Este trabalho foi apoiado pelo Departamento de Bioengenharia e Ciências Terapêuticas da UCSF, o instituto de Califórnia para Quantitativos Biociências (QB3), eo Bridging the Gap Prêmio da Fundação Rogers Família.

1. Projeto do dispositivo Dimensões e Topologias Baseado Experimental necessidades usando Computer Aided Design (CAD) Software Nota: Selecção diâmetros dos canais de emulsão mais pequenas do que as das gotículas esféricas. Isso força as gotículas para um cilíndrico ou &quot;salsicha&quot; forma e permite picoinjection mais eficaz. Para os nossos propósitos, nós projetamos 30 x 30 mm canais de gotículas que eram de 50 m de diâmetro. <ol><li> Local picoinjection Modelo (s) depois de os descritos por Abate et al. 3 com a excepção de que os canais para os eléctrodos de metal são removidas, como eles são desnecessários. </li><li> Adicionar canais para servir como o fosso de Faraday (Figura 1), que funcionam entre o local picoinjection (s) e a emulsão a montante de tal forma que eles protegem as gotículas do campo eléctrico. Nota: Este impede fusão não intencional. </li></ol> 2. Dispositivos Fabricar com SOFT fotolitoTécnicas ographic <ol><li> Gerar uma máscara de transparência fotolitografia com base no arquivo CAD usando serviços comerciais existentes. </li><li> Com a foto-mascara, curar fotorresistente em bolachas de silício para produzir um dispositivo mestre, tal como descrito anteriormente 4. </li><li> Despeje PDMS misturado com agente de cura (proporção 11:1) sobre o mestre dispositivo contido em um cinco centímetros de poliestireno placa de Petri. </li><li> Colocar o mestre com PDMS em um exsicador de vácuo durante cerca de 15 minutos para remover quaisquer bolhas de ar. </li><li> Curar o dispositivo de PDMS, colocando-o num forno de 95 ° C durante 1 hora. Em alternativa, o PDMS irá curar à RT após 24 horas. </li><li> Remova o dispositivo, cortando todo o perímetro com uma lâmina cirúrgica e descascando cuidadosamente o dispositivo com o mestre. </li><li> Soco entrada e saída buracos nas PDMS usando uma biópsia de 0,5 mm. </li><li> Ligar o dispositivo a uma lâmina de vidro usando um bonder plasma 4. </li></ol> 3. Prepare uma pressão de arPump Control para pressurizar um reservatório contendo o Fluido <ol><li> Modificar a saída da bomba de tal modo que as saídas de ar comprimido através de um comprimento de tubo de polietileno de 2,7 milímetros de diâmetro interno. </li><li> Construí-la de modo a que a tubagem termina numa seringa de ponta luer-lock ajustando a luz sobre o mamilo na parte traseira do luer. </li><li> Selar preenchendo o espaço entre os fios de luer-lock e a tubagem com epóxi. </li><li> Coloque uma agulha 27,5 G. </li></ol> 4. Preparar uma Monodisperse emulsão aquosa de Gotículas (água-em-óleo) em suspensão em um portador inerte fluorado óleo com 2% (p / p) dissolvido biocompatível Surfactante 7 Os reagentes específicos contidos nestas gotas dependem da aplicação <ol><li> Em preparação para a reinjecção, carregar a emulsão para uma seringa de 1 ml com uma agulha G 27,5. </li><li> Fixe a seringa em uma bomba de seringa e orientar a bomba vertical (agulha para cima). NotaEsta orientação faz com que as gotículas de embalar numa camada acima do óleo veicular. Quando a bomba está a funcionar, as gotículas irá ser empurrado para fora da seringa na fracção de elevado volume da camada de óleo por baixo deles. </li></ol> 5. Prepare Reagentes para Introdução ao chip microfluídico <ol><li> Perfurador três furos 0,5 milímetros para dentro da tampa de um tubo de centrífuga de 15 ml (um recipiente com uma tampa de rosca é suficiente) utilizando um perfurador de biópsia de agulha, ou broca. </li><li> Inserir um