Name: a versatile kit based on digital microfluidics droplet actuation for science education
Uploaded: 2021-04-26T13:30:00
Description: Watch this Scientific Journal Video about A Versatile Kit Based on Digital Microfluidics Droplet Actuation for Science Education at JoVE.com

Y. T. Y. would like to acknowledge funding support from the Ministry of Science and Technology under grant numbers MOST 107-2621-M-007-001-MY3 and National Tsing Hua University under grant number 109Q2702E1. Mark Kurban from Edanz Group (https://en-author-services.edanzgroup.com/ac) edited a draft of this manuscript.

1) Assembling the digital microfluidics kit
<ol>
	<li>Solder the surface mount resistors, transistors, and light-emitting diodes onto the PCB board according to the schematics in Figure 1b.</li>
	<li>Connect the output of the high-voltage power supply board to the PCB board with soldered components (Figure 2 and Supplementary Figure 1).</li>
	<li>Connect the battery to the voltage booster board to boost the voltage from 6 V to 12 V (<strong cl...

<ol>
	<li>Convery, N., Gadegaard, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=30+years+of+microfluidics.">30 years of microfluidics.</a> Micro and Nano Engineering. 2, 76-91 (2019).</li><li>Rackus, D. G., Ridel-Kruse, I. H., Pamme, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Learning+on+a+chip:+Microfluidics+for+formal+and+informal+science+education.">Learning on a chip: Microfluidics for formal and informal science education.</a> Biomicrofluidics. 13, 041501 (2019).</li><li>Legge, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemistry+under+the+microscope-Lab+on+a+chip+technologies.">Chemistry under the microscope-Lab on a chip technologies.</a> Journal of Chemical Education. 79, 173 (2002).</li><li>Fintschenko, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Education:+a+modular+approach+to+microfluidics+in+the+teaching+laboratory.">Education: a modular approach to microfluidics in the teaching laboratory.</a> Lab On A Chip. 11, 3394 (2011).</li><li>Mugele, F., Baret, J. -. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrowetting:+from+basics+to+applications.">Electrowetting: from basics to applications.</a> Journal of Physics: Condensed Matter. 17, 705-774 (2005).</li><li>Lippmann, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relations+entre+les+phenomenes+electriques+et+capillary.">Relations entre les phenomenes electriques et capillary.</a> Ann. Chim. Phys. 6, 494 (1875).</li><li>Berge, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrocapillarite+et+mouillge+de+films+isolant+par+l'eau.">Electrocapillarite et mouillge de films isolant par l'eau.</a> C. R. Acad. Sci. II. 317, 157 (1993).</li><li>Pollack, M. G., Fair, R. B., Shenderov, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrowetting-based+actuation+of+liquid+droplets+for+microfluidics+applications.">Electrowetting-based actuation of liquid droplets for microfluidics applications.</a> Applied Physics Letters. 77, 1725 (2000).</li><li>Lee, J., Kim, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface-tension-driven+microactuation+based+on+continuous+electrowetting.">Surface-tension-driven microactuation based on continuous electrowetting.</a> Journal of Microelectromechanical Systems. 9 (2), 171 (2000).</li><li>Choi, K., Ng, A. H. C., Fobel, R., 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.">Digital Microfluidics.</a> Annual Review of Analalytical Chemistry. 5, 413-440 (2012).</li><li>Jebrail, M. 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=Let's+get+digital:+digitizing+chemical+biology+with+microfluidics.">Let's get digital: digitizing chemical biology with microfluidics.</a> Current Opinion in Chemical Biology. 14, 574-581 (2000).</li><li>Pollack, M. G., Pamula, V. K., Srinivasan, V., Eckhardt, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=2011.