Damos las gracias a la Fundación Lindbäck de apoyo financiero, y el Dr. Alexander Sidorenko y Elza Chu para un debate fructífero y asistencia técnica, y el profesor Robert Smith para obtener ayuda con la C. ensayos elegans.

NOTA: En los procedimientos que se describen a continuación, las pautas de seguridad de laboratorio siempre se deben seguir. De particular importancia es la seguridad cuando se trata de alto voltaje (&gt; 500 V) y manipulación de productos químicos. 1. Recubrimiento de un sustrato conductor con la vela hollín <ol><li> Cortar en rectángulos de metal de cobre (75 x 43 mm, 0,5 mm de espesor). Limpie cada sustrato de cobre por inmersión en solución de ataque de cobre durante unos 30 segundos, lavar con agua del grifo durante unos 20 segundos, y secar con papel. NOTA: Si se utiliza el método 1 a continuación, cambie las dimensiones de 75 x 25 mm para encajar en la máquina. </li><li> Barrer una vela de parafina iluminada bajo el substrato de cobre durante 30-45 segundos, para obtener un recubrimiento de hollín aproximadamente uniforme (alrededor de 40 m de espesor). Mantenga el sustrato a ~ 1 cm dentro de la llama. No toque la superficie de hollín frágil. </li></ol> 2. La protección de la capa de hollín con Recubrimiento NOTA: La capa de hollín es muy frágil, Y debe ser cubierto para la protección. Dos alternativas simples (métodos 1 y 2 a continuación) se sugieren aquí, pero los protocolos más robustos están actualmente en desarrollo. <ol><li> Método 1 <ol><li> Cargar la muestra en el evaporador de metal o sistema de pulverización catódica. Siguiendo los procedimientos de operación del sistema, evacuar la cámara y comenzar la deposición controlada de oro sobre la capa de hollín (150-200 nm). Deje que el dispositivo se enfríe a temperatura ambiente. </li><li> Dip-revestir el sustrato metalizado en una solución de 1-dodecanotiol (1% v / v, en etanol al 95%, grado ACS / USP), durante 10 minutos dentro de una campana química. Entonces, sostiene el dispositivo en un ángulo cercano a 60 °, lavar suavemente la superficie con varias gotas de etanol sólo. Deje que los dispositivos seca, durante la noche. </li></ol></li><li> Método 2 <ol><li> En una campana química, inmediatamente después de revestir el sustrato con hollín y mientras el sustrato está todavía caliente de la llama de la vela, depositar algunas gotas de líquido fluorado en un lado de lasustrato, e inclinar el sustrato a un ángulo próximo a 90 °. Deposite más gotas, y dejar que ellos ruedan sobre la superficie entera de hollín. NOTA: Cuando la gota cae en un punto, el hollín se lavará lejos de esa zona. Dejar que las gotitas de líquido fluorado propagación tanto como sea posible. </li><li> Hornear el sustrato sobre una placa caliente (160 ° C durante 15 min) dentro de una campana química. </li><li> Deje que el sustrato reposar toda la noche a temperatura ambiente antes de su uso. Almacenar indefinidamente. </li></ol></li></ol> 3. Fabricación de electrodos superiores (Adaptado de Abdelgawad et al. 12) <ol><li> Dibuje los electrodos utilizando software de diseño gráfico. Cada electrodo es de 2 mm de largo, 0,3 mm de ancho, y la brecha entre los electrodos es de 0,3 mm. La brecha entre los contactos (para encajar en el conector, ver más abajo) es de 2,3 mm (Figura 1). </li><li> Recorte un laminado flexible de cobre (35 micras de espesor) en el formato Monarch (3,87 x 7,5 pulgadas). Utilice otros tamaños if compatible con la impresora. Cargue el laminado en la bandeja de alimentación manual de una impresora a color. </li><li> Asegúrese de utilizar &quot;negro rico&quot;, o &quot;registro negro&quot;, cuando se imprime en la hoja de cobre (ver Abdelgawad et al. 12 para más detalles) para permitir que una capa más densa de tinta negro sobre el sustrato de cobre, protegiendo el patrón impreso durante el grabado . Deje secar completamente el sustrato impreso, durante la noche. </li><li> Dentro de una campana