eléctrodo de arame de diâmetro de 0,5 mm e um cm de comprimento de tubagem de PE-2 ~ 20 através de dois dos furos de modo a que eles cheguem ao fundo do tubo. </li><li> No buraco restante, passe um ~ 2,5 centímetros de comprimento cm de tubos PE ~ 20 de tal forma que ele vai descansar acima do nível do fluido. </li><li> Vede todas as aberturas na parte superior da tampa com epóxi UV-curado. </li><li> Encha o tubo com o fluido picoinjection e parafuso na tampa. </li><li> Ligue a saída a partir da bomba de controle de pressão de ar com o comprimento mais curto de tubagem por inserçãoção da agulha para dentro do lúmen. A agulha deve caber confortavelmente. </li><li> Encher uma seringa de 1 ml com 1 M de NaCl para servir como o fosso de Faraday. </li><li> Conecte um G agulha 27,5 e segura a seringa em uma bomba de seringa. </li><li> Encha uma outra seringa de 1 ml com óleo do portador / espaçador, conecte uma agulha G 27,5, e fixá-lo em uma bomba de seringa. </li></ol> 6. Prepare o dispositivo micro para Picoinjection <ol><li> Ligar o tubo de saída (mais de comprimento) a partir do recipiente de fluido de injecção para a porta de entrada do fluido picoinjection no chip de microfluidos. </li><li> Ligar a seringa contendo a 1 M de NaCl para a porta de entrada para o fosso de Faraday no chip de microfluidos com um comprimento de tubagem de PE. </li><li> Ligar a seringa contendo o óleo do portador para a porta de entrada do chip de microfluidos com um comprimento de tubagem de PE. </li><li> Inserir tubos PE na porta de saída de emulsão sobre o chip de microfluidos. A tubulação deve terminar em um reservatório de recolha de emulsão, nemmalmente um tubo de centrífuga de 1,5 ml. </li><li> Insira o tubo PE na porta de saída para o Faraday Moat no chip microfluídico. A tubulação deve terminar em um não-condutor e recipiente isolado eletricamente para evitar um curto-circuito. </li><li> Ligue a saída do amplificador de alta voltagem (HV) através de jacaré ao eléctrodo de metal submergido no fluido picoinjection. </li><li> Conecte o eletrodo de aterramento do amplificador HV via jacaré para o metal da agulha da seringa contendo o 1 M NaCl. </li></ol> 7. Infundir Reagentes para Microfluidic Chip <ol><li> Introduzir a 1 M de NaCl (Moat Faraday) para o dispositivo, a uma taxa de 100 il / hr. </li><li> Introduzir a emulsão de gotas e transportadora de petróleo a preços adequados para as dimensões do dispositivo. Para o nosso dispositivo de demonstração, apresentamos as gotas de óleo e de 200 e 400 mL / h, respectivamente. As taxas de fluxo deve permitir que as gotas para passar o picoinjector em intervalos regulares separadaspor um intervalo de óleo do portador. </li><li> Ajustar a pressão aplicada ao fluido picoinjection tal que a pressão do fluido no orifício picoinjection está em equilíbrio mecânico com o canal de gotícula. Nota: A esta pressão (a pressão de Laplace), o fluido de injecção deve inchar dentro do canal de gotículas sem brotando e formando as suas gotas (Figura 2). A estas taxas de fluxo acima descritas, que se aplica uma pressão de ~ 13 psi para o fluido de injecção para atingir o equilíbrio no local da injecção. </li></ol> 8. Comece Picoinjection <ol><li> Como as gotas passam pelo orifício de injecção, aplica um 0-10 V, 10 kHz, o sinal AC amplificada 1000 x por HV-amplificador (Figura 3). </li><li> Modular o volume de injecção, alterando a amplitude da tensão aplicada. Nota: As tensões mais elevadas deve permitir mais fluido a ser introduzido para as gotículas. Em nossos testes, observamos injeção estável e consistente com tensões serentre 100 e 3000 V usando soluções de injecção de NaCl variando 10-500 mM (Figura 4). </li></ol>