+Applications+of+electrowetting-based+digital+microfluidics+in+clinical+diagnostics.">2011. Applications of electrowetting-based digital microfluidics in clinical diagnostics.</a> Expert Review of Molecular Diagnostics. 11, 393-407 (2011).</li><li>Abdelgawad, M., 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=Rapid+prototyping+in+copper+substrates+for+digital+microfluidics.">Rapid prototyping in copper substrates for digital microfluidics.</a> Advanced Materials. 19 (1), 133-137 (2007).</li><li>Abdelgawad, M., 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=Low-cost,+rapid-prototyping+of+digital+microfluidics+devices.">Low-cost, rapid-prototyping of digital microfluidics devices.</a> Microfluidics and Nanofluidics. 4, 349-355 (2008).</li><li>Fobel, R., Fobel, C., 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=DropBot:+an+open-source+digital+microfluidic+control+system+with+precise+control+of+electrostatic+driving+force+and+instantaneous+drop+velocity+measurement.">DropBot: an open-source digital microfluidic control system with precise control of electrostatic driving force and instantaneous drop velocity measurement.</a> Applied Physics Letters. 102, 193513 (2013).</li><li>Yafia, M., Ahmadi, A., Hoorfar, M., Najjaran, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultra-portable+smartphone+controlled+integrated+digital+microfluidic+system+in+a+3D-printed+modular+assembly.">Ultra-portable smartphone controlled integrated digital microfluidic system in a 3D-printed modular assembly.</a> Micromachines. 6 (9), 1289-1305 (2015).</li><li>Alistar, M., Gaudenz, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=OpenDrop:+an+integrated+do-it-yourself+platform+for+personal+use+of+biochips.">OpenDrop: an integrated do-it-yourself platform for personal use of biochips.</a> Bioengineering. 4 (2), 45 (2017).</li><li>Khan, P., 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=Luminol-based+chemiluminescent+signals:+clinical+and+non-clinical+application+and+future+uses.">Luminol-based chemiluminescent signals: clinical and non-clinical application and future uses.</a> Applied Biochemistry and Biotechnology. 173 (2), 333-355 (2014).</li><li>Agresti, J. 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=Ultrahigh-throughput+screening+in+drop-based+microfluidics+for+directed+evolution.">Ultrahigh-throughput screening in drop-based microfluidics for directed evolution.</a> Proceedings of the National Academy of Sciences of the United States of America. 107 (9), 4004-4009 (2010).</li><li>. Microfluidics Available from: <a target="_blank" href="https://microfluidics.utoronto.ca/dropbot/">https://microfluidics.utoronto.ca/dropbot/</a> (2020)</li><li>Busnel, J. M., 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=Evaluation+of+capillary+isoelectric+focusing+in+glycerol-water+media+with+a+view+to+hydrophobic+protein+applications.">Evaluation of capillary isoelectric focusing in glycerol-water media with a view to hydrophobic protein applications.</a> Electrophoresis. 26, 3369-3379 (2005).</li><li>Chatterjee, D., Shepherd, H., Garrell, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electromechanical+model+for+actuating+liquids+in+a+two+plate+droplet+microfluidic+device.">Electromechanical model for actuating liquids in a two plate droplet microfluidic device.</a> Lab On A Chip. 9, 1219-1229 (2009).</li></ol>

The procedure described here allows the reader to assemble and test a working EWOD system for droplet actuation and gain hands-on experience with microfluidics. We intentionally avoid expensive components and chemical samples. Currently, one kit can be constructedfor ~$130 with the most expensive component being optical color glass for fluorescent imaging and microcontroller excluding the custom acrylic enclosure (Supplementary Table 1). For such a cost, a fluorescent imaging capability and an active hum...