química, caliente (40 ° C) un vaso de precipitados con 50 ml de reactivo de ataque de cobre. Sumerja el laminado impreso en el vaso de precipitados, y agítelo suavemente en la solución durante unos 10 minutos. Tiempo de grabado depende de la solución de grabado de cobre. Cada pocos minutos, comprobar la corrosión y ver si el patrón está intacto. </li><li> Lave cuidadosamente la lámina con agua, y eliminar el recubrimiento con acetona y etanol en la campana química. Lavar una vez más, y seque con cuidado el laminado con una toalla de papel. </li><li> Conecte con cuidado el laminado con electrodos a un gladiapositiva ss (75 x 25 mm, ~ 1 mm de espesor), utilizando cinta de doble cara. Evite las bolsas de aire. </li><li> Adjunte una película de perfluoroalcoxi PFA a los electrodos utilizando cinta. Esto sirve para evitar el contacto accidental de los electrodos con la gota, que daña electrodos superiores debido a cortocircuito. </li></ol> 4. La interfaz electrónica (circuito de la Figura 2) <ol><li> Soldar los relés y los condensadores C a una placa de circuito universal. </li><li> Montar el resto de los controladores de relé 10 en un circuito sin soldadura para circuitos electrónicos. </li><li> Cable de entrada de cada conductor del relé a un canal en el tablero de control. </li><li> Romper con cuidado los electrodos superiores en un conector (Figura 3). Cada cable de salida del controlador de relés a un electrodo superior, como se muestra en la figura. Tenga en cuenta que hay un contacto del conector a tierra entre un par de cables de relés, para minimizar el ruido eléctrico. NOTA: El conector se asienta sobre una plataforma ajustable para controlar la tque la distancia (0,1-0,5 mm) entre el sustrato (hollín-revestido) superior e inferior. </li><li> Utilice un programa para controlar el tiempo para la aplicación de alta tensión (HV) (alrededor de 0,8 seg) para 4 electrodos al mismo tiempo, desplazando 1 electrodo en la dirección del movimiento (es decir, para 0,8 seg, 1234 accionar, a continuación, 2345, 3456, etc ., 0,8 seg para cada grupo, y luego hacia atrás, se mueve de modo de gotitas en la dirección opuesta también). </li></ol> 5. Visualización de la gotita y Manipulación <ol><li> Para grabar el movimiento de las gotas, utilizar el sistema de visualización, que se compone de un 24X - conjunto de magnificación 96X combinado con una cámara CCD. Conecte la grabadora de vídeo a la cámara mediante S-vídeo. </li><li> Pipetear una gota de 4 l que contiene C. elegans en los medios de comunicación en la parte inferior del sustrato recubierto de hollín. </li><li> Traiga los electrodos superiores a ~ 0,3 mm por encima de la gota. La gota debe estar cerca de la mitad, justo por debajo del quinto electrodo, para facilitar la operación. </li><li> Encienda la interfaz electrónica y alta tensión (500 V RMS), y ajustar la distancia de la parte superior del electrodo a la gota hasta que comienza a moverse. No deje que los electrodos superiores tocan la gota. </li><li> Recopilar datos mediante el registro del número de transferencias exitosas de gotitas en el dispositivo en respuesta a impulsos eléctricos. Un experimento exitoso se caracteriza por al menos 700 transferencias de gotitas, es decir, una transferencia después de cada pulso eléctrico. </li><li> Recopilar datos continuamente, hasta que la gota no se mueve más en respuesta a 5 a 10 pulsos. NOTA: Cuando la superficie comienza a degradarse, el movimiento podría ser restaurado por traer los mejores electrodos cerca de la gota. </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. R. <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+for+cell-based+assays.">Digital microfluidics for cell-based assays.</a> Lab Chip. 8 (4), 519-526 (2008).</li><li>Brenner, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+genetics+of+Caenorhabditis+elegans.">The genetics of Caenorhabditis elegans.</a> Genetics. 77 (1), 71-94 (1974).</li></ol>