<ol>
	<li>Kritikou, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=It's+cheaper+in+the+Picolab.">It's cheaper in the Picolab.</a> Nat. Rev. Genet. 6 (9), (2005).</li><li>Ahn, K., Agresti, J., Chong, H., Marquez, M., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrocoalescence+of+drops+synchronized+by+size-dependent+flow+in+microfluidic+channels.">Electrocoalescence of drops synchronized by size-dependent flow in microfluidic channels.</a> Appl. Phys. Lett. 88 (26), (2006).</li><li>Abate, A. R., Hung, T., Mary, P., Agresti, J. J., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-throughput+injection+with+microfluidics+using+picoinjectors.">High-throughput injection with microfluidics using picoinjectors.</a> Proc. Natl. Acad. Sci. U S A. 107, 19163-19166 (2010).</li><li>Harris, J., 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=Fabrication+of+a+microfluidic+device+for+the+compartmentalization+of+neuron+soma+and+axons.">Fabrication of a microfluidic device for the compartmentalization of neuron soma and axons.</a> J. Vis. Exp. (7), (2007).</li><li>Duffy, D. C., McDonald, J. C., Schueller, O. J., Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+prototyping+of+microfluidic+systems+in+poly(dimethylsiloxane).">Rapid prototyping of microfluidic systems in poly(dimethylsiloxane).</a> Anal. Chem. 70 (23), 4974-4984 (1998).</li><li>O'Donovan, B., Eastburn, D. J., Abate, 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=Electrode-free+picoinjection+of+microfluidic+drops.">Electrode-free picoinjection of microfluidic drops.</a> Lab on a Chip. 12 (20), 4029-4032 (2012).</li><li>Holtze, 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=Biocompatible+surfactants+for+water-in-fluorocarbon+emulsions.">Biocompatible surfactants for water-in-fluorocarbon emulsions.</a> Lab on a Chip. 8 (10), 1632-1639 (2008).</li><li>Chung, C., Lee, M., Char, K., Ahn, K., Lee, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Droplet+dynamics+passing+through+obstructions+in+confined+microchannel+flow.">Droplet dynamics passing through obstructions in confined microchannel flow.</a> Microfluid. Nanofluid. 9, 1151-1163 (2010).</li><li>Herminghaus, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamical+instability+of+thin+liquid+films+between+conducting+media.">Dynamical instability of thin liquid films between conducting media.</a> Phys. Rev. Lett. 83 (12), 2359-2361 (1999).</li><li>Priest, C., Herminghaus, S., Seemann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+electrocoalescence+in+microfluidics:+Targeting+a+single+lamella.">Controlled electrocoalescence in microfluidics: Targeting a single lamella.</a> Appl. Phys. Lett. 89 (13), 134101-134103 (2006).</li><li>Florent, M., Siva, A. V., Hao, G., Dirk, E., Frieder, 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-controlled+droplet+generation+in+a+microfluidic+flow-focusing+device.">Electrowetting-controlled droplet generation in a microfluidic flow-focusing device.</a> J. Phys: Condens. Matter. 19 (46), (2007).</li><li>Eastburn, D. J., Sciambi, A., Abate, 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=Picoinjection+enables+digital+detection+of+RNA+with+droplet+rt-PCR.">Picoinjection enables digital detection of RNA with droplet rt-PCR.</a> PLoS ONE. 8 (4), (2013).</li></ol>

Nós não entendemos completamente mecanismo físico exato por trás da relação entre a tensão aplicada eo volume de injeção observado em nossos experimentos. Os interesses do laboratório e áreas relevantes do conhecimento não são bem adequados para a prossecução desta pergunta persistente. Nós encorajamos aqueles com mais física e perspicácia de engenharia para explorar este fenômeno.