Microfluidics is a highly interdisciplinary field combing physics, chemistry, biology, and engineering for the manipulation of small volume of liquids ranging from femtoliter to microliters1. Microfluidics is also a very broad and active field; a Web of Science search returns nearly 20,000 publications and yet there is insufficient literature and review papers on the usage of microfluidics as educational tool2. There are two insightful, albeit outdated review articles by Legge and Fintschenko3,4. Legge introduces educators to the idea of a lab on a chip3. Fintschenko pointed out the role of microfluidics teaching lab in Science Technology Engineering Mathematics (STEM) education and simplified the philosophies into &#34;teach microfluidics&#34; and &#34;use microfluidics&#34;4. A more recent review by Rackus, Ridel-Kruse and Pamme in 2019 points out that in addition to being interdisciplinary in nature, microfluidics is also a very hands-on subject2. The hands-on activity related to the practice of microfluidics lends students to inquiry-based learning and makes it an engaging tool for science communication and outreach. Microfluidics indeed offers much potential for science education in both formal and informal settings and is also an ideal &#34;tool&#34; to enthuse and educate the general public about the interdisciplinary aspect of modern sciences.
Examples such as low-cost microchannel devices, paper microfluidics, and digital microfluidics are ideal tools for educational purposes. Among these platforms, digital microfluidics remains esoteric and peer-reviewed reports based on digital microfluidics are lacking2. Here we propose to use digital microfluidics as an educational tool for several reasons. First, digital microfluidics is very distinct from microchannel-based paradigm because it is based on manipulation of the droplets and usage of the droplets as discrete microvessels. Second, droplets are manipulated on relatively generic electrode-array platforms so digital microfluidics can be intimately coupled with microelectronics. Users can leverage on an extended set of electronic components, now highly accessible for do-it-yourself applications to electronically interface with droplets. Hence, we argue that digital microfluidics can let students to experience these unique aspects and be open-minded not overly to stick to microchannel-based low Reynold number microfluidics1.
Briefly, the field of digital microfluidics is largely based on the electrowetting phenomena, which was first described by Gabriel Lippmann5,6. The recent developments were initiated by Berge in the early 1990s7. His key contribution is the idea of introducing a thin insulator to separate the conductive liquid from metallic electrodes to eliminate the problem of electrolysis. This idea has been termed as electrowetting on dielectric (EWOD). Subsequently, the digital microfluidics was popularized by several pioneering researchers8,9. Now a comprehensive list of applications for example, in clinical diagnostics, chemistry and biology, has been proven on digital microfluidics10,11,12 and, therefore, plenty of examples are available for an educational setting. In particular, along the line of low cost, do-it-yourself digital microfluidics, Abdelgawad and Wheeler have previously reported low-cost, rapid prototyping of digital microfluidics13,14. Fobel et al., has also reported DropBot as an open source digital microfluidic control system15. Yafia et al., also reported a portable digital microfluidics based on 3D printed parts and smaller phone16. Alistar and Gaudenz have also developed the battery powered OpenDrop platform, which is based on the field effect transistor array and dc actuation17.
Here, we present a digital microfluidics educational kit based on commercially sourced printed circuit board (PCB) that allows the user to assemble and get hands-on experience with digital microfluidics (Figure 1). Fee-for-service to create PCB from digital design files is widely available, and hence we think it is a viable low-cost solution for education provided that digital design files can be shared. Meticulous choice of components and system design is made to simplify the assembly process and make an interface with the user&#39;s intuitive. Hence, a one-plate configuration is used instead of a two-plate configuration to avoid the need for a top plate. Both the components and the test chemicals need to be easily available. For example, food wrap from the supermarket is used as the insulator in our kit.
To prove feasibility of our kit, we suggest a specific chemistry experiment based on chemiluminescence of luminol and provide the protocol. The hope is that visual observation of chemiluminescence can enthuse and excite students. Luminol is a chemical that exhibits a blue glow when mixed with an oxidizing agent such as H2O2 and is typically used in forensics to detect blood18. In our laboratory setting, potassium ferricyanide serves as the catalyst. Luminol reacts with the hydroxide ion and forms a dianion. The dianion subsequently reacts with oxygen from hydrogen peroxide to form 5-aminophthalic acid with electrons in an excited state, and relaxation of electrons from the excited state to the ground state results in photons visible as a burst of blue light.
