Name: development of a 3d graphene electrode dielectrophoretic device
Uploaded: 2014-06-22T14:00:00
Description: Watch this Scientific Journal Video about Development of a 3D Graphene Electrode Dielectrophoretic Device at JoVE.com

Thanks to XG Sciences for generous donations of graphene paper. Thanks to Dr. C. Friedrich for generously letting us use the micro-drilling equipment. A special thanks is extended to Tayloria Adams for narrating the video.

1. Fabricate a Laminated Electrode/insulation 3D Structure
<ol>
	<li>For a 6 graphene layer, 5 tape layer device, cut graphene paper with a scalpel or similar razor blade and straight-edged ruler into six 0.7 cm x&#160;1.5 cm rectangles and use scissors to cut double-sided pressure-sensitive tape into five 1.3 cm x&#160;~5 cm stripes. 
	NOTE: As shown in Figure 1a, this yields a 3 ground electrode, 3 AC signal electrode device. The 7 mm conducting layer width is narrow enough to fit onto a glass s...

This manuscript details protocols for fabricating a novel 6 graphene layer and 5 tape layer microdevice. Further, device operation is illustrated via observed DEP behaviors of 6.08 &#181;m polystyrene beads along with a unique, geometrically relevant particle velocity analysis approach. This versatile approach to construct nonlinear electrokinetic devices is less costly than electrode and fluidic layer microfabrication techniques, while yielding equally reliable results.
Further, this novel 3D...

Graphene is a novel material known for its high quality electronic properties and potential chemical and biosensor applications1. Graphene nanoplatelets have been used for catalyst support2,3, biosensors4, super-capacitors5, and composite-electrodes including graphene/polyaniline and silicon nanoparticle/graphene composites6-8. This manuscript describes utilization of graphene paper as electrodes in a unique three-dimensional (3D), layered microfluidic device. Graphene paper electrodes were laminated with insulative double-sided tape and a chamber drilled within which 3D AC dielectrophoresis of polystyrene beads was performed.
Dielectrophoresis (DEP) refers to the movement of polarizable particles under non-uniform electrical fields. Positive DEP (pDEP) or negative DEP (nDEP) occurs when particles are more or less polarizable than the surrounding medium, resulting in movement toward the strongest or weakest electrical field, respectively. This nonlinear electrokinetic tool has been used for separation, sorting, trapping, and identification of particles and biological cells9-15. The dielectrophoretic force experienced by a polarized particle is a function of the electric field gradient, particle radius and shape, particle dielectric properties including conductivity and permittivity, as well as the media conductivity and permittivity. In traditional two-dimensional (2D) DEP, particle movement is in the primary plane of the electric field gradient typically formed between microfabricated surface electrodes; movement in the vertical direction is negligible compared to in-plane directions in most devices. However, harnessing this third dimension of electrical field gradients for 3D DEP allows for higher sample throughput and increases the versatility to design new and improved dielectrophoretic separations in which the flow is traverse to the field gradients16,17. Other specific designs include 3D insulator-based DEP18, 3D carbon-electrode DEP13,19, and 3D electroplating DEP10. As evidenced by the research into 3D structures, such devices can be operated in continuous flow mode to achieve higher throughputs. Observation of the 3D particle movement in our layered 3D device is achieved as a function of frequency and medium conductivity via light microscopy at different focal heights.
Fatoyinbo&#160;et al. first reported DEP in a 3D laminated electrode/insulation structure using alternatively stacked 30 &#956;m aluminum foil and 150 &#956;m epoxy resin films20. Hubner&#160;et al. then designed similar 3D laminated electrodes with 35 &#956;m copper tape and 118 &#956;m polyimide adhesive21. This work borrows the 3D-well design22,23, and uniquely utilizes the convenience of 50 &#956;m graphene paper as the conducting layers and 100 &#956;m double-sided tape as the insulating layers, which achieved sealing and sufficient electrical shielding. Graphene paper versatility is a distinct advantage for 3D electrode microdevices because the graphene nanoplatelets have the ability to concurrently act as biosensors, which this group previously demonstrated24.
The field gradients achieved within the graphene paper/polymer laminated 3D microdevices depend on the micro-well dimensions, the graphene paper layers, and the applied electric field. Critical dimensions include the vertical electrode spacing (conducting and insulating layer thicknesses) and micro-well diameter and height (determined by layers stacked). The electric signal can be tuned via amplitude and frequency. The current device structure is for batch operation, but can be tailored to a continuous flow device. The device fabrication technique described here is suitable for developing 3D laminated electrodes with a wide variety of graphene nanoplatelet properties simply by exchanging the graphene paper utilized. Advantages of utilizing graphene paper are versatility of physical and chemical properties, reduced expense, and the graphene nanoplatelets can concurrently act as biosensors to detect a wide range of bioanalytes24. Long-term goals of high throughput 3D DEP systems are to rapidly identify cell types25-27, or achieve label-free, electrically mediated cell sorting of diseased cells from populations of healthy cells28. This paper demonstrates material optimization and device preparation and operation followed by illustration and analysis of typical results.