A relação entre o volume de injecção e a tensão aplicada dependem de muitos factores, incluindo as dimensões do dispositivo, o comprimento do tubo que transporta o fluido picoinjection para o dispositivo, a molaridade de fluido picoinjection, e a velocidade das gotas, quando passam eles injector. Por este motivo, recomendamos que a relação de volume / tensão ser caracterizado antes de cada execução de picoinjection medindo volumes de injecção nas bordas das faixas de trabalho da tensão e molaridade. Além ...

Em microfluídica baseada em gotículas, gotículas aquosas escala mícron são usados ​​como &quot;tubos de ensaio&quot; para reações biológicas. A vantagem para a realização de reacções nas gotículas é que cada gota usa somente um poucos pl de reagente e, com a microfluidos, as gotas podem ser formadas e processadas em taxas kilohertz 1. Em conjunto, estas propriedades permitem que milhões de reacções com células individuais, moléculas de ácidos nucleicos, ou compostos a serem realizadas numa questão de minutos, com ul de material total. Para usar gotas para aplicações como estas, são necessárias técnicas para a adição de volumes controlados de reagentes para as gotas; tais operações são análogas às pipetando em tubos de ensaio. Um método para realizar isto é electrocoalescence, em que uma gota de reagente é fundida com a queda alvo através da aplicação de um campo eléctrico. O campo eléctrico perturba o arranjo de moléculas de surfactante sobre os interfaces das gotas, inducing uma instabilidade de película fina e provocando a coalescência em emulsões que são de outra maneira estável 2. Fusão induzidos electricamente é igualmente explorada no design do picoinjector, um dispositivo que injecta os reagentes em gotas à medida que fluem através de um canal pressurizado 3. Para aplicar o campo eléctrico, dispositivos picoinjector utilizar eléctrodos metálicos, mas a integração de eléctrodos metálicos em chips de microfluidos é geralmente um processo complexo e propenso a erros como os fios de líquido da solda são facilmente comprometidos por bolhas de ar ou poeira e outros detritos no canal , bem como fraturas de estresse ou flexão durante a configuração do dispositivo. Aqui é apresentado um método para realizar picoinjection sem a utilização de eléctrodos de metal, tornando o fabrico mais simples e mais robusto. Para acionar picoinjection, nós em vez usar o próprio fluido de injeção como um eletrodo, uma vez que a maioria dos reagentes biológicos contêm eletrólitos dissolvidos e são condutores. Nós também adicionar um &quot;Faraday Moat &quot;para proteger as regiões sensíveis do dispositivo e actuam como uma base universal (Figura 1). O fosso isola electricamente as gotículas a montante do local picoinjection proporcionando um solo, impedindo fusão gotícula não intencional. Um benefício adicional da nossa técnica é que o volume injectado nas gotas depende da magnitude da tensão aplicada, permitindo-lhe ser ajustado por meio do ajuste do sinal aplicado. Nós fabricamos os nossos dispositivos de poli (dimetilsiloxano) (PDMS), utilizando técnicas de fotolitografia suave 4,5. Nossa abordagem é compatível com dispositivos fabricados em outros materiais, como resinas, plásticos e epóxis. Os canais têm alturas e larguras de 30 mm, que são óptimas para o trabalho com gotas de 50 mm de diâmetro (65 pl). Nós introduzimos reagentes através de tubos polietileno (0.3/1.09 mm de diâmetro interno / externo) inserido portos criados durante fabricação de dispositivos com 0,50 milímetros socos biópsia, semelhantes aos métodos described anteriormente 5. A composição exacta do fluido de injecção, depende da aplicação específica. O fluido só necessita conter electrólitos dissolvidos em concentrações suficientemente elevadas para produzir condutividade suficiente para o sinal eléctrico a ser transmitido para o picoinjector. No teste de bancada, verificou-se que as concentrações iónicas superiores a 10 mm deve ser suficiente 6, embora este valor e condutividades fluido dependem das dimensões dos dispositivos específicos e magnitude da tensão aplicada.