We also report a fluorescent imaging experiment with a smart phone to demonstrate the integration of a light-emitting diode (LED) as an excitation light source. Finally, droplet evaporation is a problem in microfluidics but is rarely being addressed. (A 1 &#956;L of water droplet is lost within 1 h from an open substrate3.) We use an atomizer based on a high-frequency piezo transducer to convert water into fine mist. This creates a humidified environment to prevent droplet evaporation and demonstrates long-term (~1 h) droplet actuation.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61978/61978fig01.jpg" /> 
Figure 1: Schematics of EWOD set up. (a) A microcontroller is used to provide a control sequence to the EWOD electrode. Also, the humidity is controlled. (b) Schematics of PCB layout. Electrodes, LED for fluorescent imaging, resistor, and field effect transistors (FET) are labeled. Scale bar of 1 cm is also shown.&#160;<a href="https://www.jove.com/files/ftp_upload/61978/61978fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61978/61978fig02.jpg" /> 
Figure 2: Top view of the kit. Microcontroller board, high voltage supply board, EWOD PCB, humidity sensor, and atomizer are labeled.&#160;<a href="https://www.jove.com/files/ftp_upload/61978/61978fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Acrylic enclosure</td>
			<td>LOCAL vendor</td>
			<td></td>
			<td>23cm x 20.5 cm x 6cm</td>
		</tr>
		<tr>
			<td>Ardunion Uno</td>
			<td>Arduino</td>
			<td>UNO</td>
			<td>microcontroller board</td>
		</tr>
		<tr>
			<td>acetic acid</td>
			<td>Sigma Alrich</td>
			<td>695092-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Breadboard</td>
			<td>MCIGICM</td>
			<td>400tie</td>
			<td>4 cm x 7 cm, 400 Points Solderless Breadboard, a pack of 4</td>
		</tr>
		<tr>
			<td>BSP89 H6327 Infineon MOSFET&#160;</td>
			<td>Mouser</td>
			<td>726-BSP89H6327</td>
			<td>drain soure breakdown voltage 240V,on resistance 4.2 ohm</td>
		</tr>
		<tr>
			<td>citrid acid</td>
			<td>sigma Alrich</td>
			<td>251275-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Color glass filter&#160;</td>
			<td>Thorlabs</td>
			<td>FGL 530</td>
			<td>color glass filter for fluorescent imaging</td>
		</tr>
		<tr>
			<td>DHT11 temperature &#38; humidity sensor</td>
			<td>adafruit</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Digital multimeter&#160;</td>
			<td>Fluke</td>
			<td>17B</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescein isothiocyanate isomer I</td>
			<td>sigma Alrich</td>
			<td>F7250-50MG</td>
			<td>50 mg price, fluorescent imaging</td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma Alrich</td>
			<td>G9012-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>High voltage power supply for Nixe tube</td>
			<td>Vaorwne</td>
			<td>NCH6100HV</td>
			<td>High voltage power max dc 235V</td>
		</tr>
		<tr>
			<td>LM2596 voltage booster circuit</td>
			<td></td>
			<td></td>
			<td>boost voltage from 5V to 12 V</td>
		</tr>
		<tr>
			<td>Luminol</td>
			<td>Sigma Alrich</td>
			<td>123072-5G</td>
			<td>5 g for $110</td>
		</tr>
		<tr>
			<td>Pippet</td>
			<td>Thermal Fisher</td>
			<td></td>
			<td>1- 10 ul</td>
		</tr>
		<tr>
			<td>Printed circuit board&#160;</td>
			<td>Local vender</td>
			<td></td>
			<td>10 piece for $60</td>
		</tr>
		<tr>
			<td>Plastic food wrap</td>
			<td>Kirkland</td>
			<td>Stretch-tite&#160;</td>
			<td>food wrap Plastic food wrap</td>
		</tr>
		<tr>
			<td>Potassium ferricynide</td>
			<td>Merck</td>
			<td>104982</td>
			<td>1 kg</td>
		</tr>
		<tr>
			<td>1N Potassium hydroxide solution (1 mol/l)&#160;</td>
			<td>Scharlau&#160;</td>
			<td></td>
			<td>1 Liter</td>
		</tr>
		<tr>
			<td>Clear Office tape 3mm</td>
			<td>3M Scotch</td>
			<td></td>
			<td>semi-transparent, used as diffuser for illumination</td>
		</tr>
		<tr>
			<td>salt</td>
			<td>Great Value Iodized Salt</td>
			<td></td>
			<td>6 oz for $7 salt from supermarket</td>
		</tr>
		<tr>
			<td>Silicone oil (5Cst)</td>
			<td>Sigma Alrich</td>
			<td>317667-250ML</td>
			<td>top hydrophobic layer &#38; filling layer between electrode and insulator</td>
		</tr>
		<tr>
			<td>sucrose</td>
			<td></td>
			<td></td>
			<td>table sugar&#160; from any supermarket, 6 dollar per pound</td>
		</tr>
		<tr>
			<td>Surface mount blue LED</td>
			<td>oznium</td>
			<td>3528</td>
			<td>Oznium 20 Pieces of PLCC-2 Surface Mount LEDs, 3528 Size SMD SMT LED - Blue</td>
		</tr>
		<tr>
			<td>Surface mount resistor 180k Ohm</td>
			<td>Balance World Inc</td>
			<td></td>
			<td>3mm x 6 mm 1watt</td>
		</tr>
		<tr>
			<td>Surface mount resistor 510Ohm</td>
			<td>Balance World Inc</td>
			<td></td>
			<td>bias resistor for LED, 3mmx6mm 1watt</td>
		</tr>
		<tr>
			<td>Water atomizer</td>
			<td>Grove&#160;</td>
			<td></td>
			<td>operating frequency 100 kHz&#160; supply votage 5V max 2W&#160; The kit comes with ultrasonic transducer</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>high voltage transistor</td>
		</tr>
	</tbody>
</table>