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			<td>Reagents</td>
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			<td></td>
		</tr>
		<tr>
			<td>Name of Reagent</td>
			<td>Company</td>
			<td>Catalogue Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Polystyrene Beads</td>
			<td>Spherotech, Inc.</td>
			<td>PP-60-10</td>
			<td>6.08 um diameter</td>
		</tr>
		<tr>
			<td>Graphene paper</td>
			<td>XG Sciences, Inc.</td>
			<td>XG Leaf B-072</td>
			<td></td>
		</tr>
		<tr>
			<td>Double sided tape</td>
			<td>3M</td>
			<td>N/A</td>
			<td>136 office tape</td>
		</tr>
		<tr>
			<td>Silver conductive epoxy</td>
			<td>MG chemicals</td>
			<td>8331-14G</td>
			<td>Part A &#38;B included</td>
		</tr>
		<tr>
			<td>Mannitol</td>
			<td>Sigma Aldrich</td>
			<td>091M0020V</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffer saline</td>
			<td>OmniPur</td>
			<td>0381C490</td>
			<td></td>
		</tr>
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			<td></td>
			<td></td>
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			<td>Equipment:</td>
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			<td>Name of equipment&#160;</td>
			<td>Company</td>
			<td>Catalogue Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Microscope&#160;&#160;&#160;&#160; (CCD Camera)</td>
			<td>Zeiss</td>
			<td>Axiovert 200M</td>
			<td></td>
		</tr>
		<tr>
			<td>Function/waveform generator</td>
			<td>Agilent</td>
			<td>33250A</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe</td>
			<td>Hamilton</td>
			<td>84505</td>
			<td></td>
		</tr>
		<tr>
			<td>Paper Clamp</td>
			<td>ADAMS</td>
			<td>3300-50-3848</td>
			<td></td>
		</tr>
		<tr>
			<td>Oven</td>
			<td>Fisher Scientific</td>
			<td>280A</td>
			<td></td>
		</tr>
		<tr>
			<td>Multimeter</td>
			<td>OMEGA</td>
			<td>HHM25</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-milling machine</td>
			<td>AEROTECH</td>
			<td>ABL1500 stages/A3200 Npaq controller</td>
			<td></td>
		</tr>
		<tr>
			<td>End mill</td>
			<td>ULTRATOOL</td>
			<td>708473</td>
			<td></td>
		</tr>
		<tr>
			<td>AxioVision</td>
			<td>Zeiss</td>
			<td>Version4.8</td>
			<td></td>
		</tr>
	</tbody>
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development of a 3d graphene electrode dielectrophoretic device

The design and fabrication of a novel 3D electrode microdevice using 50 &#181;m thick graphene paper and 100 &#181;m double sided tape is described. The protocol details the procedures to construct a versatile, reusable, multiple layer, laminated dielectrophoresis chamber. Specifically, six layers of 50 &#181;m x&#160;0.7 cm x&#160;2 cm graphene paper and five layers of double sided tape were alternately stacked together, then clamped to a glass slide. Then a 700 &#956;m diameter micro-well was drilled through the laminated structure using a computer-controlled micro drilling machine. Insulating properties of the tape layer between adjacent graphene layers were assured by resistance tests. Silver conductive epoxy connected alternate layers of graphene paper and formed stable connections between the graphene paper and external copper wire electrodes. The finished device was then clamped and sealed to a glass slide. The electric field gradient was modeled within the multi-layer device. Dielectrophoretic behaviors of 6 &#956;m polystyrene beads were demonstrated in the 1 mm deep micro-well, with medium conductivities ranging from 0.0001 S/m to 1.3 S/m, and applied signal frequencies from 100 Hz to 10 MHz. Negative dielectrophoretic responses were observed in three dimensions over most of the conductivity-frequency space and cross-over frequency values are consistent with previously reported literature values. The device did not prevent AC electroosmosis and electrothermal flows, which occurred in the low and high frequency regions, respectively. The graphene paper utilized in this device is versatile and could subsequently function as a biosensor after dielectrophoretic characterizations are complete.

Dielectrophoretic experiments on 6&#160;&#181;m polystyrene beads were conducted in a 0.38 mm3 cylindrical micro-well. Results demonstrate that a 3D laminated graphene paper-based device can illustrate similar dielectrophoretic signatures as 3D metal foil laminated devices20,21, traditional 2D metal-electrode26,27, and 2D insulator devices25. In the following experiments, an 15 Vpeak-peak AC signal was applied and frequency...

Watch this Scientific Journal Video about Development of a 3D Graphene Electrode Dielectrophoretic Device at JoVE.com

Development of a 3D Graphene Electrode Dielectrophoretic Device

A microdevice with high throughput potential is used to demonstrate three-dimensional (3D) dielectrophoresis (DEP) with novel materials. Graphene nanoplatelet paper and double sided tape were alternately stacked; a 700 &#956;m micro-well was drilled transverse to the layers. DEP behavior of polystyrene beads was demonstrated in the micro-well.

The design and fabrication of a novel 3D electrode microdevice using 50 &#181;m thick graphene paper and 100 &#181;m double sided tape is described. The ...

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