<table border="0" cellpadding="0" cellspacing="0" width="1000">
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		<tr height="21">
			<td height="21" style="height:21px;width:283px;">1 mL Leur-Lok&#8482; syringes</td>
			<td style="width:143px;">BD Medical</td>
			<td align="right" style="width:160px;">309628</td>
			<td style="width:415px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LocTite UV-cured adhesive</td>
			<td style="width:143px;">Henkel</td>
			<td align="right">35241</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:283px;">PE-2 Tubing</td>
			<td style="width:143px;">Scientific Commodities</td>
			<td>BB31695-PE/2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Novec HFE-7500</td>
			<td>3M</td>
			<td style="width:160px;">98-0212-2928-5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">NaCl</td>
			<td style="width:143px;">Sigma Aldrich</td>
			<td style="width:160px;">S9888</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">1.5 mL centrifuge tubes</td>
			<td style="width:143px;">Eppendorf</td>
			<td align="right" style="width:160px;">22363531</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">BD Falcon 15 ml tube</td>
			<td style="width:143px;">BD Biosciences</td>
			<td align="right" style="width:160px;">352097</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:283px;">Air Pressure Control Pump</td>
			<td style="width:143px;">Control Air Inc.</td>
			<td style="width:160px;"></td>
			<td style="width:415px;">We recommend one under the control of DAQ and control software</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Syringe Pumps</td>
			<td>New Era</td>
			<td style="width:160px;"></td>
			<td>Must be capable of holding 1ml syringes and flowing at rates as low as 100 uL/hr</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">HV-Amplfier</td>
			<td style="width:143px;"></td>
			<td style="width:160px;"></td>
			<td>Must be capable of 1000x amplification of signals between 0.01 and 10 V</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plasma Bonder/Cleaner</td>
			<td style="width:143px;">Harrick Plasma</td>
			<td style="width:160px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3&#8221; silicon wafers</td>
			<td style="width:143px;">Sigma Aldrich</td>
			<td align="right" style="width:160px;">647535</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PDMS</td>
			<td style="width:143px;">Dow Corning</td>
			<td style="width:160px;"></td>
			<td>Sylgard 184 with curing agent should be included</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">SU-8 Photoresist</td>
			<td style="width:143px;">MicroChem</td>
			<td style="width:160px;"></td>
			<td>Viscocity depends on device dimensions</td>
		</tr>
	</tbody>
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picoinjection of microfluidic drops without metal electrodes

Métodos para picoinjecting reagentes em gotas microfluídicos existentes requerem eletrodos metálicos integrados ao chip microfluídico. A integração destes eletrodos acrescenta passos pesados ​​e propensos a erros no processo de fabricação do dispositivo. Desenvolvemos uma técnica que elimina a necessidade de eléctrodos metálicos durante picoinjection. Em vez disso, ele usa o próprio fluido de injeção como um eletrodo, uma vez que a maioria dos reagentes biológicos contêm eletrólitos dissolvidos e são condutores. Ao eliminar os eletrodos, que reduzem o tempo de fabricação de dispositivos e complexidade, e tornar os dispositivos mais robustos. Além disso, com a nossa abordagem, o volume de injecção depende da tensão aplicada à solução picoinjection; isso permite ajustar rapidamente o volume injectado por modulação da voltagem aplicada. Nós demonstramos que a nossa técnica é compatível com os reagentes que incorporam compostos biológicos comuns, incluindo tampões, enzimas e ácidos nucleicos.