a versatile kit based on digital microfluidics droplet actuation for science education

This paper describes an educational kit based on digital microfluidics. A protocol for luminol-based chemiluminescence experiment is reported as a specific example. It also has fluorescent imaging capability and closed humidified enclosure based on an ultrasonic atomizer to prevent evaporation. The kit can be assembled within a short period of time and with minimal training in electronics and soldering. The kit allows both undergraduate/graduate students and enthusiasts to obtain hands-on experience in microfluidics in an intuitive way and be trained to gain familiarity with digital microfluidics.

The droplet actuation is recorded with a smart phone. Representative results for chemiluminescence and fluorescent imaging are displayed in Figure 3 and Figure 4. For the chemiluminescence experiment, the droplet of 10 &#956;L ferricyanide is actuated to move and mix with pre-deposited 2 &#956;L droplet on the target electrode as shown in Figure 3. The time period between successive movement is set t...

Watch this Scientific Journal Video about A Versatile Kit Based on Digital Microfluidics Droplet Actuation for Science Education at JoVE.com

A Versatile Kit Based on Digital Microfluidics Droplet Actuation for Science Education

We describe an educational kit that allows users to execute multiple experiments and gain hands-on experience on digital microfluidics.

This paper describes an educational kit based on digital microfluidics. A protocol for luminol-based chemiluminescence experiment is reported as a ...

