&#34; or &#34;registration black&#34; (see text).</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Copper Etchant</td>
			<td style="width:119px;">Transene</td>
			<td style="width:161px;">CE-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Perfluoroalkoxy (PFA) film</td>
			<td style="width:119px;">McMaster-Carr</td>
			<td style="width:161px;">84955K22</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:231px;">Breadboard</td>
			<td style="width:119px;">Allied Electronics</td>
			<td style="width:161px;">70012450 or similar</td>
			<td>Large enough to allow the assemble of 10 drivers.</td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:231px;">Universal circuit board</td>
			<td style="width:119px;">Allied Electronics</td>
			<td style="width:161px;">70219535 or similar</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:231px;">Connector</td>
			<td style="width:119px;">Allied Electronics</td>
			<td style="width:161px;">5145154-8 or similar</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Control board and control program (LabView software)</td>
			<td style="width:119px;">National Instruments</td>
			<td style="width:161px;">NI-6229 or similar</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">High-voltage amplifier</td>
			<td style="width:119px;">Trek</td>
			<td style="width:161px;">PZD700</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Resistor R 27 k&#8486;, 1/4 W</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">2964762</td>
			<td></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:231px;">Capacitors C and C1, 100 nF, 60 V</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">8817183</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Transistor T, NPN</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">9350289</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Diode D, 1N4007</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">2660007</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Relay&#160;</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">8862527</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Visualization system</td>
			<td style="width:119px;">Edmund Optics</td>
			<td style="width:161px;">VZM 200i or similar</td>
			<td>System magnification 24X- 96X. It is combined with a Hitachi KP-D20B 1/2 in CCD Color Camera.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Recorder</td>
			<td style="width:119px;">Sony</td>
			<td style="width:161px;">GV-D1000 NTSC or similar</td>
			<td>It is connected to the camera by an S-video cable.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Simulations</td>
			<td style="width:119px;">COMSOL Multiphysics</td>
			<td style="width:161px;">V. 4.4</td>
			<td></td>
		</tr>
	</tbody>
</table>

taking advantage of reduced droplet-surface interaction to optimize transport of bioanalytes in digital microfluidics

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; platforms. Often, droplet motion relies on the wetting of a surface, directly associated with the application of an electric field; surface interactions, however, make motion dependent on droplet contents, limiting the breadth of applications of the technique.
Some alternatives have been presented to minimize this dependence. However, they rely on the addition of extra chemical species to the droplet or its surroundings, which could potentially interact with droplet moieties. Addressing this challenge, our group recently developed Field-DW devices to allow the transport of cells and proteins in DMF, without extra additives.
Here, the protocol for device fabrication and operation is provided, including the electronic interface for motion control. We also continue the studies with the devices, showing that multicellular, relatively large, model organisms can also be transported, arguably unaffected by the electric fields required for device operation.

Anteriormente, foram utilizados dispositivos Campo-DW para permitir o movimento de proteínas em DMF. Em particular, as gotas com albumina de soro bovino (BSA) pode ser movido a uma concentração 2000 vezes mais elevada do que o relatado anteriormente por outros autores (sem aditivos). Isto era devido à interacção reduzida entre as gotículas e a superfície; A Figura 4 mostra uma gota contendo fluorescentemente marcado com BSA (ver Freire et al 9 para obter mais informação sob...

Watch this Scientific Journal Video about Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics at JoVE.com

Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics

The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.

Aproveitando-se de Redução Interação gota-superfície para otimizar o transporte de Bioanalytes em microfluídica Digital

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; ...

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7.8K visualizações.  University of the Sciences. The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.

Vídeo: Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support1,2,3. In this context, metal nanowires are especially desirable for realizing dense routing networks4. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons5 in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires6 randomly distributed on a glass substrate7. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization8,9. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity5,9. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate9,10. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy9,11. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry.

Silver nanowires can simultaneously transport electrons and optical information in the form of surface plasmons. A procedure is described here to realize such a shared circuitry and the limitations at propagating both information carriers are evaluated.

Avaliando plasmônicos Transporte em Prata atual de transporte de nanofios

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information ...

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Characterization of Thermal Transport in One-dimensional Solid Materials

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including conductive, semi-conductive or nonconductive one-dimensional structures. This technique broadens the measurement scope of materials (conductive and nonconductive) and improves the accuracy and stability. If the sample (especially biomaterials, such as human head hair, spider silk, and silkworm silk) is not conductive, it will be coated with a gold layer to make it electronically conductive. The effect of parasitic conduction and radiative losses on the thermal diffusivity can be subtracted during data processing. Then the real thermal conductivity can be calculated with the given value of volume-based specific heat (&#961;cp), which can be obtained from calibration, noncontact photo-thermal technique or measuring the density and specific heat separately. In this work, human head hair samples are used to show how to set up the experiment, process the experimental data, and subtract the effect of parasitic conduction and radiative losses.