As imagens microscópicas feita no local picoinjection mostram que a electrificação do fluido picoinjection é suficiente para desencadear a injecção (Figura 2). O volume injectado pode ser controlada por meio da modulação da amplitude da voltagem aplicada, com tensões mais elevadas que permitam a volumes de injecção mais elevadas. Marcamos o volume de injecção contra a magnitude da voltagem aplicada durante três molaridades representativos de fluido de injecção na (Figura 3).</str...

Watch this Scientific Journal Video about Picoinjection of Microfluidic Drops Without Metal Electrodes at JoVE.com

Picoinjection of Microfluidic Drops Without Metal Electrodes

Desenvolvemos uma técnica para picoinjecting gotas de microfluidos que não necessitam de eléctrodos metálicos. Como tal, os dispositivos que incorporem a nossa técnica é mais simples de fabricar e de utilizar.

Picoinjection de Microfluidic Drops sem metal Eletrodos

Existing methods for picoinjecting reagents into microfluidic drops require metal electrodes integrated into the microfluidic chip. The integration of ...

picoinjection-of-microfluidic-drops-without-metal-electrodes

Research

JoVE Journal

Engineering

11.0K visualizações.  Unversity of California, San Francisco.  Desenvolvemos uma técnica para picoinjecting gotas de microfluidos que não necessitam de eléctrodos metálicos. Como tal, os dispositivos que incorporem a nossa técnica é mais simples de fabricar e de utilizar. 

Vídeo: Picoinjection of Microfluidic Drops Without Metal Electrodes

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Fabricação e Teste de microfluídicos optomechanical osciladores

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Engenharia

Ultrasound Velocity Measurement in a Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within &#177;2 &#176;C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

Ultrasound velocimetry is used to study mixing by fluid flow in liquid metal electrodes. The focus of this manuscript is to illustrate the methods used for making precise, spatially-resolved ultrasound measurements while limiting oxidation and controlling and monitoring temperature, applied current, and the heater power being supplied.

O ultra-som de velocidade de medição em um eletrodo de metal líquido

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently ...

Iridium Oxide-reduced Graphene Oxide Nanohybrid Thin Film Modified Screen-printed Electrodes as Disposable Electrochemical Paper Microfluidic pH Sensors

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use integrated paper microfluidic electrochemical pH sensor for resource-limited settings. Taking advantages from both pH meters and strips, the pH sensing platform is composed of hydrophobic barrier-patterned paper micropad (&#181;PAD) using polydimethylsiloxane (PDMS), screen-printed electrode (SPE) modified with IrO2-graphene films and molded acrylonitrile butadiene styrene (ABS) plastic holder. Repetitive cathodic potential cycling was employed for graphene oxide (GO) reduction which can completely remove electrochemically unstable oxygenated groups and generate a 2D defect-free homogeneous graphene thin film with excellent stability and electronic properties. A uniform and smooth IrO2 film in nanoscale grain size is anodically electrodeposited onto the graphene film, without any observable cracks. The resulting IrO2-RGO electrode showed slightly super-Nernstian responses from pH 2-12 in Britton-Robinson (B-R) buffers with good linearity, small hysteresis, low response time and reproducibility in different buffers, as well as low sensitivities to different interfering ionic species and dissolved oxygen. A simple portable digital pH meter is fabricated, whose signal is measured with a multimeter, using high input-impedance operational amplifier and consumer batteries. The pH values measured with the portable electrochemical paper-microfluidic pH sensors were consistent with those measured using a commercial laboratory pH meter with a glass electrode.

The study demonstrates the growth of iridium oxide-reduced graphene oxide (IrO2-RGO) nanohybrid thin films on irregular and rough screen-printed carbon substrate through a green electrochemical synthesis, and their implementation as a pH sensor with a patterned paper-fluidic platform.

Grafeno Oxide Nanohybrid Thin Film eléctrodos modificados serigrafado reduzida de óxido de irídio como papel Electrochemical descartável microfluídicos pH Sensores

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use ...

Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques.
This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.

The following paper presents a novel FE simulation technique (KBC-FE), which reduces computational cost by performing simulations on a cloud computing environment, through the application of individual modules. Moreover, it establishes a seamless collaborative network between world leading scientists, enabling the integration of cutting edge knowledge modules into FE simulations.

Conhecimento Baseado Simulação Nuvem FE dos Processos de formação de folha de metal

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the ...

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV2+) and 2-ammoniumethanethiol (TNS/2-AET+)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl4) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH4) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV2+ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET+ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Here, we present a protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of layered titanate films without the aggregation of AuNPs. No spectral change was observed even after 4 months. The synthesized material has expected applications in catalysis, photo-catalysis, and the development of cost-effective plasmonic devices.

In situ Síntese de Nanopartículas de Ouro sem agregação no espaço Interlayer de Layered titanato filmes transparentes

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs ...

Electrospinning of Photocatalytic Electrodes for Dye-sensitized Solar Cells

This work demonstrates a protocol to fabricate a fiber-based photoanode for dye-sensitized solar cells, consisting of a light-scattering layer made of electrospun titanium dioxide nanofibers (TiO2-NFs) on top of a blocking layer made of commercially available titanium dioxide nanoparticles (TiO2-NPs). This is achieved by first electrospinning a solution of titanium (IV) butoxide, polyvinylpyrrolidone (PVP), and glacial acetic acid in ethanol to obtain composite PVP/TiO2 nanofibers. These are then calcined at 500 &#176;C to remove the PVP and to obtain pure anatase-phase titania nanofibers. This material is characterized using scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The photoanode is prepared by first creating a blocking layer through the deposition of a TiO2-NPs/terpineol slurry on a fluorine-doped tin oxide (FTO) glass slide using doctor blading techniques. A subsequent thermal treatment is performed at 500 &#176;C. Then, the light-scattering layer is formed by depositing a TiO2-NFs/terpineol slurry on the same slide, using the same technique, and calcinating again at 500 &#176;C. The performance of the photoanode is tested by fabricating a dye-sensitized solar cell and measuring its efficiency through J-V curves under a range of incident light densities, from 0.25-1 Sun.

The overall goal of this project was to use electrospinning to fabricate a photoanode with improved performance for dye-sensitized solar cells.

Electrospinning de eletrodos fotocatalíticos para células solares sensibilizadas por corante

This work demonstrates a protocol to fabricate a fiber-based photoanode for dye-sensitized solar cells, consisting of a light-scattering layer made of ...

Scalable Solution-processed Fabrication Strategy for High-performance, Flexible, Transparent Electrodes with Embedded Metal Mesh

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a polymer film. This paper also presents a low-cost, vacuum-free fabrication method for this novel TE; the approach combines lithography, electroplating, and imprint transfer (LEIT) processing. The embedded nature of the EMTEs offers many advantages, such as high surface smoothness, which is essential for organic electronic device production; superior mechanical stability during bending; favorable resistance to chemicals and moisture; and strong adhesion with plastic film. LEIT fabrication features an electroplating process for vacuum-free metal deposition and is favorable for industrial mass production. Furthermore, LEIT allows for the fabrication of metal mesh with a high aspect ratio (i.e., thickness to linewidth), significantly enhancing its electrical conductance without adversely losing optical transmittance. We demonstrate several prototypes of flexible EMTEs, with sheet resistances lower than 1 &#937;/sq and transmittances greater than 90%, resulting in very high figures of merit (FoM) &#8211; up to 1.5 x 104 &#8211; which are amongst the best values in the published literature.

This protocol describes a solution-based fabrication strategy for high-performance, flexible, transparent electrodes with fully-embedded, thick metal mesh. Flexible transparent electrodes fabricated by this process demonstrate among the highest reported performances, including ultra-low sheet resistance, high optical transmittance, mechanical stability under bending, strong substrate adhesion, surface smoothness, and environmental stability.