We present a digital microfluidics educational kit based on a commercially-sourced printed circuit board that allows the user to get hands-on experience with digital microfluidics. This is a viable, low cost solution for education provided that digital PCB design files can be shared. We propose to use digital microfluidics as an educational tool because droplets are manipulated on generic electrode array platforms.Users can leverage on an extended set of electronic components now highly accessible for do-it-yourself applications to electronically interface with the droplets. Demonstrating the procedure will be Yu Hao Guo, a graduate student from the Yang Laboratory. Begin by soldering the surface mount resistors, transistors, and light emitting diodes onto the PCB board.Connect the output of the high voltage power supply board to the PCB board with the soldered components. Then connect the battery to the voltage booster board to boost the voltage from six volts to 12 volts. Connect the humidity sensor, the ultrasonic piezo atomizer, and the atomizer driver board to the microcontroller board.Turn on the microcontroller using the provided supplementary code. Adjust the variable resistor of the high voltage board and use the digital multi-meter to measure the voltage of the EWOD electrode. Wear clean nitrile gloves and apply 10 microliters of five centistoke silicone oil on the electrode area using a micropipette.Spread the oil evenly on the electrode area using a finger. Cut a piece of food wrap with dimensions 2.5 by four centimeters and place it on top of the electrode. Apply silicone oil on the electrode area using a micropipette and spread it evenly.To perform a chemiluminescence experiment, place two to five microliters of luminol solution on the target electrode using a micropipette. Place 10 microliters of 0.1%potassium ferrocyanide on the electrode which can be moved as a droplet for electrowetting. Turn on the microcontroller so that the potassium ferrocyanide droplet merges with the luminol.For fluorescent imaging, cut a one square centimeter piece of semi-transparent tape and place it between the excitation light emitting diode and EWOD electrodes. Attach the emission glass filter on the camera of the smartphone with tape and place 10 microliters of the potassium ferrocyanide solution on the electrodes. Record the video of the droplet actuation using a smartphone.For long-term droplet actuation, place one milliliter of water onto the ultrasonic atomizer. Place a droplet of potassium ferrocyanide and turn on the microcontroller. Then immediately close the lid of the enclosure.Check the droplet actuation after an hour. A representative droplet movement is shown here. For the chemiluminescence experiment, the droplet of ferrocyanide is actuated to move and mix with the pre-deposited luminol droplet on the target electrode at 12 seconds.A schematic setup of an LED serving as the light source for excitation, a semi-transparent clear office tape as a light diffuser, and the emission filter directly attached to the smartphone camera is shown here. Fluorescent imaging of the droplet containing fluorescein isothiocyanate in the dark is seen as a result of the semi-transparent tape serving as the diffuser to evenly distribute the excitation light. For a long-term experiment, successful droplet actuation can be observed.Representative humidity data under the action of an ultrasonic atomizer is shown here. This protocol can be used to develop an educational kit based on digital microfluidics. A luminol-based chemiluminescence experiment is reported as a specific example.The kit can be assembled within a short period of time and with minimal training in electronics. The simplified experiment described here can be extended to other experiments. For example, a paper test kit can be used by moving the droplet to the paper to be absorbed.A microcontroller with interface logic circuit can also be added to provide more sophisticated digital control and programmability. This protocol can benefit non-professional enthusiasts to learn and apply electronics to further advance their knowledge of the field.

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Engineering

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.

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.

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

Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 &#176;C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 &#176;C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 &#176;C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 &#176;C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example.

A protocol for high-temperature and high-pressure gas adsorption measurements on zeolite H-ZSM-5 using an adsorption measurement device based on a langatate crystal microbalance is presented. Prior to the adsorption measurements, the synthesis of zeolite H-ZSM-5 on the langatate crystal microbalance sensor by the steam-assisted crystallization (SAC) method is demonstrated.

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate ...

A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

In this paper, we present a protocol to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica.

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on ...