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials.

Caracterização dos Transportes térmica em materiais sólidos unidimensionais

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including ...

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

The robust device design of fringing-field electrostatic MEMS actuators results in inherently low squeeze-film damping conditions and long settling times when performing switching operations using conventional step biasing. Real-time switching time improvement with DC-dynamic waveforms reduces the settling time of fringing-field MEMS actuators when transitioning between up-to-down and down-to-up states.

Real-Time DC-dinâmico método de polarização para a mudança de melhoria no tempo em Severamente subamortecido Fringing-campo eletrostático MEMS Atuadores

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input ...

How to Build a Vacuum Spring-transport Package for Spinning Rotor Gauges

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10-4 Pa to 1.0 Pa. In this application, the SRGs are frequently transported to laboratories for calibration. Events can occur during transportation that change the rotor surface conditions, thus changing the calibration factor. To assure calibration stability, a spring-transport mechanism is often used to immobilize the rotor and keep it under vacuum during transport. It is also important to transport the spring-transport mechanism using packaging designed to minimize the risk of damage during shipping. In this manuscript, a detailed description is given on how to build a robust spring-transport mechanism and shipping container. Together these form a spring-transport package. The spring-transport package design was tested using drop-tests and the performance was found to be excellent. The present spring-transport mechanism design keeps the rotor immobilized when experiencing shocks of several hundred g (g = 9.8 m/sec2 and is the acceleration due to gravity), while the shipping container assures that the mechanism will not experience shocks greater than about 100 g during common shipping mishaps (as defined by industry standards).

Here we describe how to build a robust spring-transport mechanism for a spinning rotor gauge. This device securely immobilizes the rotor and keeps it under vacuum during transportation. We also describe packaging that minimizes the risk of damage during transport. Tests show our design works for typical shocks during transport.

Como construir um pacote Spring-transporte a vácuo para Spinning Rotor Gauges

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10-4 Pa to ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

Impressão digital de dióxido de titânio para células solares Dye sensibilizados

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

Ultrasonic Fatigue Testing in the Tension-Compression Mode

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. It is also used to simulate loading of material during operation in high speed conditions, such as those experienced by components of jet engines or car turbo pumps. It is necessary to operate only in the high and ultra-high cycle region, due to the possibility of extremely high deformation rates, which can have a significant influence on the test results. Specimen shape and dimensions have to be carefully selected and calculated to fulfill the resonance condition of the ultrasonic system; thus, it is not possible to test the full components or specimens of arbitrary shape. Before each test, it is necessary to harmonize the specimen with the frequency of the ultrasonic system to compensate for deviations of the real shape from the ideal one. It is not possible to run a test until a total fracture of the specimen, since the test is automatically terminated after initiation and propagation of the crack to a certain length, when the stiffness of the system changes enough to shift the system out of the resonance frequency. This manuscript describes the process of evaluation of materials' fatigue properties at high-frequency ultrasonic fatigue loading with use of mechanical resonance at a frequency close to 20 kHz. The protocol includes a detailed description of all steps required for a correct test, including specimen design, stress calculation, harmonizing with the resonance frequency, performing the test, and final static fracture.

A protocol for ultrasonic fatigue testing in the high and ultra-high cycle region in axial tension-compression loading mode.

Fadiga ultra-sônico de teste no modo de tensão-compressão

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...

Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement during previous phase changes and applied shear. To determine the extent of these changes, we have developed a microfluidic device that enables repeated phase transitions induced by exchange of the surrounding fluid and microrheological characterization while limiting shear on the sample. This technique is &#181;2rheology, the combination of microfluidics and microrheology. The microfluidic device is a two-layer design with symmetric inlet streams entering a sample chamber that traps the gel sample in place during fluid exchange. Suction can be applied far away from the sample chamber to pull fluids into the sample chamber. Material rheological properties are characterized using multiple particle tracking microrheology (MPT). In MPT, fluorescent probe particles are embedded into the material and the Brownian motion of the probes is recorded using video microscopy. The movement of the particles is tracked and the mean-squared displacement (MSD) is calculated. The MSD is related to macroscopic rheological properties, using the Generalized Stokes-Einstein Relation. The phase of the material is identified by comparison to the critical relaxation exponent, determined using time-cure superposition. Measurements of a fibrous colloidal gel illustrate the utility of the technique. This gel has a delicate structure that can be irreversibly changed when shear is applied. &#181;2rheology data shows that the material repeatedly equilibrates to the same rheological properties after each phase transition, indicating that phase transitions do not play a role in microstructural changes. To determine the role of shear, samples can be sheared prior to injection into our microfluidic device. &#181;2rheology is a widely applicable technique for the characterization of soft matter enabling the determination of rheological properties of delicate microstructures in a single sample during phase transitions in response to repeated changes in the surrounding environmental conditions.