Estratégia de fabricação processada e escalável para eletrodos flexíveis e transparentes de alto desempenho com malha metálica embutida

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a ...

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LAO thickness of 4 unit-cells (uc) for interfacial conductivity to emerge. Although electrostatic mechanisms have been proposed in the past to describe the existence of this critical thickness, the importance of chemical defects has been recently accentuated. Here, we describe the growth of metal/LAO/STO heterostructures in an ultra-high vacuum (UHV) cluster system combining pulsed laser deposition (to grow the LAO), magnetron sputtering (to grow the metal) and X-ray photoelectron spectroscopy (XPS). We study step by step the formation and evolution of the q2DES and the chemical interactions that occur between the metal and the LAO/STO. Additionally, magnetotransport experiments elucidate on the transport and electronic properties of the q2DES. This systematic work not only demonstrates a way to study the electrostatic and chemical interplay between the q2DES and its environment, but also unlocks the possibility to couple multifunctional capping layers with the rich physics observed in two-dimensional electron systems, allowing the fabrication of new types of devices.

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

We fabricate metal/LaAlO3/SrTiO3 heterostructures using a combination of pulsed laser deposition and in situ magnetron sputtering. Through magnetotransport and in situ X-ray photoelectron spectroscopy experiments, we investigate the interplay between electrostatic and chemical phenomena of the quasi two-dimensional electron gas formed in this system.

Crescimento e eletrostático química/Propriedades de Metal/LaAlO3/SrTiO3 estende

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide ...

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in industry. The wettability of the produced surface was analyzed by bouncing drop experiments and the topography was analyzed by confocal microscopy. In addition, we show various methodologies to measure its durability and anti-icing properties. Superhydrophobic surfaces hold a special texture that must be preserved to keep their water-repellency. To fabricate durable surfaces, we followed two strategies to incorporate a resistant texture. The first strategy is a direct incorporation of roughness to the metal substrate by acid etching. After this surface texturization, the surface energy was decreased by silanization or fluoropolymer deposition. The second strategy is the growth of a ceria layer (after surface texturization) that should enhance the surface hardness and corrosion resistance. The surface energy was decreased with a stearic acid film.
The durability of the superhydrophobic surfaces was examined by a particle impact test, mechanical wear by lateral abrasion, and UV-ozone resistance. The anti-icing properties were explored by studying the ability to repeal subcooled water, freezing delay, and ice adhesion.

We illustrate several methodologies to produce superhydrophobic metal surfaces and to explore their durability and anti-icing properties.

Fabricação de superfícies de Metal Superhydrophobic para aplicações antigelo

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in ...

Fused Filament Fabrication (FFF) of Metal-Ceramic Components

Technical ceramics are widely used for industrial and research applications, as well as for consumer goods. Today, the demand for complex geometries with diverse customization options and favorable production methods is increasing continuously. With fused filament fabrication (FFF), it is possible to produce large and complex components quickly with high material efficiency. In FFF, a continuous thermoplastic filament is melted in a heated nozzle and deposited below. The computer-controlled print head is moved in order to build up the desired shape layer by layer. Investigations regarding printing of metals or ceramics are increasing more and more in research and industry. This study focuses on additive manufacturing (AM) with a multi-material approach to combine a metal (stainless steel) with a technical ceramic (zirconia: ZrO2). Combining these materials offers a broad variety of applications due to their different electrical and mechanical properties. The paper shows the main issues in preparation of the material and feedstock, device development, and printing of these composites.

Fused Filament Fabrication FFF of Metal-Ceramic Components

This study shows multi-material additive manufacturing (AM) using fused filament fabrication (FFF) of stainless steel and zirconia.

Fabricação de fundidos de filamento (FFF) de componentes de Metal-cerâmica

Technical ceramics are widely used for industrial and research applications, as well as for consumer goods. Today, the demand for complex geometries with ...