Fabrication of Flexible Image Sensor Based on Lateral NIPIN Phototransistors

Flexible photodetectors have been intensely studied for the use of curved image sensors, which are a crucial component in bio-inspired imaging systems, but several challenging points remain, such as a low absorption efficiency due to a thin active layer and low flexibility. We present an advanced method to fabricate a flexible phototransistor array with an improved electrical performance. The outstanding electrical performance is driven by a low dark current owing to deep impurity doping. Stretchable and flexible metal interconnectors simultaneously offer electrical and mechanical stabilities in a highly deformed state. The protocol explicitly describes the fabrication process of the phototransistor using a thin silicon membrane. By measuring I-V characteristics of the completed device in deformed states, we demonstrate that this approach improves the mechanical and electrical stabilities of the phototransistor array. We expect that this approach to a flexible phototransistor can be widely used for the applications of not only next-generation imaging systems/optoelectronics but also wearable devices such as tactile/pressure/temperature sensors and health monitors.

We present a detailed method to fabricate a deformable lateral NIPIN phototransistor array for curved image sensors. The phototransistor array with an open mesh form, which is composed of thin silicon islands and stretchable metal interconnectors, provides flexibility and stretchability. The parameter analyzer characterizes the electrical property of the fabricated phototransistor.

Flexible photodetectors have been intensely studied for the use of curved image sensors, which are a crucial component in bio-inspired imaging systems, ...

A Pipette-Tip Based Method for Seeding Cells to Droplet Microfluidic Platforms

Amongst various microfluidic platform designs frequently used for cellular analysis, droplet-microfluidics provides a robust tool for isolating and analyzing cells at the single-cell level by eliminating the influence of external factors on the cellular microenvironment. Encapsulation of cells in droplets is dictated by the Poisson distribution as a function of the number of cells present in each droplet and the average number of cells per volume of droplet. Primary cells, especially immune cells, or clinical specimens can be scarce and loss-less encapsulation of cells remains challenging. In this paper, we present a new methodology that uses pipette-tips to load cells to droplet-based microfluidic devices without the significant loss of cells. With various cell types , we demonstrate efficient cell encapsulation in droplets that closely corresponds to the encapsulation efficiency predicted by the Poisson distribution. Our method ensures loss-less loading of cells to microfluidic platforms and can be easily adapted for downstream single cell analysis, e.g., to decode cellular interactions between different cell types.

This article presents a protocol for seeding scarce population of cells using pipette-tips to droplet microfluidic devices in order to provide higher encapsulation efficiency of cells in droplets.

Amongst various microfluidic platform designs frequently used for cellular analysis, droplet-microfluidics provides a robust tool for isolating and ...

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.

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

O-cresol Concentration Online Measurement Based On Near Infrared Spectroscopy Via Partial Least Square Regression

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the prediction of the components in industrial processes. The ability to record spectra for solid and liquid samples without any pretreatment is advantageous and the method is widely used. However, the disadvantages of analyzing high-dimensional near-infrared spectral data include information redundancy and multicollinearity of the spectral data. Thus, we propose to use partial least squares regression method, which has traditionally been used to reduce the data dimensionality and eliminate the collinearity between the original features. We implement the method for predicting the o-cresol concentration during the production of polyphenylene ether. The proposed approach offers the following advantages over component regression prediction methods: 1) partial least squares regression solves the multicollinearity problem of the independent variables and effectively avoids overfitting, which occurs in a regression analysis due to the high correlation between the independent variables; 2) the use of the near-infrared spectra results in high accuracy because it is a non-destructive and non-polluting method to obtain information at microscopic and molecular scales.

The protocol describes a method of predicting o-cresol concentration during the production of polyphenylene ether using near-infrared spectroscopy and partial least squares regression. To describe the process more clearly and completely, an example of predicting the o-cresol concentration during the production of polyphenylene is used to clarify the steps.

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the ...