We demonstrate the fabrication and use of a microfluidic device that enables multiple particle tracking microrheology measurements to study the rheological effects of repeated phase transitions on soft matter.

Combinando microfluídica e Microrheology para determinar as propriedades reológicas de matéria mole durante as transições de fase repetidas

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement ...

Fabrication of Refractive-index-matched Devices for Biomedical Microfluidics

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices can be implemented as part of a robust platform capable of making simultaneous complementary measurements. The primary challenge created by the combination of these two techniques is the mismatch in refractive index between the materials traditionally used to make microfluidic devices and the aqueous solutions typically used in biomedicine. This mismatch can create optical artifacts near the channel or device edges. One solution is to reduce the refractive index of the material used to fabricate the device by using a fluorinated polymer such as MY133-V2000 whose refractive index is similar to that of water (n = 1.33). Here, the construction of a microfluidic device made out of MY133-V2000 using soft lithography techniques is demonstrated, using O2 plasma in conjunction with an acrylic holder to increase the adhesion between the MY133-V2000 fabricated device and the polydimethylsiloxane (PDMS) substrate. The device is then tested by incubating it filled with cell culture media for 24 h to demonstrate the ability of the device to maintain cell culture conditions during the course of a typical imaging experiment. Finally, quantitative phase microscopy (QPM) is used to measure the distribution of mass within the live adherent cells in the microchannel. This way, the increased precision, enabled by fabricating the device from a low index of refraction polymer such as MY133-V2000 in lieu of traditional soft lithography materials such as PDMS, is demonstrated. Overall, this approach for fabricating microfluidic devices can be readily integrated into existing soft lithography workflows in order to reduce optical artifacts and increase measurement precision.

This protocol describes the fabrication of microfluidic devices from MY133-V2000 to eliminate artifacts that often arise in microchannels due to the mismatching refractive indices between microchannel structures and an aqueous solution. This protocol uses an acrylic holder to compress the encapsulated device, improving adhesion both chemically and mechanically.

Fabricação de dispositivos de refração-índice-combinada para microfluídica biomédica

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices ...

Crack Monitoring in Resonance Fatigue Testing of Welded Specimens Using Digital Image Correlation

A procedure using digital image correlation (DIC) to detect cracks on welded specimens during fatigue tests on resonance testing machines is presented. It is intended as a practical and reproducible procedure to identify macroscopic cracks at an early stage and monitor crack propagation during fatigue tests. It consists of strain field measurements at the weld using DIC. Images are taken at fixed load cycle intervals. Cracks become visible in the computed strain field as elevated strains. This way, the whole width of a small-scale specimen can be monitored to detect where and when a crack initiates. Subsequently, it is possible to monitor the development of the crack length. Because the resulting images are saved, the results are verifiable and comparable. The procedure is limited to cracks initiating at the surface and is intended for fatigue tests under laboratory conditions. By visualizing the crack, the presented procedure allows direct observation of macrocracks from their formation until rupture of the specimen.

Digital image correlation is used in fatigue tests on a resonance testing machine to detect macroscopic cracks and monitor crack propagation in welded specimens. Cracks on the specimen surface become visible as increased strains.

Monitoramento de crack em testes de fadiga de ressonância de espécimes soldados usando correlação de imagem digital

A procedure using digital image correlation (DIC) to detect cracks on welded specimens during fatigue tests on resonance testing machines is presented. It ...

Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments

Described is an experimental procedure that enables high-power laser irradiation of microfabricated targets. Targets are brought to the laser focus by a closed feedback loop that operates between the target manipulator and a ranging sensor. The target fabrication process is explained in detail. Representative results of MeV-level proton beams generated by irradiation of 600 nm thick gold foils at a rate of 0.2 Hz are given. The method is compared with other replenishable target systems and the prospects of increasing the shot rates to above 10 Hz are discussed.

A protocol is presented for automated irradiation of thin gold foils with high intensity laser pulses. The protocol includes a step-by-step description of the micromachining target fabrication process and a detailed guide for how targets are brought to the laser&#39;s focus at a rate of 0.2 Hz.

Entrega automatizada de alvos microfabricados para experimentos intensos de irradiação a laser

Described is an experimental procedure that enables high-power laser irradiation of microfabricated targets. Targets are brought to the laser focus by a ...