The authors declare that they have no competing financial interests.

El paso más importante del protocolo es la protección de la capa de hollín, directamente relacionado con el éxito en gotas en movimiento. Metalizar la capa de hollín (método 1 anterior) permite cerca de 100% de éxito de fabricación. Sin embargo, el tiempo máximo de funcionamiento es de aproximadamente 10 min; posiblemente, las fracciones de gotitas están mojando el hollín a través de agujeros en la capa de metal. El recubrimiento de la capa de hollín con el líquido fluorado es la alternativa más fácil y ...

La miniaturización de los dispositivos que funcionan con líquidos es de suma importancia para el desarrollo de plataformas de &quot;lab-on-a-chip&quot;. En este sentido, las dos últimas décadas han sido testigos de un avance significativo en el campo de la microfluídica, con una variedad de aplicaciones. 5.1 En contraste con el transporte de fluidos en los canales cerrados (canal de microfluidos), DMF manipula gotitas en matrices de electrodos. Uno de los méritos más atractivas de esta técnica es la ausencia de partes móviles para el transporte de fluidos, y el movimiento se detiene al instante apagando señales eléctricas. Sin embargo, el movimiento de gotitas depende de su contenido de gota, sin duda una característica indeseable para una plataforma universal &quot;lab-on-a-chip&quot;. Las gotitas que contienen proteínas y otros analitos se adhieren a las superficies de dispositivos, convirtiéndose en inamovible. Sin duda, ésta ha sido la principal limitación para ampliar el alcance de las aplicaciones de DMF; 6-8alternativas para minimizar el ensuciamiento superficie no deseado implican la adición de especies químicas adicionales a la gota o sus alrededores, lo que podría afectar el contenido de las gotas. Anteriormente, nuestro grupo desarrolló un dispositivo para permitir el transporte de células y proteínas en DMF, sin aditivos adicionales (aparatos de campo-DW). 9 Esto se logró mediante la combinación de una superficie basada en el hollín vela, 10 con una geometría del dispositivo que favorece la gotita de laminación y conduce a una fuerza hacia arriba en la gotita, disminuyendo aún más la interacción de gotitas en la superficie. En este enfoque, el movimiento gotita no está asociado con humectación de la superficie. 11 El objetivo del método detallado se describe a continuación es producir un dispositivo de DMF capaz de transportar gotitas que contienen proteínas, células y organismos enteros, sin aditivos adicionales. Los dispositivos de campo-DW allanan el camino para las plataformas de trabajo totalmente controladas en gran medida independiente de farmacia gotary. Aquí, también presentes simulaciones que muestran que, a pesar de la alta tensión necesaria para el funcionamiento del dispositivo, la caída de voltaje a través de la gotita es una pequeña fracción de la tensión aplicada, lo que indica efectos insignificantes en bioanalytes dentro de la gotita. De hecho, las pruebas preliminares con Caenorhabditis elegans (C. elegans), un nematodo utilizado para una variedad de estudios de la biología, muestran que los gusanos nadan sin perturbaciones como se aplican voltajes.

<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, hemos utilizado dispositivos Field-DW para permitir el movimiento de las proteínas en DMF. En particular, las gotitas con albúmina de suero bovino (BSA) se pueden mover a una concentración 2.000 veces mayor que lo reportado previamente por otros autores (sin aditivos). Esto era debido a la reducción de la interacción entre las gotitas y superficie; La figura 4 muestra una gotita que contiene marcado con fluorescencia-BSA (ver Freire et al 9 para más información ...

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.

Tomando ventaja de la reducción de la interacción de gotas en la superficie para optimizar el transporte de Bioanalytes en microfluídica digitales

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 vistas.  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.

Video: 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.

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

Investigación

Ingeniería

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.

Caracterización de Transporte térmica en materiales sólidos unidimensionales

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-dinámico Método de polarización de conmutación Tiempo Mejoras en Severamente Subamortiguado Fleco campo electrostático MEMS actuadores

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.

Cómo construir un vacío Paquete de primavera-transporte para la hilatura de rotor de medidores

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%.

Impresión digital de dióxido de titanio para células solares sensibilizadas Tinte

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.

Fatiga ultrasónica prueba en el modo de tensión-compresión

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.

La combinación de la microfluídica y Microrheology para determinar las propiedades reológicas de materia blanda durante las transiciones de fase repetido

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.

Fabricación de dispositivos emparejados de índice refractivo para microfluidos 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.

Monitoreo de grietas en las pruebas de fatiga por resonancia de especímenes soldados utilizando la correlación de imágenes digitales

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 objetivos microfabricados para experimentos de irradiación láser intensa

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