Implementation of a Nonlinear Microscope Based on Stimulated Raman Scattering

Stimulated Raman scattering (SRS) microscopy uses near-infrared excitation light; therefore, it shares many multi-photon microscopic imaging properties. SRS imaging modality can be obtained using commercial laser-scanning microscopes by equipping with a non-descanned forward detector with proper bandpass filters and lock-in amplifier (LIA) detection scheme. A schematic layout of a typical SRS microscope includes the following: two pulsed laser beams, (i.e., the pump and probe directed in a scanning microscope), which must be overlapped in both space and time at the image plane, then focused by a microscope objective into the sample through two scanning mirrors (SMs), which raster the focal spot across an x-y plane. After interaction with the sample, transmitted output pulses are collected by an upper objective and measured by a forward detection system inserted in an inverted microscope. Pump pulses are removed by a stack of optical filters, whereas the probe pulses that are the result of the SRS process occurring in the focal volume of the specimen are measured by a photodiode (PD). The readout of the PD is demodulated by the LIA to extract the modulation depth. A two-dimensional (2D) image is obtained by synchronizing the forward detection unit with the microscope scanning unit. In this paper, the implementation of an SRS microscope is described and successfully demonstrated, as well as the reporting of label-free images of polystyrene beads with diameters of 3 &#181;m. It is worth noting that SRS microscopes are not commercially available, so in order to take advantage of these characteristics, the homemade construction is the only option. Since SRS microscopy is becoming popular in many fields, it is believed that this careful description of the SRS microscope implementation can be very useful for the scientific community.

In this manuscript, the implementation of a stimulated Raman scattering (SRS) microscope, obtained by the integration of an SRS experimental set-up with a laser scanning microscope, is described. The SRS microscope is based on two femtosecond (fs) laser sources, a Ti-Sapphire (Ti:Sa) and synchronized optical parametric oscillator (OPO).

Stimulated Raman scattering (SRS) microscopy uses near-infrared excitation light; therefore, it shares many multi-photon microscopic imaging properties. ...

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

We present a high-performance source of unconditional polarization-entangled photons that have a high-emission rate, a broadband distribution, are degenerated and postselection free. The property of the source is based on the multiple quantum interference effect with a round-trip configuration of a Sagnac interferometer. The quantum interference effects make it possible to use the high generation efficiency of the polarization-entangled photons to process parametric down-conversion, and separate degenerated photon pairs into different optical modes without a postselection requirement. The principle of the optical system was described and experimentally used to measure the fidelity and Bell parameters, and also to characterize the generated polarization-entangled photons from a minimum of six combinations of polarization correlated data. The experimentally obtained fidelity and Bell parameters exceeded the classical local correlation limit and are clear evidence of the generation of unconditional polarization-entangled photons.

We describe an optical system for the generation of unconditional polarization-entangled photons based on multiple quantum interference effects with a detection scheme to estimate the experimental fidelity of generated entangled photons.

We present a high-performance source of unconditional polarization-entangled photons that have a high-emission rate, a broadband distribution, are ...

Cryogenic Liquid Jets for High Repetition Rate Discovery Science

This protocol presents a detailed procedure for the operation of continuous, micron-sized cryogenic cylindrical and planar liquid jets. When operated as described here, the jet exhibits high laminarity and stability for centimeters. Successful operation of a cryogenic liquid jet in the Rayleigh regime requires a basic understanding of fluid dynamics and thermodynamics at cryogenic temperatures. Theoretical calculations and typical empirical values are provided as a guide to design a comparable system. This report identifies the importance of both cleanliness during cryogenic source assembly and stability of the cryogenic source temperature once liquefied. The system can be used for high repetition rate laser-driven proton acceleration, with an envisioned application in proton therapy. Other applications include laboratory astrophysics, materials science, and next-generation particle accelerators.

This protocol presents the operation and principles of micron-scale cylindrical and planar cryogenic liquid jets. Until now, this system has been used as a high repetition rate target in laser-plasma experiments. Anticipated cross-disciplinary applications range from laboratory astrophysics to material science, and eventually next-generation particle accelerators.

This protocol presents a detailed procedure for the operation of continuous, micron-sized cryogenic cylindrical and planar liquid jets. When operated as ...